Innovative Biological Technologies for

Lesser Developed Countries

July 1985

NTIS order #PB86-121738
Recommended Citation:

Innovative Biological Technologies for Lesser Developed Countries— Workshop Proceedings (Washington, DC: U.S. Congress, Office of Technology Assessment, OTA13P-F-29, July 1985).

Library of Congress Catalog Card Number 85-600550

For sale by the Superintendent of Documents

U.S. Government Printing Office, Washington, DC 20402
Preface

Oversight of the Agency for International Development (AID) is the responsibility of the House Committee on Foreign Affairs. In 1980, under Chairman Clement Zablocki, the Committee requested the Food and Renewable Resources

Program of the congressional Office of Technology Assessment (OTA) to review

innovative biological technologies that AID could use to help lesser developed countries (LDCs) enhance the productivity of their soils, reduce their need for costly

chemical fertilizers, and increase food supplies,

In response to the committee’s request, OTA hosted a workshop that brought

together some 40 leading scientists, AID representatives, and congressional and

executive branch staff for 2 days of presentations and discussions on November

24 and 25, 1980 (see attendees list). On the first day of the workshop each scientist

presented a paper about innovative biological technologies and responded to questions. The second day was devoted to discussing AID and its role in using, promoting, and developing innovative biological technologies, Chapters I and II of this

report summarize those two days of discussion. Chapters III through XII contain

the scientific papers that were presented at the workshop.

These Workshop Proceedings were first released by the Committee on Foreign

Affairs in 1981. Continued requests for copies of the proceedings spurred this

reprinting. Although the papers have been edited slightly for style, they have not

been updated, OTA wishes to thank the authors of the papers, the other workshop

participants, reviewers, and the many people worldwide who have requested copies.
Workshop Participants

James Duke

USDA/ARS

Germplasm Resources Laboratory

Building 001, Room 131

BARC—West

Beltsville, MD 20705

Peter Felker

Ceasar Kleberg Wildlife

College of Agriculture

Texas A&I University

Kingsville, TX 78363

Stephen R. Gliessman

Agroecology Program

Board of Environmental

University of California

Santa Cruz, CA 95064

Jake Halliday

Battelle Kettering

Research Laboratory

Research Institute

Studies

150 East South College St.

Yellow Springs, OH 45387

William Liebhardt

Rodale Research Center

RD1 BOX 323

Kutztown, PA 19530

Thomas A. Lumpkin

Department of Agronomy and Soil Science

Washington State University

Pullman, WA 99164-6420

Cy McKell

Director of Research

N.P.I.

417 Wakara Way

University Research Park

Salt Lake City, UT 84108

John Menge

Department of Plant Pathology

University of California

Riverside, CA 92521

Frederick Mumpton

Department of the Earth Sciences

State University of New York

Brockport, NY 10003

Donald Plucknett

CGIAR

World Bank

1818 H St., N.W.

Room K1045

Washington, DC 20433

Noel Vietmeyer

National Academy of Sciences

National Research Council

JH 213

BOSTID

2101 Constitution Ave., N.W.

Washington, DC 20418
OTA Workshop Staff on Innovative Biological Technologies

for Lesser Developed Countries

Joyce C. Lashofl1and Roger Herdman,2 Assistant Director

OTA Health and Life Sciences Division

Ogechee Koffler, Division Assistant

Walter s E. Parham, Food and Renewable Resources Program Manager

Bruce Ross, Project Director

Contractors

Chris Elfring

Hugh Bollinger

Editor

Chris Elfring

Administrative Staff

Phyllis Balan3 and Patricia Durana,4 Administrative Assistant

Elizabeth Galloway, Secretary

Gillian Raney, Secretary

Nellie Hammond, Secretary

Carolyn Swarm, Secretary

1Until December 1981.

2Current Assistant Director,

3Until September 1984

4

From October 1984.
——— ——

Contents

Chapter Page

I. The Potential of Innovative Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

11. The Role of the Agency for International Development . . . . . . . . . . . . . . . . 2 3

111, Underexploited Plant and Animal Resources for Developing Country

Agriculture (Noel Vietmeyer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

IV. Native Plants: An Innovative Biological Technology

(Cyrus M. McKell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

V. Multiple Cropping Systems: A Basis for Developing an Alternative

Agriculture (Stephen R. Gliessman) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

VI. Development of Low Water and Low Nitrogen Requiring Plant

Ecosystems for Arid Developing Countries (Peter Feller) . . . . . . . . . . . . . . . 8 7

VII. Azolla, A Low Cost Aquatic Green Manure for Agricultural Crops

VIII

IX

(Thomas A. Lumpkin and Donald L. Plucknett) . . . . . . . . . . . . . . . :. . . . . . . . 107

Using Zeolites in Agriculture (Frederick A. Mumpton) . . . . . . . . . . . . . . . . . 127

Agrotechnologies Based on Symbiotic Systems That Fix Nitrogen

(Jake Halliday) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

X. Mycorrhiza Agriculture Technologies (John A. Mange) . . . . . . . . . . . . . . . . . 185

XI. A Low Fertilizer Use Approach to Increasing Tropical Food Production

(William C. Liebhardt) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

XII. The Gene Revolution (James A. Duke) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Chapter I

The Potential of
Contents

Pag e

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..., . . . . . . . . . . . . . . . . , . . . . . . . . .

What Do Innovative Technologies Offer? .,, ,..,... . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Workshop’s Conclusions . . . . . . . . . . . . . . . . . , , . . . . . . ., , . . . . . . . . . . , , ,.., . . .

Innovative Biological Technologies: Highligh

Underexploited Plant Resources . . . . . . .

Multiple Cropping . . . . . . . . . . . . . . . . . . . .

s of the workshop, , ., . . . . . . . . . . , , .

. . . . . . . . . . . ,.,,.. . . . . . . ,.,,., ,.,.

..,., . . . . . . . . . . . . ,..,,. . . . . . . . . . .

Agroforestry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . . . . . . ,

Azolla/Algae Symbiosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Underexploited Animal Species . . . . . . . . . . . . . . . . . . . . ..., , . . . . . . . . . . . . . . . .

Zeolites . . . . . . . . . . .

Biological Nitrogen F

Mycorrhizal Fungi..

. . . . . . . . . . . . . . . . . . . . . . . . . . . .,,,,,.. . . . . . . ,..,.,,,.

xation . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Chapter I

The Potential of

Innovative Technologies

INTRODUCTION

Fertile soil is the key to productive agriculture, whether for an Illinois corn farmer or a

subsistence farmer in Ghana, Haiti, India, or

other less developed country (LDC). The farmers know this; they know their soil must have

good tilth, hold water, and be rich with the necessary nutrients and minerals. They learn these

principles through education or, more likely,

through tradition and experience. But for most

LDC farmers, the old ways of maintaining soil

quality may no longer be adequate. Population

pressures and rising expectations force them

to demand more from the land, to shorten the

traditional fallow periods, and to open marginal lands that past generations could avoid

using. The farmers may turn to modern agricultural methods—e.g., commercial fertilizers

—only to find that the rising costs of these inputs prohibit even this option, This predicament is common throughout LDCs.

Most LDCs, with their growing populations,

are concentrated in a belt roughly 30 degrees

north and south of the Equator. These tropical and subtropical lands contain diverse ecosystems: mountains, rainforests, semiarid regions, and deserts, and house some 45 percent

of the Earth’s people. The concentration of

LDCs in the Tropics is not a coincidence but

stems in large part from inherent physical

limitations caused by climatic and soil constraints. As the populations of these nations

have grown, many LDCs have come to face a

myriad of severe resource problems: degraded

soil fertility, deforestation, soil erosion, water

pollution, and land-use conflicts, Concomitant

social problems—including malnutrition, poverty, and political instability—are common as

well.

The humid tropical regions have some of the

Earth’s most productive ecosystems—lush

forests that are the result of eons of long growing seasons and abundant rainfall. But this

apparent fertility is often superficial. Tropical

forests have been called “deserts covered by

trees. ” In fact, natural soil fertility in the wet

tropical latitudes is extremely low because

most of the minerals have been leached from

the soil by ages of rain and weathering, The

nutrients are trapped in the vegetation itself;

as the greenery dies and decays on the forest

floor, the nutrients are released, then quickly

absorbed into new growth.

Arid and semiarid regions face different

problems. Lack of water limits the type and

amount of crops that can be grown. Wind erosion, salinization, and temperature extremes

all work to limit the land’s productivity.

Agriculture in tropical latitudes must contend with these and other physical dictates. It

must work within increasingly severe economic constraints, too, as the costs of energy,

water, equipment, and various other agricultural inputs, from seed to fertilizer, continue

to rise,

Conventional agricultural methods, many of

which were developed for use in temperate

areas, are not wholly suitable for tropical conditions, It is not that conventional agriculture

cannot work in the Tropics; it can, in the short

run. But without continuous fertilizer inputs,

poor tropical soils cannot sustain temperate

farming methods, Also, in arid and semiarid

regions temperate farming technologies require

costly irrigation systems. Thus, with the increasing expense of irrigation development

3
4

and fertilizers derived from natural gas, it

seems inevitable that LDC farmers will look for

new ways to sustain soil fertility and to ensure

continued agricultural productivity.

The Agency for International Development

(AID) is one mechanism by which the United

States can help LDCs meet development and

resource challenges. AID has been commended

for many of its programs, but it also has been

cited for its reluctance to change and for its

lack of innovative vision at a time when innovation seems most necessary, This workshop

reviewed a number of innovative biological

technologies that might help LDCs enhance

their agricultural productivity and it takes a

special look at the role AID plays, and could

play, in developing these technologies.

WHAT DO INNOVATIVE TECHNOL0GIES OFFER?

The innovative biological technologies chosen for discussion in the workshop represent

only a sample of the diverse and adaptable approaches being studied by scientists here and

abroad. The workshop examined the following:

c promoting underexploited plant species,

especially native species already adapted

to local climates and conditions. Nature

is a storehouse of genetic possibilities including plants with potential as food, fodder, oil seeds, and export goods. Native

plants can be integrated into cropping systems, reducing the need for fertilizer and

water and enhancing resistance to pests

and disease, There is also promise in plant

breeding efforts and tissue culture, where

native stocks are used to adapt crops to

less than ideal environments, This reduces

the need to alter the environment with fertilizer, irrigation, and other expensive

inputs,

● Developing multiple-cropping and intercropping systems suitable for specific tropical environments as a way to maximize

land productivity. Multiple cropping is intensive agriculture—growing two or more

crops that share space and resources and

can produce more per unit of land than

monoculture. Proper design of the cropping pattern—e.g., using legumes—ensures

and enhances soil quality while providing

farmers with a range of products.

● Designing integrated agricultural systems

that take advantage of the special benefits

provided by leguminous trees. Various species of nitrogen-fixing trees (e. g., Prosopis

and Acacia] could be used to revegetate

deforested landscapes while providing

food, fodder, cash crops, fuelwood, and increased soil fertility. Unlike legumes used

in temperate agriculture (e. g., alfalfa),

many of these tree species can fix nitrogen under arid conditions.

● Cultivating “green” fertilizer for rice production. Azolla, a small aquatic fern native

to Asia, Africa, and the Americas, shows

great promise as a green manure, The fern

provides nutrients and a protective leaf

cavity for a strain of blue-green algae,

which in turn converts atmospheric nitrogen into a usable form. The nitrogen-rich

azolla is grown in rice paddies, either

before or along with the rice crop, It also

can be harvested and transported to upland fields,

● Using underexploited animal species to

meet local needs for high protein food as

well as to provide local populations with

innovative cash crops, For instance, in

Peru, guinea pigs are being produced as

an unconventional, but tasty and prolific,

protein source for local diets. And in

Papua, New Guinea, villagers are supplementing farm income by tending an additional garden crop—exotic butterflies for

export.

● Exploring the use of natural mineral soil

amendments, e.g., zeolite minerals, that

improve soil properties and extend fertilizer efficiency. Because of their structure, zeolites have unique properties. They
5

are used today primarily as molecular

sieves in industrial processes, but they

show promise in agriculture. They seem

able to help maintain nitrogen availability

in soils and help plants resist water stress.

More immediate benefits may show in animal agriculture, where zeolites can serve

as feed additives and as decontaminants

for feedlot wastes, and in fish farming. ●

Zeolite deposits are thought to be widespread in many LDCs.

Reducing the need for commercial nitrogen fertilizer by inoculating suitable crops

with beneficial soil bacteria—rhizobia—

that biologically take nitrogen from the air

and convert it to a usable form for the

plant. Legume rotations, of course, were

fundamental to agriculture before the development of commercial fertilizers. These

rotations relied on the natural abundance

of rhizobia, but improved strains might

garner even better results. Legume inoculants are used commercially in U.S.

agriculture and suitable strains are being

developed for LDC environments.

Increasing a plant’s capacity to absorb

nutrients by encouraging the growth of

beneficial micro-organisms–mycorrhizal

fungi—that live in association with some

plants. The mycorrhizae significantly increase the root’s surface area—the part of

the plant that assimilates nutrients from

the soil.

THE WORKSHOP’S CONCLUSIONS

Workshop participants shared a general feeling that a range of promising, innovative technologies exists in various stages of development that could help LDCs sustain soil fertility

with reduced fertilizer inputs. However, these

technologies are underused and many important ones are being ignored by the development

community. Many of the innovative approaches

discussed are “technologies” in the broadest

sense; they are new management systems, not

new pieces of hardware.

Research on such innovative techniques generally is underfunded, perhaps because of technological complexity, human reluctance to

stray too far from the norm, or well-intentioned

skepticism about radically new or unproven

approaches to agriculture. Thus, it is all the

more difficult to document their worth. Most

of the technologies, while promising, need

pilot-scale testing in appropriate environments

to determine potential problems or necessary

alterations before they can be promoted on a

wide scale. Also, workshop participants thought

that much of the development of innovative

technologies is occurring outside of, and perhaps in spite of, the national and international

institutions normally considered responsible

for maintaining natural resources and for dealing with problems of land quality and productivity.

A particularly interesting facet of these new

technologies is that many of them could benefit not only LDC agriculture but also U.S.

agriculture by providing opportunities for economic diversification, reducing soil degradation, and bolstering production while lowering capital costs.

No new technology, of course, can be a panacea. The importance of innovation lies in the

fact that each new approach increases the

number of options available to deal with problems, More choices thus provide increased

adaptability to changing social, economic, and

physical conditions.
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INNOVATIVE BI0LOGICAL TECHNOLOGIES:

HIGHLIGHTS OF THE WORKSHOP

This planet is believed to house some 80,000

species of edible plants. Man, at one time or

another, has used 3,000 of those for food. But

only about 150 plants have been cultivated on

a large scale, and less than 20 crops currently

provide almost 90 percent of the world’s food.

It is clear that mankind could exploit more

fully the range of botanical diversity found on

Earth. In developing countries, various innovative uses of plant resources show great promise and could help enhance land productivity

and increase food supplies. First, it is possible

to expand the range of crops grown by using

underexploited plant species, especially native

species already adapted to local climates and

conditions, Second, special attention could be

devoted to the potentials of leguminous species, including leguminous trees, that are capable of converting atmospheric nitrogen into

a usable form and thus enhancing soil fertility

while reducing reliance on expensive commercial fertilizers. Further, innovative and

conventional crops could be used together in

multiple cropping or intercropping systems designed for specific tropical environments to

maximize efficient resource use and land productivity.

The first day of the two-day OTA workshop

was devoted to discussions of particular innovative biological technologies—their potential

advantages for LDC users and problems limiting their use or development. Here are highlights of those discussions.

Underexploited Plant Resources

Every culture, of course, has indigenous species that have been used traditionally for food,

fuel, livestock feed, construction, fiber, medicine, and other purposes either gathered from

the wild or cultivated in various small farming systems. But until recently, these traditional

crops in LDCs had been lost in the shadows

of the Green Revolution and westernized farming techniques.

Now, however, there is renewed optimism

about the agricultural potential of many of

these plant resources. Native plants can be

innovative sources of a wide range of goods—

food for people and livestock, fuelwood for

cooking and warmth, materials for homes and

clothing, even oil seeds and other exports. The

benefits provided are compounded because

native plants can require fewer total inputs of

fertilizer, herbicides, insecticides, energy, and

in some cases water. This is because native species are adapted to local environmental conditions–soil type and quality, climate and

terrain. Indigenous species often are more resilient to stress, as well; they have evolved

defenses for local disease and pest organisms

and evolved to be efficient users of available

resources, whether water, soil nitrogen, or

other necessary nutrients. The native plant

concept is a reversal of the old philosophy of

using inputs to change the soil to suit the crop.

Here the crop is chosen to suit the soil. Examples of innovative plants include:

Winged bean (Psophocarpus tetragonolobus):

Generally identified as a “poor people’s crop”

in developing countries, the winged bean’s nutritional potential has been vastly underrated.

Actually, this plant, sometimes called a “supermarket on a stalk, ” has at least six edible parts.

The leaves are used like spinach as a vegetable

or salad; the flowers are edible, tasting somewhat like mushrooms; the pods, similar to

green beans, are nutritious and palatable; the

seeds are similar to soybeans and are composed of 17 percent oil and 42 percent protein;

the tendrils are also edible and taste like asparagus; and the below-ground tubers contain four

times the protein of potatoes.

Amaranth (Amaranths hypochondriacs):

Once the mainstay of certain ancient South

American cultures, amaranth is a fast-growing,

cereal-like crop that produces high-protein

grains in large, sorghum-like seed heads. The

grain is also exceptionally high in lysine—one

of the critical amino acids usually deficient in
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plant protein. Amaranth grain is usually parched

and milled to be used for pancakes, cooked for

gruel, or blended with other flours. Its leaves

can be eaten as a spinach substitute.

Leucaena (Leucaena Zeucocephala): Of all

tropical legumes, leucaena probably offers the

widest assortment of uses. It is a fast-growing

tree that produces good, dense firewood; it

fixes nitrogen in the soil; and its leaves make

nutritious cattle forage. This leguminous tree

is especially valuable in reforestation efforts.

Any change in the use of fertilizer, pesticides,

irrigation, or machinery would depend entirely

on the nature of the native plant chosen for

cultivation—whether the particular plant could

be used on an intensive or extensive basis, the

degree to which the plant is susceptible to

pests, and many other variables.

Water needs, too, would vary with the specific species chosen for cultivation. Species

adapted to tropical soils and moist climates

should not require irrigation provided that adequate rainfall occurs during the critical stages

of plant development. In regions of less than

optimal precipitation, farmers can choose

native plants with low water requirements

such as jojoba, atriplex, guayule, buffalo gourd,

guar, cassia, and acacia species. It is also possible to enhance the effectiveness of water use

through management (alternate fallow periods,

spaced planting, etc.), water harvesting, and

drip irrigation. Where land is not the limiting

factor, enhanced water harvesting is showing

high potential for fostering plant production

under desert conditions, The most suitable

plants for these technologies are deep-rooted

tree crops, drought adapted species, and biomass plantings.

Some native species also offer hope for intensive agriculture as certain plants could be

developed for large-scale operations. If a lowvalue crop can be replaced with a high-value

new crop, irrigation may even be justified.

Close plantings, tillage, pest control, and fertilization may then be needed to optimize production and under certain circumstances

might be economically viable. Grain amaranth,

winged bean, and guar are possible species for

intensive development, but many others may

be considered.

Equipment and labor needs also vary depending on the specific native plant in question. Some species (e.g., guar or guayule) are

amenable to mechanical harvesting. Many

others, however, require manual labor, which

could be an advantage where excessive unemployment exists.

To develop the potential of native plant resources, more effort needs to be devoted to

identifying valuable species and adapting them

to modern needs. Once identified, researchers

need to look for opportunities to expand the

plant’s use into similar environments elsewhere in the world, Perhaps a better understanding of the plant diversity available worldwide will lead to more innovation and also an

acceptance that folkways are often valid and

could be incorporated into a productive compromise between old and new customs.

Multiple Cropping

Multiple cropping is intensive agriculture

where two or more crops share space and resources, enhancing both land-use efficiency

and long-term productivity. It is not a new technology but rather is at its roots an ancient technique that mimics the diversity of natural ecosystems.

Today’s multiple cropping systems vary

greatly depending on the character of the site

being farmed. In general, multiple cropping

systems are managed so that total crop production from a unit of land is achieved by growing single crops in close sequence, growing

several crops simultaneously, or combining

single and mixed crops in some sequence. Both

“sequential cropping, ” which is growing two

or more crops in sequence on the same land,

and “intercropping,” which refers to various

ways of growing two or more crops simultaneously on the land, are included in the

broader term “multiple cropping.”

Generally, productivity on multiple cropped

land can be more stable and constant in the

long run than in monoculture. Although each
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crop in the mixture may yield slightly less than

in monoculture, combined production per unit

area can be greater with multiple cropped

fields. The overall increased yields result because the component crops differ enough in

their growth requirements so that overlapping

demands—whether for sunlight, water, or

nutrients—are minimal. Multiple cropping, in

effect, broadens the land’s productive capacity by more fully exploiting the dimensions of

time and space.

It is important to point out that not all crop

mixtures will produce better yields when multiple cropped. Certain combinations make better overall use of available resources and will

be more successful; these crops are considered

“complementary.” One of the main ways to

achieve such complementarily is by varying the

crop components temporally—i.e., using sequential planting to achieve a multiple cropping system that avoids antagonistic interactions between the components. Such systems

require special management—timely harvesting, the use of proper varieties, alteration of

standard planting distances, special selection

of herbicides so as not to create antagonisms

or residual effects.

Another way of complementing crop components is through intercropping based on

relay planting. Direct competition is avoided

by planting a second crop after the first one

has completed the major part of its development, but before harvest. Research on relay

cropping in Mexico and Latin America shows

definite yield advantages, especially for corn

and beans. The success of relay intercropping

depends on the correct combinations of timing and other variables so as to avoid shading,

nutrient competition, or inhibition brought

about by toxicity produced by the decomposition of previous crop residues. Research in

these areas is inadequate.

Finally, farmers can get maximum complementarily in systems where two or more compatible crops are grown simultaneously, either

in rows, strips, or mixed fields. For example,

traditional corn, bean, and squash systems

grown in Mexico show how three species can

benefit from multiple cropping. All three crops

are planted simultaneously, but mature at different rates. The beans, which begin to mature

first, followed by the corn, use the young corn

stalks for support. The squash matures last. As

the corn matures, it grows to occupy the upper canopy, The beans occupy the middle

space and the squash covers the ground. Research shows that the system achieves good

weed and insect control. And while the beans

and squash suffer a distinct yield reduction,

corn yields are significantly higher than in

comparable monoculture. It is still uncertain

whether the higher yields are the result of more

efficient resource use or if some mutually beneficial interaction is occurring among the crop

components.

Agroforestry

Agroforestry is a multiple cropping management technology that combines tree crops with

food crops, animal agriculture, or both. Like

other multiple cropping systems, its goal is to

optimize land productivity while maintaining

long-term yields. In the past, small-scale traditional agriculture often included trees as part

of the farm design, but interest in agroforestry’s

place in modern agriculture is just beginning.

Agroforestry systems can be used to bring marginal lands into production—lands with steep

slopes, poor soils, or widely fluctuating rainfall. But tree-crop combinations can also be

used on prime agricultural or grazing land to

further increase productivity. The main limitations to widespread use of agroforestry practices is lack of knowledge and expertise, and

unwillingness in the agricultural establishment

to accept the idea of long-term, diversified

yields.

The key to multiple cropping’s benefits is the

intensity of the cropping pattern—drawing as

much as possible from the land resource. Despite the intense demands, such systems need

not abuse the land; through proper design and

operation, multiple cropping management can

sustain and actually enhance soil fertility. Depending on the multiple cropping system used,

advantages can include:
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more efficient use of vertical space and

time, imitating natural ecological patterns

and permitting more efficient capture of

solar energy and nutrients;

more biomass (organic matter) available to

return to the soil;

more efficient circulation of nutrients, including “pumping” them from deeper soil

profiles when deep-rooted species are

used;

possible reduced wind erosion because of

surface protection;

promise for marginal areas because multiple cropping can take better advantage

of variable soil types, topography, and

steeper slopes;

less susceptible to climatic variation

[especially precipitation, wind, and temperature);

reduced evaporation from soil surface;

increased microbial activity in the soil;

more efficient fertilizer use through the

more diverse and deeper root structure in

the system;

improved soil structure, less 1ikelihood to

form “hardpan, ” and better aeration and

infiltration;

reduced fertilizer needs because legume

components fix atmospheric nitrogen for

themselves and associated nonlegumes;

heavier mulch cover aids in weed control;

better opportunities for biological control

of insects and diseases because of component plant diversity; and

potential benefits from mutualisms and

beneficial interactions between organisms

in crop mixture systems.

But as mentioned, not all crop combinations

lend themselves to successful multiple cropping and not all forms of multiple cropping are

necessarily good for the land. Sequential cropping, for instance, of two or three crops can

actually mine the land of nutrients and minerals if little thought is given to legume rotations, green manures, animal manures, or other

fertility-building activities. And in light of the

biological and physical aspects of the agroecosystem, other disadvantages in multiple cropping might include:

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competition for light, soil nutrients, or

water;

possibility of allelopathic influences between different crop plants caused by

plant-produced toxins;

potential to harm one crop component

when harvesting other components;

difficulty building a fallow period into

multiple cropping systems, especially

when long-lived tree species are included;

difficulties in mechanizing various operations (tillage, planting, harvest, etc.);

increases in evapotranspiration caused by

greater root volume and larger leaf surface

areas;

possible overextraction of nutrients, followed by their subsequent loss from the

agroecosystem if they are exported as agricultural or forest products;

damage to shorter plants from leaf,

branch, fruit or water-drop from taller

plants;

higher relative humidity in the air that can

favor disease outbreak, especially of fungi;

and

possible proliferation of harmful animals

(especially rodents and insects) in certain

types of systems.

Even though it seems that the biological and

physical advantages of multiple cropping outweigh the disadvantages, there also is a range

of social and economic factors that would influence the acceptance and use of multiple

cropping technologies in various cultures, In

terms of social stability, multiple cropping is

advantageous because it leads to a diverse agricultural system. Such a system is less susceptible to climatic variation, environmental

stress, and pest outbreaks. It is also less vulnerable to swings in crop prices and markets.

Multiple cropping also demands more constant

use of local labor and provides a more constant

output of harvested goods over the course of

the year. And because such systems are highly

adaptable, they can be melded into many different types of culture without undue stress on

existing local customs. Multiple cropping also

provides farmers with a large variety of useful

products, depending on the type and complex-
70

ity of their systems. And, of course, multiple

cropping systems can reduce the need for fertilizers and other energy imports, thus giving

LDC farmers improved economic stability and

self-sufficiency.

Reported lower yields, complexity of activities and management, higher labor demands,

and difficulty mechanizing operations are all

factors that discourage modern farmers from

multiple cropping. Conventional agriculture is

looking for short-term profits rather than at

maintaining constant income over the long

term, although it appears that the economics

of farming may be changing to favor such innovative systems, especially in the LDCs.

Although there exists the tangible disadvantage of potentially lower yields, most of the disadvantages involved in multiple cropping are

derived from lack of experience and knowledge

about the workings of complicated agroecosystems,

Azolla/Algae Symbiosis

Rice—one of the most important staple crops

in the world—demands rich, fertile soil. But

traditional legume crops do not make good

green manures for rice farmers; they are reluctant to devote part of the valuable growing

season to a relatively slow-growing legume

crop. Furthermore, most legume crops cannot

grow or fix nitrogen in flooded or waterlogged

soils. But these disadvantages can be avoided.

Through the use of azolla, a small aquatic fern

native to Asia, Africa, and the Americas, rice

farmers can produce a fast-growing green

manure that thrives in paddy-like conditions.

Azolla is a genus of small ferns that live naturally in lakes, swamps, streams, and other

bodies of freshwater. Its tremendous agricultural potential lies in the fact that azolla lives

in a symbiotic relationship with a nitrogenfixing blue-green algae, Anabaena. The delicate

azolla fern provides nutrients and a protective

leaf cavity for the Anabaena. In turn, the algae

produce enough nitrogen to meet the needs of

both plants, plus some extra. Under the right

conditions, the fern/algae combination can actually double in weight every 3 to 5 days and

fix nitrogen at a higher rate than most legume

Rhizobium symbionts. In 25 to 35 days, azolla

can fix enough nitrogen for a 4 to 6 ton/ha rice

crop during the rainy season or a 5 to 8 ton/ha

crop under irrigation during the dry season.

The nitrogen fixed by the fern/algae combination becomes available to the rice after the

azolla mat is incorporated into the soil and its

nitrogen is gradually released as the plants

decay.

Azolla’s value as a green manure for flooded

crops has been known for centuries by the people of the People’s Republic of China and Vietnam. But its use was relatively limited; few

families knew the intricate techniques needed

to overwinter and oversummer the sensitive

fern successfully, and these families controlled

the distribution of starter-stocks in the spring.

After the revolutions in China and Vietnam,

the new governments eventually recognized

the value of azolla and began promoting its use,

but their efforts were minimal and progress

was slow, It is only recently that worldwide attention has focused on the plant and serious

efforts have been made to search for hardier

varieties for widespread use.

Azolla’s ability to enhance soil fertility occurs both because it is an input of nitrogen and

of organic matter. Nitrogen, of course, is a necessary plant nutrient. Humus, the rich organic

material formed through plant decomposition,

increases the water-holding capacity of the soil

and promotes better aeration and drainage.

Organic matter also can bind soil particles together, thereby improving the soil structure.

Azolla also can be important in the cycling

of nutrients. While it is growing, the plant not

only fixes nitrogen but absorbs nutrients out

of the water, nutrients that otherwise might be

washed away. Some of both the nitrogen and

nutrients are stored in the living plant matter

until the fern/algae mat is incorporated into the

soil and begins to decompose. Because it has

a high lignin content, azolla decomposes relatively slowly—6 weeks or more before all the

nutrients are released. This natural slow release is ideal for a developing rice crop.
11

In addition, it seems that azolla suppresses

the growth of certain aquatic weeds—in part

because the thick azolla mat deprives young

weeds of sunlight and in part because the interlocking mat physically inhibits weed emergence. Rice seedlings are not harmed because,

when transplanted, they stand above the azolla

mat,

Using any green manure crop requires some

adjustments in a farmer’s crop management

system. Depending on the local environments,

azolla can be grown as a monocrop, intercrop,

or both. If the fern is grown as a monocrop,

it is grown and incorporated into the soil before

the rice is harvested or it is grown and transported for use on upland crops. Azolla is often

intercropped in areas where the growing

season is too short for successful monocropping. One method grows two rows of rice

planted about 4 inches apart with Azolla growing in two-foot spaces on either side of the double rows. The azolla is incorporated by hand

or with a rotary rice weeder. Combining monocropped and intercropped azolla provides nitrogen before transplanting and throughout the

growing season. At present, azolla’s primary

role is as a spring green manure and its secondary role is as a fall manure. It is highly susceptible to pests and temperature extremes and

generally is not grown crops in summer.

To be successful, azolla requires phosphorus

fertilizer (0.5 to 1.0 kg P/ha/week), but this is

not necessarily an increase over the fertilizer

needed to produce a rice crop. Rice also requires phosphorus; so, rather than applying it

directly to the rice the fertilizer can be given

to the azolla in small weekly doses. Once the

azolla is incorporated into the soil and begins

to decompose, the phosphorus becomes available to the rice crop. Other inputs that enhance

azolla growth in certain soils (e. g., potassium)

are usually also applied for a high-yielding rice

crop and so can be cycled in a similar way.

Water is the primary environmental constraint on azolla cultivation. As a freefloating,

aquatic fern, azolla can only grow in areas with

abundant, stable water supplies. Although it

can last for months under refrigeration, the

plant cannot survive for more than a few hours

on a dry soil surface under direct summer sun.

The azolla varieties available are not very stress

tolerant; azolla cannot live in water outside a

0° to 400 range, and for adequate growth the

daytime temperature should stay within 150 to

3 5 0

0 C. Humidity and pH also affect azolla

growth.

Because the technology to grow azolla from

seeds (spores) does not exist, some plants (1 to

10 percent of those needed for startup) must

be maintained throughout the year. Because of

azolla’s sensitivity to temperature stress, the

overwintering and oversummering periods are

critical. The plant is also susceptible to a number of insect and disease pests. The pests are

especially destructive during the summer and

must be carefully controlled. In fact, the primary reason why azolla is not cultivated during the summer is because of the destruction

caused by rampant insects.

There are also cultural and economic constraints on azolla cultivation. As with any innovation, it can be difficult for people to accept an idea that is foreign to their traditions.

The idea of growing an aquatic legume is fundamentally different from most farming societies’ norms; and in many hungry countries,

the idea of growing a crop just to plow it under

seems utterly impractical. Azolla cultivation

may be slow in gaining acceptance, too, because it demands a year-round commitment

not usually required of rice farmers, And because azolla cultivation is not applicable in

areas where rice is broadcast-sown, it is not a

viable technology for those regions that do not

plant rice in rows,

Finally, social and political factors can work

both for and against azolla’s use, In some regions, especially where there are unfavorable

land ownership patterns, low prices or other

strong disincentives, farmers are not willing

to shift from their immediate-subsistence,

“plant and harvest” approach, because they do

not see the long-term benefits. Political systems, too, can have an effect. The successful

azolla programs in China and Vietnam depend

heavily on specially trained “azolla teams”
12

made possible by the structure of their farming communes and cooperatives. Societies less

centrally organized could have difficulty adopting and transferring azolla cultivation techniques.

One of the major constraints on the development of azolla technologies is simply lack

of information. Although it is an ancient agricultural system, its use has always been limited

and it has not received much scientific attention. Research efforts are disorganized, scattered, and often repetitious. There has never

been an international discussion of azolla research priorities. And once again, traditional

segmented research approaches have proven

inadequate because many of the problems that

remain require a multidisciplinary approach.

As of 1980, azolla was cultivated as a green

manure on about 2 percent of the harvested

rice area of China and about 5 percent of the

spring rice crop. In Vietnam, azolla grows as

a winter green manure for 8 to 12 percent of

the total harvested area, and about 40 to 60 percent of the irrigated spring rice in the Red River

delta. But these two countries are only two of

many that might tap azolla’s potential. With research, strains could be found that are less sensitive to summer insects and temperature and

cultivation could increase substantially. In

essence, using azolla in rice production exchanges labor for nitrogen fertilizer. In countries with a shortage of cash but plentiful labor, azolla technology could be a step toward

sustainable agriculture productivity.

Underexploited Animal Species

People interested in helping developing

countries better their standards of living tend

to promote resources and technologies with

which they already have experience. One hears

much, for example, of how genetic engineering can be expected to make possible selffertilizing varieties of conventional crops such

as wheat and corn. While understandable, this

preoccupation with increasing the productivity

of “mainstream” species overlooks a vast potential. Indigenous species often have the

advantage of being relevant to the customs and

values of local people.

Just as there are unfamiliar plants ripe for

development as sources of food, feed, fiber, and

fuel, so are there also unfamiliar animal species at least as promising. People traditionally

have relied on a small number of animals that

have been domesticated since prehistoric

times. But domestication of some different species could pay tremendous dividends. In some

countries, in fact, this is already beginning.

For instance, small animals are particularly

suited to domestication in many developing

countries because they require little space, they

fit well into village or urban life, and they require no refrigeration since they can be eaten

in one meal. Moreover, many of these species

tolerate the climates of developing countries

better than do sheep, cattle, and pigs, and they

thrive on readily available diets. Thus, snail

farming in Nigeria, giant toad farming in Chile,

and guinea pig farming in Peru are all being

developed to provide native people with muchneeded high-quality protein at affordable costs.

In addition, at least some of these ventures

can become the basis of new industries. Thanks

to the efforts of researchers at the La Serena

campus of the University of Chile, for example, intensive methods have been developed

that furnish grocery stores, restaurants, and

canneries with 10 to 15 tons of giant toad legs

a year. Because the meat is an attractive white

and tastes like a blend of chicken and lobster,

it could prove to be a lucrative export as well.

Giant toads are reportedly easy and inexpensive to rear. Kept in isolated ponds (so that they

will not cannabilize other aquatic life) and supplied with insects attracted by flowers, shrubs,

and rotten fruit, they require little attention and

reach their market weight of about half a pound

in 2 years.

The domestication of exotic species is, in

fact, already producing foreign exchange for

at least one poor country—Papua New Guinea.

There, people who used to hunt crocodiles in

the wild are now more profitably rearing hatchlings in captivity for the world skin market.
13

And in remote jungle villages butterflies are being raised on “farms without walls” to meet

the rising international demand from museums, entomologists, private collectors, ordinary citizens, and the decorator trade.

Both the crocodile and butterfly projects

demonstrate that development and the conservation of natural resources can go hand in

hand. They also demonstrate something else:

that to succeed, such projects need not only a

concern for development but also a sensitivity

to local environmental conditions and knowledgeable inputs of science and sociology.

In Papua New Guinea, for instance, the introduction of western-style cattle ranching

could threaten the fragile tropical forest ecosystem. And such imported technologies would

be completely unfamiliar to local people. By

contrast, crocodile and butterfly farming that

can be based on sound biological principles,

would make it worthwhile for local people to

use indigenous renewable resources wisely.

Zeolites

Zeolites are natural, three-dimensional, finegrained silicate minerals composed of alkali

and earth metals crystals that have an ability

to separate gas molecules on the basis of size

and shape. Over 100 forms have been synthesized and are now the mainstay of multimillion-dollar molecular sieve businesses that are

important for industrial purposes in chemical

and petrochemical firms in the United States

and abroad.

Zeolites, however, also occur abundantly in

nature, Almost 50 species have been identified

from volcanic sedimentary deposits on every

continent. Their widespread dispersion and

special properties make them of interest to

countries wishing to rely less on costly imported inputs to produce food because they appear promising as a means to improve animal

husbandry, fish production, and crop yields.

Zeolites have such promise primarily because

they act as traps for nitrogen.

Zeolites get their name from the classical

Greek words “boiling stones” because they

froth when exposed to intense heat. Although

their existence has been known to scientists

since 1756 and they have been used since antiquity as building materials, their potential

agricultural and aquacultural applications

were virtually ignored until about 20 years ago.

Even now this technology must be said to be

suffering from neglect.

When added to animal feed, for example,

zeolites have both inhibited the development

of mold during storage and increased the

growth rates of swine, rabbits, poultry, beef,

and dairy cattle. Moreover animals raised on

zeolite-enriched rations tend not to be subject

to diarrhea or other ills. These minerals are

thus a possible alternative to the controversial

use of antibiotics in livestock feed.

Besides thriving on zeolite-supplemented

diets, animals fed these minerals produce excrement that is at once almost odorless and exceptionally good fertilizer. This is because

zeolites capture the ammonia ion from the feces and thus retain the biological availability

of the nitrogen in animal wastes. Direct zeolite

treatment of manure to reduce odor and improve its efficacy as fertilizer is also feasible,

as is using the adsorption properties of natural zeolites to obtain pure methane for energy

purposes from animal or other organic wastes.

In summary, the application of zeolites to

animal husbandry holds some promise from

the perspectives of livestock production, pollution control, crop yields, and energy alternatives.

Zeolite technology also has potential for the

commercial fish breeding and farming. For one

thing, the rations now fed to fish in such enterprises are quite expensive. As the nutritional

requirements of fish are similar to those of

poultry, the indications are that zeolite supplements could be expected to reduce feeding

costs. For another, many fish species are raised

in closed or recirculating water systems where

the accumulations of nitrogen from their waste

and the decay of uneaten food commonly

causes sterility, stunted growth, and high mortality. Although various means already are used

to deal with these problems, zeolite regulation
of the nitrogen content of fish ponds has been

reported to be cheaper and, under low temperature conditions, more reliable.

Similarly, the affinity of zeolites for nitrogen

may be important in ponds and small lakes

where eutrophication results in an oxygen-poor

environment detrimental to fish life. Evidence

suggests that the ability of these minerals to introduce free oxygen into stagnant water might

increase the number of fish that can be raised

or transported in a given volume of water.

The properties of zeolites also improve the

performances of chemical fertilizers and pesticides, fungicides, and herbicides. For example, zeolite-treated soils retain the nutrients

supplied by chemical fertilizers longer than

soils treated with the fertilizers alone. The presence of zeolites as soil conditioners (also

known as soil amendments) also has been

found to regulate the release of critical nutrients from fertilizers. Improved yields of wheat,

apples, eggplant, carrots, sorghum, radishes,

chrysanthemums, and sugar beets have been

reported.

Controlled release of micronutrients from the

soil itself—e.g., iron, zinc, copper, manganese,

and cobalt—has also been found when zeolites

are used in conjunction with chemical fertilizers; this also prevents them from caking

and hardening during storage.

Zeolites added to pesticides, herbicides, and

fungicides seem to enhance their effectiveness.

They can also be exploited to remove toxic

heavy metals from the soil, thus preventing the

toxic wastes from moving up the food chain

from plants to animals and, ultimately, to

people.

Nonetheless, the commercial use of zeolites

in agriculture has generally been on only a relatively small scale and then predominately in

Japan and other parts of the Far East. Even

though a number of domestic companies have

undertaken preliminary zeolite studies, little information is available on the long-term benefits or adverse impacts of these minerals on

food production or the environment. Furthermore, even such information as has been

developed is often proprietary. Though the desire of the private sector to keep its data confidential is understandable, this cannot help but

lead to duplication of effort and slow progress.

Developing countries of course would be

eager to reduce their costly dependence on imported fertilizers, fuels, and livestock feed. Cooperative ventures between the United States

and these countries could improve knowledge

of zeolite technology and, importantly, undertake long-term or large-scale testing projects

under field conditions.

Biological Nitrogen Fixation

One very promising multiple cropping strategy is the use of leguminous plants. Legumes

can provide food, livestock fodder, and wood

while concurrently improving soil fertility. Leguminous plants—e.g., temperate species such

as alfalfa, soybeans, and clover—have the capacity to provide their own nitrogenous fertilizer through bacteria (Rhizobia) that live in

nodules on their roots. The bacteria chemically

convert atmospheric nitrogen into a form that

the plant can absorb and use. The nitrogen also

is available in the root zone for nonleguminous

companion or follow-on crops to use.

The use of legumes is not new; generations

of farmers relied on rotations of legume plants

to restore nitrogen in the soil long before the

advent of cheap commercial fertilizers. Now,

as energy costs skyrocket and fertilizer costs

become prohibitive in many developing countries, legume use—green manure—may be the

best remaining option for maintaining soil fertility and agriculture productivity.

Leguminous species could not only help protect LDCS from burgeoning energy costs but

could also improve local nutrition. Nutritionally, legume seeds (beans or pulses) are two

to three times richer in protein than cereal

grains. Many have protein contents between

20 to 40 percent. A few even range up to 60

percent. This is particularly important because

there is chronic protein deficiency in virtually

every developing country.
15

Inoculant Technologies: Nitrogen can be

converted into forms usable by plants through

industrial processes, but only at great cost,

especially as energy prices escalate, But biological nitrogen fixation (BNF) by symbiotic

associations of plants with micro-organisms

may be an economically and environmentally

sound approach to sustainable agriculture.

Farmers can capitalize in two ways on certain plants’ innate ability to fix nitrogen biologically. First, of course, like countless past

generations of farmers they can use legumes

in their cropping systems and benefit from the

nitrogen produced, But recent innovations also

can help farmers maximize nitrogen fixation.

Using inoculant technology, selected legumes

can be inoculated with specific strains of

Rhizobium, the soil bacterium that associates

with legume roots and fixes nitrogen. This way

farmers can more fully exploit the plant’s fertilizing capabilities.

Most soils harbor various native rhizobial

populations and these strains will associate

with sprouting legumes. But because these

strains differ greatly in their effectiveness, it

can be to the farmer’s advantage to plant legume seeds that have been inoculated with

proven strains of Rhizobium. The objective of

inoculation technologies is to introduce sufficiently high numbers of preselected strains of

rhizobia into the vicinity of the emerging root

so that they have a competitive advantage over

any indigenous soil strains of lesser nitrogenfixing ability.

Commercial-scale inoculant use is common

in the United States and Australia, Brazil,

Uruguay, Argentina, India, and Egypt also produce inoculants. But while demand for inoculants is growing in many countries, it is not

enough to simply import U.S. or other inoculants because they may not be suitably

adapted to the LDCs climate, soils, and farming systems. BNF can be improved by selecting effective Rhizobium strains from the local

environment and culturing these.

The major scientific constraint on developing BNF technologies is inadequate understanding of the interactions among specific

host legumes, rhizobial strains, and various

environments. This results in an inability to

predict whether a given legume will respond

to inoculation in a particular region. A lack of

trained personnel in tropical regions also acts

to limit research and development efforts, And

because inoculant development and use requires some technical training, it may not be

an easy technology for LDCs to adopt widely.

But while legume use holds potential in all

segments of agriculture, inoculant technology

at present should only be advocated when there

is a known need to inoculate.

Most legumes in the Tropics fix about 100

kg/ha/yr of nitrogen, although the forage tree

leucaena can fix as much as 35o kg/ha/yr and

some other species can fix as much as 800

kg/ha/yr. However, the benefit to nonlegumes

is small when compared to the effects of nitrogenous fertilizer as applied in the intensive

cereal production systems of the developed

world. It is unrealistic to think that biologically

fixed nitrogen will replace commercial fertilization of cereal and root crops. These crops

are known to respond to levels of nitrogen far

in excess of those that could currently be supplied through legume BNF. Thus, it would be

profitable to determine ways to increase the

contribution of legume BNF as a complement

to nitrogen fertilizers rather than as an alternative.

Although legumes seem unlikely to replace

commercial fertilizers, fertilizer savings through

the use of legumes could represent a significant savings in foreign exchange, reduce dependence on energy-rich nations, and lend

more stability and diversity to LDC agriculture.

Leguminous Plants: A great variety of leguminous plants—both food crops and species

useful for fuelwood, fodder, and other needs—

exist that could be cultivated in moist and

arid/semiarid tropical climates, Winged bean

is one extraordinarily valuable leguminous species. Tarwi, tepary bean, and yam beans are

also nitrogen-fixing species with potential in

moist tropical environments.

But not all leguminous species have high

water requirements. Adapted plant species
could be used in arid and semiarid regions as

well, serving not only to enhance land productivity but also to stimulate depressed economies. For example, leguminous trees such as

Acacia, Leucaena, and Prosopis could be important, fast-growing fuelwood sources. Because 80 percent of the wood consumed in the

Third World is used as fuel, and wood shortages are of crisis proportions in some areas,

the potential of agroforestry should not be underestimated,

In arid/semiarid regions, of course, water

availability is a key factor in agricultural productivity. But problems are compounded in

some dry environments because soils also have

low fertility. In these areas, drought-adapted,

deep-rooted, nitrogen-fixing tree species (e.g.,

Acacia albida and Prosopis cineraria), perennial arid-adapted herbaceous legumes (e. g.,

Zornia and Tephrosia), and shrubby legumes

(e.g., Palea species) could increase soil fertility

and triple water use efficiencies. By bolstering

soil fertility with tree species, it is possible to

create a system where production of food

staples is water-limited rather than fertilitylimited. And intercropping traditional, annual

food staples such as millet, sorghum, groundnuts, and cowpeas with leguminous trees can

actually stimulate crop yields.

Livestock fodder and cash crops, too, can be

obtained from arid species. Arid-adapted, salttolerant shrubs (e.g., saltbush—Atriplex species), the pods of leguminous trees (e. g., Acacia

tortilis, Acacia albida, and Prosopis species),

and even cactus (Opuntia and Cereus) can expand the amount of forage available for local

livestock while improving soil quality and enhancing the stability of the grazed ecosystems.

LDC farmers also could benefit from growing perennial, arid-adapted plants as cash

crops, The species Jojoba is under development

in southern California, Arizona, Mexico, and

various semiarid LDCs. It produces seed that

contains a rancidity-resistant, nonallergenic,

liquid wax with lubricating properties equivalent to oil from the endangered sperm whale.

Another desert plant, guayule, contains natural rubber and could become a major semiarid

crop. Other potential lies with various species

of drought-adapted leguminous trees that might

be useful for the gums they exude, cacti that

produce table-quality fruits, and a number of

other innovative plant resources.

Surprisingly, relatively little work is being

done to further current knowledge about some

of these highly promising plant resources. But

as energy, fertilizer, irrigation, and other costs

escalate, it seems inevitable that farmers in arid

and semiarid regions will look more to adapted

crops.

Optimal water-use efficiency in an arid/

semiarid agroecosystem demands a mix of

nitrogen-fixers and water-to-dry matter conversion specialist plants. For instance, cacti are

a better supplier of the energy portion of livestock feed than legumes because they have a

fivefold greater efficiency converting water to

dry matter, However, legume leaf litter is important to create good soil fertility so the cactus

can achieve its maximum water-use efficiency.

Thus, a mix of plants is needed. And because

livestock need both energy and protein, both

energy- and protein-producing plants are required.

Similarly, appropriate use of arid-adapted

legumes can increase fertilizer-use efficiency.

Adapted legumes do not require nitrogen themselves and when properly incorporated into a

diversified agroecosystem they will reduce nitrogen needs for nonlegumes as well. Many

arid-adapted plants, both legumes and nonlegumes, have very deep root systems—an

advantage because they are thus capable of extracting nutrients and minerals from deep subsurface soil layers, Also, the deeper rooted species should capture a higher portion of any

fertilizers applied because the nutrients are not

as likely to leach beyond their deep root zone.

As an added benefit, wind and perhaps water

erosion might be reduced, as many of these

plants are perennials and thus keep the soil

more adequately protected,

There are no major scientific constraints to

using arid-adapted plant resources in LDC agriculture, but there is great need for expanded

research and development efforts. The poten-
17

tial paybacks could be great. Environmental

impacts, too, are overwhelmingly positive, including the potential to slow desertification.

Political and social constraints, however, exist that might limit the use of innovative plants.

Cultural traditions, for instance, are not easily

changed and innovation must blend into existing values systems and local behavior. If, as

in Sahelian Africa, free-roaming goats devour

young tree seedlings because tradition allows

that goats can forage unrestrained, then reforestation attempts must consider this and devise

goat-proof protection for the young trees.

Other social influences also can make the

acceptance and use of innovation all the more

difficult. This is especially clear in research

centers run by scientists either from or trained

in developed countries; consciously or not,

they often strive to promote their own cultural

values and ignore the methods and effectiveness of native farming systems, As was the case

with Acacia albida, the scientists may not be

broadly trained—the agronomists failing to see

the tree’s food potential and the foresters underestimating its potential because it does not

grow in forests and hence is not part of standard sylviculture concepts. It is not lack of concern that causes this problem. Rather, some

agricultural scientists tend to be overspecialized and limited in their experience. Also,

administrative structures often thwart attempts

to develop integrated, innovative programs.

In practical terms, such innovative biological technologies offer real hope for LDC farmers. And the scale need not be big. A farmer,

for instance, could plant 1 hectare with 200

Prosopis trees at 15 cents each for a total cost

of $30. Land, a shovel, and buckets for watering the seedlings are the only prerequisites.

With protein and nitrogen contents of 12,5 and

2,0 percent, respectively, pods from the trees

could in 2 or 3 years produce 60 kg of nitrogen and return the $30 initial investment.

Many of the innovative systems now receiving attention from the scientific community are

actually widely used by subsistence farmers in

the developing countries, However, the plants

under cultivation now are of unselected genetic

stock. It is comparable, in fact, to the use of

unselected races of maize and wheat that were

in use in the late 1800s in the United States and

Europe. Subjecting the innovative species to

a rigorous research and development effort

could be expected to produce yield increases—

perhaps twofold and threefold in 15 years—

and other beneficial refinements of immense

value to the people of the Third World. And

yield increases in tree legume production,

fuelwood production, cash crop production,

soil fertility, and ensuing staple food production would have repercussions throughout the

economy—more income; greater demands for

goods; a larger tax base to support roads,

schools, and health services; and increased employment. By working within the bounds of the

ecosystems, innovative plant resources can

help agrarian societies ensure sustainable and

stable agriculture.

Mycorrhizal Fungi

Nitrogen is only one of the nutrients essential to plant growth. So another approach to

enhancing LDC agriculture without inputs of

commercial fertilizers is to find ways to increase the effectiveness of the plant’s use of the

other nutrients available in the soil.

Selective plant breeding, of course, still holds

great potential for developing varieties of innovative and traditional crops that are more

resistant to environmental stress. Geneticists

have made extraordinary strides in breeding

varieties that respond to commercial fertilizer

inputs; similar efforts could help locate and develop plants that would grow and prosper

under less than ideal conditions—marginal

lands, variable climates, or deficient soils. This

potential amplifies the importance of preserving native plant resources, both in seed storage facilities and in their natural habitats, because geneticists necessarily turn to hardy,

native stocks as sources of genetic material to

improve cropped varieties.

There is another “biotic fertilizer” that might

aid LDCs in their quest for sustainable agro-
18

ecosystems. Mycorrhizal fungi are beneficial

soil fungi that live symbiotically with a vast

range of plants. Mycorrhizae are the structures

formed—part plant, part fungus—by the symbiosis. These structures can extend up to 8 cm

from the root into the surrounding soil, providing a bridge to transport nutrients back to

the roots, The host obtains nutrients via the

mycorrhizal fungi, while the fungus obtains

sugars or other foods from the plant. The association results in a marked increase in the host

plant’s growth.

There are many species of mycorrhizal fungi

that form mycorrhizae and can enhance plant

growth, These fungi are so common, in fact,

that literally any field soil sample from the Arctic to the Tropics will contain some, The most

common type, vesicular-arbusula (VA) mycorrhizae, occur on liverworts, ferns, some conifers, and most broad-leaved plants including

agronomically important species such as wheat,

potatoes, beans, corn, alfalfa, grapes, date

palms, sugar cane, cassava, and dryland rice.

Only 14 plant families are considered primarily nonmycorrhizal.

The fungi essentially increase the surface

area of the plant’s roots for absorbing nutrients.

They actually can increase the plant’s absorptive area by as much as 10 times. The fungi also

extend the host plant’s range of uptake; nutrient ions that do not readily diffuse through the

soil—e.g., phosphorus, zinc, and copper—can

be tapped from beyond the normal root zone

by the fungi. Absorption of immobile elements

can be increased by as much as 60 times by the

plant-fungi symbiosis. perhaps the most important benefit provided by mycorrhizal fungi is

increased phosphorus uptake. They also stimulate plant absorption of zinc, calcium, cooper,

magnesium, and manganese. Plant uptake of

mobile soil nutrients such as nitrogen and

potassium is rarely improved because normal

soil diffusion typically supplies adequate amounts

of these regardless of root size.

Mycorrhizal fungi also can enhance water

transport, prevent water stress under some

conditions, enhance salt tolerance, and increase symbiotic nitrogen-fixing bacteria such

as Rhizobium.

The potential offered by mycorrhizal fungi

as biotic fertilizers, however, is not as vast as

it might seem. Mycorrhizal fungi already occur

in most soils and thus already grow in association with most agronomic crop plants. Because these fungi are so widespread, immediate needs for inoculation are limited. The

inoculants currently available are for use on

disturbed sites (strip-mined areas where indigenous mycorrhizal populations have been

destroyed), on fumigated soils (any forest or

crop nursery or plot that has been treated to

remove soil-borne pests), and in greenhouses

(because sterile soils lack native mycorrhizal

fungi). In these situations, inoculation with

mycorrhizal fungi has proven beneficial—e.g.,

in fumigated sand or soil, VA mycorrhizal

fungi will increase the growth of citrus, soybeans pine, and peaches. Growth improvements also show in cotton, tomatoes, corn,

wheat, clover, barley, potatoes, and many other

crops.

But even though large-scale field inoculations

with mycorrhizal fungi are rare because of adequate indigenous populations and because

there is limited inoculum available, it seems

likely that such applications might be much

more valuable if, for instance, scientists develop mycorrhizal fungi inoculants that are

superior to native populations. Because many

indigenous mycorrhizae are relatively inefficient symbionts, improved strains of fungi

could enhance plant growth, even in nonsterile

soils. And because huge expanses of tropical

soils (e.g., the Brazilian Cerrado) are either deficient in phosphorus or immobilize added phosphorus fertilizers, mycorrhizal fungi could improve the productivity of the marginal lands,

if fungi having the ability to extract small quantities of fertilizer were developed and added

to the soil.

Even though mycorrhizal fungi inoculants

are used commercially in some circumstances,

their importance is limited and many questions

about their effectiveness remain unanswered.
19

For instance, fumigating fields with methyl

bromide, a biocide that is extremely toxic to

mycorrhizal fungi, often is followed by stunted

growth in following crops. Yet little work has

been done to determine the feasibility of fieldscale application of inoculants. And even in

nursery crops grown on sterile, nonmycorrhizal soils, inoculations receive limited use in

part because detailed information regarding

their value is lacking. For tree crops, however,

some of the answers may be coming; the U.S.

Forest Service is conducting a testing program

using commercial inoculum on tree nursery

sites throughout the country. When the tests

are complete they should indicate the commercial feasibility of producing and using mycorrhizal inoculum in fumigated tree nurseries.

Three major obstacles hinder further development of this biotic fertilizer, First, no largescale field experiments using mycorrhizal

fungi under normal agricultural conditions

have been conducted, yet such work is a necessary forerunner to actual use of the fungi,

Second, cost-benefit analysis is warranted to

determine the economics of mycorrhizal applications. And finally, agriculture itself must

shake loose of some conventionality; it seems

locked to practices for increasing soil fertility

that only involve use of commercial chemical

fertilizers.

Because mycorrhizal fungi increase the efficiency of fertilizer use, they can be thought of

as biotic fertilizers and might be substituted for

some fertilizer components. Considering estimates that 75 percent of all the phosphorus applied to crops is not used within the first year

and thus reverts to forms unavailable to plants,

especially in tropical soils, it appears that further work on improving mycorrhizal fungi effectiveness could aid LDCs in developing sustainable agricultural systems.
Chapter II

The Role of the Agency

for International Development
— —

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Budget and Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Current Innovative Biological Activities at AID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Two Approaches to Apply Innovative Biological Technology to

LDC Agricultural Problems . . . . . . . . . . . . . . . . . . . + +, . . . . . . . . . . . . . . . . . . . . . . . . . 25

The Need for Cooperative Ventures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

The Need for Field Demonstrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., .,,,.. 26

The Need for Innovative Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . 26

The Need for Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,., 27

The Need for Trained AID Staff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 28

Perceived Constraints ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Mission Agricultural Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , , . . . . . . . . . . 28

CGIAR ......,.. . . . . . . . . . . . . . . . . . . +, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Agricultural Staff. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Summary of workshop Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

AID Organizational Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

List of Attendees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Chapter

The Role of the Agency

for International Development

INTRODUCTION

During the second day of the workshop, AID discussions were candid and are summarized

staff reviewed their agency’s agricultural de- in the following text. An organizational chart

velopment activities and the various con- in effect for AID in November 1980 appears

straints under which AID operates when car- at the end of this chapter.

rying out its agricultural mandates. Their

BUDGET AND G0ALS

In 1980, AID carried out about $600 million

in agricultural projects and research related to

solving agricultural problems and developing

agricultural opportunities in LDCs. Further,

AID spent an additional $43 million to transfer fertilizer, much of it going to Sri Lanka,

Zambia, and Bangladesh.’ During the first

quarter of FY ’81, fertilizer transfers to India,

Kenya, Zambia, and Bangladesh were $105 million. AID’s main thrust in agriculture is to help

LDCs increase agricultural productivity, especially of the locally accepted basic food crops.

By doing so, AID’s goal is to help LDCs improve their economy, nutrition, and the general well-being of their people,

But for AID to step beyond traditional approaches and promote innovative technologies

to solve LDC food and agricultural problems

is risky. AID is not a research agency; its goal

is development. Therefore, AID commonly

supports research that holds promise of high

immediate payoff and tends to avoid research

IA I D’s flna ncerf fert i]izer purchases for F}r ’80 were at the lowest level

since 1965,

that may have long-run payoffs. Similarly, AID

feels that its development projects should focus

on the short term, have high visibility, and

show positive results quickly. It is not surprising that some AID agriculturalists believe that

“when you only have $2 to bet you don’t go

for long shots. ” To compound the problem,

AID’s small budget for innovative activities is

often one of the first targets during budget cuts.

The United States, on the basis of its gross

national product (GNP), in 1980 ranked 14th

of those countries that provide development

assistance to LDCs. For example, Sweden contributes 1.0 percent of its GNP whereas the U.S.

contributes 0.19 percent.

AID’s budget dilemma is complicated further

by a growing list of competing development

needs such as forestry, women-in-development,

and environmental concerns. AID has been

many things to many people, but it has not been

perceived by Congress as a technical transfer

agency. AID stressed that there remains a lack

of understanding among the public and Congress about how science and technology relate

to economic development.

2 3
—

24

CURRENT INNOVATIVE BIOLOGlCAL ACTIVITIES AT AID

During the workshop, AID participants presented a brief overview of some of their current activities involving various innovative

biological technologies. Examples included

biological nitrogen fixation, tissue culture, and

applied soybean research. In addition, through

a collaborative effort, AID, the Joint Research

Committee (JRC), the Board on International

Food and Agricultural Development (BIFAD),

and 30 land-grant colleges and universities

have developed three Collaborative Research

Support Programs (CRSP) to study small

ruminants, sorghum and millet, and bean/cow

pea production systems. The activities involve

30 U.S. universities, six international agricultural research centers, and one foundation.

Work is carried out at 28 LDC sites with collaboration of the local LDC institution. Two

new CRSPs are being developed in nutrition

and soils. These activities will expand the number of participating U.S. universities by eight

and LDC sites by ten.

CRSPs are viewed as long-term research

endeavors, at least five years in duration. AID

funds up to 75 percent of the CRSP and the

collaborating U.S. colleges and universities

contribute from 25 to 50 percent. At least 50

percent of AID’s CRSP budget is spent in participating countries. AID’s minimum budget

for FY ’82 CRSP activities is $11 million. AID

plans to invest a minimum of $88.3 million in

CRSP activities from FY ’82 through FY ’87.

Biological nitrogen fixation (BNF) is not a

new technology; it was recognized in Biblical

times that when certain legumes were grown

in alternate years, the yield of the following

year’s crop was improved. After five years of

research, AID recognizes that BNF technology

still could be improved. Because it can provide

nitrogen to plants in a usable form without the

expense of commercial nitrogen fertilizers, it

has important potentials for LDCs and developed countries alike.

Rhizobia, nitrogen-fixing bacteria that live in

nodules associated with the roots of certain

plants, can be used in some instances to inoculate the roots of plants to enhance nitrogen

production. No infallible technique to inoculate

seeds is known, but this is an area of research

AID is addressing. (The information of BNF

summarized elsewhere in this report is based

on research at the University of Hawaii sponsored in part by AID). BNF in tropical grasses

also is being studied. AID is working on incountry testing of BNF technology, building inoculation production and distribution systems,

developing profitable BNF cropping systems,

and providing continued help in improving

BNF technology for LDC use.

AID believes that commercial fertilizers play

an important role in LDC agriculture but also

believes that BNF technology can help these

countries reduce their need for commercial nitrogen fertilizers. Considering that commercial

nitrogen fertilizer may cost as much as $1 a

pound by the year 2000, BNF, which ultimately

may reduce the need for commercial nitrogen

fertilizers in LDCs by 25 percent, could help

tremendously.

AID is supporting some research on tissue

culture to supplement its traditional research

on standard crop-breeding practices. AID

believes tissue culture to be an inexpensive

technology and one that has good potential for

use in LDC agriculture.

In the past, agriculturalists selected superior

plants for reproduction by handpicking those

few individual plants having certain desirable

characteristics out of many thousands of the

less desirable specimens. Space and time

severely limit the number of plants screened

this way. With tissue culture, desirable plants

can be selected and propagated quickly and

easily. For example, an agriculturally desirable

plant can be used as a cell source for a desired

special characteristic such as salt tolerance

needed for growth in irrigated areas. A tiny

slice of the plant can be used to grow large

clusters of cells that can be separated in the

laboratory and screened to find the cells having the required characteristics. These cells in

turn can be grown to full plants that themselves
25

can be used for seed sources. Research has

demonstrated that the new plants will survive

the particular soil stresses for which they were

screened. This technique enhances our ability

to design plants for the especially harsh environments in LDCs and holds real promise for

improving LDC agriculture.

AID provides support for the International

Soybean Program (INTSOY) as part of its effort to support innovative biological technologies. INTSOY works to improve and adapt

soybeans for tropical developing countries

through germplasm selection. Some of their applied research deals with finding improved

ways to store seed for extended times in LDCs

and improving soybean processing using simple technologies. INTSOY also is studying the

role of soybeans in the LDC farming economies

and in the national economy as well.

TWO APPROACHES TO APPLY INNOVATIVE BIOLOGICAL

TECHNOLOGIES TO LDC AGRICULTURAL PROBLEMS

Two sharply different approaches to applying innovative biological technologies to LDC

agricultural problems, particularly the problem

of rising fertilizer costs, surfaced during the

workshop’s discussions. The first might be

called an “agroecosystem approach” and was

stressed by most non-AID participants. The

second reflected a “conventional production

approach” and was mainly an AID viewpoint.

The “agroecosystem approach” focuses on

applying biological technologies that are tailored to fit the biological, physical, and social

limitations of the local environment so that

sustainable agriculture can exist within the

constraints of the natural resource base. This

approach includes a concern for energy conservation and a desire for interdisciplinary research and development.

The “agroecosystem approach” to LDC requirements for food, fodder, and fuel also

focuses on developing new agricultural systems and on accepting rediscovered, and perhaps improved, agricultural systems. A wide

spectrum of agricultural crops is considered

including a number that might be viewed as

nontraditional. This approach emphasizes restoring, maintaining, and improving the natural resource base while offering the farmers a

reasonable chance for economic betterment.

In comparison, the “conventional production

approach” stresses production and increased

yields. It tends to focus on a more limited number of crops for which a market already exists.

The ecosystem is adjusted to provide high production of these crops by using intensive inputs of commercial fertilizers, pesticides,

pumped water, and petroleum-powered farm

equipment. Some such systems commonly are

categorized as “green revolution” technologies.

Major efforts have been devoted to mainstay

crops such as rice, corn, sorghum, and soybeans, and production increases generally have

been outstanding.

The variety of crops dealt with in this approach is more limited than in the “agroecosystem approach” and monoculture often are

economically advantageous. Production efforts

typically attempt to foster crop growth by overcoming local environmental constraints such

as infertile soils or water scarcity. In many

cases the technologies promoted are adaptations of technologies that have been used successfully in developed countries and temperate

climates.

There are, of course, instances where the two

approaches overlap, but these are exceptions.

Proponents of both approaches are trying to

help LDCs improve the well-being of the populace—their methods, however, include quite

different agricultural styles and practices. The

workshop focused on the opportunities shown

by each of the approaches for helping LDCs reduce their need for expensive commercial fertilizers while enhancing soil productivity.
26

The Need for Cooperative Ventures

Participants agreed that agricultural research

and its appropriate implementation in lesser

developed countries is an AID/LDC cooperative venture and that good communication is

essential for success. They discussed the inherent difficulties involved in using U.S. expertise in LDC projects because many U.S.

experts lack the special training that is appropriate to the physical and biological environment. Many U.S. technical experts used by AID

are drawn from U.S. land-grant universities

and consulting firms where there is little

familiarity and experience with LDCs. And because the United States historically has little

experience in LDC—i.e., tropical—agriculture,

AID has difficulty finding contractors who are

able to grasp LDC agricultural problems

quickly and recognize the appropriateness or

inappropriateness of temperate region agricultural solutions.

AID has provided grants and other support

to numerous U.S. universities to help them develop their teaching/research expertise so that

it can be tapped to help solve LDC agricultural

problems. Many of these universities have set

aside land for use in agricultural research and

teaching, but again agricultural research results commonly are not readily transferable

from region to region. Further, because pilot

studies often are cumbersome to conduct, take

considerable time, and lack significant recognition, few university scientists are eager to

devote effort to projects relevant to LDC agriculture, even though certain aspects may also

hold indirect promise for improving U.S. agriculture.

The Need for Field Demons-rations

Pilot projects, demonstrations, and field experiments carried out in LDCs by U.S. and

host-country interdisciplinary teams on innovative biological technologies are essential first

steps before new technologies can be used

widely. Section 103A of the Foreign Assistance

Act directs AID to carry out pilot studies. Further, workshop participants agreed that the private sector, whether U.S. or LDC, should be

encouraged to participate in biological technology development and its transfer to potential

users. Only where new technologies can be

shown to be economically profitable is there

the likelihood of their being pursued and

adopted by the private sector. For example,

Thailand established several innovative programs in alcohol production from cassava

through direct links between the private sector and Thai research institutions. It was also

pointed out that in many places, farmers learn

new agricultural techniques from salesmen.

AID believes that during the 1980s it will emphasize technology transfer but hopes to sponsor increased adaptive field research and do

cooperative research with LDC scientists. The

Agency sees the need for multitiered development efforts but recognized the difficulty in coordinating them. There is an acute need for

LDCs to establish their own national research

priorities rather than having the donor community do so.

pilot-scale activities that receive partial support from AID do exist at the international agricultural centers. But whether or not all such

institutions strongly emphasize the “agroecosystem approach,” especially agricultural techniques that are aimed at enhancing soil fertility

and reducing reliance on expensive commercial fertilizers, was debated. AID believes that

much of the work carried out at the international centers is innovative, but many of the

non-AID participants felt that these centers pay

little attention to low fertilizer, low-energy agricultural systems,

The Need for Innovative Research

Further, AID was criticized for spending $43

million of its $650 million agricultural efforts

on the transfer of expensive commercial fertilizers to LDCs without providing incentives

to try new agricultural methods that minimize

fertilizer use. LDCs must develop the resources

to continue appropriate fertilizer use, but along

with this should go development of efficient

new agriculture systems that rely on biological processes to complement soil nutrient availability. The use of mycorrhizal technologies,
—

2 7

for instance, seems to hold great promise for

reducing fertilizer needs, but AID is not working with this technology, Although AID agricultural professionals in the Development Support Bureau have tried to initiate mycorrhizal

research, it has failed to place high enough on

their priority list to warrant funding in each

of the last two years. AID interest in biological technologies has expanded, but the Agency

staff feels funds remain the limiting factor.

They feel their involvement in biotechnology

research might help speed transfer and implementation of its results.

Workshop participants encouraged AID to

place agricultural scientists from nonconventional fields of study on AID peer review panels

,of field projects and research activities. Because AID seemed committed to conventional

agriculture, some workshop participants

believed that AID needs fresh ideas to help

their agricultural professionals move away

from conventional paths and into new areas

having potential for high payoff for LDCs.

AID’s peer review was likened to “an old boy

system, ” one in which acceptance of new ideas

was slow, Non-AID members also viewed the

U.S. Department of Agriculture (USDA) dimly

in the field of innovative biological research

because they felt that USDA, too, primarily is

committed to conventionality. Some participants thought USDA was not helping AID with

the question of how to maintain productive

soils in LDCs while reducing the input of expensive commercial fertilizers.

In the view of “agroecosystem” proponents,

AID and some international agricultural

centers place the greater part of their efforts

on a few traditional food crops but do little to

develop underexploited, nutritionally important new food crops, AID was viewed as having no interest in these “odd-ball” crops even

though such foods contribute significantly to

LDC diets. Proponents of the “agroecosystem

approach” proposed looking into any food

crops that fit into the local ecological system,

Therefore, the resulting mix of crops might be

radically different from the crop mix recommended by the “production approach, ” but one

that could be sustained with lower fertilizer

inputs,

An agroforestry system might be instituted

that would integrate, for example, tree crops

for food, fodder, firewood, and erosion control;

native food crops; microbiological systems

such as mycorrhiza and rhizobium; and local

mineral resources such as zeolites into a lowenergy consuming system. Participants encouraged AID to set aside a certain percentage of its appropriations each year to look for

new, low-energy agricultural systems. The

Agency could continue to back its efforts in

“bread and butter” crops—corn, rice, etc.– but

should be willing to commit some of its resources to nonconventional approaches. All

participants agreed that AID should be encouraged to take some risks and not merely to

back “winner” crops,

The Need for Flexibility

Most non-AID participants, as well as some

AID staff, believed that the Agency needs a

more flexible mechanism to provide funding

for small-scale innovative activities. Currently,

AID seems unable to transfer small amounts

of money quickly or easily for such projects or

experimental activities. The Agency claims that

processing a small amount of money is as timeconsuming as processing large grants or projects. Pressure within AID to obligate program

dollars rapidly makes dealing with small projects bothersome. AID’s agricultural professionals in the Development Support Bureau,

for example, may wish to support certain inexpensive innovative activities, but they are

discouraged by internal AID procedures and

the program office’s strong control, Consequently, scientists outside of AID who have

special useful knowledge and who wish to participate in solving LDC agricultural problems

feel that AID is neither open nor interested in

outside assistance, Yet most participants felt

that many aspects of both the “conventional

production approach” and “agroecosystem approach” could be integrated with positive

results.

38-846 0 - 85 - z
28

The non-AID scientists elaborated on how it

is generally difficult for them to obtain needed

support for innovative approaches to lowenergy agricultural systems. The picture was

similar for the varied researchers. First, there

seems to be little support for funding the broad

range of innovative biological technologies that

may help improve LDC agricultural systems,

This is particularly true at most U.S. universities because the universities find it difficult

to support international activities that seem

remote. Then, too, researchers who rely on the

university for their salary commonly do not

want to jeopardize their security by conducting nonmainline research.

Some of the non-AID researchers admitted

that to carry out their chosen areas of LDCrelated research they sometimes resort to using

small amounts of money from other projects

that are not LDC-related (“bootlegging”). Other

common small funding sources for LDC-related research include a variety of Federal

agencies other than AID, although AID does

provide significant support for the biological

nitrogen fixation work at the University of Hawaii. An AID grant provides partial support for

azolla/algae research. Because Federal support

for LDC-related research has the habit of

vanishing suddenly, non-AID researchers face

constant doubt about the continuity of their

funding. The National Science Foundation,

some United Nations institutions, small university grants, and private industry and institutions sometimes are funding sources as well.

Private industry support seemed lacking for applied research in these fields.

Underlying all of the above problems was the

strong need for a significant increase in the

number of technically trained professionals in

agriculture and natural resource areas in AID

and its Missions overseas. Existing technical

professionals need to spend increased time on

the substance of their projects and less dealing with bureaucratic constraints. Without

such an environment, AID may find it increasingly difficult to maintain or expand technical

competence within its Washington offices or

Missions in LDCs. A need for improved communication between scientists and the Congress was restated several times during the

workshop, and activities similar to this workshop were cited as a step in the right direction.

PERCElVED CONSTRAINTS

AID’s major efforts in innovative agricultural

research are directed primarily to the 13 international agricultural research centers to which

AID contributes financial support. Much of the

AID activity, however, depends on the work

of the AID Missions and the ability of the professional staff to relate to the scientific community at large and to the Missions and regional or geographic bureaus. A number of

problems in these areas were identified by the

workshop participants.

Mission Agricultural Activities

AID Missions largely are removed from current science and technology developments in

the academic and private sectors. Consequently, AID faces a difficult task in channeling new science and technology to field activities in most LDCs. In addition, AID staff at the

workshop explained that many Missions feel

that adequate technology already exists and

that new science and technology are not

needed. The Missions want AID technical people to solve the problems that the Missions

identify using established technologies. This

approach frustrates AID professional staff, including staff in the Agriculture Office.

AID considers its contribution to the Consultative Group on International Agricultural

Research (CGIAR) valuable and feels that the
29

nonbureaucratic institution functions very well

in addressing agricultural development problems and in implementing research results.

AID sees Korea as a model of successful development where effective technology transfer

has occurred, and feels that the Korea example should be used as a model for development

activities by other LDCs.

Agrcultural Staff

AID agricultural professionals attempt to

maintain close contact with agricultural experts in the scientific community both within

and outside of USDA. But the number of agricultural scientists in AID is so small that maintaining regular contact with their scientific colleagues can be difficult. AID employs about

4,000 people yet its Development Support Bureau (DSB), the bureau that provides technical

support to all of AID’s regional or geographic

bureaus, has only 25 agricultural professionals.

These 25 people managed about $70 million in

agricultural projects in FY ’80. Further, only

about 10 percent of AID Mission personnel

worldwide are agricultural officers even

though some 50 percent of AID’s development

programs are agriculturally oriented. Because

AID commonly reassigns its agricultural professionals to new Missions or back to the U.S.

about every three to four years, many agricultural programs suffer from the lack of continuity. AID’s workshop participants felt personnel rotations occur too frequently.

AID workshop participants felt that the

Agency’s emphasis on natural resource management should be increased but that this area

is not receiving much Agency attention. Natural resource management requires an interdisciplinary approach, but because AID is

segmented into numerous administrative compartments it is extremely difficult to conduct

interdisciplinary activities. For example, agroforestry activities were to be transferred recently to DSB’s Office of Forestry, Environment, and Natural Resources, the successor to

the Office of Science and Technology (OST).

Agroforestry, by definition, combines aspects

both of agriculture and forestry, yet in the new

arrangement, agroforestry is separated from

agriculture.

The mandate to identify and test innovative

and/or emerging science and technology and

to transfer promising ideas to AID’s Missions

and Regional Bureaus belonged to the disbanded Office of Science and Technology. This

office served as AID’s “window” to the science

and technology community and gave AID the

opportunity to tap a broad array of innovative

science and technology to help solve LDC

problems. 2

A problem that AID workshop participants

highlighted repeatedly was that of the expanded role of AID program officers in decisionmaking and priority-setting for agriculture

projects and research. Program officers commonly are generalists having little or no technical agricultural training. Organizationally,

they sit between top bureau administrators and

agriculturalists and other professionals and exert a strong influence on AID’s agricultural efforts. AID agricultural professionals feel that

they are continually second-guessed by program office generalists and that the technical

content of proposed agricultural projects and

research many times is adversely affected by

the actions of the program office.

Program officers commonly evaluate project

or research activities. But AID’s evaluation

process seems to foster a strong desire to have

evaluations that show positive results. Without

positive evaluations, the difficulty of moving

subsequent projects through the AID system

and, therefore, through the program office may

increase. This perception, whether true or not,

discourages some technical professionals from

pursuing innovative opportunities because the

element of risk in innovative activities generally is higher than in traditional approaches.

The overall effect of having an inordinately

strong program office is that agricultural professionals introduce fewer innovative technologies into AID agricultural programs.

‘As of May 1981, a new Bureau for Science and Technology was formed.

(See section on AID organization changes.)
30

Fall 1984

Demand for the original House Foreign Affairs Committee publication on innovative

biological technologies was high in the United

States as well as many other countries and by

1984 copies were no longer available. Continuing requests for the publication have prompted OTA to reprint the document in its

workshop series. Described below are some

relevant policy changes that have occurred at

AID since the 1980 workshop.

The atmosphere at AID today is more favorable toward new biological technologies.

The current administration has expanded

work on tissue culture and sees potential in

other related areas. The attitude toward innovative crops, however, remains essentially unchanged and few resources are directed

toward new crop development.

In its overseas Missions and within AIDWashington, there is still a scarcity of professional agriculturalists. Those that are on staff

have many, diverse responsibilities so that

innovative biological technologies do not receive much attention. Nevertheless, the National Academy of Sciences Board on Science

Addendum

and Technology for International Development (BOSTID) receives AID funds to seek

new biological opportunities for developing

countries. Since the 1980 workshop, research

received increased attention in AID, however,

the substantial budget cuts recently proposed

in 1985 may adversely affect this trend.

One problem identified at the 1980 workshop concerned AID’s inability to support

small scale activities. AID appears to have improved some in this area. A new small grants

program—the Program in Science and Technology Cooperation (PSTC)—has been established in the Office of the Science Advisor.

The program is designed to stimulate new outside research on problems that confront developing nations. Priority funding is directed

to five areas: Biotechnology/Immunology,

Plant Biotechnology, Chemistry for World

Food Needs, Biomass Resources and Conversion Technology, and Biological Control of

Disease. This type of competitive, small grants

program is an important step toward providing a more flexible mechanism to support

innovative and small-scale research and technology development.

SUMMARY OF WORKSHOP SUGGESTIONS

Summarized below are a variety of suggestions generated by the 40 participants during

the course of the workshop discussions. Some

of these topics received considerable attention

and others much less. The participants were

encouraged to express their points of view

freely on any issues they felt were relevant. By

doing so, the participants touched upon a variety of topics, many of which deserved more

detailed examination than could be accomplished in two days. The issues that surfaced,

however, should help the House Committee on

Foreign Affairs in their oversight responsibilities of the Agency for International Development and in determining the role that innovative biological technologies could play in

enhancing soil fertility, improving food production, and reducing the need for expensive

commercial fertilizers throughout the world.

*

*

*

AID should greatly increase the number of

in-house agricultural professionals in Washington and in the missions, especially in

decisionmaking positions.

AID should increase the number of Mission

directors who are agricultural professionals.

Similarly, effort should be made to encourage the selection of an increased number of

people with professional agricultural training as ambassadors for LDCs.

AID should encourage the U.S. and LDC private sector to participate in pilot-scale projects testing and developing innovative biological technologies.
—

*

*

*

*

*

AID should appoint some outside experts in

nonconventional agricultural technologies to

its advisory committees and to its peer review panels.

AID should broaden its inventory of scientists who might help AID expand its efforts

into nonconventional agricultural practices.

AID should streamline its procedures to encourage increased outside participation by

U.S. scientists and technologies in smallscale innovative agricultural activities.

AID should set aside a certain percentage of

each agricultural project to integrate some

new, innovative biological technology into

the project.

AID should fund some small-scale, pilot-type

projects on the kinds of innovative biological technologies presented at this workshop

and encourage the participation of outside

scientists to work on the project as members

of interdisciplinary teams. The need for pilot

testing of a wide variety of innovative biological technologies by AID was stressed

heavily and the need for risk-taking was encouraged.

*

*

*

*

AID should increase its activities in agroforestry systems. These activities should be

expanded to include both humid tropical regions and arid/semiarid regions. Pilot testing

of the arid/semiarid systems could be carried

out in the Southwest United States and

LDCs,

An expanded inventory of innovative biological technologies that could help LDCs reduce their need for expensive commercial

fertilizers should be prepared, and institutions and individuals who have the skills for

these technologies could be identified.

OTA could conduct a full assessment of a

broad range of innovative biological technologies that could help LDCs reduce the need

for their use of expensive commercial fertilizers.

AID should emphasize the transfer of technical information to LDCs and to AID mission agriculturalists, particularly on innovative biological technologies that might help

LDCs reduce their need for expensive commercial fertilizers.

AID ORGANIZATION CHANGES

The Administrator for the Agency for International Development (AID) on May 21, 1981,

announced a reorganization for the structure

of AID (see following chart). One major change

was the formation of a new Bureau for Technology and Science to replace the old Bureau

for Development Support. Structurally, this

change gives greater prominence to the role of

science and technology in AID than has existed

previously. Unlike the other AID bureaus for

Science and Technology. Unlike the other AID

bureaus which are headed by Assistant Administrators, the Bureau for Science and Technology is headed by a Senior Assistant Administrator, thus giving added strength to science

and technology in AID.
32

AGENCY FOR INTERNATIONAL DEVELOPMENT

Authors

Dr. James Duke

USDA/ARS

Germplasm Resources Laboratory

Building 001, Room 131

BARC-West

Beltsville, MD 20705

Dr. Peter Felker

Ceasar Kleberg Wildlife Research Institute

College of Agriculture

Texas A & I University

Kingsville, TX 78363

Dr. Jake Halliday

Battelle Kettering

Research Laboratory

150 East South College Street

Yellow Springs, OH 45387

Dr. William Liebhardt

Rodale Research Center

RD1 BOX 323

Kutstown, PA 19530

Dr. Cy McKell

Director of Research

Native Plants, Inc.

417 Wakara Way

University Research Park

Salt Lake City, UT 84108

Dr. John Menge

Full Professor

Department of Plant Pathology

University of California

Riverside, CA 92521

Dr. Fred Mumpton

Department of Earth Sciences

State University College

Brockport, NY 14420
33

Dr. Donald Plucknett

Scientific Advisor

World Bank/CGIAR

Room K1045

1818 H Street, N.W.

Washington, DC 20433

Dr. Noel Vietmeyer

National Academy of Sciences

National Research Council

JH213 BOSTID

2101 Constitution Avenue, N.W.

Washington, DC 20418

Dr. Stephen R. Gliessman

Agroecology Program

Board of Environmental Studies

University of California

Santa Cruz, CA 95064

Dr. Thomas A. Lumpkin

Department of Agronomy and Soil

Washington State University

Pullman, WA 99164-6420

Other Participants

Mr. Tony Babb

DAAIDA

U.S. Agency for International Development

Dr. Hugh Bollinger

Native Plants, Inc.

University Research Park

Mr. Douglas W. Butchart

AFR/DR

U.S. Agency for International Development

Dr. Mary Clutter

National Science Foundation

Mr. Stan Dundon

Office of Rep. George Brown

U.S. House of Representatives

Dr. Lloyd Frederick

U.S. Agency for International Development

Ms. Margaret Goodman

Foreign Affairs Committee

U.S. House of Representatives

Mr. George Ingram

Foreign Affairs Committee

U.S. House of Representatives

Dr. Howard Minners

U.S. Agency for International Development

Mr. Donald Mitchell

Office of Personnel Management

Mr. Stephen D. Nelson

Foreign Affairs Committee

U.S. House of Representative

Ms. Julia Nickles

Legislative Assistant

State of California

Dr. Palmer Rogers

Office of Basic Energy Sciences

U.S. Department of Energy

Dr. Charles Simkins

U.S. Agency for International Development

Mr. Skip Stiles

Legislative Assistant

Office of Rep. George Brown

Dr. James Walker

U.S. Agency for International Development

Mr. Henry Williams

Congressional Fellow

Office of Sen. Mathias

OTA Staff

Dr. John H. Gibbons

Director

Dr. Joyce Lashof

Assistant Director

Dr. Walter E. Parham

Program Manger

Mr. Bruce Ross

Project Director

Ms. Barbara Lausche

Natural Resources Lawyer

Dr. Betty Williams

Nutrition Project Director
34

Ms. Chris Elfring Dr. Omer Kelly

Congressional Fellow Consultant

Ms. Judith Randal Dr. Michael Phillips

Congressional Fellow Project Director
Chapter III

Underexploited Plant

and Animal Resources for

Developing Country Agriculture

Noel Vietmeyer

National Academy of Sciences

Washington, DC 20418
Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ... ..$. .sO.., .O...m

Poor People’s Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Winged Bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Amaranths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conclusion . . . . . . . . . . . . ....0.... . . . . . . . . . . . . . . . . . . . . . . 0 $ . . . . . . . . . . . . . .

Tree Legumes: Shock Troops for the War on Deforestation . . . . . . . . . . . . . . . . . . . . .

Leucaena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . .

Calliandra Calothyruas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conclusion . . . . . . . . . . . . . . . . . . . . . ..+...... . . . . . . . . . . . . . . . . . . . . .......+.

Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Toads, Snails, and Guinea Pigs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Crocodiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Butterflies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Gasoline Plants. ......., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diesel Fuel You Grow on the Farm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conclusion. . . .. .. .. .. ... ... ... .$... . 4 . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . .

37

37

37

38

39

39

39

40

41

41

42

42

43

44

45

45

46

47
and

Chapter III

Underexploited Plant

Animal Resources for

Developing Country Agriculture

INTRODUCTION

The 1940s was the decade of wonder chemicals. The miraculous properties of DDT, sulfa

drugs, herbicides, nylon, and plastics blinded

us to the potentials of nature. Laboratories

were limitless, nature seemed limited. Manmade was modern, nature seemed passe. Subsequent decades seemed to confirm the euphoric view; we gave up seeking our new product needs in the kingdom of nature, the

previous wellspring for civilization’s advances.

As a result, as we move toward the 21st century, we rely on fewer and fewer plants and

animals. We ignore, or have forgotten, thousands of useful species that could broaden and

balance our fount of resources. All this, in face

of the recognition that within a few short decades the petrochemical explosion that began

in the 1940s will be snuffed out.

However, a big change is now occurring in

the scientific community. Researchers are

returning to nature’s storehouse to take stock

of its genetic possibilities; to scrutinize species

that could make useful new crops and domestic animals. Some of them are species that are

wild and untested, some even poorly identified.

Though they work largely out of the public eye,

these dedicated researchers are quietly germinating ideas and laying roots that will grow

with and shape our future. Some natural products now virtually unknown are likely to become mainstays of world agriculture.

Decisionmakers, entrepreneurs, and the general public should pay more attention to these

researchers’ results. A groundswell of support

for the development of new species could lead

to a cornucopia of new foods, fuels, and industrial feedstocks. It may help extend productive

agriculture to vast regions that today are not

arable. It may help raise from despair the ever

increasing numbers of humans in developing

countries who waste their lives away in malnourished poverty. It may show how to cultivate crops that produce raw materials that

now come from petroleum. It’s a challenge. But

some of the future’s best resources are out there

waiting in nature.

PLANTS

Botanists and ethnobotanists can reel off long Poor People's Plants

lists of obscure plants that seem to warrant recognition. Respondents to recent questionnaires A friend recently told me that he had dissent out by the National Academy of Sciences cussed the winged bean with an influential

named over 2,000 plant species that deserve Filipino family. “They were incredulous that

much greater recognition. Almost none have such a miraculous plant could exist, ” he said.

been given agronomic attention. A few strik- “SO, on a hunch, I took them out back to the

ing examples are given below. servant’s quarters. There, climbing along a

37
38

fence, was a winged bean plant laden with

pods.”

“ ‘But that’s just sequidillas,’ they said, disappointment echoing in their voices. ‘It’s only

a poor man’s crop!’ “

It is a universal phenomenon that certain

plants are stigmatized by their humble associations. Scores of highly promising crop plants

around the world receive no research funding,

no recognition from the agricultural community; they are ostracized as “poor man’s crops. ”

For information on a poor people’s crop one

has to turn, more often than not, to botanists

and anthropologists; only they will have taken

an interest in the plant. Often there has been

no agricultural research on it at all—no varieties collected or compared, no germination or

spacing trials, no yield determinations or even

nutritional analyses. And yet the crop actually

may be crucial to the lifestyle—even the survival—of millions of people.

Just 50 years ago, the soybean itself was a

poor people’s crop. In the United States, it was

spurned by researchers for more than a century after Benjamin Franklin first introduced

seeds from the Jardin des Plantes in Paris. To

be a soybean advocate then was to risk being

considered a crackpot. Early in this century,

Americans still considered the soybean a second-rate crop fit only for export to “poor people” in the Far East. But then, in the 1920s,

University of Illinois researchers established

a comprehensive soybean research program

that helped sweep aside this discrimination.

The soybean acquired new status as a “legitimate” research target, and its development

gained so much momentum that it is now the

world’s premier protein crop.

Nowhere is the neglect of poor people’s crops

greater than in the Tropics—the very area

where food is most desperately needed. The

wealth and variety of tropical plant species is

staggering. Some of the Third World’s best

crops are waiting in the poor people’s gardens,

virtually ignored by science. Merely to have

survived as useful crops, suggests that the

plants are inherently superior. Moreover, they

are already suited to the poor person’s small

plots and mixed farming, as well as to poor

soils, and the diet and way of life of the family

or village. Examples are the winged bean and

amaranths.

Winged Bean

Perhaps no other crop offers such a variety

of foods as the winged bean. Yet it, remains

a little-known, poor person’s crop, used extensively only in New Guinea and Southeast Asia.

A bushy pillar of greenery with viny shoots,

blue or purple flowers, and heart-shaped

leaves, the winged bean resembles a runnerbean plant. It forms succulent green pods, as

long as a man’s forearm in some varieties. The

pods, oblong in cross-section, are green, purple, or red and have four flanges or “wings”

along the edges. When picked young, the green

pods are a chewy and slightly sweet vegetable.

Raw or boiled briefly, they make a crisp and

snappy delicacy. Pods are produced over several months and a crop can be collected every

two days, providing a continuous supply of

fresh green vegetables.

If left on the vine the pods harden, but the

pea-like seeds inside swell and ripen. When

mature, the seeds are brown, black, or mottled.

In composition they are essentially identical

to soybeans, containing 34 to 42 percent protein and 17 to 20 percent of a polyunsaturated

oil. The protein is high in the nutritionally critical amino acid lysine.

In addition to the pods and seeds, the winged

bean’s leaves and shoots make good spinachlike potherbs. Its flowers, when cooked, are a

delicacy with a texture and taste reminiscent

of mushrooms.

But perhaps the most startling feature of the

plant is that, below ground, it produces fleshy,

edible tuberous roots. These are firm, fiberless,

ivory-white inside and have a delicious and

delicate nutty flavor. The winged bean is therefore something like a combination of soybean

and potato plants. And winged bean tubers are

uniquely rich in protein—some contain more

than four times the protein of potato.
39

When heated, amaranth grains burst and

Amaranths—major grain crops in the tropical highlands of the Americas at the time of

the Spanish Conquest, They were staples of

both Aztec and Inca. But the conquistadors

banned the cultivation of amaranths because

the grain was a vital part of native religion and

culture. With this political move the Spanish

struck a blow for their church but they also

crushed the crop. For 500 years little has been

done to study or promote it,

Amaranths belong to a small group of plants,

termed C4

, whose photosynthesis is exceptionally efficient, The sunlight they capture is used

more effectively than in most plants and amaranths grow fast. Vigorous and tough, amaranths have been termed self-reliant plants that

require very little of a gardener. They germinate and adapt well to the rural farmer’s small

plots and mixed cropping, Furthermore, they

are relatively easy to harvest by hand and to

cook.

Amaranths are annuals that reach six feet in

height and have large leaves tinged with

magenta. They are cereal-like plants producing full, fat, seed heads, reminiscent of sorghum. The seeds are small but occur in prodigious quantities. Their carbohydrate content

is comparable to that of the true cereals, but

in protein and fat amaranths are superior to

the cereals.

taste like popcorn. In many regions, however,

the grains are more often parched and milled.

Amaranth flour is high in gluten and has excellent baking qualities; bread made from it

rises and has a delicate nutty flavor,

Recently, W. J. S. Downton, an Australian

researcher, has found that the grain of at least

one amaranth (Amaranths caudatus var.

edulis) is rich in protein and exceptionally rich

in lysine, one of the critical amino acids usually deficient in plant protein. Indeed, the

amount of lysine exceeds that found in milk

or in the high-lysine corn now under development.

Conclusion

It is very hard to get grants for research on

poor person’s plants. Funding agencies resist;

the plants are unknown to most of them, and

the literature to support any claims may be

sparse.

Nonetheless, it is now time for agricultural

research facilities throughout the world to incorporate poor person’s crops into their research efforts. Third World agricultural development needs this balance, for only when his

own crops are improved will the poor man be

able to feed his family adequately. In future

decades it may be–as in the case of the soybean—that today’s poor person’s plants will be

feeding the world,

TREE LEGUMES: SHOCK TROOPS FOR THE WAR ON DEFORESTATION

Man has deforested one-third of South

America’s native forests, one-half of Africa’s,

and two-thirds of Southeast Asia’s, It is critically urgent that the remaining forest cover be

protected from indiscriminate harvest and that

many now-deforested regions be reforested. A

“thin green line” of fast-growing leguminous

trees may be either our last line of defense or

our first line of attack.

To most people legumes are limited to the

dining table, but to plant scientists legumes include not only vegetables but shrubs, vines, and

thousands of tree species, most of them indigenous to the Tropics. Actually, the family

Leguminosae is the third largest in the plant

kingdom. But out of the 18,000 different species of legumes, farmers extensively cultivate

only about 20 species including peas, beans,

soybeans, peanuts, clover, alfalfa, and even licorice. Foresters cultivate almost none.

The potential of tree legumes as useful plantation species remains largely unrecognized,

yet they offer a particularly promising area for

exploration in these days of devastating defor-
40

estation. Indeed, they seem to have special attributes that could put them in the front lines

of the battle to reclothe the scarred hillsides

throughout the Tropics.

Legumes, for example, are nature’s pioneers

in plant succession. They are among the first

plants to colonize bare land. It therefore seems

ecologically wise for man to deliberately exploit them for the same purpose: to quickly

revegetate eroding or weed-smothered terrain,

to halt erosion, and to provide protective

ground cover under which slow-growing,

climax-forest species can regenerate. Furthermore, many wood requirements might be met

by these quick-growing small trees and they

could help spare the last remnants of the natural forests.

Many woody legumes have a hardy, irrepressible character, suited to a wide range of

soils, climates, altitudes, and environments.

Like other pioneer species, they have a precocious nature and grow quickly in an attempt

to overtop and preempt the space of their plant

competitors.

Because of this innate competitiveness, many

tree legumes are easy to establish and cultivate.

Some can be direct-seeded (avoiding the expense of nurseries and transplanting fragile

seedlings), and in some tests even spraying

their seed out of aircraft has proven a suitable

way to establish plantations. Many occur naturally in dense, pure stands, suggesting that

they probably can be grown in monoculture

without being decimated by pests.

A most important feature of many legume

species is that nodules on their roots contain

bacteria, which chemically convert nitrogen

gas from the air into soluble compounds that

the plant can absorb and use. Thus, for average growth these species require little or no additional nitrogenous fertilizer. Some produce

such a surfeit of nitrogen—largely in the form

of protein in their foliage—that they make excellent forage crops and the soil around them

becomes nitrogen rich through the decay of

fallen foliage.

To give an idea of the potential of this class

of trees, three species of fast-growing legumes

are mentioned below. Not one of these trees

is widely exploited so far.

Loucaena

In the 1960s, University of Hawaii professor

James Brewbaker found in the hinterland of

Mexico certain varieties of Leucaena leucocephala that grow into tall trees. This was unexpected because the plant was previously

known only as a weedy bush. In tropical climates, Brewbaker’s varieties have grown so tall

and fast that they can be twice the height of

a man in just six months; as high as a threestory building in two years; and as tall as a sixstory building with a trunk cross-section as

large as a frying pan in only six or eight years.

In the Philippines, one hectare of these tall

leucaenas has annually produced over 10 times

the amount of wood per acre that a well-managed pine plantation produces in the United

States. Even among the world’s champion fastgrowing trees, this is exceptional.

Leucaena wood is thin barked and light colored. For such a fast-growing species, it is

remarkably dense (comparable to oak, ash, or

birch), strong, and attractive. Its fiber is acceptable for paper-making and the wood can be

pulped satisfactorily and in high yield.

But leucaena, a multipurpose plant par excellence, also has other uses. It can supply forage, for example, and researchers in Hawaii

and tropical Australia have found that cattle

feeding on leucaena foliage may show weight

gains comparable to those of cattle feeding on

the best pastures. Leucaena wood also makes

excellent firewood and charcoal. Further, the

plant is a living fertilizer factory for if its

nitrogen-rich foliage is harvested and placed

around nearby crops they can respond with

yield increased approaching those effected by

commercial fertilizer.

Although arboreal leucaena varieties have

been cultivated for only a decade or so, they
41

are already being planted over tens of thousands of hectares in the Philippines. The WorId

Bank has funded one large program, Batangas

Province has a nursery producing 10,000 leucaena seedlings daily. The province’s dynamic

governor, Antonio E. Leviste, has decreed that

other nurseries be set up throughout his province: in churchyards, cemeteries, schoolgrounds, roadsides—any idle ground. No government employee gets a paycheck until he has

set up a leucaena plantation with at least 20

trees to produce seed, The consequent greening of Batangas has made citizens keenly appreciative of deforestation’s ugliness and problems, as well as reforestation’s rewards. Tree

planting now interests the Batangas public

intensely—not entirely for the sake of revegetating eroding watersheds, but for the income and

benefits from exploiting leucaena forage, fuelwood, and “green manure. ” That the program

has been adopted with gusto by the citizenry

demonstrates the relevance of tree legumes to

tropical problems as a sort of “appropriate

forestry. ”

In more remote southern islands of the

Philippines, Ieucaena (Filipinos call it ipil-ipil)

is being planted over huge areas of former

green-deserts, wastelands lost to coarse, sharpedged “cutting-grasses,” With its vigor and persistence, leucaena—if given a little care—can

overtop the grasses, shading them out of existence, and converting waste ground to productive forest. It is essentially a permanent

forest because after felling, the stump of a leucaena tree regrows with such vigor that the

plant is said to literally “defy the woodcutter. ”

Calliandra Calothyruas

In 1936, horticulturists transported seed of

this small Central American tree to Indonesia.

They were interested in it as an ornamental,

for like other Calliandra species, it has flowers

that are gorgeous crimson powder-puffs, glowing in the sunlight like red fireballs. But Indonesians instead took up Calliandra calothyrus

as a firewood crop. Indeed, for 15 years steadily expanding fuelwood plantations of it have

been established until they now cover over

75,000 acres in Java.

This small tree—barely taller than a bush—

grows with almost incredible speed. After just

one year it can be harvested. The cut stump

resprouts readily giving new stems that can be

10 feet tall within six months. Some trees in

Indonesia that are 15 years old have been harvested 15 times!

Calliandra wood is too small for lumber, but

it is dense, burns well, and is ideally sized for

domestic cooking. It is also useful for kilns

making bricks, tiles, or lime and for fueling

copra and tobacco dryers.

Indonesian villagers now cultivate Calliandra calothyrus widely on their own land, often

intercropping it with food crops. The plant’s

value is dramatically exemplified by the village

of Toyomarto in East Java. There, land that was

once grossly denuded and erosion-pocked is

now covered with calliandra forest and is fertile once more. Today the villagers actually

earn more from selling calliandra firewood

than from their food crops.

Conclusion

These are brief descriptions of

cies of small leguminous trees

only two spethat have recently proven useful in combating deforestation in Southeast Asia. There are many other

exciting species. In South Korea, foresters intercrop bushy Lespedeza species to provide

firewood during the early years of the establishment of pine and other forests. In Central

America, there are Enterolobiurn cyclocarpurn

and Schizolobium parahyba, in South America, Mimosa scabrella (M. bracatinga),

Schizolobium amazonicum, Tipuana tipu, and

Clitoria racemosa; and in the Pacific Islands,

Albizia minahassae and Archidendron

oblongum. In Africa, several fast-growing

Albizia (A. adianthifolia, and A. zygia, for example) are indigenous, and two legume trees

introduced from India, Acrocarpus fraxinifolius and Dalbergia sissoo, have shown exceptional growth rates on appropriate sites. In

Asia, there are also Acacia auriculiformis and

Sesbonia grandiflora.

In foresters’ terms many of these species

have “poor form,” Their trunks may be too nar-
42

row or too crooked for construction timber or ●

veneer. But, these are species for “peoples’ forestry.” Their role is for:

●

●

●

farms, backyards, pasture lands, roadsides,

canal banks and fencelines;

village woodlots and energy plantations to

fuel kilns, electricity generators, cooking

●

stoves, and crop dryers;

agrisilviculture (agroforestry), because ●

they provide a wealth of products includ- -

ing forage, green manure, and food;

use in shifting cultivation, because the natural drop of protein-rich leaves, pods, and

twigs contributes nitrogen organic matter

and minerals to upper soil layers and can

markedly speed up the rebuilding of worn

out soils;

quick-rotation cash crops, both for the private landowner and the government forest department; and

utility purposes such as beautification,

shade, and- shelter belts.

ANIMAL S

When early farmers discovered that animals

could be tamed and managed, they eagerly experimented with many of the species surrounding them. In Asia and the Americas, the silkworm, yak, camel, water buffalo, llama, alpaca,

and guinea pig were selected. Egyptian tomb

paintings at Saqqara painted in 2500 B.C. show

addax, ibex, oryx, and gazelle wearing collars

and obviously domesticated. Ancient Egyptians apparently domesticated hyenas and baboons, as well.

But then the process essentially stopped.

Today’s farmers raise the same animals their

Neolithic forebears were familiar with more

than 10,000 years ago. (One exception is the

rabbit, which French monks tamed between

the 6th and 10th centuries because the Church

considered newborn rabbits to be fish and they

could be eaten when the Church calendar

demanded abstinence from meat.) Although

the world’s menagerie contains some 4,000 species of mammals alone, only a mere six domestic animals produce virtually all of the world’s

meat and milk.

As agricultural man spread himself about the

globe, he dragged with him this handful of species. He carried them beyond their natural

boundaries, forced them upon strange and

often fragile environments—usually driving out

the native species that previously predominated there, and often drastically changed the

environments to accommodate them.

Very little meat is eaten in developing countries and because most of them are in the Tropics, it is not possible to change that much with

cattle, sheep, and pigs. These animals have an

evolutionary adaptation to the temperate environments from which they originated and are

limited in their ability to adapt to new ones.

But the world’s fauna is a rich genetic bank that

may be tapped to increase world food production. Some of the potential species are unexpected ones, as highlighted below.

Toads, Snails, and Guinea Pigs

In rural areas of developing countries, it is

important to produce small animals. They fit

better into village life and they can be eaten

at one meal, so the lack of refrigeration is no

hindrance. In Chile, there’s a shiny, olive green

toad (Calyptocephalella caudiverbera). It is a

giant toad that can weigh three pounds or

more. Its meat tastes like a cross between lobster and chicken. It grows to be a foot long or

more and lacks the toxic skin glands and warty

appearance of other toads. Because of its superb and enigmatic taste, the wild toad has long

been a delicacy of Chilean gourmets. But now,

researchers at the La Serena campus of the

University of Chile are learning how to farm

them.

In 1975, the University’s Institute of Food

Technology started farms large enough to pro-
43

duce 100,000 of the choice toads

years. The intensive methods they

have made it feasible to supply 10

of scallop-sized toad legs each year

stores, restaurants, and canneries.

every two

developed

to 15 tons

to grocery

The Institute also has dug production ponds

out of otherwise useless swampland. The eggs,

larvae, tadpoles and adults are all kept apart

because the voracious toads have no hesitations about cannibalism. Normally, however,

they feed on small fish, crabs, crawfish, and

aquatic plants. The ponds are surrounded with

flowers and shrubs to attract insects and boxes

of rotten fruit are placed nearby to draw fruit

flies to the area. With their long sticky tongues,

the toads eagerly capture the insects, Other

than this, the toads reportedly are given little

attention and in two years they reach market

size: about 7 inches long and weighing one-half

pound.

Researchers are ecstatic over the ease and

cheapness of toad farming, and they are looking toward the lucrative international frog meat

market to export the tender, white drumsticks

of these unique Chilean toads.

In Nigeria, the Institute of Oil Palm Research

is developing another potentially valuable new

resource: the giant African Land snail

(Achatina species). This snail grows rapidly

and may weigh up to half a pound. It is eaten

widely in West Africa and is immensely popular in parts of Nigeria and Ghana. The meat

has as much protein as beef, but it has considerably more of the important amino acids, lysine,

and arginine, than even eggs contain. The Institute has found the snails suitable for “farming” in shaded enclosures under the trees in

rubber, cocoa, or oil-palm plantations. With

proper proportions of males and females, it has

produced as much as 150 pounds of snail meat

in the small enclosures each year,

In Peru, scientists are looking to their indigenous fauna too. One of Peru’s serious and

permanent problems is a lack of beef. Twothirds of the steaks of which Peruvians are so

fond are imported despite the nation’s chronic

dollar shortage. The situation became so serious that five years ago the military junta put

a ban on beef consumption 15 days in every

month. Chicken production was once believed

to be the answer to the problem, but although

it has grown fast, so has the population. Big

hopes were placed on fish, too, but the country lacks the financial resources to install the

facilities needed for national marketing. The

guinea pig is now believed to be the best

answer so far to the problem posed by the short

supply of animal proteins.

Guinea pig is a traditional staple. Although

domesticated in the time of the Inca, it has not

previously attracted much research attention.

Yet guinea pig is widely consumed in Peru. The

nutritional value of its meat compares favorably with that of other meats. The animals can

be raised in urban areas and in villages, where

larger animals are scarce or impossible to keep.

The fast growth and rapid reproduction makes

the guinea pig a sensible resource in the Peruvian environment, Added to this is the fact that

guinea pigs can live off vegetation that is of

inadequate nutritive value for feeding other

livestock.

These resources are strange—even repugnant—to the majority of specialists working to

increase food production and improve human

nutrition in developing countries. But to the

local inhabitants they are traditional foods that

are much sought and enjoyed.

Crocodiles

In Africa, South and Southeast Asia, Australia, and South America, the populations of

crocodiles, alligators, and caimans are fast

headed for extinction. In Papua New Guinea

(P. N. G.) in the 1960s, the two native crocodile

species were headed the same way. But not

today. In the last five years, a remarkably innovative project in this, one of the newest and

most underdeveloped nations, has caused a

dramatic turnaround in the crocodile’s drastic decline there. Though the P.N.G. story has

not been told widely, it is one with immense

implications for the survival of crocodilians

elsewhere. It is also a demonstration of how

resources can be managed to conserve a species, to minimize impact on a fragile environ-
44

ment, and to provide wealth in remote villages

in a developing country.

The P,N.G. program is based on an appreciation for crocodile biology. Each year, a female

may lay between 30 and 70 eggs. Although

most of them hatch, predators so relish the tender and remarkably vulnerable young hatchlings that almost none survived the 15 years

needed to reach breeding size. In nature, then,

there can at any time be found a plethora of

tiny crocodiles, but a paucity of breeders. Commercial hunting worsens the imbalance because hunters always seek the biggest specimens, regardless of the resulting damage to the

breeding populations.

Recognizing that a ban on hunting would be

largely unenforceable in remote areas (and

grossly unpopular where man-eaters sometimes occur), the P.N.G. Government decided

in 1970 to restructure the trade so that shooting breeders would lose its attraction and the

profit would come from exploiting the hordes

of tiny hatchlings that would result. This was

done through a law banning the sale of large

skins, supplemented by a stiff tariff on small

skins.

Today, villagers in the steamy swamps of

P.N.G. have tens of thousands of tiny crocodiles in their care. They raise them for a year

or two and can sell them for up to $100 each.

Crocodile farming has already become the

main cash earner for the people there. I personally met a village leader in Wewak who had

come to oversee shipment of $14,000 worth of

skins headed to New York by airfreight.

The P.N.G. crocodile project is characterized

by:

● Good Science: Despite popular “maneater” impression, crocodiles live mainly

on fish, though the researchers in P.N.G.

have found that young ones also grow well

on frogs, snails, and beetles. The feeding

efficiency is astounding: One and one-half

pounds of food gives one pound of weight

gain, and foot-long animals can grow to be

five and six feet long in less than two years.

(Conventional domestic livestock require

●

●

●

●

five to eight pounds of food to produce one

pound of weight gain.) Crocodile farming

is also space efficient: dozens of animals

are raised in an area the size of a household living room; in a swamp or jungle,

that’s important.

Good Conservation: Because the program

is based on harvesting young hatchlings

from the wild, the economic value of the

wild populations and their habitats becomes forcefully apparent. The program’s

future depends on them. It gives economic

value to wildlife protection. Out of pure

self-interest, the people become guardians

and conserves of habitats and wildlife. In

a sense, the farming project is just a tool

for conserving the species in its own wild

habitat.

Good Sociology: The villagers have a sophisticated knowledge of the crocodile; the

animal is part of their culture and heritage.

They don’t have to be taught how or where

to catch crocodiles, and they take quickly

to the program. Introducing cattle or Western-style crop-raising would require massive and tedious education and training.

Good Environmental Management: The

program is based on living with the existing landscape and resources. It requires

none of the bush-clearing fencing, foragegrass planting, or pesticide spraying that

rearing other domestic animals would demand. That’s important in a fragile tropical rainforest ecosystem.

Good Economic Development: What other

agricultural product could give a $14,000

income in a remote jungle village?

Butterflies

In remote jungle towns in the north of Papua

New Guinea are operating butterfly farms—

some of the most unusual farms in the world.

Around the edge of a field, flowering shrubs

are planted to attract the adult butterflies

whose mouthparts are adapted for drinking

nectar from flowers. These butterfly “forages”

include hibiscus, flame-of-the-forest, and the

strange, pipe-like aristolochia. Within half-acre

circlets of these flowers are planted leafy plants
45

that the caterpillars feed on. The combination

provides a complete habitat where butterflies

find everything they need for their life cycle.

Thus few leave, and the farmer retains his livestock without fencing or walls.

Butterflies may seem exotic livestock to us,

but even in the remotest P.N.G. jungle, a villager knows and understands their habits, location, and lifestyle. And butterflies don’t require

bank loans, veterinary services, artificial insemination, or the other impediments of conventional livestock. Also, when farming insects, the villager can work when and if he

wants to: there are no deadlines, No hard labor and no danger, either. To a Papua Guinean, the strange thing is that people are willing to pay for a butterfly.

And pay well they do. Ounce for ounce, exotic butterflies are far more valuable than cattle. And worldwide demand for butterflies is

rising. Millions are caught each year and sold

to museums, entomologists, private collectors,

and perhaps most of all, to ordinary citizens.

The fragile, iridescent creatures, mounted in

plastic, decorate purses, trays, tabletops,

screens, and other ornamental objects.

With their butterfly farms many rural Papua

New Guineans are for the first time participating in a cash economy and butterflies are beginning to improve the welfare of many villages.

At Bulolo, the government has established an

insect-buying agency to help the butterfly

farmers of Papua New Guinea. It purchases insects from farmers and fills specific orders requested by overseas buyers. Profits go to the

villager.

Perhaps the most striking feature of the program is that it is actually conserving, and even

increasing, the numbers of butterflies. Basically, it is an exciting, pioneering conservation

project because it develops a tremendous economic incentive to preserve populations and

habitats–the program relies on healthy wild

populations to keep the farms stocked.

Because of this, conservation organizations

are becoming excited by the program, seeing

in it a model that could be duplicated to help

save endangered exotic butterflies everywhere.

The fuels paradise of recent decades has

blinded us to the possibilities of alternative

energies, especially those for powering vehicles. The internal combustion engine, however, remains the most immediately practical

prime mover for motor transport. Finding alternative energy sources for it poses one of the

most severe problems facing the world. The

world is not so much running out of energy as

it is running out of liquid and gaseous fuels.

Living plants that produce liquid fuels would

indeed be boons for the future. Farmers would

become energy producers. Today this is already a distantly glimpsed possibility. Two examples are given below.

The Gasoline Plants

Near Irvine in southern California can be

found a field of what is perhaps the most

revolutionary and little-explored development

in modern agriculture. The crop is Euphorbia

lathyris and this field is the first attempt at cultivating this wild cactus-like shrub. It is the

brainchild of Melvin Calvin, professor of

chemistry at the University of California at

Berkeley. Euphorbia lathyris and related species produce a milky latex, one-third of which

is composed of hydrocarbons—compounds

similar to those found in crude petroleum oil.

Although there are as yet few hard facts on

which to base firm projections, Calvin estimates that the plants might be capable of each

year producing 10 to 50 barrels of oil per acre.

The hydrocarbon in Euphorbia lathyris and

similar species is principally polyisoprene, the

same molecule that makes up rubber in the rubber tree. But in Euphorbia, it is liquid rather

than solid. This is because it is a smaller mol-
46

ecule, but Calvin points out that its hydrocarbon molecules are similar in size to those found

in crude oil. He thinks that Euphorbia type

hydrocarbons might even be processed into

fuels and petrochemicals in existing oil

refineries.

A distinguished scientist, Calvin received the

1961 Nobel Prize for Chemistry in recognition

of his achievements in unraveling the chemical processes of photosynthesis. Growing petroleum plants is a new venture for him, but

already he projects that this country’s vast petroleum demands could be met by plantations

covering an area the size of the State of

Arizona. He calculates the costs of harvesting

petroleum from trees to be competitive with

current oil prices: a total of between $5 and $15

per barrel for growing and processing the

plants.

A plantation of such plants should be economic in dry lands unsuitable for growing

food, Though little is known of their requirements or yields, Euphorbia species are hardy

and need little or no irrigation and care. Calvin

foresees that the plants will be mowed near the

ground and the harvested plants crushed to release latex in much the same fashion as is done

with sugar cane. The stumps quickly resprout

new stems so that replanting would be unnecessary.

This is truly a pioneering concept, and the

field near Irvine is the first small step in evaluating its practicality. Already, larger plantations are planned. The University of Arizona

has a million-dollar grant from the Diamond

Shamrock Corporation to develop Euphorbia

lathyris into a crop; the Government of Kenya

is investing (perhaps unwisely) $10 million in

plantations. If such projects are successful, this

obscure wild plant will enable the world’s desert countries to have oil fields on top of the

ground.

Diesel Fuel You Grow on the Farm

Ohio State University (OSU) in Columbus,

Ohio, transports students around its spread-out

campus using a fleet of buses. Nothing unusual

in that. But, this year (1980) OSU is using soybean oil as fuel.

Over the past decade, various student projects at the OSU engineering school have shown

that vegetable oils can be used as fuel for diesel

engines. For a full year the university has run

a large, 60-passenger bus partly on soybean oil.

The experiment proved so successful that in

September the whole university fleet was

switched to the new fuel.

The soybean oil is collected from deep-fat

fryers in cafeterias and kitchens across the

University, filtered through muslin cloth by the

engineering students to remove gunk and

solids, and blended into diesel fuel. A ratio of

one part soybean oil to four parts diesel was

settled on as it gave a stable mixture, lowest

fuel consumption, and actually smoked less

than diesel fuel alone.

The first bus maintained its normal 40 hour

a week schedule. After 4,5oo miles on the soydiesel blend the engine was taken apart and inspected. Little or no abnormal wear had occurred. The engine was actually in such fine

shape that it was merely reassembled and

returned to service without further attention.

Although it is little-known to the general populace that diesel engines can be run on vegetable oils, this knowledge is not new. In the

1890s, Rudolf Diesel concluded that any material that was injectable and would ignite at

the temperatures generated by compressing air

could serve as fuel for his engine.

During World War II this knowledge was put

to use. When Japan was cut off from petroleum

supplies, the 65,000 ton Yamoto, the largest and

most powerful battleship of its time, used edible, refined soybean oil as bunker fuel. Japanese forces occupying the Philippines and

Allied troops trapped in northern Burma used

coconut oil for fueling diesel trucks and

generators.

Since then, that experience has been largely

forgotten. But in the U. S., South Africa, Australia, Brazil, Canada, Thailand, Japan, and

perhaps elsewhere, individual researchers are

rediscovering that diesel tractors, buses, and
47

stationary engines can operate when fueled

with sunflower, soybean, peanut, rapeseed,

and other vegetable oils.

The experiences are usually solitary and

most involve only very short running times.

The practical potential of vegetable oils as commercial diesel fuel substitutes is therefore uncertain. But, at least in the short run, they work.

Of all the research laboratories testing diesel

engines fueled by vegetable oils, the South African government’s Division of Agricultural Engineering has the most experience. At its laboratory near Johannesburg it is running 10

tractors on sunflower oil. Fiat, International

Harvester, John Deere, Landini, Massey Ferguson, and Ford tractors are being used, With

two exceptions the tractors started satisfactorily on undiluted sunflower oil, All operated normally, delivered almost full power, and

had virtually the same fuel consumption as on

diesel fuel. A Ford 7000 tractor has run troublefree for almost 1,400 hours of operation on a

farm using a blend of 20 percent sunflower oil

and 80 percent diesel fuel. At the end of this

time it was found that deposits in the combustion chamber, cylinders, and piston ring

grooves were no worse than those formed

burning normal operation on diesel fuel. On

the other hand, carbon deposits on the injector nozzles were worse and contributed to an

eventual 4 percent power loss and serious gumming of the crankcase oil.

The rapid compression of fuel and air in the

cylinder of diesel engines generates enough

heat to ignite the mixture and power the engine. Unlike a gasoline engine, no spark is

needed. Injecting the fuel into the combustion

chamber is the most crucial step in a diesel engine. The fuel must be forced in against the

pressure of the compressed air and to make this

doubly difficult, the fuel has to be in the form

of mist. If not atomized, the fuel burns slowly

and unevenly, reducing engine efficiency, raising unburned pollutants in the exhaust and the

lubricating system, and even forming deposits of solid carbon in the engine itself.

Vegetable oils are more viscous and less easily atomized than diesel fuel and are therefore

more difficult to inject successfully. This is

probably why the injector tips suffered buildups of carbon. Coking and the resulting incomplete combustion diluted the lubricating oil and

gummed it up because vegetable oils will polymerize when they are hot and next to metal.

The South African engineers, however, have

found a way that seems to avoid these difficulties, They slightly modify the sunflower oil in

chemical reactions using small amounts of

ethanol or methanol. The resulting ethyl or

methyl esters derived from sunflower oil

caused much less coking than diesel fuel itself.

Furthermore, they produced much less exhaust

smoke, and the engine ran quieter so that the

characteristic diesel knock was less audible,

And, against all expectations, the engine gave

more power with the new fuel than with diesel

fuel. Thus tractors were running on a renewable fuel grown by farmers and achieving better results than on diesel fuel, Much yet remains to be done to test the widespread

applicability of these results, but it is a line of

research that is bright with promise,

CONCLUSION

Development specialists usually promote re- snails, guinea pigs, and butterflies. Instead they

sources and technologies that are familiar to recommend and sponsor the introduction of

their own lives. Most agronomists, foresters, species that are foreign and unconnected to the

animal scientists, and nutritionists know little lives of those they want to help.

about the wealth of plants and animals to be

found in the developing world. They all but ig- This paper identifies just a few exciting unnore the significance poor people’s crops, le- derexploited resources for developing country

guminous trees, and animal resources such as agriculture. Detailed information on them and
48

many others can be found in the following National Academy of Sciences reports (all of

which are available without charge from the ●

Commission on International Relations, JH

215, National Academy of Sciences, 2101 Con- ●

stitution Avenue, N. W., Washington, D.C.

20418): ●

● The Winged Bean: A High Protein Crop

for the Tropics

●

● Leucaena: Promising Forage and Tree

Crop for the Tropics Underexploited Tropical Plants With Promising Economic

Value

Tropical Legumes: Resources for the

Future

Guayule: An Alternative Source of Natural Rubber

Making Aquatic Weeds Useful: Some Perspectives for Developing Countries

Firewood Crops: Bush and Tree Species

for Energy Production
-.

Chapter IV

Native Plants: An Innovative

Biological Technology

Cyrus M. McKell, Ph.D.

Director of Research

Plant Resources Institute

Salt Lake City, Utah 84108
Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Role of Native Plants in Sustaining Food and Forage Production . . . . . . . . . . . . . . . .

Where Native Plants Are Being Used Today . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Research Efforts on Native Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

How Do/Could Native Plants Increase or Decrease the Need for Fertilizer,

Pesticides, Irrigation, and Machinery? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Is the Potential Role of Native Plants to Restore, Improve, or Sustain

Food Production on Tropical and Subtropical Soils? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Research, Development, and Implementation Scenarios Could Help Native

Plants Realize Their Potential of Enhancing Tropical Soil Productivity? . . . . . . . . . . . . .

Scenario A.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scenario B . . . . . .

Scenario C . . . . . .

What Changes in Attit

Cultivators . . . . . .

Legislators . . . . . .

Financiers . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ude Are Needed? . . . . . . . . . . . . . . . . . . . . . . . . . , , . . . . . , . . . . . . . , ,

. . . . . .,0.., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...!

. . . . . . 4....., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .!

International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Biophysical, Cultural, and Socioeconomic Conditions Would Be

Conducive to Project Implementation?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Biophysical Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cultural Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Socioeconomic Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Are the Major Constraints on Development and Implementation of

Native Plant Use?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scientific Constraints. . . . . . . . . . . . . . . . ....4...0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Environmental Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Culture Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Economic Constraints ..., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Political Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

How Would Implementation of a Native Plant Technology Affect the

Need for Capital? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Would Be the Impact of Wide-Scale Implementation of

Native Plant Use on Socioeconomic Structure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table

51

51

52

53

56

58

58

.59

59

60

60

61

61

61

61

62

62

62

62

62

62

63

63

63

63

63

64

64

64

64

65

65

66

Table No. Page

1. Little Used But Potentially Useful Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Chapter IV

Native Plants: An Innovative

Biological Technology

ABSTRACT

The concept of native plants reflects a new

direction in botanical development. The term

implies the idea that rather than adapting the

environment to the plant, an indigenous plant

expresses the best adaptation to an environment and improving on this expression will

yield various benefits. Bringing marginal lands

into widespread agricultural use often employs

technologies and plant species inappropriate

to these situations. This occurs with a total disregard for the climatic limitations of the environments. A new approach is required.

Development of native or indigenous plants,

particularly those adapted to tropical and subtropical soils, could be beneficial at different

economies of scale, In some instances, their development will be small and amenable to use

by individual farmers or farming groups, On

the other hand, there will be instances where

development will be large scale and have international implications.

Native plants can be particularly useful in

sustaining fertility on depleted or marginal

soils and improving general productivity. They

use an “agroecosystem approach” to obtain

necessary production. Polycultural (mixed)

cropping systems are especially applicable in

tropical locations; they rely heavily on the potential of adapted or indigenous plants. Native

plants represent an underused resource and

constitute an opportunity for positive botanical developments,

The coordinated, integrated development of

indigenous plants could allow for multiple and

additional benefits greater than the initial goals

of soil fertility, food production, or raw materials, There is an immediate need for inventories

of existing native crops for their development

potential. The world’s tropical and subtropical

germplasm is poorly known, Throughout the

world, knowledge of plants and their uses by

indigenous peoples is disappearing because

farming systems are being converted to monocultural uses. Germplasm storage of potentially

valuable varieties and strains requires immediate attention. Demonstration of practical

working models with specific native plants

must be performed.

One factor limiting the development of native

or other unconventional plants is an institutional bias against them. The major emphasis

of plant research during the last 100 years has

been directed at the dozen or so primary food

crops—to the exclusion of almost everything

else.

To overcome this institutional bias will require innovation in policy, research and development, and program implementation. Development of native or adapted plants should

allow for an integration of these concerns. The

capabilities of various governmental and nongovernmental institutions should be directed

toward the goal of sustaining soil productivity

in both the short- and long-term context,

INTRODUCTION

The purpose of this paper is to present a non- nology to improve productivity on soils in troptechnical description and evaluation on the ical/subtropical areas. The paper addresses sevutility of “native” plants as an innovative tech- eral major questions that appear as subsections,

51
52

The term native plant needs clarification. All

plants may be considered native or indigenous

to some location on the earth, but when a plant

is taken to an area where it is not naturally

found, it becomes an introduced species. This

distinction is too constraining and can overlook the importance of adaptation—judged either from actual observation or from scientific

evidence of ecological similarity. In this report,

native species are those plant species growing

in an area that have not been exploited for commercial development and export. Some native

species may have desirable attributes and a potential for intensive use while others may

merely serve to “fill in the spaces” of the plant

community and have only minor development

potential. This paper is limited to indigenous

species that have not been extensively developed.

Native plants hold great promise for meeting

the expanding needs of society for food, fiber,

fuel, and enhanced land productivity. In the

search for a plant or plant product to serve a

market or domestic need, plants native to a

given region may already express the range of

adaptation necessary for sustained use. But

they are often overlooked in favor of an imported species. A good example of indigenous

plants being overlooked is in rangeland improvement programs in the Western United

States where native shrubs were removed in

order to plant introduced grasses (11). Although plant exploration and introduction has

been emphasized by the economically developed nations, the search for new plant

materials has been directed along conventional

lines and the potential of native species has

been overlooked.

In the past, the common procedure has been

to examine existing files or materials found in

plant introduction stations to find new plants

and plant products rather than to explore locally for possible new products. Because of the

increase in energy costs and the energy component in existing production activities, a new

look for alternatives is justified. A particularly

attractive opportunity to develop native plants

exist in tropical and subtropical areas. These

areas generally have not been of interest as a

source of plant materials because the developed nations are, to a large extent, located in

temperate climates. This has limited germplasm collection, research testing, and introduction of new crop species. Additionally,

most American primary crop species are introductions from the Old World, and these

have been genetically developed over long periods of time for intensive agricultural use.

THE ROLE Of NATIVE PLANTS ON SUSTAININ0

FOOD AND FORAGE PRODUCTION

Native plants serve a traditional role in many

tropical and subtropical countries. Various indigenous species have been used for food, fuel,

livestock feed, construction, fiber, medicines,

and other purposes on a sustained yield basis.

The species are either gathered from natural

plant communities (forests, rangelands, marshes,

etc.) or harvested from small farmed plots

under various degrees of cultivation. Cultures

as diverse as Mexico, Sri Lanka, and Indonesia have well-documented histories of wide use

of indigenous plants for medicines, foods, and

other uses. Most of these native plants have not

reached a level of development sufficient to

make them commercially useful. Notable exceptions include rubber, corn, pineapple, and

potatoes. Most species, however, are unspectacular in their attributes and find beneficial

use only in the day-to-day existence of the local

people.

Overuse of native species brought about by

population increases and energy shortages is

creating adverse impacts on many species and

their systems of production. Where previously

a conservative level of plant use generally assured their natural replacement and did not reduce their genetic diversity, exploitation of
53

land resources by overgrazing, intensive agricultural development, forest clearing, industrial development, and widespread soil degradation threatens to eliminate many useful

species.

For example, a recent National Academy of

Science assessment of environmental degradation of the groundnut basin of Senegal (12) indicates that overuse due to population increase

and cyclic drought has resulted in the disappearance of many native species used for fruit

and livestock fodder. Theoretically, some of

these species are still present in the noncultivated bush areas. An example is Ziziphus

maritiana, a desirable fodder shrub, that had

essentially been eliminated from areas adjacent

to intensively cultivated farmlands by overuse.

At a conference in Australia on Genetic Resources of the World, concern was expressed

that valuable genotypes and gene combinations

were being lost due to the impacts of human

population expansion. Associated with the direct loss of genetic resources is a substantial

reduction in soil fertility and an increase in less

desirable plants.

Native plants also play an especially important role in improving crop performance and

diversity. Indigenous or locally cultivated

relatives of many common crop plants offer

significant potentials for crop improvement

programs within the temperate and tropical

latitudes. Recent discoveries of wild perennial

relatives of corn (Zia mays) could prove extremely important to the future development

of this crop. Similarly, the expression of expanded environmental adaption often inherent

in many native plants could allow for much

wider cultivation of the species while reducing artificial inputs. Recent work with salt tolerance in major grain crops and tomatoes relies heavily on the adaptive qualities of various

native and overlooked indigenous relatives of

these important crops (13).

WHERE NATIVE PLANTS ARE BEING USED TODAY

Native plants are being used all over the

world, Many species find extensive use in developed agriculture and some native species already enjoy limited commercial use in areas

of optimum adaptation (table 1). Opuntia cactus

fruits in central Mexico are collected and sold

locally. Fibers are removed from the Leghugea

cactus for use in making Mexican mats, shoes,

and baskets. Numerous species of native trees

such as Mangosteen (Garcinia mangostana) in

southeast Asia, Naranjilla (Solarium quitoense)

in Colombia and Ecuador, pejibaye peach palm

(Gudiema gasipaes) in Central America, and

soursop (Annona muricata) of the West Indies

produce exotic fruits for local markets.

The important point is that the usefulness of

some species is known only to local people or

is generally not appreciated by a wide audience. A number of examples of fruit, vegetable, fiber, oil, and forage species are described by the National Academy of Sciences

in their studies on underexploited plants (18).

Such underdeveloped species may possess

unique features that could be useful in new applications or supplement existing crop plants

if they were screened for optimum size, shape,

product quality, and adaptability to various

management practices.

The genus A triplex is an example of a group

of semiarid, subtropical plants currently used

but possessing significant potential for increasing rangeland productivity. Various shrubby

A triplex species are valuable as livestock forage during seasonal dry periods when most

grasses are below required levels of crude protein for animal nutrition. The protein content

in A triplex is high and balanced. The exploitive

subsistence level grazing practices and extensive gathering of A triplex on the rangelands of

Syria, Iraq, and other Middle Eastern nations

has nearly caused the disappearance of these

palatable shrubs (23). An integrated development program of collection and revegetation

with this native species and other adapted
54

Table 1 .—Little Used But Potentially Useful Plants

Present Yield

Common useful Potential Present Growing State of Per Hectare Time to First

Name Scientific Name Portion use Areas Cultivation Per rear. Harvest

A. Humid Tropics

Cocoyam carbohydrate,

protein

carbohydrate,

oil, protein.

“heart of palm”

carbohydrate

Tropical Americas,

West Africa

CentraI and Northern

South America

domesticated 30-60 tons

wet weight

domesticated 3 tons

3-10 months

fruit and 6-8 years

stem

Peach

palm or

pejibaye

Taro and

tiecss

Buriti

Egypt, Philippines,

Hawaii,Caribbean

Amazon Basin.

Veneuela,

Guianas

domesticated 22-30 tons

wet weight

mostly wild ?

6-18 months

9

tuber

fruit

kernel.

Shoots

trunk and

leaves

fruit and

kernel

fruit and

kernel

oil, starch,

vitamins A and

C, timber, cork.

fiber, heart of

palm”

oil* protein,

fuel

oil. fuel

Babasaat

palm

Pequi

tree

Orbigrrya martinia

Caryocar bresilienss

Amazon Basin mostly wild 1.5 tons

mostly wild ?

10-15 years

Amazon Basin, 9 years

Central Brazil,

Guianas

Seje Amazon Basin

palm

winged

Jczzenie polycarpa

~P~ tetw

nolobus

Durio Zibcthinus

fruit oil resembling

olive oil

protein, oil.

carbohydrate.

livestock feed

carbohydrate,

fat; vitamins,

flavor

highly prized

flavor

large citrus

fruit

wild 22 kg/ tree

per year

domesticated 2.5 tons of

dry beans

?

pods, beans, 10 weeks

tubers,

foliage

fruit

Papua New Guinea.

southeast Asia.

Sri Lanka

Southeast Asia haphazardly ?

cultivated

7 years

Mangosteen

tree

Pummelo

tree

Scuncn

tree

ckrcinit nsan@stana

Citrus grandis

fruit

fruit

fruit

Southeast Asia

Southeast Asia

domesticated 50 kg/tree

per year

domesticated ?

15 years

several years

* Anrrona muricara fruit and

juice

Southern China,

Australia, Africa.

tropical Africa.

West Indies

Western Amazon

domesticated 6-10 tons

[ !villa

tree

(%aya

bush

Ramsc

herb

Cauassu

herb

Lcucacna

Ptmrrmma crrrnpiarfoiw

Cnidwcvlus CIIa,l,anlansa

I%whmcti mwa

Calafhca lutea

Ieucaena Icucocephala

fruit grapelike

fruit

vitamin-rich

leafy vegetable

fiber and livestock feed

commercial

wax

livestock feed,

timber. fuel.

paper, soil

fertilizer, dye

stuffs, human

food. erosion

and watershed

control, nurse

tree, fire and

wind breaks

wild 7

domesticated ?

3 years

Mexico and 2-3 months

Central America

East and Southeast

Asia. Brazil

Amazon Basin.

Central America

Central America.

Mexico. Southeast

Asia. Northern

South America.

Australia. Hawaii.

East and West Africa,

Papua New Guinea,

Caribbean. India

stems and

foliage

leaves

domesticated 1.4 tons fiber, 2 months

20 tons feed

wild 0.8 tons 9 months

of wax

domesticated 12-20 tons less than 1 year

and wild of forage, to more than

20-50 tons 3 years,

of wood depends on

variety

planted

Ieaves,

wood, pek.

seeds. bark

8. Scmwld and Arid Tropics and Subtropics

seed. leaveS.

and stems

seed. root

seed. leaves.

and stem

Channel .L”chinochkm [uncmna

mdlc!

Buffalo <“ucwhiro focridlssima

courd

Guar C)”amopns tctrapxroloba

(cluster

bcln I

carbohydrate.

protein. livestock feed

oil. protein.

starch

Central Australia wild v several months

after heavy

rain

mostly 2.5 tons of 2 years

wild seed, 22 tons

starch

domesticated 18-24 tons 3-5 months

green fodder.

0.9-2 tons

seed

Mexico. Southwestern

United States

gum, protein,

oil. livestock

feed

United States.

Pakistan, India.

Australia. Brazil. ,

South Africa
Table 1 .—Little Used But Potentially Useful Plants—Continued

pfescnt yield

Common U“)cful PotcntmJ Present Growing Slate of ?CI Hectqr. Time 10 k’ust

Nam e Scicntirsc Name Portion Usc Areas C’ultlwation Pet rear }14rt CSi

Appk-ting AwCiO albida

..—

acacia tree

Ramon Brosimum alicaurum

tree

Icavei, shoots,

pods, Sceda

leaves, twigs.

nuts

leave>

leaves and

shoots

stems and

leaves

pods and Icave}

seeds

whole p~t

livestock feed,

human protesn

livestock feed,

atbohydrate,

protein

Iivcstock feed

Tropicaf and Wikf

Southern Africa

CentraJ America, mo>tly WSIJ

Southern Mexico,

Caribbean islands

Australia. Isrucl .411d ~n.f

usttivalui

worldwldc in w lid and

warm arid ztinc~ WI Iwawd

United States and Wdd

Mexican dcstrt.s

Atacoma desert 01 cultlv Alcbl

~ik, Canq island>

United States and mostl) wdd

Mexican deserts.

Israel

United Scsws. Mcxuxn mostl) udd

deserts. Spain. Turkc}

2(MJ kg several years

Scverd years

protein

●

cawiJ Ca:sb sfurtil

shrub

SaJtbush Atriplcx spp.

i ,’2 um df )

Wesght

Iivcstock tcul 1-1.5 tons

Gnddiua k“uphorbsa anrrsyphilitsca

shrub

Tumxrugo bosopu tansarugu

tree

JOjOtM &nwsondsu chutcnsu

shrub

hard wax .

high protcm.

Jives[ock Iced

Iiquld wax

idcnticd to

Sperm oiJ

naturaf rubber

I tJ-2tJ SJlccp

2 tons

Guayuk Parthentum argentatum

shruh

It. j j Ion

C Afountaltt kmvronmctm oj”low Lrttrude$

Grws A mamrtthus COUd<SiS,

amarJssth etc

high IyUtW.

htgh proteus,

starch, VIUUISIJU

Andeao re~wr UI

!bulh Amcrw

seed prolcin.

arbohydratc

carbohydrate.

livestock feed

fruit and Iuicc

Andcan rcgicm nf

Sou[h America

Andean re:irm O(

South Americ~

Centraf and

Northern SOIIIII

America

Papua New Gvsinca.

Sosrthcast .4sia.

Sri Lanka

donwticztcd *

tlomr~ticxtcd ‘

dwrwttcatcd I-2 tons

of fmil

d~mcsticatcd 2_S tons of

dry bean<

Iubcrs. stcms.

IC8VCS

ftuil

pnds. beans.

tuhcrs.

foliacc

protein. oil.

cxrbohydratc.

livestock fcesf

seed carhohydratm.

prolcin

tidaf flats and

estuaries in

aU latitudes.

brackish marshy

areas in Thailand

world w-idc. includln~

salty soih and saline

irrigation watcm

Atacama desert of

Chifc, Canaty Isfands

sescoasts from

AustralL :: 2~AArgentina to Baia

Cafifomia

1

domesticated ‘

rnasflv wild I -1.5 tnrl<

frrmt citrus fmit

I?avcs and

Shonts

hiph profcin,

livestock feed

pods and leaves high protein.

IJvestock feed

Ilvcstock feed.

sand stabilization

cultivated 1 ~20 sheep

leaves wrd mostly wifd ?

stems

Spirulina. Spirsdirsa platcnsis

hfuc-green S@irulina maawna

*ac

—

mstitc alga poultry feed. Lake Chad, Vafky cultivated 3 tons vvcrd days

of Mcx ico ~rolcin

tein human food

very high pr~
Atriplex species from similar climates could

substantially restore rangeland productivity to

this region.

Another example of a native plant that is receiving considerable attention on a pilot-scale

level is jojoba (Simmondsia chinensis), an evergreen shrub indigenous to the Sonoran deserts

of the United States and Mexico. The plant is

valued for the liquid wax contained in its seeds.

RESEARCH EFFORTS

Research on native plants is being conducted

by many different groups ranging from private

individuals and companies to State, national,

and international agencies. However, no coordinated research effort can be expected because of the diversity of potentially useful native species, the various countries where they

are growing and could be grown, and the risks

involved in developing new crops for illdefined markets.

As has probably been the case throughout

history, plant resources have been developed

to meet existing and short-term needs. The difference today is the high cost of bringing new

products into a highly competitive market. Opportunities for new products or uses from native plants can occur as a result of changes (or

potential for changes) in consumer preferences

or as existing products come into short supply

and can be replaced by a native plant product.

It is difficult to identify organizations performing research on native plants, but they fall

into the following categories:

1 Broad spectrum agencies sponsoring exploration collection and evaluation. Examples:

● USDA: plant introduction, plant

materials centers (nationwide).

● FAO (Food and Agriculture Organization of the United States) seed exchange, international development.

● SIDA (Swedish International Development Agency): sponsoring projects to

preserve genetic resources.

The wax is similar to sperm whale oil and has

a potential for use in many industrial processes. Field test plantings have been made in

Arizona, California, Israel, Mexico, and Australia. Because the plant is adapted to areas of

extremely low rainfall (less than 10 inches), it

could become an important cash crop for the

appropriate arid areas (10).

ON NATIVE PLANTS

2. Agricultural experiment stations doing

work on individual plant species with local concern. Examples:

● University of California Agricultural

Experiment station, Riverside: jojoba

wax.

● University of Hawaii Agricultural Experiment Station: Leucaena trees.

3. Private organizations, agricultural enterprises working to develop products from

various species. Examples:

●

●

●

Firestone Rubber Company: guayule

for rubber development.

Native Plants, Inc.: developing new

technology for tissue culture propagation of various plants.

Jojoba International, Inc.: encouraging commercial plantings of jojoba.

Funding of native plant research is very dependent on the species in question. Obviously the

potential for some species is greater than others

depending on the scarcity and quality of the

expected product, the abundance of the plants,

and the needs of society. Currently, there is a

high interest in native plants with potential as

sources for biomass energy. Unfortunately,

there is little, if any, coordination in research

funding for native plant development or in the

establishment of priorities. As of 1979, the total U.S. funding for research and development

of underexploited plants was limited to less

than $10 million, half devoted to jojoba.

The uncertain path of development for a natural rubber product from the native shrub
57

guayule (Parthenium argentatum) illustrates

the problems of developing a native plant. The

National Academy of Sciences (13) pointed out

that in 1904 a company was formed to extract

rubber from the guayule bush, By 1910 this

company was the sixth largest in Mexico but

the wild stands of plants quickly became

depleted. Expelled from Mexico by Pancho

Villa, the company continued limited operations in Salinas, California. Cut off from natural rubber supplies from Southwest Asia in

1942, the United States took over the company

and planted over 12,000 hectares of production

and experimental plots of guayule. These fields

were just coming into production after the war

in 1945, but because natural rubber was again

plentiful and a fledgling synthetic rubber industry gained the Federal price supports, the

guayule fields were destroyed. Recognizing the

need for dependable supply of natural rubber,

Congress passed the Native Latex Commercialization Act of 1978 which makes $30 million

in Federal funds available for research. Subsequently, Firestone Tire and Rubber Company

and Goodyear Tire and Rubber Company have

initiated field trials of guayule in the Southwest. In Mexico, plans are underway for a natural rubber industry using guayule from native

stands and later from established plantations,

Obviously, a more integrated and organized

effort will be needed to bring the benefits of

other native plants into reality. The research

community and society simply cannot be subjected to the vagaries of 70 years when a plant

of national value takes so long to be developed.

Coordination is needed to stimulate innovation

in policy planning, research and development

funding, and commercial implementation.

Substantial, integrated programs are necessary to bring native plants into commercial

production. We know that genetic quality of

conventional crops and appropriate cultural

practices have been improved over a long

period of time. With this history of development, we can expect that new crops/products

from native plants can be developed with even

greater efficiency. Significant breakthroughs

may take place (such as the application of various biotechnologies) but for the most part, research funds, time, and vision will be needed

to unlock these new resources.

One of the first research steps must be to

identify promising native plants and describe

some of their characteristics. A survey sponsored by the National Science Foundation (22)

described six new crops with a potential for

development in the United States. A thorough

coverage was given to ten new agricultural

crops (20) that already have received some attention. Goodin and Worthington (8) helped

stimulate interest in native plants with their

conference on Arid Land Plant Resources.

Probably the greatest stimulus to the development and use of native plants in recent years

has been the series of bulletins published by

the National Academy of Sciences. Underexploited Tropical Plants With Promising Economic Value. NAS (18) describes 36 tropical

and subtropical plants that have a high potential for use as cereal, root, vegetable, fruit, oilweed, forage, and fuel. The Winged Bean—A

High Protein Crop for the Tropics (17) provides

information on a tropical legume native to

Southeast Asia and New Guinea with a potential for improving human nutrition. Guayule:

An Alternate Source of Natural Rubber (14) is

a report on the development potential of a subtropical desert shrub of Mexico and Southwestern United States that produces a latex product similar to natural rubber from Southeast

Asia. Leucaena: Promising Forage and Tree

Crop for the Tropics (15) provides information

on a vigorously growing tree and bushy plant

that produces nutritious forage as well as restoring soil fertility. Other benefits include timber, fuel, and pulpwood as well as soil conservation and stabilization. Tropical Legumes,

Resources for the Future (13) reports the findings of a group of legume specialists on 200

species that warrant research and development

to achieve their optimum potential. Products

From Jojoba (16) gives a review of the chemistry of the liquid wax obtained from this shrub

native to Southwestern U.S. deserts.

These publications all highlight the immense

potential existing within the botanical world

to benefit agriculture, forestry, and horticul-
58

ture, particularly in the developing countries. conservation of existing habitats. The rapid disThese and other surveys consistently document appearance of extensive semiarid, subtropical,

the immediate need to inventory indigenous or tropical plant community compounds the

knowledge concerning native plants and their problem of collecting, researching, and develuses, germplasm collection and storage, and oping these under-exploited plant resources.

How DO/COULD NATIVE PLANTS INCREASE OR DECREASE THE NEED

FOR FERTILIZER, PESTICIDES, IRRIGATION, AND Machinery?

Any change in the present use pattern of fertilizer, pesticides, irrigation, and machinery

would depend completely on the nature of the

native plant being developed—whether the particular plant could be developed on an intensive or extensive basis, or the degree to which

the plant is susceptible to insects and diseases.

However, any move to increase productivity

would generally require an increase in the level

of inputs. The adaptation of some indigenous

plants to multicropping systems or polycultures could significantly reduce the need for

artificial inputs. The development of such production systems is just in its infancy, however,

and models appropriate to widespread application are virtually nonexistent.

Some specific examples of inputs required

by various native plants will illustrate their

variable nature.

Fertilizer

Three possibilities for fertilizer use may be

seen:

1.

2.

3.

Legume species may have minimal fertilizer requirements, needing mainly phosphorus, sulfur, and micronutrients.

Some native species may not require high

levels of fertilizer because of their adaptation to low nutrient environments.

Non-1egume species may require substantial amounts of fertilizer to achieve optimal

production levels.

Leguminous native plants are particularly attractive because they can serve to increase soil

nitrogen as well as provide useful products

such as fuel, forage, and wood biomass. Fast

growing Leucaena trees have been shown to

provide foliage containing 1,000 to 1,300 lbs.

of nitrogen a year and can restore the fertility

of tropical soils depleted of nitrogen and organic matter (15). Felker (15) suggested that

mature tree legume orchards receiving no irrigation or nitrogen after establishment may increase soil fertility up to four times greater than

non-leguminous tree species. Numerous legume shrubs and trees such as Acacia, Prosopsis, Desmodium, Cassia, and Stylosanthes

enhance soil fertility while at the same time

serving as live fences, crop interplantings, or

range and pasture fodder. Many examples of

soil fertility increase are presented in Tropical Legumes: Resources for the Future (13),

Tropical Pastures (21), and in papers presented

at the International Symposium on Browse in

Africa.

Some native species may not require large

amounts of fertilizer because they are adapted

to soils of medium to low fertility. Under such

conditions, plant growth and production could

be expected to be correspondingly low. If high

yields for commercial production are desired,

the level of fertility must be increased accordingly. Intensive cropping has been shown to

deplete soil fertility and any continuous production in a new agricultural location would

eventually require regular soil fertilization.

Non-legume native plants may require large

increments of fertilizer to produce at levels

sufficient to be commercially attractive and to

cover costs of production and development.

These species are those requiring optimal soil

and water conditions. Possible requirements

for fertilizer and other inputs for such crops
—

59

are summarized in a report prepared for the

National Science Foundation (22).

Another potential strategy is represented by

the selection and development of native plants

adapted to saline environments. The ability to

tolerate environmental constraints and still

produce utilitarian byproducts is one potential

avenue for overcoming high fertilization inputs. This is an approach to native plant development that has been virtually ignored in

plant research. The existence of salt tolerant

wild selections of existing crops could improve

the infertility tolerance of these species and

therefore reduce their needs for fertilization.

Such possibilities will require concerted efforts

to enhance the range of adaptability for most

crop species.

Pesticides

Very few, if any, of the native plants having

a high potential for development have been

studied from the aspect of insect, disease, or

weed problems normally associated with intensive cultivation, Whereas many insect or disease organisms may be held in check in a diverse plant community, they may increase to

epidemic proportions when their host plant is

grown in a pure stand. An example of such an

epidemic occurred when black grass bug populations nearly devastated pure stands of introduced wheatgrasses that had been seeded

to replace sagebrush and other plants in western rangelands (9). Plantings of native species

will require research and plant protection

measures similar to those already necessary for

the production of conventional crops.

In tropical countries where multicropping

systems represent the most sustainable method

of farming systems, the pesticide requirements

could be minimized by host/predator interaction within the farm plots (7), Testing and development of such models needs to be greatly

expanded, however.

Irrigation

Requirements for irrigation will depend on

the kind of native plant selected. As a concept,

the use of native plants indicates an adaptability to the specific environment and its constraints. Species adapted to tropical soils may

not require irrigation if the pattern of rainfall

is adequate and meets the critical stages of

plant development. Areas of subtropical soils

typically have periods of rainfall deficiency and

various strategies must be employed to obtain

production under such conditions, These strategies include:

1.

2.

3.

Choose native plants with low water requirements that can be grown in desert or

semi-desert conditions. Some examples

are: jojoba, atriplex, guayule, buffalo

gourd, guar, cassia, acadia species (19).

Develop technologies to increase the effectiveness of natural precipitation or irrigation. Alternate fallow, spaced plantings,

water harvesting, or drip irrigation can be

effective. Where land is not a limiting factor, these extensive practices can be economically effective. Evanari, et al. (4), demonstrated how an ancient civilization

survived in the Negev desert by using precipitation optimizing practices such as

water harvesting and spaced plantings. Recent work at the University of Arizona (6)

indicates high potential for using water

harvesting to foster plant production under desert conditions. Biomass plantings,

deep rooted tree crops, and drought

adapted species would be most suitable for

these technologies.

Use available irrigation water to support

maximum production of new crops from

high yielding native plants. Where soils

with a high productive potential may be

available for intensive use, possibly by

replacing a lower value traditional crop

with a high value new crop, irrigation may

38-846 0 - 85 - 3
60

be justified. Close plantings, tillage, pest

control, and fertilization may also be

needed to optimize production. Grain

amaranth, winged bean, and guar are possible species for intensive development,

but many other may be considered.

Machinery

Because of the varied nature of native species available for development, no definite

statement can be made regarding machinery

requirements. Equipment for land preparation,

tillage, and transportation of crops to storage

and market would be needed. Harvesting may

be done by machinery in the case of a uniform

plant such as guar or guayule where leaves and

seeds are easily available. Where fruits, stems,

or roots are not uniformly exposed and are retained on the plant, either hand labor or a specialized piece of machinery may be needed.

In regions of the world where hand labor is

abundant for planting, cultivating, and harvesting, the development of new native crops

that require hand labor rather than machinery

is most appropriate. In other nations, labor intensifying machinery can be developed, This

has been the pattern followed in the development of conventional crops.

It is important to recognize that the development of native plants for their various uses

can be aimed at local needs as well as at wider

industrial and international markets. Machinery and labor requirements will depend on

what level of development is pursued.

WHAT IS THE POTENTIAL ROLE Of NATIVE PLANTS TO RESTORE,

IMPROVE, OR SUSTAIN FOOD PRODUCTION ON TROPICAL AND

SUBTROPICAL SOILS?

There is a high potential for some native

plants to positively affect food production on

tropical and subtropical soils. One of the most

promising strategies is the increased use of leguminous plants as food, livestock fodder, and

wood to concurrently improve soil fertility (21).

As fertilizer costs continue to escalate in response to energy expenses, fertilizers will become economically prohibitive in many developing countries. Incorporation in the cropping

system of a legume rotation, green manure, or

animal manures derived from legume feeds

may be the best remaining option to replace

fertilizers (12) and maintain agricultural

productivity.

Non-legume native species have various

potentials for positive benefits to food production. Many species are already known locally

but have not received sufficient notice to be introduced or developed for use in other (similar) regions. To achieve such recognition will

require:

1

2

3

A shortage in food from existing crop

plants.

Development of new lands that are better

suited for new crops.

Adaptation of new crops to compete economically with conventional crops,

Some form of research and development intervention will be needed to raise the perspective and incentives of local peoples. The likelihood of general use depends on the individual

species. For example, the general qualities of

seeds from the jojoba plant have been known

for many years (10) but only recently has any

development effort appeared substantial

enough to bring the plant into widespread use,

The shortage and cost of sperm whale oil is

a big factor motivating jojoba development in

more than five countries. Some applications

will be less spectacular, but no less needed.

P1antings of the legume tree Acacia albida in

Mali (24) hold considerable promise for im-
61

proving subsistence agricultural production

there, but the effort is but a “drop in the

bucket” compared with the needs in that area

of West Africa.

In view of the diversity of native plants available for development and the number of countries with suitable environments, judicious support of native plant development programs

seem justified. The likelihood of spontaneous

development or widespread use of native plant

resources seems unlikely without external encouragement. Otherwise, many useful native

plant species and ecotypes stand in jeopardy

of being lost as deforestation, land depletion,

industrial development, or other activities eliminates the natural plant communities.

WHAT RESEARCH, DEVELOPMENT, AND IMPLEMENTATION

SCENARIOS COULD HELP NATIVE PLANTS REALIZE THEIR POTENTIAL

OF ENHANCING TROPICAL SOIL PRODUCTIVITY?

Scenario A

The program of planting seedlings of Acacia

albida legume trees in Mali (24) serves as a

model for the development of the potential of

a native plant. In this program, CARE set up

production nurseries to produce tree seedlings

in soil-filled plastic tubes. Acacia albida is an

indigenous legume tree native to sub-Saharan

Africa. The tree has the unique feature of being leafless during the rainy season. This allows for cultivation of other crops directly under the tree. The leaves and pods provide

fodder and green manure and the roots fix nitrogen. It is an ideal candidate for selection,

improvement, and application to various semiarid agroforestry systems.

Teams of local farmers were employed to

plant the seedlings in preselected agricultural/

pasture areas of good soils. Planters were paid

on a per tree basis for planting and protection.

Subsequently, these local people were encouraged (in their work training orientation) to take

a special interest in the seedlings to see that

they received appropriate management and

protection to ensure their survival from grazing animals. Benefits expected are increases

in soil productivity and livestock feed.

Scenario B

A scenario for planting a living fence of a legume shrub to enhance soil fertility by Nfixation and livestock manure might be as follows. Seedlings could be propagated at a government research station after selection from

depleted stands of palatable shrubs. These

plants would then be distributed to village

elders for allocation to heads of families for

planting around the fields and houses in the

immediate vicinity of the village. This would

enhance kitchen garden production and feed

small livestock through the dry season, Excess

fodder could be used on the farm plots as green

manure.

Scenario C

A scenario to develop a high value, native

tree, fruit crop would logically start with a program of selecting the most desirable biotypes

for their fruit quality, tree size and form, and

maturity pattern. Because of the long-term requirements for genetic improvements that

would combine the best qualities in various

selections, a dual development program would

be undertaken. The first would be to vegetatively propagate (by rooted cuttings of a few

plants or by tissue culture for thousands) the

best selection(s). Propagules would normally

be grown in containers until ready for field

transplanting. Sufficient acreage would be

planted to provide experience in intensive

management and production for a local, regional (city), or international cash market. As

experience is gained with product acceptance,

the criteria for the genetic breeding program
62

would be modified, By the time suitable genetic Levels of capital and manpower needed

materials would be available, the market re- could be determined or extrapolated on the

quirements would be sufficiently known to “ basis of experience with a pilot program. Piguide large-scale development plantings and lot demonstration programs are a plausible

improved cultural practices, possibly involv- way to approach development of the most

ing machinery. promising native plants,

One of the most critical attitudinal problems

in developing new crops from native plants is

one of institutional interest in sustainable

and diversified plant development. Traditional

crops, mostly of temperate origin, have received the majority of institutional attention

from government, research, and commercial

organizations. A new and more innovative approach to plant development is required when

referring to native or adapted plant development. The various groups that directly affect

these development efforts include the following:

Cultivators

All efforts should include the local farmers.

The objective would be to seek sufficient involvement on planning, planting, and management to bring local people to thinking that the

project is theirs—not something imposed from

outside by government. The active efforts of

an individual farmer in the Dakotas to bring

sunflower into widespread cultivation is an example of the importance of this element in the

introduction of “new” crops.

LegisIators

Politicians should be encouraged to provide

a favorable and stable policy for product development, to be optimistic but not raise

unrealistic expectations, and finally to be willing to support financial needs of the pilot project. The efforts of the Guayule Commission is

an example of this coordinated effort at policy and implementation.

Financiers

Banks and bankers need to be educated about

the realities and potentials for development of

a new crop. Available capital for second phase

development would be needed if the private

sector is to follow the pilot development. Orientation and involvement would be needed to

assure support when it is needed. Tax incentives and loan guarantees may be useful ways

for financial institutions to foster more rapid

development and diversification of new crops.

International

Policymakers within the international donor

community need to understand the risks as

well as the opportunities for a successful program. Stepwise project implementation is a

desirable approach where needed research and

development experience is gained as the program develops. This approach could be implemented directly by requiring agricultural, forestry, and horticultural development projects

to direct a certain percentage of the program

to native species or varieties. Means for involving host country politicians, research people,

and local farmers are crucial.

WHAT BIOPHYSICAL, CULTURAL, AND SOCIOECONOMIC CONDITIONS

WOULD BE CONDUCIVE TO PROJECT IMPLEMENTATION?

Obviously, the best place for a native plant needed most. However, there are qualifications

development project would be where it is to this simplistic statement.
63

Blophysical Conditions

To be successful, a native species needs a

high degree of adaptation to the climate, soils,

topography, and animal uses, including resistance to parasites. From an ecological standpoint, the approach should be to seek areas that

are ecologically equivalent to the original habitat of the native plant species. This is usually

done by testing plantings in various locations

of similar climate. However, the time period

during which the plantings are under observation may not be sufficient to experience the

range of environmental extremes that is common to the area. Detailed experiments under

greenhouse and controlled environment chambers may help to document the full range of

adaptation possessed by the species.

For a new crop or agricultural product to be

successfully produced, it must not be contrary

to the cultural traditions of the people to grow,

consume, or use. For example, an improved

high protein maize (corn) variety was considered in India, where there were food shortages.

However, the yellow color of the seed coat was

objectional because it resembled a grain product fed to animals (l). A social custom study

would be advisable to determine if any taboos,

customs, or adverse values exist regarding the

potential crop and its required production

practices,

Socioeconomic Conditions

Critical to the development of any new crop

from a native plant is whether the product is

socially acceptable and whether local people

can handle the costs of development. There is

less chance of gaining social acceptance of a

project if the payoff period is far into the future. An early return on the investment may

be needed to maintain interest and commitment to a project. Further, the amount of capital required may exceed the capacity of individuals or banks to handle. Thus, smaller

increments of development and interim returns

to investment may be necessary. An example

with animals should illustrate this point. A

farmer could finance the purchase of several

animals of an improved breed of goat or a pen

of rabbits, but he may not be able to finance

a cow or bull. There is also greater risk in having a high amount of capital tied up in one individual.

The above conditions are most likely to exist in the less developed tropical countries, in

the more rural and remote regions of such a

country, and with people of tribal or nomadic

social organization. The less educated people

would likely be more difficult to reach and less

willing to accept a development program,

Communication tools such as radio, newspapers, and films could be used to help both

in the search for useful plants as well as disseminate information on new uses and opportunities for economic diversification.

WHAT ARE THE MAJOR CONSTRAINTS ON DEVELOPMENT AND

IMPLEMENTATION OF NATIVE PLANT USE?

Development of a native plant species to Scientific Constraints

commercial or economically significant levels

would not be easily accomplished based on A major scientific problem in plant developcurrent observations of jojoba and guayule. ment is lack of technical information. A suffiMany constraints must be overcome to satis- cient amount of general information is needed

factorily develop the potential of a native plant. to identify plants of high potential. Additional
64

species information can help determine feasibility for development and the suitability of

products or uses to meet identified needs. Progress toward development may well depend on

technical data regarding planting, management, harvest, processing, and conservation.

Pilot demonstration programs designed to answer technical problems are essential.

Particularly needed are scientific studies on

ways to establish plants and obtain optimum

productivity under arid, semiarid, and tropical conditions. Problems dealing with microorganisms and plant growth, drought resistance, physiology of stress, and application of

engineering to improve adaptation present

challenges for scientific research on indigenous plants.

Environmental Constraints

Existing land uses may pose one of the

largest constraints to native plant development.

But such commitments of land must be seen

in relation to the long-term values. Where decreasing soil fertility and vegetation degradation are occurring, a shift to a leguminous native plant could bring multiple benefits. For

native plants with industrial potential (i.e.,

guayule), processing may influence air and

water quality. Whether costs can be internalized in the value of the product of plant use

must be determined. In most instances, the

environmental benefits of developing native or

adapted plants will most likely outweigh the

negative impacts. The potential to reduce existing environmental degradation and more

sustained land use must be considered positive

consequences.

Culture Constraints

Native plant development may cause social

change, community growth, and increased

need for services. Such changes need to be addressed, but at this time little information is

available. In general, the cultural impacts from

developing new crops or practices from native

plants should be positive or neutral. In the context of tropical countries, the perceptions of regional, community, tribal, or family groups

must be considered. Resistance to change may

be manifested by refusal to cooperate or allow

project development. Involvement of local

leaders and decisionmakers is a necessity.

Economic Constraints

The major economic constraint to development is probably the lack of seed money, venture capital, or government support to conduct

pilot-scale programs. From the pilot program,

cost data can be extrapolated for planting, production, transportation, and marketing. From

these preliminary data, decisions can be made

toward major financing and long- or short-term

commitment of funds, either by the private sector or through government grants and loans.

Because of the generally speculative nature of

developing high potential native plants to meet

needs that are not clear, private sector funding may have to be government subsidized.

Political Constraints

A major political constraint is the instability and short longevity of many political leaders

in less developed countries. Although a new

crop development program may be highly favored by one political leadership, the prospect

of change must be considered. Because agricultural development is highly important and

not as politically sensitive as other sectors of

a country, it should be possible to work within

political constraints as long as the project does

not appear to run counter to current political

and social philosophy.

For example, pilot plantings of palatable fodder shrubs in Syrian rangelands by FAO and

the Syrian Ministry of Agriculture were described as an extension of cooperative marketing and fattening units to increase meat production and increase the stability of the

livestock industry (2). In reality, the system had

many free enterprise profitmaking opportunities to increase the incentive of individuals to

participate in the scheme. Yet political leaders

touted the success of this cooperative project

and declared it to be in harmony with the so-
cialistic philosophy mandated by the govern- provide benefits equitably. Additionally,

ment. New crops must not appear to compete adapted crops that could represent a higher

with existing production systems, but should cash return than traditional crops should recomplement them. Constituents must be con- ceive special attention from the international

vinced that the proposed developments will donor community.

HOW WOULD IMPLEMENTATION OF A NATIVE PLANT TECHNOLOGY

AFFECT THE NEED

Because of the varied types of native plants,

no specific capital requirements can be determined for all native plants. There is no doubt

that a native plant development program would

require significant inputs of technology and

capital. However, those plants that produce a

crop would require greater inputs than those

used for reforestation, improving soil fertility,

or increasing rangeland forage production.

Careful analysis of the infrastructure of a region or county may give an indication of available processing capacity. For example, vegeFOR CAPITAL?

table oil extraction facilities are available in the

groundnut basin of Senegal and might be available in the off-season to extract hydrocarbon

latex from giant milkweed plants that grow in

waste places and margins of fields. A small

pilot program with these native plants could

provide some of the data necessary to determine the feasibility of proceeding to larger

phases of development. In a like manner, any

proposed new crop should be analyzed for capital inputs and available facilities for production processing and transport.

WHAT WOULD BE THE IMPACT OF WIDE-SCALE IMPLEMENTATION OF

NATIVE PLANT USE ON SOCIOECONOMIC STRUCTURE?

It would be false to assume that only a large

commercial-type farm or a family-sized farm

would be suitable for native plant development.

Much depends on the nature of the plant species and the magnitude of development necessary. From table 1, it can be seen that some

crops such as cocoyam and buffalo gourd

could easily be grown on small plots and collected for commercial markets. In contrast, industrial feedstocks, biomass, and high volume

crops such as guayule, ramie, leucaena, and

guar would better be grown in large fields and

be harvested and treated mechanically.

Small field operations would cause little

change on socioeconomic structure except to

provide an additional income stream to communities, Large operations may disrupt communities by increasing their population or requiring the establishment of new communities.

An excellent example in the United States is

the 110,000 acre Navajo Irrigation project near

Farmington, New Mexico. This large commercial farm operation has left little opportunity

for community development of a traditional native culture, nor has it provided an opportunity for family farm or cooperative group farm

development. The project has addressed only

the large-scale production-economic aspects of

development. Socioeconomic problems remain

unsolved as illustrated by the attempts being

made to resettle Navajo workers in a modern

subdivision quite foreign to existing patterns

of community settlement.

In summary, the various options available in

native plants of high potential for development

could enhance existing social and economic

patterns or could disrupt them with large developments depending on the suitability of the

land, the adaptability of native plants to given

locations, and the institutional insensitivity that

might prevail in their development.
66

References

1. Cummings, Ralph, personal communication

from the Rockefeller Foundation Project Director in India, 1972.

2, Draz, Omar, personal communication while on

a field trip to Waddi A1-Azib Experiment Station in Syria, 1978.

3, Epstein, E. et al., “Saline Caltese of Crops: A

Genetic Approach, ” Science 210:399-404, 1980.

4, Evanari, Michael; Shanan, Leslie; and Todmor,

5

Naphtali, The Negev, the Challenge of a Desert

(Cambridge, MA: Harvard University Press,

1971), 345 p.

Felker, Peter, “Mesquite, An All-Purpose Leguminous Arid Land Tree, ” pp. 89-132. In:

Ritchie, Gary A. (cd.) New Agricultural Crops,

AAAS Selected Symposium 38 (Boulder, CO:

Westview Press, 1979)0

6. Frasier, G. W., “Proceedings of the Water Harvesting Symposium, ” U.S. Department of Agriculture, Agricultural Research Service, Western

Region (ARS) W-22, 1975, 329 pp.

7. Gliessman, S., “The Ecological Basis for the Application of Traditional Agricultural Technology in the Management of Tropica l

8.

9.

10.

110

12.

Agroecosystems,” Agroecosystem (in press),

1980.

Goodin, Joe R., and David Worthington (eds.),

“Arid Land Plant Resources,” Proc. of the International Arid Lands Conference on Plant Resources, Texas Tech. University, Lubbock, TX,

19790

Haws, B. Austin (cd.), “Economic Impacts of

Labops hesparius on the Production of High

Quality Range Grasses,” final report of Utah

Agric. Exp. Stn. to Four Corners Regional Commission, Utah State University, Logan, UT,

1978, 269 pp.

Hogan, Le Moyne, “Jojoba, A New Crop for

Arid Regions,” pp. 177-205. In: Ritchie, Gary

A. (cd.), New Agricultural Crops, AAAS

Selected Symposium Series 38 (Boulder, CO:

Westview Press, 1979).

McKell, C. M., “Shrubs-A Neglected Resource

of Arid Lands, ” Science 187:803-809, 1974.

National Academy of Sciences, “Preliminary

Report Assessment of Environmental Degradation and Agricultural Productivity in the

13.

14,

15.

16.

17s

18,

19,

20,

21,

22,

23

24

Senegalese Groundnut Basin, ” NAS report to

AID, Senegal, 1980.

National Academy of Sciences, Tropical Legumes: Resource for the Future, report of ad

hoc panel of the advisory committee on technology innovation, 1979.

National Academy of Sciences, Guayule: An

Alternate Source of Natural Rubber, report of

ad hoc panel of the advisory committee on technology innovation, 1977.

National Academy of Sciences, Leucaena,

Promising Forage and Tree Crop for the Tropics, report of ad hoc panel of the advisory committee on technology innovation, 1977.

National Academy of Sciences, Products From

Jojoba: A Promising New Crop for Arid Lands,

report of ad hoc panel of the advisory committee on technology innovation, 1975.

National Academy of Sciences, The Winged

Bean: A High Protein Crop for the Tropics, report of ad hoc panel of the advisory committee

for technology innovation, 197.5.

National Academy of Sciences, UnderexpZoited

Tropical Plants With Promising Economic Value, report of ad hoc panel of the advisory committee on technology innovation, 1975.

Revelle, Roger, “Flying Beans, Botanical

whales, Jack’s Beanstalk and Other Marvels, ”

National Academy of Sciences, Board on

Science and Technology for International Development, 1978.

Ritchie, Gary A,, New Agricultural Crops,

AAAS selected symposium series 38 (Boulder,

CO: Westview Press, 1979), 259 p.

Sherman, P. M., “Tropical Forage Legumes, ”

Food and Agricultural Organization of the

United Nations, Rome, Italy, 1977.

Soil and Land Use Technology Inc., “Feasibility of Introducing Food Crops Better Adapted

to Environmental Stress, ” National Science

Foundation Report NSF/RA 780289, 1978.

Thalen, D. C. P., EcoZogy and Utilization of Desert Shrub Rangelands in Iraq (Dr. W. Junk Publishers, The Hague Netherlands, 1979), 448 p.

Weber, Fred, and Dulansey, M,, “Midpoint

Evaluation, Chad Reforestation Project, ” Prepared for CARE by Consultants in Development, New York, NY 10014, 1978.
Chapter V

Multiple Cropping Systems:

A Basis for Developing an

Alternative Agriculture

Dr. Stephen R. Gliessman

Environmental Studies

University of California
Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Concepts and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

The Basis of Multiple Cropping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Yield Advantages of Crop Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

General Resource Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Specific Resource Use, Conservation, and Management . . . . . . . . . . . . . . . . . . . . . 75

Agroforestry: A Multiple Cropping System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Socioeconomic Implications of Multiple Cropping Systems:

Perspectives for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

List of Tables

Table No. Page

l. Definitions of the Principle Multiple Cropping Patterns . . . . . . . . . . . . . . . . . . . . . . 71

2. Related Terminology Used in Multiple Cropping Systems . . . . . . . . . . . . . . . . . . . . 71

3. Biological and Physical Factors: The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or Monoculture Systems. . . . . . . . 72

4. Social and Economic Factors: The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or Monoculture Systems . . . . . . . . 73

S. Yields of Corn, Beans, and Squash Planted in Polyculture as Compared to Low

and High Densities of Each Crop in Monoculture . . . . . . . . . . . . . . . . . . . . . . . . . . 74

6. Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake of

Corn and Pigeon Peas in St. Augustine, Trinidad, Expressed as Relative Yield

Totals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7. Biomass Distribution of Dry Matter in a Corn/Bean Polyculture as Compared to

a Corn Monoculture, in Tacotalpa, Tabasco, Mexico . . . . . . . . . . . . . . . . . . . . . . . . . 76

8. Classification and Examples of Agroforestry Technologies. . . . . . . . . . . . . . . . . . . . 80

Figure

Figure No. Page

l. Distribution of the Relative Yield Totals of Mixtures Based on 572 Published

Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Chapter V

Multiple Cropping Systems:

A Basis for Developing an

Alternative Agriculture

This paper presents a general discussion of

the concept of multiple cropping, including a

description of the different types of systems,

and the advantages and disadvantages of their

widespread use, both biological and socioeconomical. These systems are designed to intensify agricultural production both in terms

of yields per unit area and through the more

efficient use of space and time.

Examples of yield increases with multiple

cropping systems are expressed in terms of

Relative Yield Totals (RYT) or Land Equivalent

Use (LER) where the production per unit area

with the multiple crops is greater than the sum

of equivalent areas planted to monoculture.

This increase in production is explained by

higher overall efficiency of resource use.

Specific examples of the effects of multiple

cropping systems on resource use, conservation, and management are discussed, Variables

considered include microclimate, light, soil,

water, pests, diseases, weeds, crop interactions, space, and time. The special case of

agroforestry, which combines trees with crops

and grasses, is discussed.

In conclusion, the socioeconomic implications, both advantageous and disadvantageous,

are discussed. Also, the great potential for

multiple cropping systems in agriculture in the

United States is presented. Research needs to

be directed to test these alternatives.

Multiple cropping is not a new form of agricultural technology, but instead is an ancient

means of intensive farming. Multiple cropping

has been practiced in many parts of the world

as a way to maximize land productivity in a

specific area in a growing season. Generally,

the practice of planting two or more crops on

the same field is more common in tropical regions where more rainfall, higher temperatures, and longer growing seasons are more

favorable for continual crop production. As

population has increased, increasing the need

for agricultural production, the use of multicropping systems is more prevalent. Though

the history of multiple cropping is old, the concept has received very little attention from agricultural scientists, and what limited interest exists has come about very recently.

Why was this interest increased so dramatically in such a short time? Food shortages in

many parts of the world, as well as the threat

of insufficient supplies in the near future, continues to stimulate more intensive agricultural

investigation in a search for more productive

alternatives. As a consequence, it appears that

69
70

we are about to embark on a new phase of agricultural research. Exactly what form it will take

is still not known, but the reasons for this new

approach are rapidly becoming apparent.

First, we have begun to observe a leveling off

in yield increases brought about by the types

of genetic manipulation that gave us such rapid

and impressive yield increases during the

“Green Revolution.” It is as if we have reached

a “yield plateau” with the current lines of re

-

search and crop selections. Large-scale use of

single varieties (e.g., some of the International

Rice Research Institute (IRRI) varieties of rice),

with broad adaptability, produced major breakthroughs in yields. But it appears that these varieties have almost reached their maximum

yield potentials. In many areas with specific

soil and climatic conditions, they have not performed as well as hoped, especially on land

more difficult to mechanize or irrigate. Thus

we must begin to look for varieties with more

specific adaptability and selected for specific

environments, or else consider alternative

cropping systems.

best agricultural lands–areas with good soil

and easy water control. Future increases in

production, therefore, will demand a new and

innovative way of managing these highly productive lands, as well as looking for methods

to make marginal lands increasingly productive. Only 20 percent of Asia rice land, for example, is irrigated, and the new high yielding

rice varieties (which also require high levels of

fertilizers, water use, and pest control) have not

penetrated much beyond this boundary (16).

The third factor is the oil crisis. Oil prices

continue to soar, and with them, the cost offertilizers, pesticides, and fuel needed to build and

run farm equipment and move irrigation water.

Costs continue to mount for those inputs most

responsible for achieving the dramatic yield increases of the “Green Revolution. ” We are

faced with the necessity of having to consider

other alternatives that might allow us to substitute innovative biological or agronomic practices and varieties for these high cost inputs.

Multiple cropping offers one of the most important and promising of these alternatives.

Second, most of the dramatic yield increases

during the past few decades have been on the

CONCEPTS AND DEFINITIONS

Multiple cropping systems use management

practices where the total crop production from

a single piece of land is achieved by growing

single crops in close sequence, growing several crops simultaneously, or combining single

and mixed crops in some sequence. The most

important aspect of multiple cropping is the

intensification of crop production into additional dimensions. Multiple cropping includes

the dimensions of time and space; for example, when two crops share the same space at

the same time.

A classification of types of multiple cropping

systems is presented in table 1. Note that

special emphasis is placed on the distinction

between intercropping, where two or more

crops are grown at the same time, and sequential cropping, where two or more crops are

grown on the same piece of land, but one following the other.

Some additional terms used in multiple cropping are presented in table 2. Agroforestry, as

a particular type of intercropping system, will

be discussed in some detail. Also, “mixed cropping, “ “polyculture,” and “multiple cropping”

will be used interchangeably in this review. By

combining different aspects of simultaneous

and sequential cropping systems, it is possible

to visualize a truly complex pattern of different

multiple cropping systems. This classification

will be used throughout the following discussion, based on a symposium sponsored by the

American Society of Agronomy, in support of

the need to standardize terminology (34).
—

71

Table 1 .—Definitions of the Principal Multiple

Cropping Patterns

● Multiple Cropping: The intensification of cropping in time

and space dimensions. Growing two or more crops on the

same field in a year.

c Intercropping: Growing two or more crops simultaneously

on the same field per year. Crop intensification is in both

time and space dimensions. There is intercrop competition during all or part of crop growth. Farmers manage more

than one crop at a time in the same field.

—Mixed intercropping: Growing two or more crops simultaneously with no distinct row arrangement.

—Row intercropping: growing two or more crops

simultaneously with one or more crops planted in rows.

—Strip intercropping: Growing two or more crops simultaneously in different strips wide enough to permit independent cultivation but narrow enough for the crops

to interact agronomically.

—Relay intercropping: Growing two or more crops simultaneously during part of each one’s life cycle. A second

crop is planted after the first crop has reached its

reproductive stage of growth, but before it is ready for

harvest.

● Sequential Cropping: Growing two or more crops i n sequence on the same field per year. The succeeding crop

is planted after the preceding one has been harvested. Crop

intensification is only in the time dimension. There is no

intercrop competition. Farmers manage only one crop at

a time.

—Double cropping: Growing two crops a year in sequence.

— Triple cropping: Growing three crops a year in sequence.

—Quadruple cropping: Growing four crops a year in sequence.

—Ratoon cropping: Cultivating crop regrowth after harvest,

although not necessarily for grain.

SOURCE Andrews and Kassam, 1976 (5)

Table 2.— Related Terminology Used in Multiple

Cropping Systems

Single Stands: The growing of one crop variety alone in pure

stands at normal density. Synonymous with “solid planting, “ “sole cropping. ” Opposite of ‘(multiple cropping. ”

Monoculture: The repetitive growing of the same crop on the

same land.

Rotation: The repetitive growing of two or more sole crops

or multiple cropping combinations on the same field.

Cropping Pattern: The yearly sequence and spatial arrangement of crops, or of crops and fallow on a given area.

Cropping System: The cropping patterns used on a farm and

their interactions with farm resources, other farm enterprises, and available technology that determine their

makeup.

Mixed Farming: Cropping systems that involve the raising

of crops and animals.

Cropping Index: The number of crops grown per annum on

a given area of land multiplied by 100.

Relative Yield Total (RYT): The sum of the intercropped yields

divided by yields of sole crops. The same concept as land

equivalent ratios. “Yield” can be measured as dry matter

production, grain yield, nutrient uptake, energy, or protein

production, as well as by market value of the crops.

Land Equivalent Ratios (LER): The ratio of the area needed

under sole cropping to the one under intercropping to give

equal amounts of yield at the same management level.

The LER is the sum of the fractions of the yields of the

intercrops relative to their sole-crop yields. It is equivalent

to RYT, expressed in commercial yields.

Income Equivalent Ratio (IER): The ratio of the area needed

under sole cropping to produce the same gross income

as is obtained from 1 ha of intercropping at the same

management level. The IER is the conversion of the LER

into economic terms.

SOURCE Sanchez, 1976 (39)

THE BASIS OF MULTIPLE CROPPING

Yield Advantages of Crop Mixtures

In areas of the world where multiple cropping is a common aspect of agroecosystem

management, productivity generally is more

stable and constant in the long term (24,45).

Farmers often are able to achieve a combined

production per unit area greater with a crop

mixture than with an equal area divided among

separate crop units. In such cases the Relative

Yield Total (RYT) is greater than 1.0. It may

be that each crop in the mixture yields slightly

less than the monoculture, but the combined

yield of the mixture on less total land area is

the important aspect.

In one study (43), the results of 572 comparisons of crop mixtures demonstrated that

the majority (66 percent) had RYTs close to 1.0,

indicating no distinct advantage to the mixture

(fig. 1). On the other hand, 20 percent of the

mixtures had RYTs greater than 1.0, ranging

up to 1.7, indicating advantages to the mixtures. Only 14 percent had less than 1.0, indicating distinct disadvantages. It must be

remembered that most of the cases studied
72

Figure 1 .—Distribution of the Relative Yield Totals of

Mixtures Based on 572 Published Experiments

0.5 0.7 0.9 1.1 1.3 1.5 1.7

Relative yield totals (RYT)

SOURCE Trenbath, 1974(43)

were experimental planting and not actual

multiple cropping systems. Farmers would

tend to choose the systems that yield more, as

we have observed in traditional agroecosystems in the lowland tropical areas of southeastern Mexico (24,25).

The fact that advantageous mixtures do exist demonstrate the need for detailed research

to take proper advantage of such systems. But

for such systems to be considered as actual

alternatives we need to understand thoroughly

the biological and agronomic basis responsible for the observed response, as well as the

advantages and disadvantages to their use.

Before beginning a discussion of each aspect,

a basic outline of such characteristics is presented, separated broadly into biological and

physical aspects (table 3) and socioeconomic

aspects (table 4). In many cases it is understood

that there may be overlap between the two

classifications, yet it is hoped that in the course

of the following discussion that such aspects

will be clarified.

Table 3.—Biological and Physical Factors:

The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or

Monoculture Systems (priority is not established)

Advantages -

1. It is possible to obtain a better use of vertical space and

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

time”, imitating natural ecological patterns in regards to

structure of the system, and permitting efficient capture

of solar energy and nutrients.

Greater amounts of biomass (organic matter) can be

returned to the system, sometimes even of better quality.

There exists a more efficient circulation of nutrients, including their “pumping” from the deeper soil profiles

when deeper rooted shrubs or trees are included.

The damaging effects of wind sometimes can be

reduced.

Systems can be designed that are appropriate for (but

not restricted to) marginal areas because multiple cropping systems can better take advantage of variable soil,

topography, and steeper slopes.

Multiple cropping systems are less subject to variability in climatic conditions, especially extremes of rainfall,

temperature, or wind.

Reduction of water evaporation from the soil surface.

Increased microbial activity in the soil.

Avoidance or reduction of surface erosion.

Fertilizer use can be more efficient because of the more

diverse and deeper root structure in the system.

Improved soil structure, avoiding the formation of a “hard

pan” and promoting better aeration and filtration.

Legumes (as well as a few other plant families) are able

to fix and incorporate nitrogen into the system.

Heavier mulch cover aids in weed control.

Better opportunities for biological control of insects and

diseases.

Crop mixtures better permit the functioning of complex

mutualisms and beneficial interactions between organisms.

Better use of time, with more crops per unit time in the

same area.

Disadvantages

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Competition between plants for light.

Competition between plants for soil nutrients.

Competition between plants for water.

Possibility for allelopathic influences between different

crop plants due to plant-produced toxins.

Harvesting of one crop component may cause damage

to the others.

It is very difficult to incorporate a fallow period into multiple cropping systems, especially when long lived tree

species are included.

It is sometimes impossible, and many times very difficult,

to mechanize multiple crop systems.

Increased evapotranspiration loss of water from the soil,

caused by greater root volume and larger leaf surface

area.

Possible over-extraction of nutrients, followed by their

subsequent loss from the system with the increased exportation of agricultural or forest products.

Leaf, branch, fruit, or water-drop fall from taller elements

in a mixed crop system can damage shorter ones.

Higher relative humidity in the air can favor disease outbreak, especially of fungi.

Possible proliferation of harmful animals (especially

rodents and insects).
73

Table 4.—Social and Economic Factors:

The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or

Monoculture Systems (priority is not established)

Advantage s

1.

2.

3.

4.

5.

6.

7.

8.

Dependence on one crop is avoided so that variabiIity I n

prices, market, climate, and pests and diseases do not

have such drastic effects on local economics,

Less need to import energy, pay for fertilizers, pay for externally produced materials, or depend on machinery,

WiIdlife is favored, and with rational use it can be an important source of protein.

Greater flexibility of the distribution of labor over the year

Recovery of investments can occur in much less time,

especially where trees are combined with short term

agricultural crops,

Harvest is spread over a longer period of time,

In areas and times of high unemployment, multiple cropping systems can use much more labor.

Farmers can produce a large variety of useful products,

depending on the type and complexity of the multiple

cropping systems, such as firewood, construction materials, flowers, honey, crops for home consumption, thus

lowering the outflow of funds,

9. Certain multiple cropping systems permit a gradual

change from destructive farming practices to more appropriate technologies, without a drop in productivity,

10, Multiple cropping can promote a return to the land, and

its maintenance.

11. In systems which include trees and/or animals, such components can constitute a type of “savings” for the future,

while short term crops satisfy immediate needs.

12. Because of their diverse nature, multiple cropping systems promote interdisciplinary activities, stimulate interchange and group activities, and lead to social cohesion

in the long term,

Disadvantages

1. The systems are more complex and less understood

agronomicalIy and biologically. Statistical designs for experimental analysis are much more complex.

2. Yields sometimes are lower, providing only subsistence

level production.

3. In many systems, multiple cropping is not considered to

be economically efficient due to the complexity of activities necessary.

4. These systems require more hand labor, which can be

considered a disadvantage in some circumstances.

5. Some mixed crop systems do not offer sufficient reward

to lower income farmers to raise their standard of living.

6. For producers with limited economic resources, it may

take longer to recover the entire initial investment.

7. Farmers initiating multiple cropping systems may encounter opposition from the prevalent social, economic,

and political system.

8. There is a shortage of trained personnel (technical and

scientific) capable of installing and managing multiple

cropping systems.

9. There is a general lack of knowledge or understanding

of multiple cropping by “decision makers, ” affecting

especially funding for research to make such systems

viable alternatives.

General Resource Use

The most commonly accepted reason explaining why it is possible to obtain better

yields with crop mixtures is that the component crops differ in their growth requirements.

Such combinations of components can be said

to be “complementary” (46).

A mixture makes better overall use of available resources. Negative influences (e. g., competition for light, water, or nutrients) between

the component members of a successful multiple cropping system would be reduced considerably. To maximize the advantages of such

a system, it is important to maximize the degree to which one component complements

another. With a greater range of requirements

between different elements of the mixture,

theoretically the greatest advantages would be

achieved.

One way to achieve complementarily is by

varying the crop components temporally—

using sequential planting to achieve a multiple cropping system that ensures that antagonistic interactions between the components

are avoided, Following a crop with another that

has different growth requirements would

enable the maximum use of resources. This

concept has been used for a long time and is

the basic rationale behind crop rotations.

The most advantageous use of soil, for example, would be to follow one crop with

another that requires different soil nutrients.

A subsequent crop would thus be able to absorb fertilizer residues left over from the previous crop, thus reducing the need for fertilizer

applications. For the Eastern United States, it

has been concluded (31) that double cropping

systems such as soybeans after wheat or barley, or the production of silage crops after grain

corn or sorghum, can function well,

Depending on the length of the growing

season, numerous sequential plantings can take

place during a single year. Such systems require special management, with timely harvest,

use of proper varieties, alteration of the stand-
74

ard planting distance, special selection of herbicides so as to not create antagonisms or residual effects, and also the possibility of using

no-tillage planting with certain of the row

crops.

Another form of complementing different

crop components is through an intensification

of the sequential cropping system known as

relay planting. The same avoidance of overlapping plant growth requirements is gained, as

well as the avoidance of direct plant interference, by planting a second crop after the

first one has completed the major part of its

development, but before harvest. Relatively little research on relay cropping has been done

in the United States, and most has demonstrated little if any yield advantage (31). On the

other hand, in Mexico and Latin America innumerable examples of relay planting with definite yield advantages have been reported,

especially for corn and beans (35,39).

Again, the important, and as yet little studied, aspect of relay planting success depends

on the correct combinations of timing and varieties so as to avoid shading, nutrient competition, or inhibition brought about by toxicity

produced by the decomposition of a previous

crop residue.

Finally, maximum complementarily can be

achieved by growing two or more crops simultaneously, either in rows, strips, or mixed, but

taking advantage of the spatial arrangement of

the different crops and knowledge of their individual growth requirements. Again, most examples of such systems come from outside the

United States. One particularly well-documented example is a traditional corn, bean, and

squash system in Tabasco, Mexico (4].

Corn is planted at a density of 50,000 plants/

ha, climbing beans in the same hole at a density of 40,000 plants/ha, and the squash intermixed among the rows of corn and beans at

a density of 3,330 plants/ha. All are planted at

the same time in this case. Beans begin to

mature first, using the corn stalks for support;

the corn matures second; the squash is the last

to mature. Aerial space is divided such that

corn occupies the upper canopy, beans the

middle, and squash covers the ground. Better

weed control is achieved, and insect pests are

largely controlled by natural enemies. Corn

yield was significantly higher for the polyculture as compared to different densities of

monoculture, but beans and squash suffered

a distinct yield reduction (table 5). Interestingly, the LER (Land Equipment Ratio) value

of 1.73 tells us that the sum of the yields in the

mixture can only be equaled in monoculture

by planting 1.73 times the area divided proportionally among the three sole crops,

Table 5.–Yields of Corn, Beans, and Squash (kg/ha)

Planted in Polyculture as Compared to Low and High

Densities of Each Crop in Monoculture

Total grain or fruit yields

Crop Monoculture Polyculture

Corn:

Density ... , 33,300 40,000 66,600 100,000 50,000

Yield . . . . . . 990 1,150 1,230 1,170 1,720

Beans:

Density . . . . 56,800 64,000 100,000 133,200 40,000

Yield . . . . . . 425 740 610 695 110

Squash:

Density . . . . 1,200 1,875 7,500 30,000 3,330

Yield . . . . . . 15 250 430 225 80

Crop Total biomass dry weight

Corn . . . . . . . . 2,822.

9 3,119.

4 4,477,5 4,870.9 5,927.2

Beans . . . . . . . 852.9 895.1 842.6 1,390.4 253.1

Squash . . . . . . 240.9 940.9 1,254.0 801.9 478.3

Total Polyculture Biomass 6,658.6

LER (Land Equipment Ratio) = Sum of yields of each polyculture

Sum of highest yield each

monoculture

LER = 1,720 + 110 + 80

1,230 740 43 0

LER = 1.73

SOURCE Amador, 1980 (13)

The advantage of producing a greater yield

altogether on less land is obvious. The much

higher total yield of biomass in the mixture is

also important because much of this organic

matter is returned to the soil, bringing important consequences in soil fertility, humidity

conservation, microbial activity, etc., all related

to the success of the following crops, Currently,
75

studies are being conducted to determine if the

higher yields are the result of more efficient

resource use, or if in fact some mutually beneficial effect between crop components is taking place, for example, the bean producing nitrogen that the corn can absorb (12). This

example demonstrates the enormous potential

that multiple cropping systems offer for the

future.

Specific Resource Use, Conservation,

and Management

An intensified land-use system of agriculture

will certainly put greater pressures on the available natural resources of our crop and rangelands. Considerable discussion has focused on

the harmful or beneficial aspects of this intensification, and a review of some of the more

important aspects can aid greatly in understanding this problem:

1) Microclimate and Light: In any agroecosystem, a very important aspect of productivity

is related to the amount of light converted

directly to carbohydrate, hence to vegetative

material, through photosynthesis. Each cropping system has a photosynthetic potential,

based on its capacity of conversion (2). Monoculture, especially of annuals, generally have

a lower potential because either the plant cover

is not complete, or the soil is occupied only

during one short season, leaving the surface

bare of photosynthetic capacity until the next

crop is planted. Light is not like other resources, where a reservoir exists and the plants

tap it as the need arises, Rather, it has to be

used when it is available, thus leaf area becomes a very important factor. A multi-layered

polyculture would be able to capture much

more light energy, raising efficiency, and potentially, production.

Apart from the quantity of light absorbed, its

quality is also important. Light that has passed

through a leaf layer is altered as certain light

waves are absorbed and others penetrate.

Plants in the lower layers of the canopy need

to be adapted to this alteration—an aspect well

studied only in natural vegetation (7). For cropping systems, light has been studied in detail

only for monoculture systems (2) from the point

of view of increasing effective photosynthetic

leaf area for the single crop, By manipulating

species with different light requirements,

greater photosynthetic potential can be achieved.

This is made easier by using dominant species

in the polyculture that do not develop a closed

canopy, allowing considerable penetration to

the next levels. The most shade-tolerant plants

should be in the lowest levels. In such a system, the soil surface is in essence completely

covered by plants. This manipulation of plant

architecture has been studied in detail ecologically (28) and has considerable application in

multiple cropping systems.

Other aspects of the crop microclimate are

also affected. Crops in the lower layers would

be subject to less water stress, but care must

be taken that root system competition for water

does not become a problem. Water loss by soil

surface evaporation could be reduced, but transpiration from leaf surfaces might be increased

in the crop mixture. Soil temperatures would

be lowered, an advantage especially in warmer

and drier environments, aiding in the conservation and buildup of organic matter in the soil.

Protection from wind would be provided for

the lower canopy species. Care would need to

be taken that the increased humidity in the

lower canopies does not promote higher incidence of certain diseases, especially fungi,

either of the roots or foilage.

2. Soil-Plant Relations in Multiple Cropping

Systems: Any time that we try to combine two

or more crops simultaneously in one area,

there exists the possibility for complex interactions between the plants and their soil environment (39). When total complementarily is

achieved, the roots of the component species

occupy different soil horizons, reducing considerably the potential competition between

species and increasing the efficiency of total

nutrient uptake. In combinations of deeprooted with shallow-rooted species, especially

when trees are planted with grasses or annual

crops, the trees are capable of absorbing uncaptured nutrients as they are leached into the
76

soil. Then, through their transport to foliage,

they can be deposited on the soil surface again

as the leaves drop (47).

Intercropping systems have been shown to

extract more nutrients from the soil than do

single crop plantings per unit area of land. In

a very complete study with corn and pigeon

peas in Trinidad (19) (table 6), various parameters of crop response were measured. The

highest single crop yields of grain were obtained in monoculture, but by adding yields

of two crops planted mixed or in intercropped

rows, Relative Yield Totals (RYT) were higher.

Total dry matter production was higher in the

mixtures as well. The most interesting aspect

is the uptake of nutrients (N, P, K, Ca, and Mg).

The total uptake is based on the sum of the two

crops together, and in all cases the total nutrient content of the dry matter production was

higher for the mixtures, demonstrating the

greater extractive capacity of the multiple cropping system. Apparently, for corn and pigeon

peas, row intercropping gave the best results,

demonstrating that at times two crops together

can negatively influence each other, but the

total yield makes up for the reduction. Each

crop mixture needs to be examined in detail.

The greater uptake of nutrients in crop mixtures could deplete the soil more rapidly. But

an aspect of multiple cropping that needs to

be considered is what proportion of this nutrient content is removed from the system with

the harvest, as compared to the part reincorporated back into the system. In table 7, a

corn/bean polyculture is compared to a corn

monoculture. Total biomass production, as

well as yield removed from the system, is considerably higher from the mixture (10,24 tons/

ha versus 6.68 tons/ha total biomass). The percentage of this total that leaves the system is

slightly lower for the mixture (61 percent

versus 66 percent), but the actual amount of

organic matter returned to the soil in the polyculture (3.98 tons/ha) as compared to the sole

Table 6.—Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake of Corn (C) and Pigeon Peas

(PP) in St. Augustine, Trinidad, Expressed as Relative Yield Totals (RYT)

Sole crop Mixed intercrop Row intercrop

Parameter c PP c PP RYT C PP RYT

Grain yields (tons/ha) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 1.9 2.0 1.7 1.54 2.6 1.8 1,78

Total Dry Matter (tons/ha) . . . . . . . . . . . . . . . . . . . . . . . . 6.4 5.1 4.2 3.8 1.40 5.0 4.9 1.74

N uptake (kg/ha) . . . . . . . . . . . . . . . . . . . . . ...........-66.0 119.0 48.0 100.0 1.56 54.0 127.0 1.88

P uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.0 6.0 9.0 5.0 1.52 11.0 7.0 2.01

K uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . ............51.0 37.0 37.0 32.0 1.59 46.0 33.0 1.79

Ca uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . ...........10.0 22.0 10.0 15.0 1.68 9.0 19.0 1.76

Mg uptake (kg/ha) . . . . . . . . . . . . . . . . . . . . . ...........12.0 14.0 9.0 8.0 1.32 9.0 12.0 1.61

SOURCE’ Adapted from Data, 1974, (19), cited by Sanchez, 1976, (39)

Table 7.—Biomass Distribution (in tons/ha) of Dry Matter in a Corn/Bean Polyculture

as Compared to a Corn Monoculture, in Tacotalpa, Tabasco, Mexico

Leaves (B) (B) (A)-(B)

and (A) Removed (A) Total

Crop Roots Crown stem Grai n

a Tota l matter percent reincorporated

Corn 0.49 0.60 2.29 4.76b

plus 10.24 6.26 61 % 3.98

Beans 0.15 0.00 0.45 1.50b

Corn

Alone 0.34 0.41 1.57 4.36b

6.68 4.36 65 % 2.32

aWeight of grain of corn is unhusked, including cob and husk, in the manner that the harvest iS removed from the field in

this region.

bIndlcates the removed portion of the biomass.

SOURCE: Adapted from Gliessman and Amador, 1979 (24)
77

crop (2.32 tons/ha) demonstrates that although

more material is produced by the intercrop system, a greater amount returns to this system.

This possibly offsets any increase in extraction

of soil nutrients and permits the long-term

management of the system.

Another way to increase the return of nutrients to the system is to plant “nurse plants. ”

These plants do not contribute directly to the

biomass harvested and removed from the system, but their capacity to capture nutrients and

continually recycle them in the soil would be

an advantage. Local farmers in Tabasco, Mexico, use this concept in the management of

weeds (14), leaving those that don’t interfere

with the crops and removing those that are

harmful. This practice also provides a constant

cover over the soil and helps maintain better

soil structure, conserves water, fosters more

microbial activity, and over the long run, requires fewer chemical fertilizers. By including

plants that “trap” nutrients, such as legumes,

such benefits can be improved even more. The

widespread use of legume trees for shade in

coffee and cocoa plantations is a classic example (27).

3. Water Use in Multiple Cropping Systems:

Any discussion of water use should consider

rooting patterns. In multiple cropping systems,

especially with several crops with differently

arrayed root systems, a greater volume of the

soil typically is occupied and thus water use

efficiency is higher. This is useful, on the one

hand, in areas where water supplies are limited. It also helps make more complete use of

costly irrigation water. It has been proposed

that cover crops in orchards stimulate deeper

rooting by the trees (10). Different peak periods of water use in the crop mixtures would

avoid competition and increase overall water

use efficiency (8). A crop such as corn that uses

relatively little water in its early stages of development could be interplanted with an early

maturing crop that could take advantage of the

unused moisture (30).

In areas where water is severely limited, care

must be taken not to plant crops with overlapping water requirements because in dry

years one member of the mixture could be outcompeted by the other (36). Combining two

crops with slightly overlapping water needs,

on the other hand, could be used to an advantage in areas with widely fluctuating rainfall

regimes. In a dry year, one component would

be favored, and in a wet year the other, guaranteeing profitable harvests of at least one crop

every year. Studies on water availability in each

region, coupled with studies of water needs of

each component crop of multiple cropping systems, are critical for proper management.

The important effects of multiple cropping

on the conservation of water and soil are primarily achieved through the maintenance of

a more complete vegetative cover over the soil

(26,40). It is important to remember that apart

from improving cover while the crop is growing, multiple cropping systems aim toward

maintaining this cover between harvests. This

is achieved by reducing the time between

harvest and replanting in sequential systems,

planting a new crop into another in relay cropping, and continually interplanting in an intercropped system. The use of trees, either as

windbreaks, for soil stabilization on eroded

hillsides, or in areas subject to desertification,

can be enhanced greatly by combining them

with crops or pasture grasses (see discussion

on Agroforestry).

In summary, although it appears that multiple cropping systems use more water, their

ability to obtain water not available to monoculture, use the water more efficiently, and

contribute significantly to soil conservation,

demonstrate a further potential for their more

widespread use.

4. Pest, Disease, and Weed Relations: As discussed, possibilities exist for multiple cropping

systems to be both advantageous and disadvantageous in relation to problems of pests, diseases, and weeds (29,32). The problem has to

do with the great complexity of environmental

factors and their dynamic interactions within

the cropping systems. Where capital is not

available or technical assistance has not been

accepted, we observe that the main means of

pest, disease, and weed control is through bio-
78

—

logical control, and through the management

of a great diversity of cropping patterns, both

in time and space (23).

It has been suggested that multiple cropping

systems permit such a control because they are

much less subject to attack (6,29,38). This

comes about because the mixed cropping system: 1) prevents spread of diseases and pests

by separating susceptible plants; 2) one species

sometimes serves as a trap crop, protecting the

others; 3) associated species sometimes serve

as a repellant of the pest or disease to which

the other crops are subject; and 4) a greater

abundance of natural predators or parasites of

pests are present due to a higher diversity of

adequate microsites and alternate prey.

However, there are also reasons why a multiple cropping system may be more susceptible

to attack: 1) reduced cultivation and greater

shading due to the presence of associated species, 2) associated crops serve as alternate

hosts, and 3) crop residues from one crop may

serve as a source of inoculum for the others.

All of these advantages and disadvantages can

exist, and further study is necessary to achieve

the combinations that give the most positive

results.

A few examples might serve to demonstrate

the potential of multiple cropping for biological control. In one study (22), it was shown that

the planting of a locally used medicinal herb

(Chenodium ambrosioides) in sequence with

corn or beans reduced the incidence of nematode populations in the soil, demonstrating a

potential for reducing attack on the roots of the

food crops, The herb added substances toxic

to the nematodes into the soil. In another study,

yields of cotton untreated with insecticides, but

interplanted with sorghum, were 24 percent

higher than sprayed monoculture. The reason

was that sorghum served as a microhabitat for

cotton bollworm predators (18). In another

case, fall army worms were less a problem on

corn associated with bush beans than on purestand corn (21). Beans intercropped with corn

were attacked less by rust compared to beans

in pure stands, probably because corn functions as a barrier to the dissemination of the

fungal spores (41).

Weeds, on the other hand, present another

problem. It has been reported that weeds are

much less a problem in multiple cropping systems, especially in intercropping (32), because

the space normally available to weeds is filled

with other crops, The aggressive nature of

weeds is well known (9), but recent work has

begun to show that weeds can fill an important ecological role in cropping systems, by

capturing unused nutrients, protecting the soil,

altering soil fauna and flora, serving as trap

plants for pests and disease, and changing the

microhabitat to allow for high populations of

pest predators and parasites (3,17). In rural

tropical Mexico, farmers understand and use

a “non-weed” concept (14), where each is

classified according to positive or negative effects. We need to understand in more detail the

biological functions of each component of the

agroecosystem to establish the structure that

will allow adequate weed, pest, and disease

control, If part of this control can be achieved

by merely manipulating the crop mixture in

time and space, great strides toward more efficient agricultural management can be made.

5. Mutualisms and Crop Coexistence: In natural ecosystems, a great number of interactions

between different species are mutually beneficial for those organisms involved, leading us

to believe that there is a strong selective pressure operating to select combinations that

coexist rather than compete (37). On the long

term, such a coexistence permits a more efficient use of resources, with the component

organisms aiding one another rather than interacting negatively. This frees more energy for

growth and reproduction.

To a certain extent, nurse crops or companion plants function in this way. Legumes, because of their symbiosis with nitrogen-fixing

bacteria, can coexist with corn without competing for nitrogen. In fact, part of the legume’s

nitrogen may be available for the corn (12), reducing overall need for fertilizers. Studies with

coffee and cocoa shade trees have demon-
79

strated the same relationship; the trees provide

shade, nitrogen, and an organic mulch over the

soil.

As mentioned, the presence of one crop may

have beneficial effects on others through alteration in the microclimate, pest and disease protection, etc. Thus, apart from looking for crops

that complement one another by avoiding

overlap in requirements, we need also to look

for crops that are interdependent and that

mutually benefit from the association, This will

be a very stimulating challenge for crop selection programs.

6. Use of Space and Time: One of the most

important aspects of the management of multiple cropping systems is the facility they offer

for the intensification of production through

manipulation of space and time. By achieving

the most ideal combination of the two, we will

achieve the greatest productivity. On the one

hand, we attempt to occupy the available resource space as efficiently as possible, combining species that complement each other, yet attempting to avoid overlaps that lead to negative

interactions.

Resource use in space is then combined with

its use in time, trying to achieve constant use

of the resources available. For this reason,

multiple cropping systems are intensified by

sequential, relay, and mixed planting that

establish constant resource use within the environmental limits imposed by the ecological

conditions of each region. In this sense, we can

even visualize the possibility of including cold

resistant trees in association with annual crops

or pasture, so that during the winter the trees

continue to occupy the area. Thus, any yield

reduction during the normal frost-free growing season is compensated for by the long-term

tree production,

Additionally, multiple cropping systems permit greater stability in production, despite

variability in climate or physical factors in the

planting area. Whatever the conditions in one

location and for one growing season, at least

one member of the multiple cropping system

will succeed. Since most of the better drained

and structured soils are already in production,

the more marginal lands will require special

technology to make them produce. We cannot

consider for the moment massive programs of

soil and water manipulation needed to install

mechanized high-yielding monoculture, To do

so is economically, if not ecologically, prohibitive. The basic framework is available in

multiple cropping, Innovative combinations

need to be searched for and tested.

Agroforestry: A Multiple Cropping

System

Agroforestry is a technology of land management that combines trees with agricultural

crops, with animals, or any combination of the

two. Combinations can be simultaneous, or

staggered in either time and space. The major

objective of agroforestry is to optimize production for each unit of surface area, keeping in

mind the need to maintain long-term yield

(11,13,42). Small-scale, traditional agriculture

has always included trees as integrated elements of farm management, but only recently

has interest been revitalized in the application

of agroforestry practices into modern agriculture.

The renewal of interest in agroforestry is

based on many of the same reasons for multiple cropping systems in general: the everincreasing demand for production, yet the rising cost of obtaining it. The explosive demand

for firewood and lumber has placed incredible pressures on the world’s forests, especially

in tropical and subtropical regions. Deforestation continues at an accelerated rate (20,44).

But programs of reforestation or multiple-use

forest management do not satisfy basic needs

for food, clothing, and other necessities that

come from crop and range lands. It would

seem logical that these pressures for both forest and agricultural products would stimulate

their combination in agroforestry systems.

Agroforestry practices can be broadly classified into three types (15): 1) combined agrosilvicultural (crop plus trees) systems, 2) combined forestry and grazing, and 3) simultaneous

combinations of forestry with crops and grazing. Examples of each of these classifications
80

are presented in table 8. The focus varies from

soil improvement, erosion control, wind breaks,

and shade to lumber, firewood, and reforestation. The combinations are essentially unlimited, depending on the needs of each region.

At first glance it might appear that agroforestry

systems are most applicable on marginal lands,

on steep slopes, poor soils, or areas with widely

fluctuating rainfall regimes. But agroforestry

should also be considered for widespread application, even on prime agricultural or grazing land, because production needs to be increased—both by opening up new areas and by

looking for innovative ways to increase productivity of lands already in use.

The principle limitations to widespread use

of agroforestry practices are economic and

technological. Ecologically, the advantages are

well known, but technically we still do not have

the information necessary to begin immediate

implementation. With the present focus in agriculture aimed at maximizing single crop yields,

there is a lack of acceptance of the idea that

yields need to be thought of more on a longterm, diversified basis. Agricultural research

has not yet accepted the challenge that an integrated focus to forest and farm management

requires.

Socioeconomic Implications of

Multiple Cropping Systems:

Perspectives for the Future

In all of the aspects of multiple cropping systems that this review has considered—yield, resource use, pest and disease control, weeds,

use of space and time, types of planting systems—much of the evidence indicates that

generally there are more advantages than disadvantages of a biological, physical, or agronomic nature. But we need to consider the

social and economic implications of the possible more widespread use of multiple cropping

systems in present day agriculture.

As was seen in table 4, the types of advantages derived from multiple cropping are many

and varied. With a greater diversity of crops,

Table 8.—Classification and Examples of Agroforestry

Technologies

Combined agrosllvicultural systems (trees with crops):

1. Agrosilviculture—establishment of trees, intercropped

with agricultural crops during initial stages of tree growth,

until tree canopies close and force the elimination of the

crops. Production available in early stages of tree development, and cultivation activities simultaneously benefit both

crops and trees.

2. Forest trees of commercial value in crop systems. Maintain trees in crop areas, either planted or natural, at low

densities that do not interfere, yet provide value in the

future.

3. Fruit trees in crop systems. A system that allows fruit production and grain or vegetable production simultaneously.

4. Trees that serve as shade for certain crops or improve the

soil through nitrogen fixation, organic matter incorporation, mulch, and microclimate modification.

5. Trees used as hedgerows, fence lines, or windbreaks

around cropping areas, where management is intimately

linked with the needs of the crops.

6. Trees around rivers, lakes, or artificial reservoirs or tanks,

integrated with fish or waterfowl management, providing

shade, food, and roosting.

Combined forestry and grazing systems (trees with grasses):

1. Grazing or forage production takes place within forestry

plantations, aiding in avoiding weed or brush build up,

lowering fire risk.

2. Grazing or forage production in young natural forests, with

same advantages as above.

3. Forest trees of commercial value in pastures, either planted

or natural, at densities that do not interfere with the pasture

species.

4. Timber trees in pasture, either planted or natural, with the

capacity to fix nitrogen and improve soil, thus lowering the

need to fertilize and provide commercial value.

5. Trees in pastures that provide shade for the animals and

aid in improving the soil through nitrogen fixation and

nutrient extraction from deeper soil levels.

6. Trees, either in or around pastures, or in forests, that produce foliage of forage value for animal consumption. Can

allow the reduction of feed supplement for animals.

7. Fruit trees in pastures, allowing for commercial production of both fruits and animals.

8. Trees around pastures as hedgerows, fence lines, or windbreaks.

Simultaneous combinations of forestry with crops

and grazing:

1.

2.

3.

—

Forest plantations planted with crops and grasses, permitting the management of grazing animals, either free to

wander or enclosed in specific areas. Especially adapted

to smaller animals, such as ducks or pigs. Requires close

control of activities and use of specific crops.

Trees associated with crops and grazing, either planted or

natural, in densities that will not adversely influence the

crops. Trees scattered in and around cropping areas can

be periodically pruned and used as forage for animals, with

the timber harvestable at some later date.

Hedgerows or living fence lines around rural communities,

serving as shade, windbreak, property divisions, forage,

fruits, timber, and firewood. In this sense, the system is

truly multiple use.

SOURCE: Combe and Budowski, 1979 (15)
81

a farmer is less affected by market fluctuations

and is able to shift from one crop to another

depending on price and demand, At the same

time, the harvest is spread out over a longer

period of time. Less dependence on outside

energy sources has obvious advantages, especially in areas where capital is limited. Labor,

instead of being concentrated in certain periods of the year, can be more evenly distributed,

an important consideration in relation to the

migrant farm worker problem. In times of

higher unemployment, multiple cropping systems can offer more and steadier work.

Most of the economic disadvantages are

derived from our lack of experience and knowledge with multiple cropping systems. Reported

lower yields, complexity of management activities, higher labor demands, and the difficulty

in mechanizing such systems are all important

factors that discourage modern farmers from

participating in multiple cropping practices.

An important aspect of this resistance comes

from the emphasis on large profits that governs

so much of modern agriculture today. Maximum profits in the short term, rather than concern with maintaining constant income in the

long term, governs the decisionmaking process on most American farms today, But with

the incredible rise in farm costs, a new focus

is necessary. All of these increases cannot be

passed onto the consumer. Many of the advantages of multiple cropping systems definitely

need to be stressed more for use on farms

today. Smaller farms, with a greater diversity

of products and activities, can function quite

profitably because they are less dependent on

high-cost energy inputs. Lower costs mean

food can be produced at a lower price, the benefits being transferred to the general population,

Smaller farms would require more farmers,

To a certain extent multiple cropping systems

mean a return to the land, with the incentives

necessary to keep the farmers there. The great

diversity of activities in multiple cropping systems would promote an increase in interdisciplinary activities in their investigation,

installation, management, and use in agriculture. This stimulation of interchange and

collaboration can, in the long term, lead to

greater social cohesion, Rural regions might

once again take on the social importance they

enjoyed in the past. The problems of lack of

trained personnel, and social, political, and

economic restrictions on multiple cropping

systems, all can be overcome by thorough and

conscientious programs of research aimed at

determining the proper methods, varieties, and

practices necessary.

The belief that multiple cropping is only suitable for marginal or underdeveloped regions

ignores the fact that just a relatively short time

ago, such systems were the most common type

of agriculture. Only recently have they been

replaced by monoculture systems dependent

on the use of massive quantities of inexpensive

high energy inputs. For the moment, this time

has passed and we need to learn from the past

to reshape agriculture for the future. This will

be a great challenge for agricultural research.
82

1,

2.

3.

4.

5.

6.

7.

8

9

10.

11.

12.

13.

14.

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, .,
Chapter VI

Development of Low Water

and Low Nitrogen Requiring

Plant Ecosystems for Arid

Land Developing Countries

Peter Felker

Department of Soil and Environmental Sciences

University of California

Riverside, CA 92521
Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Beneficial Aspects of Semiarid Plant Production Technologies on Semiarid

Developing Countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Where Technology is Used and Stage of Development

(Subsistence, Commercial, or Research) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Development of Tree Legumes for Fuelwood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Use of Nitrogen Fixing Trees to Increase Soil Fertility. . . . . . . . . . . . . . . . . . . . . 89

Development of Cash Crops on Semiarid Lands . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Production of Livestock Food and Forage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Intercropping Traditional Food Staples With Arid-Adapted Legumes to

Sustain High Food Staple Yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Slowing the Spread of Desertification in Arid Regions . . . . . . . . . . . . . . . . . . . . . 93

Fertilizer, Pesticide, Irrigation, and Machinery Requirements . . . . . . . . . . . . . . . . . . 93

Irrigation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Fertilizer Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Pesticide Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Machinery Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Research, Development, and Implementation of Arid-Adapted

Plant Ecosystem Production Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Constraints Facing Development and Implementation of Arid-Adapted

Plant Production Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Effect of Technology Implementation on Capital, Labor, and

Land Requirements.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Impact of Wide-Scale Technology Implementation on the Socioeconomic

Structure of Agriculture in Developing Countries.. . . . . . . . . . . . . . . . . . . . . . . . . . 100

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Work Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Table

Table No. Page

l. Outline of Research Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Development of Low

Nitrogen Requiring Plant

Chapter VI

Water and

Ecosystems

for Arid Land Developing Countries

This paper describes a low industrial input,

commodity-oriented approach to stimulating

economies of arid land countries using aridadapted plant species. It suggests legume tree

biomass farms using Acacia, Leucaena, and

Prosopis genera to provide increased fuelwood.

Increased soil fertility and ensuing water use

efficiency could be achieved by using deeply

rooted, drought-adapted species such as Acacia

albida and Prosopis cineraria that fix nitrogen.

Arid-adapted shrubs such as jojoba (Simmondsia chinensis), and guayule (Parthenium argentatum) could provide stable production of cash

crops. Prosopis and Acacia pods, atriplex forage, Leucaena forage, and cactus pads could

increase livestock food supplies, Increased production of traditional food staples such as millet, sorghum and peanuts can be achieved by

intercropping them with arid-adapted legumes.

Aggressive management of these plants could

help reduce the spread of desertification.

Little government support has been made

available for these activities despite their widespread use by indigenous farmers at subsistence levels. A research and development program is suggested that would establish living

germplasm collections and select and propagate superior clones, Several months after

stand establishment, these plant systems can

be grown without supplemental irrigation by

using ground water within 10 m of the surface

or by using a minimum of 250 mm annual rainfall. Phosphate fertilizer, micronutrients, and

rhizobial inoculation are required, but the nitrogen needs will be provided by nitrogen fixing plants. Less machinery will be needed to

till these systems.

Wide-scale implementation of these systems

would greatly enhance agricultural productivity at the local level, where it is most needed,

and indirectly stimulate nonagricultural sectors of the economy. The increased economic

well-being of farming classes could lead to decreased political unrest and greater stability of

governments in arid lands, Foreign policy efforts to strengthen the peace by buildup of military hardware systems has proven futile in

Ethiopia, Iran, and Iraq. Development of arid

land plant production systems is a viable alternative to enhancing peace in politically volatile

arid land countries.

INTRODUCTION

This document was prepared at the request follows OTA’s specific issues and questions.

of the Office of Technology Assessment (OTA) For the convenience of the reader, these reof the U.S. Congress to provide guidance in de- quests are reproduced in appendix A.

velopment of low energy, nitrogen, and machinery requiring agricultural systems for semi- Identifying plant physiological, morphologarid developing countries, The format closely ical, and ecological characters that lend them87
88

selves to a minimal machinery, capital, and

fossil fuel input is the subject of a paper by

Felker and Bandurski (14) in which orchards

of leguminous trees were suggested to most

closely approximate an ideal system for minimizing industrial inputs. Other closely related

shrub ecosystems have been suggested to

achieve similar objectives (32). Identification

of arid land plant species that would lead to

more stable and productive ecosystems has

been intensively investigated by Felger (11). Recent review volumes (42) and symposia (27,6)

have dealt at length with arid land plant resources. This document attempts to synthesize

the knowledge of arid land plant species, focusing on minimal energy input agriculture and

a pragmatic commodity-oriented approach designed to provide major needs such as fuel, forage, and food staples required for arid land

economies.

BENEFICIAL ASPECTS OF SEMIARID PLANT PRODUCTION

TECHNOLOGY ON SIMIARID DEVELOPING COUNTRIES

Development of leguminous trees (14) and

associated semiarid ecosystem plant components such as saltbush (A triplex spp.) (19), leucaena (Leucaena leucocephala) (15), cactus

(Opuntia and Cereus spp.) (33,52), jojoba (Simmondsia chinensis) (23), and guayule (Parthenium argentatum) (50) can make a significant

contribution to meeting the major commodity

needs of people in semiarid developing countries. Some of the main biological needs and

appropriate approaches to supplying them are

as follows:

1. Need: increased availability of inexpensive fuelwood.

Approach: use of leguminous tree biomass

farms with Prosopis, Leucaena, a n d

Acacia species.

2. Need: increased soil fertility to triple or

quadruple water use efficiencies of food

staples so that productivity is water-limited

and not fertility-limited.

Approach: use locally respected, droughtadapted, nitrogen-fixing legume tree such

as Acacia albida and Prosopis cineraria,

use shrubby legumes such as Dalea species, and use perennial arid-adapted herbaceous legume such as Zornia a n d

Tephrosia.

3. Need: production of cash crops for

farmers and for foreign exchange.

4.

5.

6.

Approach: use perennial arid-adapted

plants, such as jojoba, guayule and high

value, drought-adapted annuals, and ephemerals, such as sesame when grown in conjunction or rotation with arid-adapted nitrogen fixers.

Need: production of livestock food and

forage.

Approach: use arid-adapted, salt-tolerant

shrubs, such as saltbush (Atriplex species)

in conjunction with high water to dry matter conversion plant specialists, such as

spineless cactus (Opuntia ficus-indica) and

high protein and/or sugar content pods of

leguminous tree species of Acacia tortilis,

Acacia albida, and Prosopis spp.

Need: sustained production of traditional

food staples, such as millet, sorghum,

groundnuts, and cowpeas.

Approach: intercrop the annual staples

with nitrogen fixing trees previously demonstrated to stimulate annual legume

yields such as the association with Acacia

albida and peanuts.

Need: slow the spread of desertification.

Approach: when intensive management

of forage, fuelwood, and staple products

are carried out as outlined above, desertification will slow.
89

WHERE TECHNOLOGY IS USED AND STAGE OF DEVELOPMENT

(SUBSISTENCE, COMMERCIAL, OR RESEARCH)

Development of Tree Legumes

for Fuelwood

Areas of use: Prosopis alba and P. nigra were

reported to have fired industrial boilers and

steam locomotives during World War II in

Argentina (10). In Chile, the leguminous trees

chanar (Geoffrea decorticans) and espino

(Acacia caven) have been widely harvested by

Indians and present day subsistence farmers

for fuel (2). Mesquite wood and charcoal (Prosopis species) is highly esteemed and widely

used in the Southwestern United States in

steakhouses for barbecues and home heating,

From 1956 to 1965, 78,000 metric tons of mesquite charcoal and 200,000 m3 of mesquite

firewood were recorded as items of commerce

in Mexico (29), In the Jodphur state of India,

Prosopis was declared the “royal plant” because it provided the bulk of the fuel to the local

population (20). Acacia forests are harvested

along the Nile 400 km upstream from Khartoum, Sudan, and brought to Khartoum for

brick making and other industrial uses (24). In

the Sahelian zones of Africa, many of the

Acacia species such as A. tortilis, A. seyal, and

A, senegal are consumed for woody biofuel.

Research organizations: The Central Arid

Zone Research Institute in Jodphur has been

conducting research on leguminous trees as

sources of biofuels since the early 1940s (1),

Their work is meagerly documented in the

scientific literature and, from the lack of recent

papers in the literature, their current research

on tree legumes does not appear to be very

active.

The Forestry Research Institute in Khartoum,

Sudan, has received about $200,000 from the

International Development Research Center

(Ottawa) to evaluate Prosopis species under

200, 300, and 400 mm annual rainfall regimes.

Much of the seed material for this experiment

was supplied by the University of CaliforniaRiverside mesquite project. The United Nations Development Program (UNDP) provided

support for Felker to supply seeds, mesquite

rhizobia, plants, containers, and consultation

to conduct varietal trials with 30 selections of

leguminous trees (most Prosopis) in the Sudan

at the Forestry Research Institute, Over 400

acres of Prosopis have been planted along irrigation canals in the Sudan courtesy of the Sudan Council of Churches to prevent sand from

blowing into and filling the canals (26).

Dr. J. Brewbaker at the University of Hawaii

has been conducting extensive research in Hawaii, Colombia, and the Philippines, on the development of leucaena as a biofuel crop. In the

United States, the U.S. Department of Energy

has funded research on Prosopis under Felker

at the University of California-Riverside to develop an arid-adapted germplasm collection;

to evaluate the collections in field conditions

under drought, heat, and frost stress; to study

nitrogen fixation and salt tolerance; and to

clonally propagate outstanding single trees.

Use of Nitrogen Fixing Trees to

Increase Soil Fertility

Areas of use: Prosopis cineraria has been

used on a subsistence level by farmers in the

India-Pakistan region to increase the yields of

their pearl millet crops. Soil chemistry studies

(46) corroborated increased nutrient contents

and forage yields under P. cineraria tree s

versus other trees and open control areas.

Acacia albida is widely used on a subsistence

level in the West African countries of Senegal,

Upper Volta, Mali, Niger, and Chad to increase

the yields of sorghum, millet, and peanuts

grown beneath the tree canopies (12). Parkia

biglobosa was observed by this author growing in sorghum fields in a 400 mm annual rainfall regime where farmers stated the Parkia also

increased the yields of their crops.

Yields of grasses and forbs grown in a growth

chamber on soil from beneath mesquite canopies were four times greater than herbage

yields grown on soils from outside mesquite

canopy cover (49). The stimulation of forage

yields after mesquite removal in the Southwest-
90

ern United States is probably due to increases

in soil fertility supported by nitrogen fixation

and reduction in competition for water. Mesquite nitrogen fixation and soil fertility increases on the 72 million acres (38) presently

occupied by mesquite in the Southwestern

United States is an unrecognized resource.

Leucaena (Leucaena leucocephala) has been

widely used in the Philippines in rotation with

other crops, as a companion crop, and as a

green manure with other crops to increase soil

fertility.

Research organizations: Dr. Y. Dommergue,

working for ORSTOM in Dakar, Senegal, West

Africa, has conducted rhizobial inoculation

trials with many African Acacias including

Acacia albida and at this writing is actively involved in nitrogen fixation aspects of semiarid

soils. Dr. Habish at the University of Khartoum,

Sudan, published excellent papers on characterization of Acacia-rhizobia symbioses (21),

but is now a dean at the University and no

longer actively involved in research. A University of Arizona group, funded by the National

Science Foundation (NSF), with Dr. Pepper as

principal investigator, is collecting and characterizing rhizobia strains from many aridadapted legumes.

A three-year $650,000 NSF grant has been

awarded to study nitrogen cycling in a mesquite dominated desert ecosystem in southern

California. This project involves: 1) an ecology

group headed by Dr. Philip Rundel at the

University of California, Irvine, that is conducting dry matter productivity analyses; 2) a

University of California-Riverside soils group

headed by Dr. Wesley Jarrell, that is converting the dry matter productivity measurements

of the Irvine group into nitrogen productivity

and conducting soil moisture profile measurements with 20 ft deep neutron probes, quantitating soil chemical characteristics on and

around the site, quantitating denitrification,

and developing in situ acetylene assays; and

3) a Washington University (St. Louis) group

headed by Dr. D. H. Kohl that is correlating the

above-mentioned findings with natural abundance 15N

14N measurements to develop qualitative and perhaps semiquantitative assays of

nitrogen fixation from dried plant samples,

The Department of Energy has funded studies

on cross-inoculation of 13 Prosopis species (15),

has conducted greenhouse studies of the effect

of heat and drought stress on Prosopis nitrogen fixation, and has developed models comparing efficiencies of water and nitrogen inputs to increasing productivity of semiarid

rangelands (16). USDA scientists have demonstrated that fertility can dramatically increase

water use efficiency of rangeland species in a

lo-year study on Montana rangelands (51). The

USAID-supported Niftal group at the University of Hawaii maintains large stocks of

rhizobia. Basak and Goyal (3) at the Central

Arid Zone Research Institute at Jodphur have

published cross-inoculation data and temperature and salinity tolerance characteristics for

rhizobia for semiarid adapted leguminous trees

in India,

Development of Cash Crops on

Semiarid Lands

Areas of use: Jojoba (Simmondsia chinensis),

a non-legume, is one of the most promising

cash crops for arid lands. Jojoba seeds contain

a rancidity-resistant, non-allergenic, liquid wax

with lubricating properties equivalent to an oil

obtained from the endangered sperm whale. Jojoba is under development in southern California, Arizona, Mexico, and many of the

semiarid less developed countries (53). Mature

jojoba plantations should yield over 1,000 kg/

ha 1 at over $1 per kg. This yield could earn

a gross return of over $1,000 per hectare.

Guayule (Parthenium argentatum) a plant

native to the Chihuahua deserts, contains natural rubber and is under extensive development by both the United States and Mexican

governments (50). There is no reason guayule

could not be cultivated in other semiarid regions of the world as a cash crop.

Hydrocarbon bearing plants such as Euphorbia lathyris have been suggested as raw materials for oil and gasoline production (7). The
91

drought-adapted legume trees Acacia senegal

exudes a gum from wounds of the trunk known

as gum arabic that has many industrial and

food uses (18), Eighty-five percent of the

world’s annual supply of gum arabic, about

50,000 to 60,000 metric tons, is harvested and

exported from the Sudan at prices of about $1

per kg (18), Other Acacia and legume trees,

such as Prosopis, exude gums that could be developed for cash crops. Seeds of the fastgrowing, drought-tolerant, annual sesame sell

for $1 to $2 per kg and show potential for an

arid zone cash crop (53). The fruits of the

cactus Opuntia ficus-indica can produce

dessert or table quality fruits. This author was

served an excellent cactus fruit with a meal on

a Chilean airline. Commercial (5 ha and larger)

Opuntia ficus-indica orchards are currently

operating in southern California to supply

these fruits to supermarket chains. There are

several little-known species of cactus that

possess fruits equal or superior in quality to

Opuntia ficus-indica that could also be developed (11). Because cactus use water very efficiently, they should support fruit and cash crop

production in semiarid areas.

The pods of carob (Ceratonia siliqua) are broken into pieces, kibbled, and separated into

seed and pod fractions, The pod fractions are

sold for livestock food in Europe and are imported into the United States where they are

manufactured into chocolate substitutes (34).

Industrial quality gums are extracted from the

seeds, In 1970, the world production of carob

seed gum was 15,000 tons. Prices ranged from

$0,62 to $1,10 per kg (43). The pods of Parkia

biglobosa and P, clappertoniana, and a fermented product of the seeds known as dawadawa, are sold for human food on the subsistence levels in markets in Senegal and other

parts of West Africa.

Research organizations: The most extensive

germplasm collections, plantings, and cytogenetic studies of jojoba are being made at the University of California-Riverside under Dr. D. M,

Yermanos. This has been funded by the United

Nations Development Programme (UNDP),

NSF, and the California State Legislature.

Another large-scale jojoba research operation

is being carried out at the University of Arizona

under Dr. L. Hogan. There are numerous commercial jojoba developers, some of whom are

less than scrupulous. Donor agencies should contact Yermanos or Hogan before dealing with

private jojoba developers, Dr. Yermanos has

also developed nonshattering sesame types and

mechanical harvesting devices with UNDP

support. The USDA has a multi-million-dollar

budget to develop guayule in the Southwestern United States.

The Diamond Shamrock Co. is supporting a

multi-million-dollar project at the University of

Arizona Office of Arid Land Studies to develop

potential of hydrocarbon producing plants

such as Euphorbia lathyris,

The Canadian International Development

Research Center (IDRC) is supporting a research program to develop gum arabic for West

Africa through the “Eaux et Foret” in Dakar,

Senegal. The University of Chapingo, Mexico,

has a program to develop spineless cactus (52),

Dr. Richard Felger at the Arizona/Sonora Desert Museum has identified numerous arid land

crops with potential including several outstanding cactus varieties.

Production of Livestock Food

and Forage

Areas of use: In Mexico, Prosopis glandulosa

var. glandulosa, and Prosopis laevigata are

harvested from wild trees and sold to wholesale dealers who incorporate it into livestock

rations. In 1965, 40,000 tons of mesquite pods

were sold in commercial operations in Mexico (29). Undoubtedly, many more pods were

used or bartered locally that were never

entered into the agricultural statistics. One

thousand ha of P. juliflora has been established

in the Peruvian coastal desert under partial irrigation. By providing 250 mm of irrigation the

first year and 160 mm thereafter, pod production of 6 to 7 t/ha- have been obtained from

the Peruvian plantings (39), In nearby Chile,

30-year-old P. tamarugo trees growing in the

Atacama salt desert have produced 6,000

kg/ha-’ of leaves and pods that are used to

support a sheep-raising industry (44). Twenty38-846 0 - 85 - 4
92

two thousand hectares of P. tamarugo have

been planted by the Chilean corporation CORFO

(54). Felker has visited these areas to assist

CORFO with vegetative propagation, selection

techniques, and nitrogen fixing inoculants.

In the Southwestern United States, mesquite

pods were the staple for Indians in southern

California and Arizona deserts (13), but today

are only marginally important in supporting

wildlife. In West and East Africa the pods of

A. albida and A. tortilis are highly regarded as

a supplemental livestock feed (12,34). Some A.

albida pods are collected and stored for later

rationing to cattle on a subsistence level, but

no organized or commercial use of pods has

been attempted (12). The forage of Acacia xanthophlea and A. hockii supplies much of the

diet of giraffes in the Serengetti National Park

in East Africa, Pellew (41) has suggested that

the Acacia-giraffe ecosystem be managed for

meat production,

Forage systems based around the spineless

cactus (Opuntia ficus-indica) have been widely

used in Mexico and North Africa where the

spineless pads are fed to cattle. Selections of

saltbush (A triplex species) are high in protein

and carotenoids and constitute a useful livestock forage. The Chilean corporation CORFO

has planted thousands of hectares of saltbush

in contour ridges along the Chilean coast for

use as cattle food (Felker, personal observation). In Tunisia, commercial-scale, government-supported plantings of saltbush provide

forage for grazing animals (22).

In Mexico, cattle rations have been formulated from high energy, sweet, highly palatable

mesquite pods; high protein, high carotenoid

and low palatability saltbush foliage; and highenergy containing cactus pads (29). These three

plants possess the complimentary physiological characters of high salt tolerance in saltbush,

high water to dry matter conversio n

efficiencies of cactus, and nitrogen fixing properties of mesquite.

Research organizations: Surprisingly little

research is being done about these forage

plants. The Tunisian and Chilean governments

support the largest developments of forage-producing plants, The Chilean company CORFO

has planted thousands of hectares of Atriplex.

CORFO has investigated plant spacing, canopy

closure, and pod productivity as a function of

age for 36-year-old Prosopis tamarugo plantations (44). They are just beginning to become

involved with selection work, nitrogen fixation,

and vegetative propagation.

The Tunisian government has employed

large earth-moving equipment and water transport vehicles to establish saltbush and cactus

plantings (22). The Algerian government also

has initiated some Opuntia plantings (33). Dr.

Henri LeHouerou, formerly of the International Livestock Center (ILCA) in Addis Ababa,

has been a key figure in North African developments of Atriplex and Opuntia. The Chapingo Agricultural Experiment Station outside

of Mexico City has made selection of Opuntia

with promising economic characters (52).

Lopez, et al. (28), at the Antonio Narro Agricultural University in Saltillo, Mexico, has conducted a thorough analysis of the productivity

and ecosystem characteristics of economically

important aspects of Opuntia production in

Mexico. The International Development Research Center, Ottawa, is supporting a Prosopis

juliflora forage production project in Peru.

In the United States, Dr. C. M. McKell, Plant

Resources, Inc., Salt Lake City, and Dr. J.

Goodin of Texas Tech University have conducted extensive research on saltbush as an

economically important forage crop. Felker,

while at University of California-Riverside,

made Prosopis selections for pod producing

characteristics in cooperation with Becker and

Saunders at the USDA Western Regional Research Center. They also have conducted proximate analyses and feeding trials on the pods.

lntercropping Traditional Food

Staples With Arid Adapted Legumes

To Sustain High Food Staple Yields

Areas of use: Prosopis cineraria has been

widely used in the Indian-Pakistan region on

a subsistence level to increase yields of pearl

millet and other forage crops grown beneath

its canopy (31). Acacia albida has been used
93

in West Africa to increase yields of millet,

sorghum, and peanuts (9,8,12). Farmers in the

400 mm annual rainfall region of Senegal

remarked to this author that Parkia biglobosa

had the same fertilizing effect as Acacia albida

on millet and sorghum.

Research organizations: The French

overseas development organization ORSTOM

commissioned soil fertility studies carried out

by Dancette and Poulain (9) and Charreau and

Vidal (8). AID commissioned a state-of-the-art

report on Acacia albida in 1978 (12). FAO supported a nursery scheduled for termination in

1978 in Kebemer, Senegal, dedicated to raising enough Acacia albida seedlings to plant

1,000 ha per year at 45 trees per hectare. A

CARE project in Chad was involved in reforestation with Acacia albida. No serious field

study has ever been conducted to develop improved genetic stock and management practices for arid-adapted leguminous trees.

Slowing tho Spread of Desertification

in Arid Regions

Little work is being carried out to slow desertification. K. O. Khalifa, working for the Sudan

Council of Churches, has planted 400 acres of

Prosopis along irrigation canals to prevent the

wind from filling them. The Indian government has been planting shelterbelts with Prosopis and other arid adapted trees since the

1920s and 1930s (25). No serious efforts employing arid-adapted shock, e.g., Prosopis,

Acacia, or Leucaena, and modern forestry

practices have been applied to control of desertification in less developed countries.

FERTILIZER, PESTICIDE, IRRIGATION, AND

MACHINERY REQUIREMENTS

Irrigation Requirements

Over 90 percent of the land in semiarid regions must rely on rainfall without supplemental irrigation (excluding areas where water

harvesting technologies are possible). All of the

desert-adapted trees, shrubs, and ephemerals

described here have the capability to grow

without irrigation in semiarid zones, If water

is not available, these plants can close stomates,

shut down photosynthesis and transpiration,

allow their finely divided leaflets to reach air

temperature, and adjust their water potentials

to minus 40 to 50 bars and wait for the next

rain (17). Annuals would wilt and die under the

same conditions.

Reasonable production from reproductive

structures, such as mesquite pods, jojoba nuts,

or cactus fruits cannot be expected below 250

mm annual rainfall unless they are located in

water drainage areas or areas where water accumulates. Growth of vegetative parts for wood

or forage production probably will continue

from 150 to 250 mm annual rainfall. Deeprooted tree and shrub systems are not as susceptible to moisture stress as are shallowrooted annuals. To get optimal water use, an

agroecosystem needs an optimal mix of nitrogen fixers and water to dry matter conversion

specialists. When it is possible to use cactus,

which has a fivefold greater efficiency of converting water to dry matter than legumes (17),

legumes should not be used to produce the

energy portion of livestock feed. However, legume leaf litter will be required to create good

fertility so the cactus can achieve its maximum

water use efficiency. For the same reason,

cactus should not be used to produce the protein and nitrogen needs of livestock when it is

possible to use legumes. Livestock need both

energy and protein rations and both energy and

protein producing plant specialists are required.

Fertilizer Requirements

A central component of this approach to developing country agriculture is widespread in-
94

corporation of arid-adapted, nitrogen fixing

legumes that are capable of fixing nitrogen

under conditions too harsh for temperate legumes (e. g., clover, alfalfa, etc.). These legumes

require no nitrogen themselves and when properly incorporated into a diversified ecosystem,

they will reduce nitrogen needs for non-legumes as well. Many of these plants, both leguminous (e. g., mesquite) and non-leguminous

(e.g., jojoba) have very deep root systems (13)

capable of mining nutrients found in clays,

bedrock, and parent materials. Additionally,

these deeper rooted shrubs would be expected

to have a higher capture ratio of applied fertilizers because they are less likely to allow nutrients to leach beyond the deep root zone.

Also, many of these plants are perennial, and

they would be expected to reduce wind and

water erosion.

Under rainfall as low as 300 mm, it may be

desirable to practice clean cultivation or use

herbicides between rows of mesquite, cactus,

saltbush, jojoba, and guayule to increase water

infiltration and to reduce water competition

from grasses and forbs. Once established, the

risk of wind and water erosion present with

clean cultivation should be less than the similar risk with annual crops, Drought-hardy

shrubs and trees should make more effective

use of applied nutrients than water-stressed,

herbaceous, annual crops.

If drought-adapted legumes are widely incorporated into managed arid ecosystems, phosphate and sulfate will ultimately become limiting and will have to be supplied. Both nutrients

stimulate legume production and can be supplied in single superphosphate.

Pesticide Requirements

It is difficult to imagine how the plant ecosystems described here would be any more or

less susceptible to insect or bird attack than any

other ecosystem. Once established, perennial

tree and shrub crops would survive competition from grasses and forbs without weed control measures. However, their productivity

probably will be greatly enhanced if herbicides

or cultivation were used to eliminate water

competition from grasses and forbs. For the

first few years of shrub and tree stand establishment, competition from grasses and forbs

must be eliminated either by herbicides or

cultivation.

Machinery Requirements

A variety of options employing varying

degrees of mechanization are available to establish tree and shrub plantations. This author envisions that most plantations will employ containerized seedlings planted with a liter or two

of water. This can be accomplished manually

with dibbles or post-hole diggers or mechanically with an 80 hp tractor pulling a transplanter capable of planting 1,000 trees per

hour, It may prove useful to establish a seedbed

for seedling transplant with the same level of

preparation given to annual crops. However,

after the first year an annual deep cultivation

as required for annual crops will not be necessary. Where fruits are to be harvested (e.g.,

jojoba, mesquite beans, etc.), light surface harrowing or disking will prove useful for weed

control, to increase water infiltration, and to

provide a clean surface to pick up the fallen

fruits. Pruning of tree and shrub crops will be

necessary to allow access for harvesting of

fruits.

In biomass farming operations, where complete canopy closure is desired, annual cultivation would be unnecessary and impossible to

carry out after canopy closure. An annual

ground preparation and planting, carefully

timed with arrival of rains to allow germination and full use of the rainy season, will not

be necessary for the tree and shrub crops.

Established annual and perennial crops will

not face a labor shortage at planting time as

do annual crops, The light cultivation that may

be useful with tree and shrub crops can be performed on a much less rigid schedule when labor, draft animals, and machinery are available. If herbicides are available and acceptable,

they can be used in lieu of light cultivation.

Tree and shrub crops would require much

lighter equipment than annual crops and the

annual site preparation necessary for annuals

could be avoided.
95

RESEARCH, DEVELOPMENT, AND IMPLEMENTATION OF ARIDADAPTED PLANT ECOSYSTEM PRODUCTION TECHNOLOGIES

An outline of research required to develop

these plants and cost estimates to do so are

given in table 1. Research centers are proposed

in six locations to collect and store germplasm,

to plant germplasm nurseries, to reevaluate

promising nursery selections in larger sized

plots, to compare input/output resource ratios

of different plant systems, to evaluat e

monoculture and polyculture arid-adapted systems, and to provide material and administrative support for the research.

The research program outlined in table 1 is

appropriate for the first phase of the research,

Extensive germplasm collections and plantings

would be required once at a cost of approximately $1,500,000. A funding effort 15 percent

of the initial level would be appropriate after

initial collections and plantings were made.

Funds used for collections and plantings in the

first phase should be allocated to weed and insect control, cultural operations such as harvesting, pruning, and planting methods for

nursery stock, and extension short courses during the second phase of the research.

Large genetically diverse germplasm collections and promising plant selections are available for some of the plants described here such

as jojoba, guayule, and atriplex species, For

other plants, germplasm collections and selections of promising lines will have to be made.

The plants that require germplasm collection

and selection and the methodology for accomplishing that is outlined below.

Seeds should be taken and maintained as

single plant selections from Acacia tortilis and

A. seya] in East Africa, from A. albida in East

and West Africa, from Parkia biglobosa in West

Africa, from Prosopis cineraria in the Mideast

and India-Pakistan region, and from P. alba,

P, chilensis, P. tamarugo, P. pallida, P. articulata, P. tamarugo, etc. in Argentina, Chile,

Peru, Mexico, and Hawaii. Short, shrubby legumes of the genus Dalea should be collected

in Southwestern United States, Tephrosia in

Texan-Mexican area, and Zornia in Sahelian

Africa, Cactus genera such as Opuntia a n d

Cereus should be collected in Southwestern

United States. During these collections, attempts should be made to collect for as much

diversity as possible as well as to collect for

economically desirable characteristics, e.g.,

heavy pod production, size and sweetness of

fruit, large trees, presence of large amounts of

leaf litter, and presence or absence of thorns.

The plant should be collected over its entire

geographical and ecological range.

All of the collections should be evaluated in

uniform plantations with a minimum of four

replicates of five trees per replicate. For the

trees, height measurements should be performed

the first year, stem diameter measurements for

biomass estimation should be performed every

year, and pod productivity measurements

should continue indefinitely, One germplasm

planting should be evaluated in a 300 and 500

to 600 mm annual rainfall regime in the IndiaPakistan region, in East Africa, in West Africa,

in the United States, and in South America.

The purpose of the American planting would

be to provide American researchers with biological research material and exposure to these

different cropping systems. An additional site

should be located near a seacoast to use seawater irrigation to screen for salt-tolerant

germplasm.

The Hawaiian Niftal rhizobia collection

should be evaluated for rhizobia for the legumes and techniques developed to ensure effective modulation of field plantings, Soil

samples from native stands might contain

rhizobia with unique properties and should be

used to inoculate native plants for comparative

purposes,

Most Acacias (Sief-el-Din, 1980) and probably

all Prosopis (47) are obligately outcrossed. As

a result, trees will not breed true and seed and

clonal propagation techniques will be required,

Both tissue culture propagation and traditional

rooting of cuttings should be examined,

Rooting of stem cuttings is difficult for Pro-
96

Table 1 .—Outline of Research Procedure

Level of support

per year

($ 1,000)

100

100

100

100

200

100

100

25

100

100

100

100

100

100

60

100

120

450

(6 sites x 75)

1,200

(200 x 6 sites)

180

(30 x 6 sites)

1,200

(200 x 6 sites)

400

(200 x 2 sites)

600

(200 X 3 sites)

1. Develop germplasm collections where none exist

A. Collect single tree selections of leguminous trees over broad range for:

1) pod production

2) large size

3) thorn characteristics

4) leaf litter

B. Collect following genera:

1) Acacia tortilis and A. seyal in East Africa

2) Acacia albida in East and West Africa

3) Parkia biglobosa in West Africa

4) Prosopis cineraria in Indian-Pakistan region

5) Prosopis alba, P. articulate, P. chilensis, P. nigra, and P. tamarugo

in Mexico, Hawaii, Southwestern United States, Argentina, Chile,

and Peru

6) Make cactus collections in Southwestern United States and Mexico

7) Short, shrubby legumes, Dalea in Southwestern United States,

Tephrosia in deep South, and Zorrria in Sahelian Africa

2. Obtain good selection of following arid crops already subjected to

germplasm collection and screening:

A. Jojoba—Drs. Yermanos and Hogan

B. Guayule—USDA

C. Euphorbia—Dr. Calvin

D. Atriplex— Drs. McKell and Goodin

E. Leucaena—Dr. Brewbaker

3. Plant out four replicates of five trees (plants) of all accessions for

germplasm nursery at a 300 mm and 500-600mm annual rainfall

regime in:

A. East Africa, e.g., Sudan

B. West Africa—Senegal

C. India-Pakistan region

D. South America

E. Southwestern United States

F. Site along coast to irrigate with seawater for salinity trials

4. Evaluate Niftal collection of rhizobia suitable for tree legumes.

Develop techniques to insure effective modulation.

5. Conduct protein, sugar, fiber, and toxicity analyses on pods that are

produced.

6. Develop clonal propagation techniques at central facility:

A. Rooting of cuttings

B. Via tissue culture

7. Evaluate germplasm nursery for:

A. Height measurements first year

B. Stem diameter measurements yearly

C. Pod production and/or pod chemical characters

D. Make clones of outstanding single trees

8. Evaluate clonal outstanding material in replicated 0.1 ha minimumsized plots.

9. Multiply and distribute best selections to interested individuals

and organizations.

10. Evaluate comparative advantages of selections developed above in

mono- and poly-culture with Opuntia, jojoba, guayule, atriplex, etc.

11. Evaluate large N fixing trees with staple cereal crops in

field plantings.

12. Evaluate short N fixers with jojoba, guayule, saltbush, etc.

5,735 ‘ Total direct research

4,265 Support facilities, travel, secretarial, library, statistical analyses, computer

services, etc.

Grand total
97

sopis. To achieve success for large-scale plantings, a thorough evaluation of rooting methods including evaluation of mist, atomized

fogging, and tent humidification devices,

screening trials of hormone mixtures, evaluation of out-of-doors and greenhouse grown

stock, and use of growth chambers to determine optimal light, temperature and humidity

level for cuttings will be required.

Most annual legumes are highly self-fertile

and breed true to type. These selections will

not require vegetative propagation, but germplasm multiplication areas will be required.

Laboratory analysis of crude protein, sugar,

and fiber should be conducted on pods, fruit

or other economically important plant

structure.

Single tree selections should be made from

the germplasm nursery on the basis of: 1 )

height and biomass determinations, 2) pod production and pod chemical characters, 3) presence or absence of thorns, and 4) other characteristics deemed important. These selections

should be clonally multiplied and reevaluated

with four replicates of 0.1 ha minimum sized

plots per selection. Sufficient quantities of the

clonally multiplied material should be made to

allow distribution to requesting individuals and

organizations.

Once reasonably productive selections of the

leguminous trees and cactus have been developed, they should be compared with advanced

strains of jojoba available from Yermanos and

Hogan, from guayule available from USDA,

and from saltbush available from McKell and

others. The comparative advantages and relative resource requirements for these crops

should then be evaluated as monoculture and

polycultures. The large nitrogen fixing trees P.

cineraria and A. albida should be evaluated in

various spatial configurations with the staple

crops millet, sorghum, and peanuts. The short

shrubby and herbaceous legumes of the genera

Tephrosia, Zornia, and Dalea should be evaluated with jojoba, guayule, saltbush, and

opuntia.

As with all crops, solutions to weed problems, insect problems, and cultural practices

will have to be developed for these ecosystems.

Herbicide and cultivation methods should be

examined for weed control and insecticide,

biocontrol, and integrated pest management

should be evaluated for insect control. Harvesting, pruning, plant spacing, and planting

methods also require development.

It has been the experience of Dr. Yermanos

with jojoba and of this author with mesquite

that once genetically superior strains have been

produced the demand for the strains and the

technology associated with them will greatly

outstrip the supply. Elderly ladies with 100

square feet of desert in their backyard in Yucca

Valley, California, business executives, and

ministers of agriculture in arid developing

countries will ask the project leader to visit

their backyard or country to set up the appropriate technology. It is imperative to develop

sufficient plant material for further multiplication and to train extension personnel to help

farmers, businessmen, or government leaders

use the technology. Short extension courses

provided by staff involved in germplasm nurseries and evaluation centers would be an ideal

method of disseminating the information.

The staff of the germplasm nursery and evaluation centers would require a Ph.D. project

leader for: 1) Acacia tortilis and A. seyal, 2)

Acacia albida, 3) Prosopis cineraria, 4) Parkia

bioglobosa, 5) the American Prosopis species,

6) the shrubby and herbaceous legumes, 7) the

cactus, 8) the atriplex complex, 9) guayule, 10)

jojoba, and 11) other overlooked species. A central tissue culture and clonal propagation center should develop the techniques for clonal

propagation and have at least two Ph.D.’s, six

B.S. ’S and/or master’s level technicians and six

to eight support personnel preparing media,

washing dishes, etc. Each research center

should have two B.S. or M.S. full-time personnel and six nonskilled laborers rooting cuttings

and/or multiplying germplasm for research

and/or further distribution. The availability of

a statistician and computer for analysis of field

experiments is essential.

A major effort will be required to develop

support facilities for research in arid develop-
98

ing countries of Africa. Telephone service, mail solutely essential that the plant research be conservice, ground transportation, and freight ducted in the climate and on the soils where

services to and from Europe are too unreliable it is to be used and this requires development

to make effective research possible in East of support services for the research.

Africa and perhaps other countries. It is abCONSTRAINTS FACING DEVELOPMENT AND IMPLEMENTATION

OF ARID-ADAPTED PLANT PRODUCTION TECHNOLOGIES

There are no major or theoretical scientific

constraints on using these technologies, but applied research efforts are required in several

areas. Techniques need to be developed for

clonal propagation of the species described

here—both rooting of cuttings and tissue culture. Planting techniques, greenhouse and field

cultural practices need to be optimized. A continued effort to identify and propagate better

genetic selections is required,

Environmental constraints to development

of these systems are minimal, as increased

vegetation in arid developing countries has the

effect of halting desertification. There are, however, serious cultural constraints to development of perennial production systems, For

instance, in Sahelian Africa the perennial vegetation is viewed as community-owned (48),

Thus, the pods or fruits from trees can be taken

by anyone, even if the trees are on privately

owned land,

Similarly, people can cut branches from nonprotected species of trees for fuelwood even

if the landowner planted the trees for his own

fuelwood use. Freely roaming goats that eat

young seedlings constitute a major problem in

establishing perennial production systems.

Control of the movement of goats is probably

an insoluble cultural problem and thus goatproof devices to protect young seedlings will

have to be devised,

Political constraints on the development of

these technologies stem from politicians’ and

bureaucrats’ unfamiliarity with use of these

perennial crops, This is most accurately described in Pelissier’s explanation of whv

Acacia albida is not more widely used in West

Africa (14).

One cannot help but be astonished that an

agronomic research center established to study

the Serer people (in Senegal, West Africa) is not

more interested in the methods and effectiveness of native farming systems. These researchers ignore the milieu of naturally-regenerating Acacia stands by which they are

surrounded. This mark of indifference and incomprehension for African techniques is too

often manifest by European specialists or those

trained in Europe. In order to promote their

own cultural values, these researchers use the

terms “modern” and “scientific” as if laboratory and field techniques are completely inapplicable, for social or economic reasons, to the

truly native farming systems.

Acacia albida suffers from the division of the

technical services. The agronomist regards the

presence of the tree in the field as an adversary to be eliminated. The forester is not interested in the tree because Acacia albida does not

grow in what could be termed a forest and is,

therefore, not capable of being dealt with by

standard silviculture concepts. The role of

Acacia albida, including its growth and germination conditions, illustrates its marvelous

character which cannot be dissociated from its

genuine agricultural setting and illustrates the

necessity for deep-seated action to aid the

farming population. At this time in our intimate knowledge of political techniques for rural management, an end must be placed to the

absurd division of agriculturally related

disciplines which enclosures agricultural development specialists. It is not lack of concern

in the development specialists that causes this

problem but rather their overspecialized training, and above all the administrative structures

that thwart their action and hinder an integrated development plan which alone can be

effective, /
99

EFFECT OF TECHNOLOGY IMPLEMENTATION ON CAPITAL, LABOR,

AND LAND REQUIREMENTS

The initial inputs required for the systems described in this paper are low but the output/input ratio of the system is high. Yield increases

will tend to stimulate more investment in the

technology. For example, assume a farmer will

plant 1 ha with 200 Prosopis trees, The wholesale seedling cost should be approximately

$0.15, requiring an outlay of $30. These seedlings could be planted on his own land with

only a shovel, and some buckets for watering

the seedlings after transplant. If planted in regions at 500 mm annual rainfall, at year 10 the

tree should be producing 4,000 kg of pods per

hectare (16). These pods typically have protein

and nitrogen contents of 12.5 percent and 2.0

percent, respectively (4). Thus, the pods contain 80 kg of N, which is worth $40 at today’s

price of $50 per 100 kg of N. To achieve capture of 80 kg of N in pods from chemical fertilization, at least double the amount of nitrogen in the pods, or 160 kg of N, would have

had to have been applied. Thus, the cost to provide the nitrogen found in the pods would have

been $80 per year. Recalling that the farmer’s

cash outlay for seedlings was $30, his annual

return on the seedling investment from nitrogen alone is 270 percent. His $30 investment

in seedlings probably would be returned from

60 kg of N fixed by the plants in 2 to 3 years.

Because most of these trees are outcrossed

and planted only once every 30 to 50 years, it

would be most advantageous to plant clonal

material from outstanding individual trees.

Thus, commercial tree nurseries would be required to supply young trees to villages in the

countryside. Hopefully, farmers would recognize the importance of obtaining high quality,

clonally propagated seedlings for long-term

plantings, and would support commercial

village level nurseries that would deliver superior genetic stock to the local population,

Fertilizers other than nitrogen would be required. Phosphate and, to a lesser extent,

sulfate fertilizers stimulate nitrogen fixation in

legumes and would be a worthwhile investment. Phosphate fertilizers have approximately

the same unit price as nitrogen fertilizers but

only 10 percent as much phosphate is required.

Annual crops such as maize may capture only

40 to 50 percent of applied fertilizer partially

because of leaching beyond the root zone (37).

Shrubs and trees such as Acacia, Prosopis, and

jojoba commonly root to 10 meters (13) and

would achieve higher capture ratios of applied

fertilizer.

There is no reason to suspect that any more

or less pesticides would be required than in

other kinds of systems since insects would be

just as likely to attack tree or shrub crops as

annual crops. Due to the low till or no tillage

requirement for many of these shrub and treebased production systems, agricultural machinery requirements would be expected to be less

than those of conventional plant production

systems. Most harvesting in arid developing

countries is done by hand. With increased

yields of traditional crops stimulated by association with leguminous companion crops, the

demand for labor at harvesting time will increase. Production of large quantities of tree

legume pods, jojoba nuts, and fuelwood will

also increase the labor demand for harvesting

operations,

The low requirements for tillage machinery

and the lack of a nitrogen fertilizer requirement

will greatly reduce credit requirements for

these two traditionally high credit requiring

areas, On the other hand, the several years’

wait prior to harvest of perennial crops will require credit to pay for the seedling costs.
100

IMPACT OF WIDE-SCALE TECHNOLOGY IMPLEMENTATION

ON THE SOCIOECONOMIC STRUCTURE OF AGRICULTURE IN

DEVELOPING

Most of the plant systems (technologies) discussed in this report are widely used by subsistence farmers in the developing countries.

The plants used are primarily volunteer seedlings of unselected genetic stock that the farmers may prune and care for (40). This system

is comparable to use of unselected races of

maize and wheat as would have been done in

the late 1800s in the United States and Europe.

Placing these widely used, but scientifically unmanipulated plants into a research and development framework will probably yield increases

similar to that achieved by first inbred and then

hybrid lines of maize and other cereals.

Vigorous, naturally occurring tree legume

hybrids have been observed and clonally propagated by this author and demonstrate the

ease with which hybrids can be formed. Maize

yields increased from less than 20 bushels per

acre in the early 1900s to close to 100 bushels

per acre at present. The plant systems described here probably have the potential of

achieving the same yield increases. Perhaps a

two- to three-fold increase in plant productivity

can be expected in 5 to 15 years and a five- to

ten-fold increase in 50 to 100 years. Unlike

maize, these systems are based around nitrogen-fixers and will not require fossil-fuelCOUNTRlES

derived and energy-intensive nitrogen fertilizers.

Assuming these kinds of yield increases in

tree legume pod production, fuelwood production, cash crop production, soil fertility, and

ensuing staple food production, returns to

farmers can be expected to increase in the

same approximate fashion. As the farmers income rises, his demands for goods and services will rise and stimulate the economy as a

whole. A greater tax base will then be available to support more roads, schools, and health

services, which will in turn decrease unemployment.

The economy of a country with an agrarian

society is inextricably tied to the primary productivity of the ecosystem. As long as substantial progress is being made toward achieving

the economic goals of the rural population,

there will be fewer economic grounds fostering political instability. Past efforts to stabilize

the political systems of arid developing countries, such as Iran, with military hardware systems have proven futile. It is imperative to develop plant systems that have the capability to

directly impact the smallest farmers on the

local level to increase his well-being and decrease economically fostered political unrest.
101

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11

12.

13.

14

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51. Wight, J. R., and Black, A. L., “Range Fertiliza52

53

tion: Plant Response and Water Use,”]. Ranger

Manage. 32:345-349, 1979.

Xolocotzi, E. H., “Mexican Experience, ” Arid

Lands in Transition, H, E. Dregne (cd.), Amer.

Assoc. Adv. Sci., Publication No. 90.317-344,

1970.

Yermanos, D. M., Professor of Plant Sciences,

University of California-Riverside, personal

communication, 1980.

54. Zelada, L, G., Coordinator, Programma Pampa

del Tamarugal, CORFO, Santiago, Chile, personal communication, 1980.
103

Work Statement

Topic

Development of low energy input technologies to increase and stabilize productivity of

agricultural ecosystems in dry regions of less

developed countries. The contractor shall:

1.

2.

3.

4.

Describe how the technologies operate and

what beneficial or adverse impacts they

have or might have on enhancing the sustained production of food and forage from

tropical and subtropical soils.

Describe where the technologies are being

used. Describe whether each technology

is being used on a commercial level, a subsistence level, as a pilot program, or is

being applied only in the research state.

Describe who is conducting the major research on the technology. Describe what

organizations (AID, FAO, and others using

U.S. funds) are funding development of the

technology and what organizations are implementing it on a project scale.

Explain in some technical detail how these

technologies increase or decrease the need

for fertilizers, pesticides, irrigation, and

machinery when applied to tropical/subtropical soils.

Discuss the potential role of these technologies being used to restore, improve, or

sustain in perpetuity the food and forage

productivity of tropical and subtropical

soils, and the likelihood that they will be

used widely.

We appreciate that the author may not be a

specialist in economics or sociology; however,

his experience and insights on the following

questions are still of interest to OTA, especially

as they relate to lesser developed countries.

Therefore the contractor shall:

5. Describe a plausible research, development, and implementation scenario in

which these technologies realize their potential in enhancing productivity of tropical soils. What organizations would be involved? What levels of capital and trained

6.

7.

8.

personnel would be necessary? What degree of attitudinal changes would be necessary for consumers, farmers, government agricultural experts, bureaucrats,

politicians, foreign advisors, policy makers

in foreign aid or lending institutions, etc. ?

What biophysical (soils, climate, topography), cultural, and socioeconomic conditions would be most conducive to successful implementation of the technology?

Where do these conditions exist or where

are they likely to develop? To indicate the

priority of the various steps that need to

be taken on this technology, contractor

shall discuss how he (if he were the head

of a wealthy foundation) would spend $10

million on research, development, or implementation of the technology.

Describe the major scientific, environmental, cultural, economic, and political

constraints on development and implementation of these technologies.

Describe how implementation of these

technologies would affect the need, in the

region where they were implemented, for

inputs of capital (agricultural chemicals,

machinery, credit, seed, and other materials from the implemention farm), labor,

and land.

Describe what the impact of wide-scale implementation of these technologies would

be on the socioeconomic structure of agriculture in the implementing regions. For

example, does the technological implementation give rise to economies of scale,

or diseconomies of scale, that would make

large or small farm units more competitive? How would the technologies either

displace or create demand for farm laborers.

Deliveries

The contractor shall deliver to OTA the

original copy (not a reproduction) of the typewritten 25- to 35-page report, acceptable to

OTA, with abstract and literature citations, by

November 24, 1980.
Chapter VII

Azolla, A Low Cost Aquatic

Green Manure for

Agricultural Crops

A. Lumpkin

Soil Science

Agriculture

Thomas

Department of Agronomy and

College of Tropical

University of Hawaii

Honolulu, Hawaii

a n d

Donald L. Plueknett

Consultative Group on international

Agricultural Research

World Bank

Washington, D.C.
Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

What Is Azolla? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

What Are the Benefits of Using Azolla? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

The Present Status of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Where Azolla Is Being Used in Agriculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

How Azolla Is Used as a Green Manure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Who Is Doing Azolla Research? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

What Organizations Are Financing Azolla Research? . . . . . . . . . . . . . . . . . . . . . . 114

Azolla’s Effect on the Need for Agricultural Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. ... ... ...O... 115

Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Machinery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

The Potential Use of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

How Does Azolla Affect the Productivity of Tropical Soils? . . . . . . . . . . . . . . . . 116

The Potential Use of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

A Research, Development, and Implementation Program . . . . . . . . . . . . . . . . . . . . . . 117

The Program Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

What Organizations Should Be Involved? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

What Is the Necessary Level of Financial Support?. . . . . . . . . . . . . . . . . . . . . . . . 118

What Are the Personnel Requirements? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

What Are the Attitudes of Those Who Would Be Affected? . . . . . . . . . . . . . . . . . 119

What Are Conducive Conditions for Implementation of the Technology? . . . . . 119

Where Do Conducive Conditions Exist and Where Are

They Likely to Develop? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

What Is the Sequence of Steps Leading to Successful Implementation?. . . . . . . 120

Constraints on the Development and Implementation of Azolla Technology . . . . . . 120

Scientific Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Environmental Constraints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Cultural and Economic Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Political Constraints .. .. .. .. .<. ... .$..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

The Effect of the Implementation of Azolla Technology on the Need for Inputs . . 122

Capital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Farm Labor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Figures

Figure No. Page

l. Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

2. Azolla as Food and Fodder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

3. Geographic Distribution of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

4. Incorporating Azolla Into Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Chapter Vll

Azolla, A Low Cost Aquatic Green

Manure for Agricultural Crops

INTRODUCTION

The air we breathe is 79 percent nitrogen.

Plants need nitrogen to make the proteins that

allow them to harvest sunlight and carry on

natural processes. Unfortunately, nitrogen in

the air is in an inert N2 form that cannot be

used by plants. Only two kinds of organisms

have the ability to convert inert atmospheric

nitrogen to a usable form such as ammonia,

These two organisms are blue-green alga (cyanobacteria) and certain species of bacteria.

Rhizobium bacteria are the nitrogen-fixing

partners of the well-known legume/Rhizobium

symbiosis of soybeans, alfalfa, etc. The bluegreen alga anabaena are the nitrogen-fixing

partners of the virtually unknown Azolla/Anabaena symbiosis,

Until this century, nitrogen-fixing bacteria

and blue-green alga, existing under freeliving

or symbiotic conditions, produced most of the

new nitrogen entering the cropping system.

Almost all farmers had to include legumes in

their crop rotation in order to maintain soil

fertility. This traditional practice continued

until the discovery of fossil-fuel-dependent

methods of producing nitrogen fertilizer that

radically changed the economics of agriculture,

The use of legumes in crop rotation was soon

considered to be too expensive and troublesome and fell into disuse, except when grown

as a cash crop. The change was most apparent in developed countries and in developing

countries that adopted the “green-revolution”

technology.

However, during the 1970s this change began

to reverse itself, The rapidly rising price of

fossil fuel-dependent nitrogen fertilizers caused

the economics of agriculture to shift again,

Rising prices are causing researchers to seek

alternative methods for producing synthetic

fertilizer and causing farmers to reconsider

traditional methods for maintaining soil fertility.

The traditional legume crops are and will

continue to be the most commonly used nitrogen-fixing green manures, especially for

upland crops. However, they have certain

weaknesses for rice farmers. One of these

weaknesses is that rice is traditionally grown

on the most fertile and, consequently, intensively managed land. Rice farmers are reluctant to use part of the valuable growing season

on a relatively slow-growing, legume green

manure crop, Another problem is that many

rice paddies are flooded or waterlogged, particularly during the potentially productive early

part of the rice season when most of the transplanted rice is still in the nursery beds. Unfortunately, under waterlogged or flooded conditions most legumes cannot grow or fix nitrogen,

so usually the paddy fields stand idle for a

month or more while the rice seedlings mature

in the nursery beds. The fast-growing aquatic

Azolla has neither of these two weaknesses,

What Is Azolla?

Azolla is a genus of small aquatic ferns that

are native to Asia, Africa, and the Americas

(figure 1), Three Azolla species are native to

parts of the United States, They live naturally

in lakes, swamps, streams, and other bodies of

water, Some have been spread by man or natural means to various parts of the world. Some

are strictly tropical or subtropical in nature,

while others grow and thrive in either temperate or tropical climates. Azolla has been of interest to botanists and agriculturists for years

because of its symbiotic relationship with a

nitrogen-fixing, blue-green alga, Anabaena.

107
108 —

Figure 1.—Azolla

Vietnam.

The Azolla/Anabaena Relationship

The most remarkable feature of azolla

symbiotic relationship with the blue-green

is its

alga,

Cells of the nitrogen-fixing blue-green algae, Anabaena, look

like a string of beads. The larger egg-shaped cells specialize in producing nitrogren fertilizer while the more numerous smaller cells harvest sunlight.

Anabaena azollae. The delicate fern provides

nutrients and a protective leaf cavity for the

Anabaena, which in turn provides nitrogen for

the fern. Under suitable field conditions, the

fern/alga combination can double in weight

every 3 to 5 days and fix atmospheric nitrogen

at a rate exceeding that of the legume/Rhizobium symbiotic relationship. Azolla can accumulate up to 2 to 4 kilograms of nitrogen/
109

ha/day (equivalent to 10 to 20 kg of ammonium

sulfate), and since the Azolla/Anabaena combination grows in aquatic conditions, it can

provide a potential nitrogen source for flooded

crops such as rice. The exploitation of this potential is a challenge to agricultural scientists.

What Are the Benefits of

Using Azolla?

Producing Nitrogen Fertilizer for

increasing Crop Yields

Azolla plants are described by the Chinese

and Vietnamese as being miniature nitrogen

fertilizer factories. Indeed the Vietnamese call

them indestructible fertilizer factories, since

azolla continued to produce nitrogen fertilizer

for Vietnamese rice paddies even during the

height of the Vietnam war.

The nitrogen fertilizer fixed by azolla becomes available to the rice after the azolla mat

is incorporated into the soil and its nitrogen

begins to be released through decomposition.

In 25 to 35 days azolla can easily fix enough

nitrogen for a 4 to 6 ton/ha rice crop during

the rainy season, or a 5 to 8 ton/ha crop under

irrigation during the dry season.

Maintaining Soil Fertility

As a green manure, azolla’s influence on soil

fertility is due to its organic matter and nitrogen. A humus compound is formed as a result

of the incorporation and decomposition of

azolla. Humus increases the water holding capacity of soil and promotes aeration, drainage,

and the aggregation essential for highly productive soils, Organic matter can bind together

soil particles and makes clayey soils more

friable.

In addition to its influence on soil physical

properties, azolla is important in the cycling

of nutrients, While azolla is growing in the

paddy, it fixes nitrogen and also absorbs nutrients out of the water that might otherwise

be washed away. When the azolla is incorporated into the soil and humus is formed,

these nutrients are slowly released into the soil

as decomposition progresses.

Even though azolla appears to be a rather

delicate plant that would rapidly decompose,

it actually takes six weeks or more for most of

the nutrients to be released because the plant

has a rather high lignin content. Slow decomposition gives a natural slow release effect that

is ideal for efficient absorption of the nutrients

released. Another factor in azolla effectiveness

as a green manure is its low carbon to nitrogen ratio of about 10:1. This high ratio ensures

that azolla nitrogen will not be tied up by

bacteria that are involved in decomposition of

an over abundance of carbonaceous plant

residues.

Producing Fodder for Pigs, Ducks,

and Fish

Azolla has traditionally been used as a fodder throughout Asia and parts of Africa. It is

fed to pigs, ducks, and fish (figure 2), The grass

carp (Ctenopharyngodon idella), Israeli Carp

(Cyrinus carpis), and Tilapia mossambica prefer azolla over most other aquatic weeds as a

source of food, Small lots of azolla growing in

canals and ponds as food for pigs and ducks

are ubiquitous throughout southern China.

Azolla as a fodder probably has a longer history than as a green manure, There may even

be potential for direct consumption by man,

In India, women make a tasty deep fried dish

of azolla mixed with batter (7),

On a dry weight basis, azolla has a protein

content between 13 to 24 percent, One hectare

of azolla can produce 1 to 2 tons of fodder per

hectare per day, equivalent to 10 to 30 kg of

protein per day. When these statistics are considered, azolla has a tremendous potential as

a fodder crop in developing countries and also

in the United States.

Recent work in India at G. B. Pant University indicates that azolla maybe useful as a fodder for cattle. In trials there, growing heifers

gained 0.33 kg/day when fed 0.9 kg of dried

azolla with 2.1 kg of a 2:1 ratio of dry wheat

straw and sugarcane tops. Control animals that

were fed the same amount of wheat straw and

sugarcane tops, but also received 1.5 kg of a

concentrate feed, gained only 0.14 kg/day (l).
110

Figure 2.—Azolla as Food and Fodder

Although azolla is most commonly used

(center) and fish and as a compost (right)

as an organic fertilizer for rice, it can also be used as a fodder for pigs (left), duck

for upland crops. Many of the pigs which are grown to produce China’s famous Jinhua hams are fed on a diet which includes azolla.

Azolla is a preferred forage for many species of herbivorous fish. Azolla may also have potential for direct consumption

man if attractive uses can be developed. The photo on the right shows a deep fried dish of azolla mixed with batter.

by

Suppressing the Growth

of Aquatic Weeds

Agricultural economists have estimated that

Asian farmers, particularly women, spend

more time weeding than on any other activity

required for rice production. Although research is insufficient, it is commonly believed

that azolla suppresses the growth of certain

aquatic weeds. Weed growth is suppressed

when azolla forms a thick, virtually light-proof

mat. There are probably two mechanisms for

this suppression, the most effective being the

light-starvation of young weed seedlings by the

blockage of sunlight. The other is the physical

resistance to weed seedling emergence created

by a heavy, interlocking azolla mat. In some

weed-infested rice fields, the benefit from

azolla weed suppression may even surpass its

benefit as a nitrogen source. Rice seedlings are

not affected by azolla’s weed suppression effect because, when transplanted, they stand

above the azolla mat.
111

THE PRESENT STATUS OF AZOLLA

Where Azolla Is Being Used in

Agriculture

Azolla is already being grown commercially

in China and Vietnam, where its usefulness has

been known for years, Once restricted in use

because of propagation problems, the fern is

now being used in larger crop areas (figure 3),

Chinese use of azolla goes back hundreds of

years, at least to the Ming dynasty, Its use in

Vietnam dates to the 1lth century. These two

are the only countries with a long history of

azolla cultivation. The practice probably began

with recognition that the spontaneous growth

of wild azolla in rice fields had a beneficial effect on the crop. Organized use of the fern

could not occur, however, until reliable methods were developed to overwinter and oversummer the fern. Since azolla can only be

grown from vegetative material, it must be protected during seasons that are too severe for

its survival.

The original sites of azolla cultivation are

thought to have been Zhejiang Province in

China and Thai Binh Province in Vietnam. Until recently certain villages in these places had

temples dedicated to the mythological discoverers of azolla. At the end of the 19th century azolla was being cultivated at favorable

sites along the east Asian Coast as far south

as 200 N latitude on the Red River delta in Vietnam and northeastward through Guangdong

and Fujian Provinces to Wenzhou District near

280 N latitude in Zhejiang Province, China.

A major push for expanding the use of azolla

began in China and Vietnam in the early 1960s.

Before that time it was common for certain

families or villages that had mastered the intricate techniques of oversummering and overFigure 3.—Geographic Distribution of Azolla

Distribution of Azolla species throughout the world, This distribution map is rapidly becoming outdated because many azolla

species and varieties are being moved about and introduced into new places as research on azolla grows.
112

wintering azolla to control the supply of azollastarter-stocks in the spring. Peasants had to

travel to these villages to purchase their spring

plants.

After the revolutions in China and Vietnam,

the new governments eventually recognized

the worth of azolla and began officially promoting its use and organizing the construction

of propagation centers.

During colonial days in Vietnam, French

scientists reported on the use of azolla and did

some preliminary research, but its cultivation

was never promoted officially. At the end of

the colonial period, azolla was grown on about

40,000 hectares1 as a green manure during the

winter for the spring rice crop. In 1958, the

new government established an azolla research

center at the Crop Production Research Institute and set up an extension network with over

1,000 inoculum production bases to stimulate

use.

Despite this promising beginning, the big

push in azolla research did not come until the

early 1960s. Articles on azolla began appearing in 1962, culminating in several articles and

a large book (9).

Since the introduction of high yielding rice

varieties to Vietnam in the early 1960s, most

azolla has been grown as a monocrop before

the spring rice. The cultivated area reportedly

doubled from 1965 to about 700,000 hectares

in 1978. As in China, azolla cultivation in Vietnam is seldom practiced in summer because

the A. pinnata var. imbricata native to the

Asian continent is sensitive to high temperatures and insects.

Vietnamese scientists have collected over 30

varieties of local azolla and have selected

superior strains for heat, cold, salt, and acid

tolerances. Despite these advances, reportedly

most communes and cooperatives have not

adopted these improved azolla varieties.

The Chinese story is much the same as that

of Vietnam, although much more was known

of the Vietnamese experience because of the

‘ 1 hectare = 2.47 acres.

availability of publications in English and

French as well as in Vietnamese. Recently, information from China has become available

(3,4,11,2,5).

Today, azolla is grown as a green manure on

about 1.3 million hectares of rice in China. Research and development activities have increased significantly, as have extension activities to promote its use. Large posters have been

produced to inform the public of azolla’s usefulness and of its management requirements.

How Azolla Is Used as a Green Manure

Azolla can be used as a green manure (figure

●

●

●

4):

by growing it as a monocrop and then incorporating it as a basal manure before the

rice is transplanted; or transported to

another site for use on upland crops;

growing it as an intercrop and incorporating it as a top dressing manure after the

rice is transplanted; or

by growing it both as a monocrop and an

intercrop.

All three systems can be successful but, as

is common in agriculture, use of the green

manure crop requires some adjustments in

management of both the green manure and the

main crop.

Monocrop Azolla is used in China and Vietnam during winter and spring to produce nitrogen for the spring rice crop. The same technique is used to produce nitrogen for the early

summer rice crop, but this is less common

since the growth of Azolla pinnata is affected

by high temperature and heavy pest attack during mid to late summer.

Intercropped Azolla is usually grown with

the rice in places where there is no time available in the cropping system for the monocropping of azolla. As an intercrop azolla will be

initially incorporated by hand or rotary rice

weeder and then later killed by heavy shading

and/or high temperatures—with subsequent

decomposition and release of nitrogen to the

crop—at the stage of maximum rice tillering.
113

Figure 4. — Incorporating Azolla Into Soi l

-4-

Two of several methods for soils incorporating a monocrop of azolla as a basal green manure for rice. Both photos were taken

during the spring of 1980 in Guangdong province, China. The photo on the left is A. filiculoides, the photo on the right IS Azolla

imbricata

The photo on the left shows an azolla beater being used to spread inoculum azolla after it was introduced into the field of

a second later summer rice crop to grow with the-rice as an intercrop.

The top center photo shows an azolla pusher which is used to spread inoculum azolla if it is applied to a rice crop after the

rice is transplanted, or is used to concentrate and collect azolla in a nursery. The bottom center photo shows a bamboo pole

being used to collect azolla growing in a canal.
114

Growing both monocrop and intercropped

Azolla is a technique that is designed to use

the growing period for azolla before the planting of the rice crop, plus production of added

nitrogen for the crop through cultivation of intercropped azolla, In this system two different

varieties of azolla may be used in each of the

different periods. Different temperature and

light sensitivities of azolla varieties make this

possible.

Who Is Doing Azolla Research?

A number of centers are conducting azolla

research. Most of this work is less than 5 years

old. Both China and Vietnam are studying

Azolla pinnata var. imbricata under their own

conditions. Recently, the Zhejiang Academy of

Agricultural Sciences has had an opportunity

to evaluate the other Azolla species (carolinian, filiculoides, mexicana, microphyhlla,

and nilotica) for use in China.

Many developing country rice research

centers have begun azolla research, but with

little success to date. Probably the most successful program is in Thailand, where the Ministry of Agriculture has been sponsoring an

azolla program that has progressed through the

regional extension stations and has now

reached the stage of demonstration plots in the

fields of progressive farmers.

The International Rice Research Institute

started an azolla research program nearly 8

years ago (10), IRRI is studying the use of several azolla species for use in flooded rice.

There are three major centers of azolla research in the United States. One is the University of Hawaii, where agronomic and physiology studies are underway to characterize and

understand the usefulness of all azolla species

in tropical crop production systems, including

rice and taro (5). The work is led by T. A. Lumpkin who was selected by the National Academy of Sciences to conduct research on azolla

in the People’s Republic of China in 1979 and

1980 at its foremost azolla research center, the

Zhejiang Academy of Agricultural Sciences at

Hangzhou.

Studying azolla management to fit temperate,

broadcast-sown production systems is the

focus of the research program at the University of California at Davis (8). Research objectives at UCD include use of A. filiculoides a s

a monocrop basal green manure crop for

springsown rice and A. mexicana as an intercrop in rice. The UCD program received a

grant from the USDA Competitive Grants Program in 1980 and a grant from the National

Science Foundation.

Basic physiology studies are the focus of the

program at the Kettering Laboratory focused

on understanding the Azolla/Anabaena relationship (6). The program has been supported

by a grant from the National Science Foundation and a grant in 1979 from the USDA Competitive Grants Program.

Another azolla research program that we

know less about is at Virginia Commonwealth

University, where the isolation and reconstitution of the Azolla/Anabaena association are being studied. This work has been supported by

a grant from the USDA Competitive Grants

Program; the first grant was made in 1979. Dr.

Jack Newton of the USDA in Peoria, Illinois,

has done some research on isolation of Anabaena from Azolla.

Countries that have initiated or plan to initiate azolla research include: India, Nepal, Thailand, Bangladesh, Burma, Indonesia, Malaysia,

The Philippines, Sri Lanka, Egypt, Peru, and

the West African Rice Development Association, headquartered in Liberia. In addition, several other countries have expressed an interest in the fern and its uses.

What Organizations Are Financing

AzoIla Research?

Current financial support for azolla research

in the U.S. comes from AID (a small 211(d)

grant), the National Science Foundation (2

grants), and the USDA (Section 406 and Competitive Grants). The USDA Competitive Grants

office has made three grants totaling $278,000

to the University of California at Davis, Ket-
115

tering Laboratory, and Virginia Commonwealth University. The National Science Foundation has made two grants: one each to

University of California at Davis and Kettering Laboratory. In all probability, less than

$300,000 per year is now being invested i n

azolla research in the United States, The work

at Hawaii is sponsored by small 211(d) grant

for nitrogen fixation from the Agency for International Development and by a research

grant from the U. S.D.A. under the Section 406

program of the 1966 Food for Peace Act, and

by Hawaii Agricultural Experiment Station

funds,

AZOLLA’S EFFECT ON THE NEED FOR AGRICULTURAL INPUTS

Fertilizers

Successful cultivation of azolla requires the

application of a certain amount of phosphorus

fertilizer (0.5 to 1.0 kg p/ha/week), but this does

not necessarily mean an increase in the amount

of phosphorus fertilizer required to produce a

crop of rice. The application of phosphorus is

usually necessary for a good crop of rice, but

instead of applying it directly to the rice, the

phosphorus can be given to the azolla first in

small weekly applications. Once the azolla is

incorporated into the soil and begins to decompose, the phosphorus becomes available for the

rice crop. Thus phosphorus originally intended

for the rice crop is first cycled through the

azolla. The phosphorus enables the azolla to

grow and fix nitrogen that will be used by the

rice. One kilogram of phosphorus applied to

azolla results in the fixation of 5 kilograms of

nitrogen, North Vietnam is deficient in petroleum products for the production of nitrogen

fertilizer, but has sufficient phosphate deposits to fuel its miniature azolla nitrogen factories.

In certain deficient soils, azolla responds to

the applications of other nutrients such as

potassium, but these usually must also be applied for a high yielding rice crop. In some rare

deficient soils, the addition of small amounts

of molybdenum and/or iron have proved useful

to increase azolla’s rate of nitrogen fixation.

The Chinese often apply river mud, ash, and

animal manure to supplement the phosphorus

given to azolla.

Pesticides

Azolla is attacked by larvae of several species of moths and midges and by certain kinds

of snails and beetles. These pests are especially

destructive during the summer season and

must be carefully controlled or the azolla can

be devastated. However, azolla is usually not

cultivated on a large scale during the seasons

when insects are rampant, but is maintained

in oversummering nurseries, In addition, even

when azolla is cultivated in the field during the

summer season, the pesticides normally used

on rice crops, such as diptenex, sumithion,

malathion, and carbofuran are usually adequate for controlling azolla insects,

Irrigation

Azolla is a delicate, freefloating aquatic plant.

Although it can last for months in a refrigerator, it cannot survive for more than a few

hours on a dry soil surface under direct summer sunlight, Since technology has not been

developed for the use of azolla seeds (spores)

in cultivation, a small amount (1 to 10 percent

of inoculation requirements) of azolla plants

must be maintained through the seasons when

azolla is not being cultivated in the fields. This

means that in tropical and subtropical areas a

certain amount of water must be available

throughout the year either to maintain azolla

in nurseries or to cultivate it in the fields. The

oversummering maintenance of azolla should

not be a problem in regions where standing
116

water is present throughout the year, such as

in Bangladesh, or in regions where azolla can

be maintained in small nurseries beside mountain springs.

The period when irrigation is most critical

is when azolla is to be grown in the fields as

a green manure. If azolla is cultivated as a

monocrop before the rice, which is the most

effective way, water must be available for

flooding the fields. If water is not available,

azolla cultivation will have to be delayed until

it can be grown as an intercrop with the rice.

Azolla grows as an intercrop with rice during

the first 20 to 30 days after transplanting. In

this period, the paddy fields must remain

flooded with at least a few centimeters of

water, Although some species of azolla can survive on mud, as is commonly seen in Hawaiian taro fields, they need standing water for

good growth. Thus rice paddies dependent

upon rain water, where short periods of

drought often occur during the first month of

rice cultivation, will not be suitable for azolla

cultivation. Also, if extremely hot periods occur when water temperatures exceed 400 C,

cooler water must be available for pumping

into the fields to prevent the azolla from dying of heat stress.

Even though azolla cultivation require some

extra irrigation water, it must be remembered

that in fields where little or no nitrogen fertilizer is used, the cultivation of azolla will significantly increase the efficiency of water use.

If azolla increases the yield of rice from 2.5 tons

to 5 tons, then the efficiency of water use has

nearly doubled.

Machinery

The need for machinery is not a handicap to

successful azolla cultivation. Even the most

primitive villages can manufacture the basic

tools required for the cultivation of azolla.

These are made from such locally available raw

materials as bamboo and wood. A simple

metal/wood tool, costing a few dollars, for incorporating intercropped azolla into the soil

can be manufactured in villages by a blacksmith. This tooI is not essential, but is more efficient than soil incorporation by hand. An

even more efficient multiple row incorporating

machine, with a small gas engine, would have

to be manufactured commercially.

How Does Azolla Affect the

Productivity of Tropical Soils?

Azolla affects soils in the same way as any

other nitrogen-fixing green manure. It contributes nitrogen, which, after water, is the most

common limiting factor to higher crop yields.

The application of nitrogen to increase crop

yields is the cornerstone of the “green revolution.” All new rice varieties are bred for high

yielding response to nitrogen fertilizers.

The loss of organic matter is a primary cause

of decreasing crop yields in the Tropics. A decrease in soil organic matter results in soil

structure deterioration, lower plant nutrient reserves from the organic matter, and a lower

cation exchange capacity. Cultivated tropical

soil tend to have lower organic matter contents

and soil nitrogen than undisturbed tropical

soils. This is especially true with Oxisols and

Ultisols.

What is the likelihood of Azolla widespread

use? Azolla is cultivated as a green manure on

about 2 percent of the harvested rice area of

China and about 5 percent of the spring rice

crop. In Vietnam, azolla is grown as a winter

green manure for 8 to 12 percent of the country’s total harvested rice area, and about 40 to

60 percent of the irrigated spring rice in the
117

Red River delta. Estimates of China’s terrestrial

green manure crop (mostly legumes) are as

high as 7 million hectares, or about five times

the total estimated cultivation area of azolla.

As strains or species of azolla are found that

are less sensitive to high water temperatures

during summer, the areas of azolla in China

and Vietnam will probably expand.

The major areas where azolla should prove

useful in rice production in the Tropics are

those where: 1) rice is transplanted, 2) labor is

plentiful, and 3) some control of irrigation

water is possible. Also, countries with effective research and extension services may have

more success with popularization of azolla.

Azolla technology is not applicable yet for

areas where rice is broadcast-sown, except as

a monocrop, preplant, basal green manure. An

azolla mat can suppress tiny, broadcast-sown

rice seedlings; for that reason, intercropped

azolla will probably not be successful in broadcast-sown rice unless it is inoculated in the

fields after the rice seedlings have become

established and are growing well above the

water surface.

With the above criteria in mind, the most

likely countries to adopt azolla include parts

of India, Bangladesh, Thailand, Indonesia,

Philippines, Nepal, Peru, and the Dominican

Republic.

RESEARCH, DEVELOPMENT, AND IMPLEMENTATION PROGRAM

The Program Elements

Two basic azolla management systems need

research attention; these are: 1) tropical, labor

intensive systems; and 2) temperate, capital intensive systems, The tropical systems will be

focused mainly on developing countries, and

will include these principles:

●

●

●

●

●

●

●

labor intensive,

land intensive,

small farm based,

crop intensive,

maximizing opportunities for year-round

production,

first priority to more intensive use of azolla

in transplanted rice systems, and

second priority to use in broadcast-sown

systems.

The tropical program should set the following objectives:

1. To find azolla varieties that are less sensitive to high water temperatures (above

27° C) and pest and disease attack. This

would have the effect of expanding azolla

use from its present primary role as a

spring green manure and its secondary

role as a fall green manure to the point

2.

3.

where it could be a primary green manure

in summer in transplanted rice.

To collect and characterize all of the six

known azolla species, and to evaluate

them for use year-round in tropical transplanted rice production systems. [Note: in

1980 preliminary studies by Lumpkin and

his Chinese co-workers in China, A. microphylla shows great promise as a summer

green manure in south Central China, and

a winter green manure in the south. Also,

A. nilotica shows promise as a fall green

manure in China. Neither of these species

has ever been tested in rice before. Further

mission-oriented research could have high

payoff in the near future.]

After characterization and early testing,

distribute promising strains to- national

program centers for synthesis, design, and

testing of new rice cropping systems based

on azolla as a green manure.

Temperate, capital-intensive rice production

systems, primarily centered on broadcast-sown

or drill-sown rice. This work should focus on

developed countries, and on middle-income

countries (e.g., Brazil and Colombia, and other

countries, primarily in Latin America where

similar rice production systems are used).
118

What Organizations Should Be

Involved?

In the United States there are two places

where azolla is being studied for use in agriculture. The University of California at Davis

is conducting research on azolla for use in

temperate zone, broadcast-sown rice, and

would be the logical leader for the temperate

rice work, The University of Hawaii has a program on evaluation of azolla for use in tropical production systems, and would be the

logical leader for the tropical efforts. Kettering Laboratory, Virginia Commonwealth University and USDA have specialized programs

that could play supporting basic research roles

for the temperate and tropical programs.

Links to developing countries will be necessary. Important programs elsewhere include

the Zhejiang Academy of Agricultural Sciences,

Hangzhou People’s Republic of China, (the

University of Hawaii has a cooperative program there already); the Fujian Province, PRC

(IRRI has links with this group); IRRI, and national programs in Thailand, India, and Nepal.

Several national research programs were initiated after an FAO-sponsored azolla training

mission by T. A. Lumpkin in 1977. Also T. A.

Lumpkin and J. L. Walker of the University of

Hawaii, on behalf of the Inter-American Development Bank, visited Uruguay, Brazil, Peru,

and Colombia in 1979 to assess the potential

for azolla in those countries.

The West African Rice Research and Development Association (WARDA) is also interested in establishing an azolla research program, and they should be tied into the tropical

network,

What Is the Necessary Level of

Financial Support?

We will speak first of priority areas of research. There is need to carry out several

priority activities soon. These include:

c More extensive and complete collection of

azolla species and varieties for evaluation

in agriculture. Indeed, collection should

take precedence over efforts to breed

azolla because the array of variability available in nature is clearly great, and this

should be collected and characterized

before beginning breeding programs.

Characterization of azolla varieties as to

tolerance of high and low temperature,

phosphorus levels in water, pH, light, and

other growing conditions should be of high

priority.

Testing and fitting existing azolla varieties

into rice production systems should receive high priority.

These three priority areas should receive first

attention for funding. Related basic research

on physiology of the Azolla/Anabaena symbiosis, biochemistry of the association, etc., can

probably be funded through basic research

grants from NSF or USDA.

The applied aspects of collection, characterization for use in agriculture, and fitting into

rice production systems could be done for the

Tropics for about $400,000 to $600,000 per

year. This would allow funds for collaborative

collecting trips to assemble a wider germplasm

base, to conduct screening trials for tolerance

to the physical and growing environment, and

to run first assessments of potential usefulness

in production systems. Such funding would

also allow some limited funds for working with

collaborators in a tropical azolla network, It

would be desirable to have some funds for

assisting, through small subgrants, the conduct

of specific desired research programs in cooperating countries.

Training, both nondegree and degree, should

receive attention early in the program. The first

training should emphasize azolla research techniques (e.g., many programs have failed because researchers did not know how to keep

azolla alive during hot or cold weather). Later,

training could begin to stress field management, We believe the general principle to follow in funding azolla research is probably that

continuity of funding over the first several

years will be more effective than heavy funding over a shorter time. Collecting, characterizing, and evaluating production systems needs

to be done by a team that will require continuity for effectiveness. Such a team should in-
119

elude an algologist or cyanobacteria specialist.

It should have access to laboratory, greenhouse, and field facilities. The tropical leading

institution should be able to grow azolla in the

field at any time of the year, and to grow azolla

in such a way that all growth stages can be

available at any time.

The temperate program will probably require

funding in the same order of magnitude as the

tropical program. The temperate network may

be easier to establish because: 1) the potential

countries involved are either in the developed

or middle income categories and therefore may

have more resources at their disposal, and 2)

the countries’ institutional research capacity

will be much stronger than those of the tropical LDCs.

Some savings may be made and efficiency

gained through close cooperation between the

temperate and tropical programs. Joint collection trips and close adherence to jointly—

determined protocols for testing and evaluation within the networks should save both time

and funds.

What Are the Personnel Requirements?

We believe the major research networks

should be oriented toward practical adaptation

of azolla to agricultural production. Therefore,

agronomists with strong physiology and field

production backgrounds will be required, As

was previously stated, specialists in blue-green

alga should be available in the parent institution or nearby.

The program should provide for laboratory

and greenhouse assistance, as well as field

workers for the field experiments, It is probable that some of this work may be provided

by graduate students and student help and by

existing institutional farm staff, but some fulltime assistance will be needed.

Research assistantships should be provided

in the program; this will get the training program going as early as possible.

What Are the Attitudes of Those

Who Would Be Affected?

Most research organizations have become

aware of azolla and have some idea as to its

potential. A few extension specialists (notably

in rice) probably also know something about

it. Beyond that, except in China and Vietnam

and a few individuals in developed countries,

the farmers would know nothing of the plant

and its potential use in rice. It may be that since

azolla is already used successfully in China and

Vietnam it may be easier to popularize

elsewhere.

What Are Conducive Conditions for

Implementation of the Technology?

Conditions conducive to azolla use in the

Tropics include:

●

●

●

●

transplanted rice;

rural labor supply;

assured water supply and some control of

water; and

also, for now, places that grow spring or

late summer/fall rice crops because of the

high temperature susceptibility of A. pinnata in summer.

For rice in temperate zones, the conducive

conditions are much less certain because success has not yet been conclusively demonstrated. Factors thought to be important for

broadcast-sown rice include:

●

●

●

growing cold-tolerant azolla (e.g., A .

filiculoides) as a monocrop green manure

to be incorporated into the soil before

sowing;

growing heat-tolerant, shade-sensitive

azolla as an intercrop with the broadcast

sown rice during the summer; and

having an assured source of water to grow

the monocrop azolla before planting of

rice.
120

Where Do Conducive Conditions Exist

and Where Are They Likely to Develop?

Most of the countries of Asia have conducive

conditions for use of azolla. Special opportunities for success seem to be present in Thailand, Bangladesh (aus crop), and the Philippines (irrigated dry season crop). In Latin

America, Peru and the Dominican Republic appear to have the proper rice production systems to make Azolla use a possibility.

What IS the Sequence of Steps Leading

to Successful Implementation?

The first two things a country must learn to

do are how: 1) to keep azolla plant materials

alive year-round and 2) to multiply azolla stocks

in order to have inoculant materials available

for use in the rice crop. Principles for such

techniques can be learned in training programs

at the network headquarters or azolla research

centers. Such techniques need to be taught

widely to extension workers and to innovative

farmers.

In some conditions in Asia, A. pinnata, A.

pinnata var. imbricata and perhaps A .

filiculoides could be used now as a monocrop

basal fertilizer before transplanting of rice.

This should be easy to popularize for the late

winter or early spring rice crops.

Before azolla is used in rice, however, it

should be tested under local conditions. As was

stated, keeping azolla alive throughout the year

and finding ways to multiply it for field use are

the most important steps in beginning a program. The next step is testing under local conditions to find ways to fit it into the existing

production system. Use as a basal fertilizer

before transplanting is probably easiest, but if

the crop cycle doesn’t allow time to grow an

azolla green manure crop between rice crops,

then it will be necessary to grow it as an intercrop. In that case the rice must be grown in

rows so that incorporation of the azolla can be

done. This is just an illustration of some of the

considerations to be dealt with in using azolla

in agricultural production systems.

CONSTRAINTS TO THE DEVELOPMENT AND IMPLEMENTATION

OF AZOLLA TECHNOL0GY

Scientific Constraints

The global azolla research effort is disorganized and much of the work is repetitious and

often useless. Certain problem areas, such as

those involving agricultural engineering, have

been ignored. Much of the support is going to

finance esoteric work, while many of the people doing the research have little understanding of the problems that prevent azolla’s widespread use by peasant farmers. Much of the

work is involved in trying to improve laboratory specimens of azolla, while the vast differences in wild varieties remain unexamined.

Many of the problems preventing the widespread use of azolla require a multidisciplinary

research approach, but so far azolla research

has been cloistered into individual departments, even in the international institutes.

Funding agencies can assist in ensuring that

azolla research will be directed toward real

problems and needs by requiring multidisciplinary, linked efforts that focus on use of

azolla on farms. This does not mean that basic

research will be precluded, but it will ensure

that practical, mission-oriented research will

not be neglected.

Environmental Constraints

Water is the primary environmental constraint to the cultivation of azolla. Azolla is a

freefloating aquatic fern and is therefore limited to locations that have an abundant, stable

water supply during field cultivation.

Temperature and humidity: For practical

purposes, azolla survives within the water temperature range of O to 400C; beyond this range,
121

death will result, For adequate growth during

field cultivation, the daytime water temperature should stay within the range of 15° to

35 ‘C. Humidity and temperature interact in

their effect on azolla. Very high humidity and

high temperature or very low humidity and low

temperature are both detrimental to the growth

of azolla.

pH: The pH of the paddy water plays an im

portant part in the ability of azolla to survive

Besides directly affecting the growth of azolla,

pH also affects the availability of nutrients,

especially phosphorus. Low pH and high pH

can cause formation of insoluble compounds

that tie up available phosphorus; the phosphorus in such insoluble compounds is unavailable to azolla. Azolla grows best within a

pH range of 5 to 7 and can survive a range of

3.5 to 10.

Available nutrients: Azolla growth depends

on an adequate supply of essential elements in

the water or in the surface layer of mud. These

elements must also be relatively balanced, Usually the addition of phosphorus and sometimes

potassium is all that is necessary to ensure

good growth.

Cultural and Economic Constraints

For most farmers, azolla cultivation would

be an entirely new way of using green manure.

The idea of using an aquatic plant for such purposes is not part of most agricultural heritages,

Farmers in tropical Asia traditionally have

grown upland legume crops, such as milk vetch

or lentils (as a cash crop), after harvesting the

monsoon rice crop. Most have never grown an

aquatic green manure, and many have rarely

grown a legume that is not a food or forage

crop. To some, especially the hungry, growing

a crop that is to be plowed under as a green

manure may seem impractical.

Azolla can be used as a forage for pigs,

ducks, and fish. However, the raising of swine,

ducks, and fish is uncommon in some places.

Also, it is generally believed, although untested,

that cattle and water buffalo will not eat azolla.

The year-round cultivation of azolla is more

complex than the cultivation of rice. Without

support, many poor uneducated rice farmers

probably would not or could not grow azolla,

Diligent rice farmers, such as those in Nepal

or Thailand, probably could master azolla

cultivation techniques, just as farmers in China

and Vietnam have. As a result of unfavorable

land ownership patterns, low grain prices, and

other social or economic difficulties, some

peasant rice farmers do little more than haphazardly plant their fields and then wait for

harvest time. For them, meticulous farming

does not yield sufficient benefits to their family,

Furthermore, transplanted rice in some parts

of Asia is not planted in rows, a necessary

measure for azolla to be incorporated as a basal

fertilizer.

Also, many farmers who could not be convinced to use nitrogen fertilizer in the 1960s

when it was inexpensive, will be unlikely to

cultivate azolla. The exceptions might be peasant farmers who want to improve their crop

yields but do not have the capital to purchase

nitrogen fertilizers. Also, farmers who have

given up using nitrogen fertilizer because of

the high cost might be convinced to use azolla

as long as they can afford the cash outlay for

relatively small amounts of phosphorus fertilizer and pesticides. They would have to purchase about 100 kg of single superphosphate

to grow one hectare of azolla for 4 to 5 weeks.

If properly applied, the phosphorus would result in as much nitrogen as 500 kg of commercial ammonium sulfate fertilizer,

Azolla cultivation could significantly reduce

the fertilizer input costs of raising high yielding

rice crops, but would still require the purchase

of certain inputs, especially phosphorus fertilizer. Farmers unable to obtain these inputs

would probably find it difficult or impossible

to raise azolla.

Political Constraints

The widespread cultivation of azolla is found

only in Communist countries. Azolla was

cultivated in both China and Vietnam before
122

the present governments came to power, but

on only a small fraction of the area that azolla

covers today. Analyzing the elements of this

situation is difficult because the cultivation of

azolla in China and Vietnam cannot be compared to its cultivation in countries with different political systems. Because azolla cultivation is just being introduced to farmers

elsewhere, there has been insufficient time for

other countries to develop successful azolla

programs that are in line with their political

systems.

Even without an adequate comparison, it is

obvious that the successful azolla programs in

China and Vietnam owe a considerable amount

to the way their farming systems are organized.

The commune and cooperative organizations

of these countries that use azolla have highly

trained azolla teams, whose sole function is to

ensure the success of azolla cultivation. Training workshops to learn the newest techniques

are held annually from the national level down

to the local azolla team level. In addition, every

level regularly publishes pamphlets about the

practical applications of azolla.

The higher levels of the Chinese and Vietnamese systems can be transferred with minor

modifications to other countries, but not the

lower local levels. Most governments do not

have the power to enforce their will on independent peasant farmers as effectively as China

and Vietnam can influence their communes

and cooperatives. Nor can a peasant farmer be

expected to master all the intricacies of successful azolla cultivation that are known by a

highly trained commune azolla team.

THE EFFECT OF THE IMPLEMENTATION OF AZOLLA TECHNOLOGY ON

THE NEED FOR INPUTS

capital

Capital requirements for azolla cultivation

are quite small. For most farmers, only a small

amount of phosphorus fertilizer, often no more

than would be required for the rice crop, and

pesticides to protect the azolla from pests and

diseases are all that will be required.

Farm Labor

In essence, the cultivation of azolla exchanges labor for nitrogen fertilizer. The present azolla technology is based on the Chinese

and Vietnamese models and thus is extremely

labor intensive. In fact, the cultivation of azolla

cannot be adopted by countries with mechanized rice farming systems until new capital

intensive technology is developed.

Adoption of azolla cultivation by a developing country can only increase the demand for

farm labor, especially when nursery stocks are

being multiplied and during field cultivation.

In addition, a few workers will have employment year-round because of the need to maintain azolla nurseries during the off season.

Rice requires about 20 kg of nitrogen per ton

of the harvested crop. About half of this is

recycled into the soil in the crop residue; therefore about 10 kg of nitrogen is removed per ton

of harvested grain. A 6 ton rice harvest removes about 60 kg of nitrogen from the soil,

equivalent to 300 kg of ammonium sulfate fertilizer. If azolla was substituted for ammonium

sulfate, nearly all of the money required to purchase the 300 kg of ammonium sulfate fertilizer

could theoretically be used to pay farm labor

to grow azolla, or to gain a greater return on

family labor.

Azolla appears to offer special opportunities

for small farms, particularly family farms with

abundant labor. Conversely, suitable azolla

technology for large mechanized farms is not

available.

Azolla is used successfully on large communes in China, but the organization of these

communes is difficult to relate to family farms.
123

Land

The land required for azolla cultivation

mainly is related to nursery and field multiplication. For overwintering or oversummering, very small protected greenhouse or field

areas are required, more in the area of small

garden plots than large field areas. However,

when azolla multiplication for field inoculation

is to be achieved, much more land is required.

Perhaps as much as 10 percent of the rice crop

area to be inoculated is a good estimate of the

land area needed for azolla field multiplication.

This land is not tied up permanently, however,

but it will be devoted to azolla multiplication

for a month or so prior to inoculation.

For farming systems that use azolla as a

basal, soil incorporated green manure before

the rice crop, all of the land to be planted into

rice and fertilized with azolla will need to be

devoted to azolla cultivation for about a month

prior to transplanting.

In situations where azolla is used as a soilincorporated, top-dressed green manure or as

an unincorporated intercrop with rice, no land

will be required to be devoted solely to azolla,

except for the inoculation nurseries.

CONCLUSIONS

Azolla

nitrogen

is being used as a primary source of

on an increasing land area in transplanted rice crops in China and Vietnam. The

largest use of azolla in these countries is in the

spring rice crop, mostly as a monocrop grown

before rice as a basal, soil-incorporated green

manure. Less is used as an intercropped topdressing green manure in transplanted rice that

is planted in rows.

Use of azolla in the summer rice crop is hampered by high water temperatures and heavy

pest attack. A search for suitable temperaturetolerant species or varieties could have high

payoff.

Species used in agriculture today are: A. pinnata, A. pinnata var. imbricata (sometimes referred to as A. imbricata, and A. filiculoides.

A. pinnata and imbricata have been used for

a long time in China and Vietnam, but their

susceptibility to high temperatures and pest attack makes them suitable only for spring and

some fall rice crops. A. filiculoides has just

begun to be used widely in China, especially

in areas where-because of its cold tolerance—

it can be grown in late winter and early spring

as a green manure for early spring rice. Although A. filiculoides has proved useful in

China because of its cold tolerance, it is even

less tolerant of high water temperatures (above

250 to 270 C) than A. pinnata. What

then, is an azolla that can tolerate

mer temperatures, up to 400 C

is needed,

high sumor so. A .

microphylla, collected by T. Lumpkin in the

Galapagos Islands, shows promise of becoming a suitable summer green manure for central China and a winter green manure in south

China.

There is a great need to collect and characterize species and varieties of azolla extant

in nature. This work is of the highest priority.

The potential worth of A. microphylla in China

has already been mentioned. However, it may

be useful to point out that A. nilotica, collected

by T. Lumpkin in the Sudan, has shown the

highest nitrogen fixation of any azolla studied.

Lumpkin was only able to collect three specimens of A. nilotica, yet many more strains and

types are available in the Nile Basin and these

should be collected and characterized as soon

as possible.

All species could prove useful. For example,

varieties of filiculoides look promising now for

use in certain agricultural situations. The same

can be said about microphylla, imbricata, pinnata, and caroliniana.

Research programs should stress multidisciplinary approaches, with close links between

38-846 0 - 85 - 5
124

institutions. Both tropical and temperate farming systems should be emphasized, but these

programs should be centered in different

places. Both temperate and tropical research

programs should be linked, and should cooperate in collection and characterization of species and varieties. The tropical program should

focus on using azolla in tropical farming systems, notably small peasant farms, and the

temperate program should focus on capital intensive mechanized rice production systems.

An international meeting should be held that

will have as its major agenda item the setting

of international research priorities for azolla.

The primary focus of research programs

should be to find a useful role for azolla in

farming systems. Basic research should not be

neglected, but the potential usefulness of azolla

is too great to delay its wider use in agriculture through emphasis on more esoteric topics

at the expense of applied research.

1.

2,

3.

4.

References

Dolbert, Frands, DANIDA, personal communication, 1980.

Food and Agriculture Organization, China:

Azolla propagation and small-scale biogas technology, Food and Agriculture Soils Bull. No. 41,

FAO, Rome, 1978.

Guandong Academy of Agricultural Science,

Red Azol]a (People’s Publisher, Guandong (in

Chinese), 1975).

Guandong Bureau of Agriculture, Questions

and Answers Concerning Azolla Cultivation

5.

6.

7,

8.

9.

10,

11

12.

13.

14,

(People’s Publisher, Guandong (in Chinese),

1975),

International Rice Research Institute, International Bibliography on Azolla, IRRI (Los Ganos,

Philippines, 1979), 66 pp.

Lumpkin, T. A., “Environmental Constraints to

Azolla Cultivation, ” Proc. Second Review

Meeting I.N.P. U.T.S. Project (Honolulu, Hawaii, May 18-19, 1978), pp. 175-180.

Lumpkin, T. A, and Plucknett, D. L., “Azolla:

Botany, Physiology, and Use as a Green Manure,” Econ. Bet. 34(2): 111-153, 1980.

Moore, A. W., “Azo]la: Biology and Agronomic

Significance, ” Bet. Rev. 35: 17-35, 1969.

Peters, G. A., “The Azolla-Anabaena Symbiosis,” In: Alexander Hollaender (cd.), Genetic

Engineering for Nitrogen Fixation (Plenum

Press, New York and London, 1977), pp. 231-

258.

Singh, P. K., “Use of Azolla in Rice Production

in India,” In: Nitrogen and Rice (International

Rice Research Institute, Philippines, 1980), pp.

407-418.

Talley, S. N., and Rains, D. W., “Use of Azolla

in North America, ” In: Nitrogen and Rice (International Rice Research Institute, Philippines,

1980), pp. 419-431.

Vo, M. K, am-l Tran, Q. T., Beo Hoa Dau ~Azo)la)

(Agricultural Publisher, Hanoi, 1970), 171 pp.

Watanabe, I., Espinas, C. R., Berja, N. S., and

Alimagno, V. B., “Utilization of the AzollaAnabaena Complex as a Nitrogen Fertilizer for

Rice,” International Rice Research Institute,

Res. Paper Ser. No, 11, 1977.

Zhejiang Academy of Agricultural Science,

Cultivation, Propagation and Utilization of

Azolla (Agricultural Publishing House, Beijing

(in Chinese]. 1975).
Chapter VIII

Using Zeolites in Agriculture

Frederick A. Mumpton

Department of the Earth Sciences

State University College

Brockport, NY 14420
Contents

Pag e

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Natural Zeolites . . . . . . . . . . . . . . . . . . . . . . . . 127

Chemistry and Crystal Structure of

Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Properties of Zeolites. . . . . . . . . . . . . . . . . . 129

Applications in Agronomy ......,,.,.. . . . 133

Fertilizer and Soil Amendments . . . . . . . . 133

Pesticides, Fungicides, Herbicides. ,,.... 135

Heavy Metal Traps . . . . . . . . . . . . . . . . . . . 135

Applications in Animal Husbandry . . . . . . . 136

Animal Nutrition . . . . . . . . . . . . . . . . . . . . . 136

Poultry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Swine . . . . . . . . . . . . . . . . . . . . . . .+....... 136

Ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Excrement Treatment . . . . . . . . . . . . . . . . . 141

Malodor and Moisture Control . . . . . . . . . 141

Methane Purification. . . . . . . . . . . . . . . . . . 142

Aquacultural Applications . . . . . . . . . . . . . . . 143

Nitrogen Removal From Closed or

Recirculation Systems . . . . . . . . . . . . . . . 143

Aeration Oxygen Production . . . . . . . . . . . 144

Fish Nutrition . . . . . . . . . . . . . . . . . . . . . . . . 144

Occurrence and Availability of Natural

Zeolites .....,...,,.. . . . . . . . . . . . . . . . 144

Geological Occurrence. . . . . . . . . . . . . . . . . 144

Geographic Distribution . . . . . . . . . . . . . . . 146

Mining and Milling . . . . . . . . . . . . . . . . . . . 149

Discussion, ..,,.... . . . . . . . . . . . . . . . . . . . . 150

Agronomic Applications . . . . . . . . . . . . . . . 150

Animal Nutrition Applications ., ..,.,.., 151

Excrement Treatment Applications . . . . . . 152

Conclusions and Recommendations . . . . . . . 152

References .,.. . . . . . . . .,..,..+, . . . . . . . 155

Tables

Table No. Page

l. Representative Formulae and Selected

Physical Properties of Important

Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

2. Growth Response of Radishes to

Ammonium-Exchange Clinoptilolite . . . . 134

3, Growth Response of Radishes to

Natural Clinoptilolite Plus Urea ,....., 134

4. Caloric Efficiencies of Zeolite

Supplements in Poultry Feeding . . . . . . . 136

5. Apparent Caloric Efficiency of Zeolite

in Chicken Rations . . . . . . . . . . . . . . . . . . 137

6. Caloric Efficiency of Zeolite

Supplements in Swine Feeding . . . . . . . . 137

7. Effect of Zeolite Diets on Health

of Swine . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8. Effect of Prenatal Zeolite Diet on

Newborn Pigs, .,, . . ., ..,,.,.., ..,.,. 138

9. Effect of Zeolite Supplementing the

Diets of Early Weaned Pigs . . . . . . . . . . . 139

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

Effect of Zeolite Supplement in

Molasses-Based Diets of Young Pigs .,. 139

Effect of Clinoptilolite Supplemental

in the Diet of Swine . . . . . . . . . . . . . . . . . 140

Occurrence of Diarrhea and Soft-Feces

Among Calveson Diets Supplemented

With 5% Clinoptilolite . . . . . . . . . . . . . . . 141

Effect of Zeolite Additions to Chicken

Droppings . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Effect of Clinoptilolite Additions to the

Diet of Trout . . . . . . . . . . . . . . . . . . . . . . . 144

Reported Occurrences of Sedimentary

Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Countries Engaged in Zeolite Mining . . 150

Organizations Engaged in Zeolite/

Agronomic Investigations . . . . . . . . . . . . 151

Organizations Engaged in Animal

Nutrition Studies Using Zeolites . . . . . . . 152

Zeolite Property Holders and

Zeoagricultural Research Efforts. ..,,,. 153

Figures

FigureNo. Page

l. Simple Polyhedron of Silicate and

. .

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Aluminate Tetrahedra . . . . . . . . . . . . . . . . 130

Arrangements of Simple Polyhedra to

Enclose Large Central Cavities .., ...,, 130

Solid Sphere Models of Synthetic

Zeolite and Chabazite . . . . . . . . . . . . . . . . 131

Stylized Illustration of the Entry of

Straight-Chain Hydrocarbons and

Blockage of Branch-Chain Hydrocarbons

at Channel Apertures ,, ......,,,,,,., 131

Langmuir-Type Isotherm for Adsorption

on Crystalline Zeolites Illustrating

Almost Complete Saturation at Low

Partial Pressures of the Adsorbate ,,... 131

Types of Ion-Exchange Isotherms for the

Reaction As + BZ = AZ + Bs

, . . . . . . . . . 132

Change of Soil Nitrogen of Paddy Soil

With Time . . . . . . . . . . . . . . . . . . . . . . . . . 133

Yield of Chrysanthemums as a Function

of Potassium Level Supplied by OneTimeAdditions of Clinoptilolite . . . . . . . 134

Cumulative Leachate NO3

-N for Banded

NH4

-Exchanged Clinoptilolite and

Banded Ammonium Sulfate ..,,,,,. . . . 135

Methane-Purification System, Pales

Verde Landfill . . . . . . . . . . . . . . . . . . . . . . 142

Field Exposure of Zeolite Beds ,,, ,,,.. 145

Scanning Electron Micrograph of

Clinoptilolite Laths With Minor Mordenite

From a Saline-Lake Deposit Tuff Near

Hector, CA . . . . . . . . . . . . . . . . . . . . . . . . . 146
Chapter Vlll

Using Zeolites in Agriculture

AS agriculturalists the world over increase

their effort to expand crop and animal production, more and more attention is being paid to

various mineral materials as soil amendments

and as dietary supplements in animal husbandry. The close relationship between the

agricutura1 and geological sciences is not

new--crop production depends on the existence and maintenance of fertile soil and

agronomists rely on knowledge of mineralogy

and geochemist}’ of clays and other soil constituents. In the animal sciences, the addition

of crushed limestone to chicken feed to

strengthen egg shells is well known, as is the

use of bentonite as a binding agent in pelletized

anima1 feed stuffs.

Recently, one group of minerals has emerged

as having considerable potential in a wide variety of agricultural processes. This group of

minerals is the zeolite group. The unique ionexchange, dehydration-rehydration, and adsorption properties of zeolite materials promise to contribute significantly to many years of

agricultural and aquacultural technology (60).

Most of the initial research on the use of zeolites in agriculture took place in the 1960s in

Japan, Japanese farmers have used zeolite rock

for years to control the moisture content and

malodor of animal wastes and to increase the

pH of acidic volcanic soils. The addition of

small amounts of the zeolites clinoptilolite and

mordenite to the normal protein diet of pigs,

chickens, and ruminants gave noticeable inZeolites are crystalline, hydrated aluminosilicates of alkali and earth metals that possess

infinite, three-dimensional crystal structures.

They are further characterized by an ability to

lose and gain water reversibly and to exchange

creases in the body weight and general “health”

of the animals (52). The use of zeolites in rations also appeared to reduce odor and associated pollution problems and to provide a

means of regulating the viscosity and nitrogen

retentivity y of animal manure. These same zeolites were also found to increase the ammonium content of rice paddy soils when added

with normal fertilizers.

Although most of these were preliminary results and often published in rather obscure

journals or reports from local experiment stations, they did suggest that zeolites could act

as traps or reservoirs for nitrogen both in the

body and in the soil. The growing awareness

of such phenomena and of the availability of

inexpensive natural zeolites in the Western

United States and in geologically similar parts

of the world has aroused considerable commercial interest. Zeolites are fast becoming the subject of serious investigation in dozens of agricultural laboratories both here and abroad.

Some of the ways in which zeolites can contribute to more efficient crop and livestock production are discussed below, along with their

role in the rapidly expanding areas of fish

breeding and aquiculture. At this stage, the

number of published papers dealing with “zeoagriculture “ is quite small, and hard data are

few; however, the potential of these materials

in such areas is apparent, and zeolites show

promise of contributing directly to increased

agricultural productivity in the years to come.

ZEOLITES

some of their constituent elements without major change of structure. Zeolites were discovered in 1756 by Freiherr Axel Fredrick Cronstedt, a Swedish mineralogist, who named

them from the Greek words meaning “boiling

127
128

stones, “ in allusion to their peculiar frothing

characteristics when heated before the mineralogist’s blowpipe. Since that time, nearly 50

natural species of zeolites have been recognized, and more than 100 species having no

natural counterparts have been synthesized in

the laboratory. Synthetic zeolites are the mainstays of the multimillion-dollar molecular sieve

businesses that have been developed by Union

Carbide Corp., W. R. Grace& Co., Mobil Corp.,

Norton Co., Exxon Corp., and several other

companies in the last 25 years in the United

States and by chemical firms in Germany,

France, Great Britain, Belgium, Italy, Japan,

and the Soviet Union.

Natural zeolites have long been known to

members of the geological community as ubiquitous, but minor constituents in the vugs and

cavities of basalt and other traprock formations. It was not until the late 1950s that the

world became aware of zeolites as major constituents of numerous volcanic tuffs that had

been deposited in ancient saline lakes of the

Western United States or in thick marine tuff

deposits of Italy and Japan. Since that time,

more than 2,000 separate occurrences of zeolites have been reported from similar sedimentary rocks of volcanic origin in more than 40

countries. The high purities and near-surface

location of the sedimentary deposits has

prompted intense commercial interest both

here and abroad. Many industrial applications

based on the exciting bag of chemical and physical tricks of zeolites have been developed.

The commercial use of natural zeolites is still

in its infancy, but more than 300,000 tons of

zeolite-rich tuff is mined each year in the

United States, Japan, Bulgaria, Hungary, Italy,

Yugoslavia, Korea, Mexico, Germany, and the

Soviet Union. Natural zeolites have found applications as fillers in the paper industry, as

lightweight aggregate in construction, in pozzolanic cements and concrete, as ion-exchangers in the purification of water and municipal

sewage effluent, as traps for radioactive species in low-level wastewaters from nuclear facilities, in the production of high purity oxygen from air, as reforming petroleum catalysts,

as acid-resistant absorbents in the drying and

purification of natural gas, and in the removal

of nitrogen compounds from the blood of kidney patients (58).

The applications and potential applications

of both synthetic and natural zeolites depend,

of course, on their fundamental physical and

chemical properties. These properties are in

turn related directly to the chemical composition and crystal structure of individual species.

CHEMISTRY AND CRYSTAL STRUCTURE OF ZEOLITES

Along with quartz and feldspar, zeolites are tassium (K+) elsewhere in the structure. Thus,

“tektosilicates, ” that is, they consist of three- the empirical formula of a zeolite is of the type:

dimensional frameworks of silicon-oxygen

(SiO4

) 4 tetrahedral, wherein all four corner M 2

/ nO . Al2O a . xSiO2 ● y H2O

oxygen atoms of each tetrahedron are shared where M is any alkali or alkaline earth element,

with adjacent tetrahedral. This arrangement of n is the valence charge on that element, x is

silicate tetrahedral reduces the overall oxygen: a number from 2 to 10, and y is a number from

silicon ratio to 2:1, and if each tetrahedron in 2 to 7. The empirical and unit-cell formulae of

the framework contains silicon as its central clinoptilolite, the most common of the natural

atom, the structures are electrically neutral, as zeolites, is:

is quartz (SiO2

. In zeolite structures, however, (Na,K)2O . Al2O 3 ● 10SiO2 ● 6 H2O or

some of the quadrivalent silicon is replaced by

trivalent aluminum, giving rise to a deficiency

of positive charge. This charge is balanced by Elements or cations within the first set of pathe presence of mono- and divalent elements rentheses in the formula are known as exsuch as sodium (Na +

), calcium (Ca2 + ), and po- changeable cations; those within the second set
129

of parentheses are called structural cations, because with oxygen they make up the tetrahedral framework of the structure. Loosely bound

molecular water is also present in the structures of all natural zeolites, surrounding the exchangeable cations in large pore spaces.

Whereas the framework structures of quartz

and feldspar are dense and tightly packed,

those of zeolite minerals are remarkably open

and void volumes of dehydrated species as

great as 50 percent are known (table 1). Each

zeolite species has its own unique crystal structure and, hence, its own set of physical and

chemical properties. Most structures, however,

can be visualized as SiO4 and AlO4 tetrahedral

linked together in a simple geometrical form.

This particular polyhedron is known as a truncated cube-octahedron. It is more easily seen

by considering only lines joining the midpoints

of each tetrahedron, as shown in figure 1.

Individual polyhedra may be connected in

several ways; for example, by double four-rings

of oxygen atoms (figure 2a), or by double sixrings of oxygen atoms (figure 2b), the framework structures of synthetic zeolite A and the

mineral faujasite, respectively. Solid-sphere

models of synthetic zeolite A and of the mineral

chabazite are illustrated in figures 3a, 3b.

once the water is removed from a zeolite,

considerable void space is available within

both the simple polyhedra building blocks and

the larger frameworks formed by several polyhedra. Although water and other inorganic and

organic molecules would appear to be able to

move freely throughout a dehydrated zeolite

framework, the passageways leading into the

simple polyhedra are too small for all but the

smallest molecules to pass; however, ports or

channels up to 8 A in diameter lead into the

large, three-dimensional cavities (figures 2a, 2b,

3a, 3b).

Properties of Zeolites

Adsorption properties: Under normal conditions, the large cavities and entry channels of

zeolites are filled with water molecules forming hydration spheres around the exchangeable cations. Once the water is removed, usually by heating to 3000 to 4000 C for a few hours,

molecules having diameters small enough to

fit through the entry channels are readily adsorbed on the inner surfaces of the vacant central cavities. Molecules too large to pass

through the entry channels are excluded, giving rise to the well-known “molecular sieving”

property of most crystalline zeolites (figure 4).

Table 1.— Representative Formulae and Selected Physical Properties of Important Zeolites

Void Channel Thermal Ion-exchange

Zeolite Representative unit-cell formulaa

volumeadimensions astability capacity b

Analcime

Chabazite

Clinoptilolite

Erionite

Faujasite

Ferrierite

Heulandite

Laumontite

Mordenite

Phillipsite

Linde A

Linde X

18%

47

39?

35

47

39

28

31

47

50

2.6 A

3.7 X 4.2

3.9 x 5.4

3.6 X 5.2

7.4

4.3 x 5.5

3.4 X 4.8

4.0 x 5.5

4.4 X 7.2

4.1 x 4.7

4.6 X 6 . 3

2.9 X 5.7

6.7 X 7 . 0

4.2 X 4 . 4

2.8 X 4.8

3.3

4.2

7.4

High

High

High

High

High

High

Low

Low

High

Low

High

High

4.54 meq/g

3.81

2.54

3.12

3.39

2.33

2.91

4.25

2.29

3.87

5.48

4,73

aTaken mainly from Breck, 1974, Meier and Olson, 1971 Void volume is determined from water content

bCalculated from unit-cell formula
130

Figure 1. —Simple Polyhedron of Silicate and Aluminate Tetrahedra

a b

(a) Ball and peg model of truncated cube-octahedron. (b) Line drawing of truncated cube-octahedron,

lines connect centers of tetrahedral

Figure 2.—Arrangements of Simple Polyhedra to

Enclose-Large Central Cavities

a b

(a) Truncated cube-octahedra connected by double four-rings of oxygen in structure of synthetic zeolite A. (b) Truncated cube-octahedra

connected by double six-rings of oxygens in structure of faujasite.

The internal surface area available for adsorption ranges up to several hundred square meters per gram, and some zeolites are capable

of adsorbing up to about 30 weight percent of

a gas, based on the dry weight of the zeolite.

In addition to their ability to separate gas

molecules on the basis of size and shape, the

unusual charge distribution within a dehydrated void volume allows many species with

permanent dipole moments to be adsorbed

with a selectivity unlike that of almost all other

sorbents. Thus, polar molecules such as water,

sulfur dioxide, hydrogen sulfide, and carbon

dioxide are preferential] y adsorbed by certain

zeolites over nonpolar molecules, such as methane, and adsorption p recesses have been developed using natural zeolites by which carbon

dioxide and other contaminants can be removed from impure natural gas or methane

streams, allowing the gas to be upgraded to

high-Btu products. In addition, the small, but

finite, quadripole moment of nitrogen allows

it to be adsorbed selectively from air by a dehydrated zeolite, producing oxygen-enriched

streams at relatively low cost at room temperature. Both of the above processes may find application in agricultural technology.

Dehydration-rehydration properties: Because

of the uniform nature of the pores of structural

cages, crystalline zeolites have fairly narrow

pore-size distributions, in contrast to other

commercial absorbents, such as activated alumina, carbon, and silica gel. Adsorption on zeolites is therefore characterized by Langmuir-type

isotherms, as shown in figure 5. Here, percent

of adsorption capacity is plotted against partial pressure of the adsorbate gas. Note that almost all of the zeolite’s adsorption capacity for
Figure 3.—Solid Sphere Models of Synthetic Zeolite and Chabazite

a b

(a) Solid-sphere model of the crystal structure of synthetic zeolite A (b) Solid-sphere model of the crystal structure of chabazite

Figure 4.—Stylized Illustration of the Entry of Straight.

Chain Hydrocarbons and Blockage of Branch-Chain

Hydrocarbons at Channel Apertures

Figure 5.—Langmuir-Type Isotherm for Adsorption on

Crystalline Zeolites Illustrating Almost Complete

Saturation at Low Partial Pressures of the Adsorbate

a particular gas (including water) is obtained

at very low partial pressures, meaning that although their total adsorption capacity may be

somewhat less than those of other absorbents,

(e.g., silica gel), zeolites are extremely efficient

ad sorbents even at low partial pressures. This

property has been used in the zeolitic adsorption of traces of water from Freon gas lines of

ordinary refrigerators that might otherwise

freeze and clog pumps and valves. The extreme

nonlinearity of the water adsorption isotherms

of zeolites has been exploited recently in the

developrnent of solar-energy refrigerators (81),

lon-exchange properties: The exchangeable

cations of a zeolite are also only loosely bonded

to the tetrahedral framework and can be removed or exchanged from the framework

structure easily by washing with a strong solution of another element. As such, crystalline

zeolites are some of the most effective ion exchangers known to man, with capacities of 3

to 4 meq per gram being common. This com-
132

pres with the 0.8 to 1.0 meq per gram cationexchange capacity of bentonite, the only other

significant ion-exchanger found in nature,

Cation-exchange capacity is basically a funct ion of the degree of substitution of aluminum

for silicon in the zeolite framework: the greater

the substitution, the greater the charge deficiency of the structure, and the greater the

number of alkali or alkaline earth atoms required for electrical neutrality. In practice,

however, the cation-exchange capacity is dependent on a number of other factors as well,

In certain species, cations can be trapped in

structural positions that are relatively inaccessible, thereby reducing the effective exchange

capacity of that species for that ion, Also, cation sieving may take place if the size of the

exchanging cat ion is too large to pass through

the entry channels into the central cavities of

the structure.

Unlike most noncrystalline ion exchangers,

such as organic resins or inorganic aluminosilicate gels (mislabeled in the trade as “zeolites”), the framework of a crystalline zeolite

dictates its selectivity toward competing ions.

The hydration spheres of high-charge, smallsize ions (e. g., sodium, calcium, magnesium)

prevent their close approach in the cages to the

seat of charge of the framework; therefore ions

of low charge and large size (e. g., lead, barium,

potassium), that normally do not have hydration spheres are more tightly held and selectively taken up from solution than are other

ions, The small amount of aluminum in the

composition of clinoptilolite, for example, results in a relatively low cation-exchange capacity (about 2.3 meq/g); however, its cation selectivity is:

Cesium > Rubidium > Potassium > Ammonium >

Barium > Strontium > Sodium

Calcium > Iron > Aluminum >

Magnesium > Lithium (3).

Synthetic zeolite A, on the other hand, is more

selective for calcium than for sodium, and thus,

acts as a water softener in laundry detergents

where it picks up calcium from the wash water

and releases sodium (75).

Cation exchange between a zeolite (Z) and

a solution (S) is usually shown by means of an

exchange isotherm that plots the fraction of the

exchanging ion (X) in the zeolite phase against

that in the solution (figure 6). If a given cation

shows no preference of either the solution or

the zeolite, the exchange isotherm would be the

straight line “a” at 450

. If the zeolite is moderately or very selective for the cation in solution,

curve b and c would result, respectively. If the

zeolite is rejective of a particular cation, curve

d would result. Such is the selectivity of clinoptilolite for cesium or ammonium, for example. Clinoptilolite will take up these ions readily

from solutions even in the presence of high

concentrations of competing ions, a facility

that was exploited by Ames (4) and Mercer, et

al. (50), in their development of an ion-exchange process to remove ammoniacal nitrogen from sewage effluent.

Figure 6.—Types of Ion-Exchange Isotherms for the
133

APPLICATIONS

Fertilizer and Soil Amendments

Based on their high ion-exchange capacity

and water retentivity, natural zeolites have

been used extensively in Japan as amendments

for sandy soils, and small tonnages have been

exported to Taiwan for this purpose (52,31),

The pronounced selectivity of clinoptilolite for

large cations, such as ammonium and potassium, has also been exploited in the preparation of chemical fertilizers that improve the

nutrient-retention ability of the soils by promoting a slower release of these elements for uptake by plants, In rice fields, where nitrogen

efficiencies of less than 50 percent are not uncommon, Minato (52) reported a 63 percent improvement in the amount of available nitrogen

in a highly permeable paddy soil 4 weeks after about 40 tons/acre zeolite had been added

along with standard fertilizer (figure 7), Turner

(84), on the other hand, noted little change in

the vitrification of added ammonia when clinFigure 7.—Change of Soil Nitrogen of Paddy Soil

With Time

Vertical water seepage in soil = 1.35 cm/day (Yamagata Prefecture

Board of Agriculture and Forestry, 1966; reported in Minato, 1968.)

IN AGRONOMY

optilolite was mixed with a Texas clay soil, although the overall ion-exchange capacity of the

soil was increased. He attributed these conflicting results to the fact that the Japanese soils

contained much less clay, thereby accounting

for their inherent low ion-exchange capacity

and fast-draining properties. The addition of

zeolite, therefore, resulted in a marked improvement in the soil’s ammonium retentivity.

These conclusions support those of Hsu, et al.

(31), who found an increase in the effect of zeolite additions to soil when the clay content of

the soil decreased. Although additions of both

montmorillonite and mordenite increase the

cation-exchange capacity of upland soils, the

greater stability of the zeolite to weathering allowed this increase to be retained for a much

longer period of time than in the clay-enriched

soils (22),

Using clinoptilolite tuff as a soil conditioner,

the Agricultural Improvement Section of the

Yamagata Prefectural Government, Japan, reported significant increases in the yields of

wheat (13 to 15 percent), eggplant (19 to 55 percent), apples (13 to 38 percent), and carrots (63

percent) when from 4 to 8 tons of zeolite was

added per acre (83). Small, but significant improvements in the dry-weight yields of sorghum in greenhouse experiments using a sandy

loam were noted when 0.5 to 3.0 tons of clinoptilolite per acre was added along with normal

fertilizer (47). However, little improvement was

found when raising corn under similar conditions. Hershey, et al. (29), showed that clinoptilolite added to a potting medium for chrysanthemums did not behave like a soluble K

source, but was very similar to a slow-release

fertilizer, The same fresh-weight yield was

achieved with a one-time addition of clinoptilolite as with a daily irrigation of Hoagland’s

solution, containing 238 ppm K, for three

months (total of 7 g potassium added), with no

apparent detrimental effect on the plants (figure 8).

Experiments by Great Western Sugar Co. in

Longmont, CO, using clinoptilolite as a soil

amendment, resulted in a significant increase
134

Figure 8.— Yield of Chrysanthemums as a Function

of Potassium Level Supplied by One-Time Additions

of Clinoptilolite

tops also increased with the zeolite treatment

compared with an ammonium sulfate control

(table 2). These authors also found that natural clinoptilolite added to soil in conjunction

with urea reduced the growth suppression that

normally occurs when urea is added alone (table 3). The presence of zeolites also resulted

in less NO3

-N being leached from the soil (figure 9).

Both zeolite treatments apparently made considerably more ammonium available to the

plants, especially when clay-poor soils were

employed. The authors suggested that ammonium-exchanged clinoptilolite acted as a slowrelease fertilizer, whereas, natural clinoptilolite acted as a trap for ammonium that was produced by the decomposing urea, and thereby

prevented both ammonium and nitrate toxicity by disrupting the bacterial vitrification

process. The ammonium selectivity of zeolites

was exploited by Varro (85) in the formulation

of a fertilizer consisting of a 1:1 mixture of sewage sludge and zeolite, wherein the zeolite apparently controls the release of nitrogen from

the organic components of the sludge.

Coupled with its valuable ion-exchange properties which allow a controlled release of micronutrients, such as iron, zinc, copper, manTable 2.—Growth Response of Radishes to Ammonium-Exchange Clinoptilolitea

130/0 clay soilb6°/0 clay soilc

Parameter N H4

-Clinoptilolite (NH4) 2S 04 N H4-Clinoptilolite (NH4) 2S 04

Leaf area (cm2/plant) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 187 187 150

Plant weight (dry weight) (g). . . . . . . . . . . . . . . . . . . . . . . . . . . 1.84 1.12 1.40 1.1

Root weight (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 8.5 11.6 7.6

N uptake (mg N/plant top) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.2 35.9 42.6 38.9

a

Lewis, et al., 1980.

bPlants sampled 36 days after planting.

cLeached five times; plants sampled 34 days after planting.

Table 3.—Growth Response of Radishes to Natural Clinoptilolite Plus Ureaa

13% clay soilb

6°/0 clay soilc

Parameter Zeolite + Urea Urea Zeolite + Urea Urea

Leaf area (cm2

/plant) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 187 208 116

Plant weight (dry weight) (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.59 1.23 1.38 0.71

Root weight (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8 12.4 6.3

N uptake (mg N/plant top) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45.5 38.6 44.4 18.9

a

Lewis, et al., 1980.

bPlants sampled 36 days after planting.

cLeached five times; plants sampled 34 days after planting.
Figure 9. —Cumulative Leachate N03

-N for Banded

NH4

-Exchanged Clinoptilolite and Banded

Ammonium Sulfate (Lewis, et al., 1980)

135

issued to Aleshin, et a], (2), for grouting compound containing 3 to 5 percent clinoptilolite

to control herbicide percolation from irrigation

canals to ground waters.

Heavy Metal Traps

Not only do the ion-exchange properties of

certain zeolites allow them to be used as carriers of nutrient elements in fertilizers, they can

be exploited to trap undesirable metals and prevent their uptake into the food chain. Pulverized zeolites effectively reduced the transfer of

fertilizer-added heavy metals, such as copper,

cadmium, lead, and zinc, from soils to plants

(18). The selectivity of clinoptilolite for such

ganese, and cobalt, the ability of clinoptilolite

to absorb excess moisture makes it an attractive addition to chemical fertilizers to prevent

caking and hardening during storage and to animal feedstuffs to inhibit the development of

mold (82). Spiridonova, et a]. (78), found that

0.5 percent clinoptilolite added to ammonium

nitrate fertilizer decreased caking by 68 percent.

pesticides, Fungicides, Herbicides

Similar to their synthetic counterparts, the

high adsorption capacities in the dehydrated

state and the high ion-exchange capacities of

many natural zeolites make them effective carriers of herbicides, fungicides, and pesticides.

Clinoptilolite can be an excellent substrate for

benzyl phosphorothioate to control stem blasting in rice (88). Using natural zeolites as a base,

Hayashizaki and Tsuneji (26) found that clinoptilolite is more than twice as effective as a carrier of the herbicide benthiocarb in eliminating weeds in paddy fields as other commercial

products. Torii (82) reported that more than 100

tons of zeolite were used in Japan in 1973 as

carriers in agriculture. A Russian patent was

ers (e. g., 74,19,1 1,76).

In view of the attempts being made by sanitary and agricultural engineers to add municipal and industrial sewage sludge to farm and

forest soils, natural zeolites may play a major

role in this area also. The nutrient content of

such sludges is desirable, but the heavy metals

present may accumulate to the point where

they become toxic to plant life or to the animals or human beings that may eventual] y eat

these plants. Cohen (12) reported median values of 31 ppm cadmium, 1,230 ppm copper,

830 ppm lead, and 2,780 ppm zinc for sludges

produced in typical U.S. treatment plants. Zeolite additives to extract heavy metals may be

a key to the safe use of sludge as fertilizer and

help extend the life of sludge-disposal sites or

of land subjected to the spray-irrigation processes now being developed for the disposal of

chlorinated sewage. Similarly, Nishita and

Haug (64) showed that the addition of clinoptilolite to soils contaminated with radioactive

strontium (Sr90) resulted in a marked decrease

in the uptake of strontium by plants, an observation having enormous import in potential

treatment of radioactive fallout that contaminates soils in several pacific atolls where nuclear testing has been carried out,
136

APPLICATIONS IN ANIMAL HUSBANDRY

Animal Nutrition

Based on the successful use of montmorillonite clay in slowing down the passage of nutriants in the digestive system of chickens and

the resultant improvement in caloric effieiency

(73), experiments have been carried out in Japan since 1965 on the application of natural

zeo1ites as dietary supplements for several

types of domestic animals. Because much of

this work was superficial or not statistically significant, it has been repeated and enlarged

upon in recent years by researchers in the

United States and several other countries seeking agricultural applications for zeolites.

Poultry

Using clinoptilolite from the Itaya r-nine,

Yamagata Prefecture, and mondenite from

Karawago, Miyagi Prefecture, Onagi (67) found

that Leghorn chickens required less food and

water and still gained as much weight in a 2-

week trial as birds receiving a control diet.

Feed efficiency values (FEV)l were markedly

higher at all levels of zeolite substitution; feedstuffs containing 10 percent zeolite gave rise

to efficiencies more than 20 percent greater

than those of normal rations (table 4). Adverse

effects on the health or vitality of the birds were

not noted, and the droppings of groups receiving zeolite diets contained up to 25 percent less

moisture than those of control groups, after a

1 Weight gain/feed intake, excluding zeolite,

12-day drying period, making them conSiderably easier to hand1e.

Broiler chickens fed a diet of 5 percent c1inoptilite from the Hector, CA, deposit gained

slight1y 1ess weight over a 2-month period than

birds receiving a normal diet, but average FEVS

were noticeably higher (table 5) (6). Perhaps of

greater significance is the fact that none of the

48 test birds on the zeolite diet died during the

experiment, while 3 on the control diet and 2

on the control diet supplemented with antibiotics succumbed. In addition to an apparent

feed-efficiecy increase of 4 to 5 percent, the

prescnce of zeolite in the diet appears to have

had a favorable effect on the mortality of the

birds.

Hayhurst and Willard (27) confirmed many

of Onagi’s observations and reported small increases in FEV for Leghorn roosters over a 40-

day period, especially during the first 10 days.

The birds were fed a diet containing 7.5 percent clinoptilolite crushed and mixed directly

with the normal rations. Feces were noticeably dryer and less odoriferous. Unfortunate\,

only 17 birds were used in the study and extensive statistical evaluation of the results

could not be made.

Swine

Kondo and Wagai (39) evaluated the use of

zeolites in the diets of young and mature Yorkshire pigs in 60- and 79-day experiments, reTable 4.—Caloric Efficiencies of Zeolite Supplements in poultry Feedinga

Zeolite conten t Averag e Averag e Averag e Averag e Feed efficiency

Group no. of rations starting wt. (g) final wt. (g) weight gain (g) feed intakeb (g) ratioc

1 . . . . . . . . . . . . . . . . . . . . 10 percent Cpd553.7 795.6 241.9 668 0.362

2 . . . . . . . . . . . . . . . . . . . . 5 percent Cp 540.7 778 237.3 697 0.340

3 . . . . . . . . . . . . . . . . . . . . 3 percent Cp 556.7 796 239.3 748 0.320

4 . . . . . . . . . . . . . . . . . . . . 10 percent Mo 532.3 757.3 225.0 634 0.355

5 . . . . . . . . . . . . . . . . . . . . 5 percent Mo 552.3 814.6 262.3 775 0.338

6 . . . . . . . . . . . . . . . . . . . . 3 percent Mo 534.5 791.3 256.8 769 0.334

7 . . . . . . . . . . . . . . . . . . . . Control 556.5 789.3 232.8 782 0.298

aOnagi (1966) Tests carried out on 48-day-old Leghorns over a 14-day period, 30 birds/group. Normal rations consisted of 16.5 Percent crude Protein and 66 Percent

digestible nutrients

bExcluding zeolite.

c

Feed efficiency - weight gain/feed intake (excluding zeolite).

d Cp = clinoptilolite, Mo - mordenite.
137

Table 5.—Apparent Caloric Efficiency of Zeolite in Chicken Rationsa

Average Average

Treatment of weight (g) consumption (g) —

4-week datad

Control diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730 1175

Control diet + antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708 1116

Control diet with 5 percent clinoptilolite . . . . . . . . . . . . . . . . . . . . . . . . 703 1070

8-week dataf

Control diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1869 3978

Control diet + antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1882 3869

Control diet with 6 percent clinoptilolite . . . . . . . . . . . . . . . . . . . . . . . . 1783 3647

Average Survivors of

F.E.V.C

48 birds

0.622 46

0.634 47

0.657 48

0.470 45

0.486 46

0.489 48

aAdapted dStarter rations (O to 4 weeks) from data of Arscott (1975)

bFeed consumed, excluding zeolite e55 ppm Zinc bacitracin

CFeed efficiency value = weight/feed consumed (excluding zeolite) fFinisher rations (4 to 9 weeks)

spectively, and found that the weight gain of

animals of both ages receiving diets containing 5 percent clinoptilolite was from 25 to 2 9

percent greater than that of animals receiving

normal diets (table 6). Feed supplemented with

zeolites gave rise to feed efficiencies about 35

percent greater than those of normal rations

when fed to young pigs, but only about 6 percent greater when given to older animals. In

addition, the particle size of the feces of the

control group was noticeably coarser than that

of the experiment group, suggesting that the

digestive process was more thorough when

zeolites were added to the diet. The feces of

animals in the control group were also richer

in all forms of nitrogen than zeolite-fed animals, indicating that the zeolites contributed

toward a more efficient conversion of feedstuff

nitrogen to animal protein.

The digestibility of crude protein and nitrogen-free extracts tended to be improved as zeolite was substituted for wheat bran in swine

diets at levels from 1 to 6 percent over a 12-

week period (24,26). Anai, et al. (5), reported

similar results using 5 percent zeolite for 8 pigs

over a 12-week period and realized a 4-percent

decrease in the cost of producing body weight.

They also noted a decrease in malodor and

moisture content of the excrement, Toxic or

other adverse effects were not noted for any

of the test animals described. On the contrary,

the presence of zeolites in swine rations appears to contribute measurably to the wellbeing of the animals. Tests carried out on 4,000

head of swine in Japan showed that the death

rate and incidence of disease among animals

fed a diet containing 6 percent clinoptilolite

was markedly lower than for control animals

over a 12-month period (83). As shown in table 7, the decrease in the number of cases of

gastric ulcers, pneumonia, heart dilation, and

in the overall mortality is remarkable, The savings in medicine alone amounted to about 75

cents per animal, to say nothing of the increased value of a larger number of healthy

pigs.

In one test, the addition of zeolite to the diet

of piglets severely afflicted with scours markedly

reversed the progress of this disease within a

few days (53). Four underdeveloped Laundry

Table 6.—Caloric Efficiency of Zeolite Supplements in Swine Feedinga

Age of pigs Average weight

Start Finish Start Finish Average Average b

Average c

Zeolite

(days) (kg) (kg) wt. gain (kg) feed intake (kg) F.E.V. improvement

Experimental d

60 120 15.43 44.43 29.00 85.0 0.341

Control d

60 120 14.85 35.78 22.93 90.6 0.253 35 percent

Experimentale

99 178 30.73 85.30 54.57 167.6 0.326

Control e99 178 31.20 73.50 42.30 136.2 0.308 6 percent

aKOndo and Wagai (1968) Tests carried out using 5 percent clinoptilolite in rations of experimental groups

bExcluded zeolite

cFeed efficiency value - weight gain/feed intake

‘Eight Yorkshire pigs

eTwenty Yorkshire Pigs
138

Table 7.—Effect of Zeolite Diets on Health of Swinea

Zeolite content Sickness causes Heart Mortality Medicine

Period of rations Gastric ulcer Pneumonia dilatation rate (percent) cost/head

2/72 to 1/73 . . . . . . . . . ........0 77 128 6 4.0 $2.50

2/73 to 1/74 . . . . . . . . . ........6 percent clinoptilolite 22 51 4 2.6 $1.75

aTest carried out on 4,000 swine at Keai Farm, Morioka, Iwate Prefecture, Japan (Torii, 1974)

pigs were fed a diet containing 30 percent zeolite for the first 15 days and 10 percent zeolite

for the remaining part of a month-long experiment. The severity of the disease decreased

almost at once, and feces of all pigs were hard

and normal after only 7 days. Although the pigs

consumed an average of 1.75 kg of zeolite per

head per day, no ill effects were noted, and

once they had recovered from diarrhetic ailments, the pigs regained healthy appetites and

became vital. A recent Japanese patent disclosure claimed a method of preventing and treating gastric ulcer in swine by the addition of

zeolite to their diets (49); supportive data, however, were not reported.

Apparently the vitalizing effect of a zeolite

diet can be transferred from mother to offspring. Experiments at the Ichikawa Livestock

Experiment Station, where 400 g of clinoptilolite was fed each day to pregnant sows and continued through the 35-day weaning period of

their offspring, showed substantial increase in

the growth rate of the young pigs, As shown

in table 8, test animals weighed from 65 to 85

percent more than control-group animals at the

end of the weaning period (9). Young pigs

whose dams received the zeolite diet also suffered almost no attacks of diarrhea, while those

in control groups were severely afflicted with

scours, greatly inhibiting their normal growth.

The addition of 5 percent zeolite to the rations

of pregnant sows 20 to 90 days after mating

gave rise to improved FEVs and increased litter weight at parturition (46), The earlier the

zeolite was added, the greater was the apparent effect.

Similar studies were conducted at Oregon

State University with young swine using rations containing 5 percent clinoptilolite (16).

Although lesser increases in growth rates were

found than in the Japanese studies, the incidence of scours was significantly reduced for

animals receiving the zeolite diet. Currently,

heavy doses of prophylactic antibiotics are

used to control such intestinal diseases, which,

left unchecked, result in high mortality among

young swine after they are weaned. Federal

regulations are becoming increasingly stringent in this area, and if antibiotics are prohibited, other means must be found to control such

diseases. Natural zeolites may be the answer.

In a preliminary study involving 16 early

weaned pigs over a 19-day period, animals on

an antibiotic-free diet containing 10 percent

clinoptilolite gained about 5 percent more

weight per pound of feed than those on a control diet without antibiotics and about 4 percent more than those on an antibiotic-enriched

diet (table 9) (70). The small number of pigs

used, however, limits the significance of these

findings. In another study, a 30 percent improvement in FEVs occurred for 35 young pigs

on a molasses-based diet when 7.5 percent

Table 8.—Effect of Prenatal Zeolite Diet on Newborn Pigsa

Average weight (kg)

Species No. of pigs Group Newborn 21-days 35-days Weight gain improvement

Yorkshire 6 Experimental 1.25 4.3 7.83

Yorkshire 10 Control 1.10 4.2 4.81 63 percent

Laundry 6 Experimental 1.20 4.7 8.68

Laundry 10 Control 1.10 4.0 4.67 96 percent

aTest carried out at lchikawa Livestock Experiment station, Japan Four hundred grams of clinoptilolite given to sows n experimental group per day and continued

to end of weaning period (Buto and Takenashi, 1967)

bweight-gain of experimental animals - weight-gain of control animals x 100.
139

Table 9.—Effect of Zeolite Supplement in the Diets of Early Weaned Pigsa

Basal dietb Zeolite dietc Antibiotic dietd

Number of pigs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 4

Average daily weight gain (g). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 245 304

Feed efficiency value (FEV)e (weight gain/feed intake) . . . . . . . . . . . . . . 0.432 0.455 0.437

aPond and Mumpton (1978

b62% ground yellow corn 10% cerelose, 23% soybean meal, 0.5% salt, 0.5% Hopro R vitamin supplement, 1.5% ground limestone, 2.5% dicalcium phosphate

cBasal diet less 10% cerelose plus 10°/0 clinoptilolite, -200 mesh, Castle Creek, Idaho

dBasal diet plus 0.3% Aurofac 10 antibiotic

eExcluding zeolite

clinoptilolite was substituted in the diet during the 35 to 65 kg growth period (table 10) (10).

Feces of the zeolite-fed animals were also less

liquid than those on a control diet.

The addition of zeolites had little effect on

the FEVs in the 65 to 100 kg growth range.

Heeney (28) supplemented normal corn-soy rations of 36 pigs with 2,5 and 5 percent clinoptilolite in a 120-day experiment (table 11). He

found little overall difference in the FEVs; however, for the first 30 days after weaning, FEVs

of 0.455 and 0.424 were obtained for 2.5 and

5.0 percent zeolite, respectively, compared

with a value of 0.382 for the control animals,

an increase of about 15 percent due to the presence of zeolites in the diet. Little improvement

was noted between 30 and 120 days of the

treatment.

Ruminants

In an attempt to reduce the toxic effects of

high NH, + content of ruminal fluids when

nonprotein nitrogen (NPN) compounds, such

as urea and diuret, are added to the diets of cattle, sheep, and goats, researchers introduced

both natural and synthetic zeolites into the rumen of test animals (87). Ammonium ions

formed by the enzyme decomposition of NPN

were immediately ion exchanged into the zeolite structure and held there for several hours

until released by the regenerative action of

Na + entering the rumen in saliva during the

after-feeding fermentation period. Both in vivo

and in vitro data showed that up to 15 percent

of the NH4 + in the rumen could be taken up

by the zeolite. Thus, the gradual release of

NH4 + allowed rumen micro-organisms to synthesize cellular protein continuously for easy

assimilation into the animals’ digestive systems. The zeolite’s ability to act as a reservoir

for NH4 + “. . . permits the addition of supplemental nitrogen to the animal feed while protecting the animal against the production of

toxic levels of ammonia” in the rumen (87).

Clinoptilolite added to the feed of young

calves improved their growth rate by stimulating appetite and decreased the incidence of diTable 10.—Effect of Zeolite Supplement in Molasses-Based Diets of Young Pigsa

Zeolite level (%)

o 2.5 5 7.5 10

35-65 kg growth stage

Daily gain ( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 694 700 704 659

Daily intake (g). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2900 3110 3090 2970 3040

Daily feed intakec (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2900 3030 2940 2750 2740

Feed efficiency value (FEV)d (weight gain/feed intake) . ............0.214 0.229 0.238 0.256 0.241

65-100 kg growth stages

Daily gain ( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 582 526 562 535

Daily intake (g). ., ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3550 3900 4260 4430 4140

Daily feed intakec (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3550 3800 4050 4100 3730

Feed efficiency value (FEV)d (weight gain/feed intake) . ............0.152 0.153 0.130 0.137 0.143

aCastro and Elias (1978)

b

lncluding zeolite C

lntake less zeolite

‘Excluding zeolite.
140

Table 11 .—Effect of Clinoptilolite Supplemental in the Diet of Swinea

Control

Average initial weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.6----

30-days:

Average weight (lb)..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.0

Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.09

Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.62

Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.382

60-days:

Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.7

Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.59

Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.80

Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.357

90-days:

Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.7

Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.72

Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.33

Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300

120-days:

Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188.2

Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.56

Feed/pound of gain (lb)b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.94

Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.254

Overall

Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.49

Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.42

2.50/o

Clinoptilolite

31.7

62.2

1.12

2.20

0,455

107.3

1.61

3.05

0.328

149.6

1.51

3.43

0.292

177.8

1.28

5,63

0.178

1.40

3.45

50/0

Clinoptilolite -.

31.7

62.5

1.17

2.36

0.424

106.2

1,52

3.09

0.324

150.0

1,57

3.67

0.272

176.4

1.27

4.30

0.233

1.37

3.34

Feed efficiency-valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.292 0.290 0.299

aFrom Heeney (1977), 6 pigs in each treatment. Control diet - 76.9% ground corn, 20% soybean 011 meal, 1.5% dicalcium phosphate, 0.5% CaCo3, 0.5% salt, 0.1%

trace mineral 0.25% vitamin premix, 025°/0 ASP250 antibiotic Zeolite diets contained 25 and 5°A replacement of corn.

bExcluding zeolite

CWeight gain/feed Intake, excluding zeolite

arrhea and soft feces (38). Five percent zeolite

was added to the normal grass and hay diets

of lo-and 184-day-old heifer calves over a 180-

day period. The animals on the zeolite-supplemented diets gained approximately 20 percent

more weight than those in control groups, and

although the test calves consumed more feed,

the feeding costs per kilogram of weight gained

were significantly less than for control animals.

No deleterious effects were noted, and the feces of the test animals contained slightly less

water and fewer particles of undigested solids.

The incidence of diarrhea and soft-feces was

markedly less in zeolite-fed calves than in control animals (table 12)

Watanabe, et al. (86) raised six young bullocks for 329 days on a diet containing 2 percent clinoptilolite, along with 72 percent digestible nutrients and 11 percent crude protein.

Although little difference in the final weights

of test and control animals was noted, test

steers showed slightly larger body dimensions

and reportedly dressed out to give slightly higher quality meat. These differences were reflected in the overall higher prices obtained for

the test animals and a 20 percent greater profit.

In addition, diarrhea and other intestinal ailments were noticeably less prevalent in the animals on the zeolitc diet, and the excrement

from these animals was significantly less odoriferous, again testifying to the retentivity of

clinoptilolite for ammonia. It is unfortunate

that a higher level of zeolite was not used in

these experiments; earlier studies in the United

States showed that as much as 40 percent clay

could be added to animal rations without adverse effects (68),

One study found increased protein digestion

when 5 percent powdered clinoptilolite was

added to a high-volubility protein diet of 18 Holstein steers and cows over a 118-day period;

however, statistically significant weight increases were not noted, The addition of 2 percent zeolite to the rations of cows was effective in preventing diarrhea and in increasing

milk product ion (20). These effects were appar-
141 — —— ——.—

Table 12.–Occurrence of Diarrhea and Soft-Feces Among Calves on Diets Supplemented With

5% Clinoptilolite

a

—

Incidence of diarrhea Incidence of soft-feces

Grass-fed Hay-fed Control Grass-fed Hay-fed - Contro l

30 . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0

36-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 1

61-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O 0

91-120 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0

121-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . O 0

151-184. . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0

4 0 0 4

2 9 4 13

2 1 1 13

1 2 0 13

4 4 0 8

0 0 0 0

Total 1 1

aData summarized from Kondo et al (1969)

Excrement Treatment

In the Unitcd States, livestock production

creates more than 1 billion metric tons of solid

wastc and nearly 400 million tons of liquid

waste each year (43). Accumulations of such

magnitude pose serious problems to the health

of man and beast alike and can pollute nearby

streams and rivers. In addition, the large

amount of undigested protein remaining in the

excrement represents a valuable resource that

for the most part is being wasted because of

our growing dependence on chemical fertilizers. The physical and chemical properties of

many natural zeolites lend themselves to a wide

variety of applications in the treatment of animal wastes, including the:

c reduction of malodor and associated pollution,

c creation of healthier environments for confined livestock,

Q control of the viscosity and nutrient retentivity of the manure, and

c purification of methane gas produced by anaerobic digestion of the excrement.

Malodor and Moisture Control

The semifluid droppings in large poultry

houses commonly emit a stench that is discomforting to farm workers and to the chickens

themselves. The noxious fumes of ammonia

and hydrogen sulfide contribute to decreased

13 16 5 51 —

reSistance to respiratory diseases and result in

smaller and less healthy birds (15,35). In many

areas of Japan clinoptilolite is now mixed with

the droppings directly or packed in boxes suspended from ceilings to remove ammonia and

thereby improve the general atmosphere in

chicken houses (82). The net result is reported

to be an overall increase in egg production and

healthier birds.

One study used a zeolite-packed air scrubber to improve poultry-house environments

(36). By passing ammonia-laden air over a

series of trays containing crushed clinoptilolite, 15 to 45 percent of the NH3

-N was removed

even though the contact time was less than one

second. There was an associated reduction in

odor intensity. The use of such a scrubber

could improve the quality of the air in poultry

houses without the loss of heat that accompanies normal ventilation. The ammonium-loaded

zeolite could then be used as a valuable soil

amendment on disposal.

Water content, maggot population, and ammonia production can be all minimized when

chicken droppings are mixed with one-third

zeolite (table 13). Similar results can be obtained if powdered zeolite is added directly to

the rations of the birds, all without affecting

the vitality or growth rate of the chickens (67).

Apparently, gaseous ammonia reacts with the

hydrous zeolite to form ammonium ions that

are selectively ion-exchanged and held in the

zeolite structure. These experiments suggest

that the addition of zeolites to poultry wastes

could reduce labor costs associated with airdrying or the high energy costs of thermal treat-
142

Table 13.—Effect of Zeolite Additions to

Chicken Droppings

Property 2.1 3:1 5:1 10,1 Control

Moisture content (%) 123 131 134 157 185

Maggot content (counts per

unit area) 38 101 172 387 573

Ammonia generation (relative

quantities) 315 370 245 500 450

aOnagi (1965) Clinoptilolite was spread on droppings of Leghorn chickens

every third day for a 15-day period The total amount of droppings iS the same

in all tests, Including the control

ment, whilc at the same time retain the valuable fertilizer components and meet ecological standards.

In swine raising, pigs fed a diet containing

10 percent cinoptilolite had feces richer in all

forms of nitrogen after drying than those from

control groups (vide supra) (39). As a result of

this study and of other investigations, about 25

tons of clinoptilolite per month is spread on

the floors of a Sapporo swine-raising facility

to adsorb urine and other liquid wastes (82).

The buildings were said to be dry, clean, and

considerably less odoriferous. In Akita Prefecture, Japan, a zeolitic mudstone is used to treat

offensive odors and to reduce moisture content

of swine excrement (30). The dried manure is

then sold as an inexpensive rice fertilizer.

An innovative application of zeolites in excrement treatment was patented and involves

the addition of a natural zeolite and ferrous sulfate to chicken droppings (37), The ferrous sulfate inhibits zymosis and decomposition of the

droppings, and the zeolite stabilizes the hygroscopic nature of this compound and captures

N H4 + produced in the manure. The mixture

is dried at 1200 to 1500 C and used as an odorless, organic fertilizer, It is also used as a protein-rich feedstuff for fish, fowl, and domestic animals.

Methane Purification

Although it is well known that anaerobic digestion of animal excrement and other organic

wastes produces an impure methane-gas product, this source of energy has generally been

ignored for anything except local or in-house

use (32). One major drawback is the fact that

in addition to methane, copious quantities of

carbon dioxide and sulfur compounds are also

produced during the digestion process, giving

rise to low-Btu products that are extremely corrosive. Nevertheless, the process is still an attractive one, and Goeppner and Hasselmann

(21) estimated that a billion cubic feet of 700

Btu/ft 3 methane gas could be produced by treating the 250,000 tons of manure produced each

day in the United States. The methane produced by the anaerobic digestion of the organic

wastes of a typical New York State dairy farm

of 60 head may be equivalent to the farm’s entire fossil-fuel requirements (32).

A recent development of Reserve Synthetic

Fuels, Inc., using the adsorption properties of

natural zeolites, suggests that this methane can

be economically upgraded to high-Btu products. In 1975, this company opened a methanerecovery and purification plant to treat methane gas produced by decaying organic matter

in the Pales Verde landfill near Los Angeles,

As shown schematically in figure 10, raw gas

containing about 50 percent methane and 40

Figure 10. —Methane-Purification System,

Pales Verde Landfill
143

percent carbon dioxide is fed to two pretreat- feet of methane meeting pipeline specifications

ment vessels to remove moisture, hydrogen sul- is produced each day and delivered to local

fide, and mercaptans. The dry gas is then utility companies (65). Such a zeolite-adsorprouted through three parallel columns packed tion process to upgrade impure methane prowith pellets of dehydrated chabazite/erionite duced by the digestion of animal manure apand carbon dioxide is removed by adsorption pears to be technically feasible and awaits

on the zeolite. Approximately 1 million cubic detailed economic and engineering evaluation.

AQUACULTURAL APPLICATIONS

In recent years, more and more fish products

have found their way to the dinner tables and

feeding troughs of every country, and the commercial breeding and raising of fish as a source

of protein is becoming a major business in the

United States and other countries, Many varieties of fish, however, are extremely sensitive

to minor fluctuations in such factors as water

temperature, pH, O2

, H2S, and NH4+. The

chemical and biological environment of aquacultural systems must be maintained within

close limits at all times. Processes based on the

selective adsorption and ion-exchange properties of several natural zeolites for oxygen aeration of hatchery and transport water and for

the removal of toxic nitrogen from tanks and

breeding ponds may contribute significantly to

increased product ion for human and animal

consumption.

Nitrogen Removal From Closed

or Recirculation Systems

In closed or recirculating aquacultural systems, NH4 + produced by the decomposition

of excrement and unused food is one of the

leading causes of disease and mortality in fish.

I n oxygen-poor environments, even a few

parts-per-million NH4 + can lead to gill damage, hyperplasia, and substantial reduction in

growth rates (42). Biological vitrification is a

common means of removing NH4 + from culture waters; however, processes similar to

those used in municipal sewage-treatment

plants based on zeolite ion exchange have been

found to be effective in controlling the nitrogen content of hatchery waters (40). Zeolite ion

exchange might be a useful alternative to biofiltration for NH4+-removal and have the advantages of low cost and high tolerance to

changing temperatures and chemical conditions (33).

Unpublished tests conducted in 1973 at a

working hatchery near Newport, OR, indicated

that 97 to 99 percent of the NH, + produced

in a recirculating system was removed by clinoptilolite ion-exchange columns (34). Trout also

remained healthy during a 4-week trial when

zeolite ion exchange was used to regulate the

nitrogen content of tank waters (69), Becker Industries of Newport, OR, in conjunction with

the U.S. Army Corps of Engineers, has developed a single-unit purification facility for

hatchery-water reuse. The system incorporates

a zeolite ion-exchange circuit for nitrogen removal and is designed to handle typical concentrations and conditions encountered at

most of the 200 fish hatcheries operating in the

Pacific Northwest (34).

A similar ammonium-ion removal system

using zeolite ion exchange for fish haulage applications, where brain damage due to excess

NH, + commonly results in sterility, stunted

growth, and high mortality has also been developed (63). Three-way cartridges and filters

containing granular clinoptilolite will also be

available for home aquaria. The U.S. Fish and

Wildlife Service investigated zeolite ion-exchange processes for the treatment of recirculating waters in tank trucks used to transport

channel catfish from Texas hatcheries to the

Colorado River in Arizona (48). If NH4+ can

be removed, the number of fish hauled in such

trucks can be nearly tripled.
144

Aeration Oxygen Production

Oxygen-enriched air can be produced by the

selective adsorption of nitrogen by activated

zeolites. A pressure-swing adsorption process

capable of producing up to 500 m

3 of 90 percent oxygen per hour was developed in Japan

for secondary steel smelting (80). Smaller generators with outputs of as little as 15 liters of

50 percent O2 per hour are also manufactured

and used to aerate fish breeding tanks and in

the transportation of live fish. Carp and goldfish raised in such environments are said to be

livelier and to have greater appetites (41), In

closed tanks and stagnant ponds, oxygen aeration could markedly increase the number of

fish that could be raised per unit volume.

Oxygen produced by small, portable units

containing natural zeolite absorbents could be

used to replenish free oxygen in small lakes

where eutrophication endangers fish life. Fast,

et al. (1 7), showed that the oxygen of hypolimnion zones could be increased markedly by aeration using liquid O2 as a source. Haines (23)

demonstrated side-stream pumping could improve the dissolved oxygen in the hypolimnion

of a small lake in New York State.

Fish Nutrition

The high-protein rations used in commercial

fish raising are quite expensive and their cost

has been a limiting factor in the development

of large-scale aquacultural operations. The

physiology of fish and poultry is remarkably

similar, and if the results achieved with chickens can be duplicated with fish, the substitution of small amounts of inexpensive zeolites

in normal fish food, with no adverse change

in growth and perhaps a small increase in feed

efficiency, could result in considerable savings.

The quality of the water in recirculating systems should also be improved by the use of zeolite-supplemented food, as should that of the

effluents. Leonard (44) reported preliminary results of experiments where 2 percent clinoptilolite was added to the normal 48 percent protein food of 100 rainbow trout: after 64 days,

a 10 percent improvement in the biomass increase was noted, with no apparent ill effects

on the fish (table 14).

Table 14.—Effect of Clinoptilolite Additions to the

Diet of Trouta

Control Test

100% normal 98% normal feed

feedb2% clinoptilolite

Average starting weight (g) 10.2 10.1

Average 64-day weight 48,6 52.3

Average weight gain 38.4 42,2

Mortalitv. ... ~ ~ 4 3

a100 rainbow trout.

bStandard 48% protein fish food

OCCURRENCE AND AVAILABILITY OF NATURAL ZEOLITES

Geological Occurrence other hand, are ideally suited for simple, inexSince their discovery more than 200 years

pensive, open-pit mining.

ago, natural zeolite minerals have been widely Most sedimentary zeolite deposits of ecorecognized by geologists as cavity and fracture nomic significance were formed from finefillings in almost every basaltic igneous rock. grained volcanic ash or other pyroclastic maAttractive crystals up to several centimeters in terial that was carried by the wind from an

size adorn the mineral museums of every coun- erupting volcano and deposited onto the land

try; however, such traprock occurrences are surface, into shallow freshwater or saline lakes,

generally too low-grade and heterogeneous for or into the sea fairly close to the volcanic

commercial extraction. The flat-lying and near- source. Much of the land-deposited material

ly monomineralic sedimentary deposits, on the was quickly washed into lakes where it formed
beds of nearly pure ash. Successive eruptions

resulted in sequences of ash layers interstratified with normal lake or marine Sediments,

such as mudstoncs, silt stone, sandstones, and

limestones, as well as beds of diatomite, bentonite, and chert (figure 1 I).

The layers of volcanic ash (called volcanic

tuff) vary in thickness from less than a centimetcr to several hundred meters and may

stretch for 10 kilometers. Many of these bedded tuffs have been transformed almost completely into well-formed, micrometer-size zeolitc minerals. Zeolitically altered tuffs occur in

relatively young sedimentary rocks in diverse

geological environments. Sedimentary zeolite

deposits of this kind have been classified into

the following types, with many gradations between the types, Sheppard (77), Mumpton (54),

and Munson and Sheppard (62):

1.

2.

3.

4.

5.

6.

7.

145

deposits formed from volcanic materials

in hydrologically ‘closed" salin e

lake systems;

deposits formed in hyrdrologially ‘open”

fresh-water lake or ground watcr systems;

deposits formed in marine environments;

deposits formed by low-grade, burial metamorphism;

deposits formed by hydrothermal or hotspring activity in bedded Sediments:

deposits formed from volcanic materials

in alkaline soils;

deposits formed without direct evidence

of volcanic precursors.

The most common zeolites in sedimentary

deposits are analclime, chabazite, c1inoptilolite,

erionite, heulandite, laumontite, mordenite,

phillipsite, and wairakite, with clinoptilolite

ranking first in abundance. Except for heulanFigure 11.— Field Exposure of Zeolite Beds
146

dite, laumontite, and wairakite, “sedimentary”

zeolites are alkalic and are commonly more silicic than their igneous counterparts. Commercial interest is mainly in deposits of the first

four types. Zeolite tuffs in saline-lake deposits

are generally a few centimeters to a few meters

thick and commonly contain nearly monomineralic zones of the larger pore zeolites, erionite

and chabazite that are relatively uncommon in

other types of deposits. “Open-system” deposits and marine tuffs deposited close to their

source are generally characterized by clinoptilolite and/or mordenite and may be several

hundred meters thick. Zeolitic tuffs are commonly soft and lightweight, although some

hard, siliceous deposits of clinoptilolite and

mordenite are known. Many sedimentary zeolite beds contain as much as 95 percent of a

single zeolite species, while others consist of

two or more zeolites with minor amounts of

calcite, quartz, feldspar, montmorillonite clay,

and unreacted volcanic glass.

Most zeolites in sedimentary rocks crystallized from volcanic ash by reaction of the amorphous, aluminosilicate glass with pervading

pore waters derived either from saline lakes or

descending ground waters. Others originated

by the alteration of preexisting feldspars, feldspathoids, biogenic silica, or poorly crystalline

clay minerals. Although the exact mechanism

of formation is still under investigation, zeolites in sedimentary rocks probably crystallized

as well-formed, micrometer-size crystals by

means of a dissolution-reprecipitation mechanism, with or without an intermediate gel

stage (55) (figure 12).

The factors controlling whether a zeolite or

a clay mineral formed or which of several zeolites formed from a given starting material are

also only poorly understood, although temperature, pressure, reaction time, and the concentrations of the dissolved species, such as H+,

silica, alumina, and alkali and alkaline earth

elements, seem to be paramount in importance.

Early formed species also tend to react further

with pore fluids of different composition, thereby yielding even more complex assemblages.

Figure 12.–Scanning Electron Micrograph of

Clinoptilolite Laths With Minor Mordenite From a

Saline-Lake Deposit Tuff Near Hector, CA

(from Mumpton and Ormsby, 1976)

Geographic Distribution

The distribution of zeolite deposits in various geographic regions of the world is governed solely by the geology of those regions.

Regions that have undergone past volcanic activity are likely to contain significant deposits

of zeolite minerals. Although the zeolite phillipsite is known to have formed within the last

10,000 years in a small saline-lake deposit at

Teels Marsh, NV (79) by the alteration of volcanic ash from the explosion of Mt. Mazuma

(Crater Lake), and chabazite has been identified in deposits on the walls of ancient Roman

baths in France, most potentially commercial

deposits of zeolites are of Tertiary or lower

Pleistocene age (70,000 to 3 million years ago).

Thus, any part of the Earth that was subjected

to volcanic activity during this period undoubtedly contains extensive deposits of volcanic

ash, and if these ash deposits had an opportunity to react with percolating ground waters

or alkaline pore waters from former saline

lakes, beds of high-grade zeolites are apt to

exist.

Although zeolites are now considered to be

some of the most abundant and widespread au-
147

thigenic silicate minerals in sedimentary rocks,

their existence as major constituents of altered

volcanic tuffs is still not common knowledge

among the geologists of many countries. Because of their inherently fine crystal size, zeolites are not easily identified by ordinary microsscopic techniques and have often been missed

by geologists and mineralogists studying these

formations. In general, zeolite identification requircs sophisticated X-ray diffraction and electron microscopic equipment not available in

many geological laboratories; however, once

a particular soft, lightweight, clay-like rock

from a particular area is identified in the laboratory as a zeolite rock, similar materials are

easy to locate in the field.

Table 15 lists the countries where zeolites

have been reported from sedimentary rocks of

volcanic origin and estimates the chances of

discovering additional deposits in these countries. Sedimentary zeolites have been found on

every continent, although few have been reported from the Middle East, Latin America,

or the East Indies, mainly because geologists

in these regions generally have been unaware

of the widespread occurrence of zeolites in

altered volcanic tuffs. Wherever zeolites have

been found, however, man has used the soft,

lightweight tuffs for hundreds of years as easily carved stone in a variety of structures ranging from walls and foundations of buildings to

barns and corrals to house livestock. Zeolitic

blocks have been found in buildings associated

with the Mayan pyramids at Monte Alban and

Mitla in southern Mexico (56) and are used

today in the construction of modern dwellings

in the Tokaj region of eastern Hungary. Zeolites are mined in only a dozen countries (table 16), but the potential is much greater.

The high probability of finding minable deposits of zeolites in countries where they have

not yet been reported, but where there has been

considerable volcanic activity in the past, is illustrated by the discovery of major bodies of

sedimentary zeolites in Mexico and in central

Turkey in the early and late 1970s, respectively.

Both countries show promise of becoming major suppliers of mineral raw materials in the

years to come, but, as with most developing nations, they have only limited in-house geological expertise to service their blossoming mineral industry.

During the late 1950s and 1960s the geological similarity}’ of the Western United States and

northern Mexico led geologists to speculate

about the existence of zeolite deposits south of

the border. It was not until 1972, however, that

this author (56) discovered the first such deposit in southern Oaxaca after visiting a large

stone quarry during an unrelated project. The

rock was being used as a local dimension stone

and closely resembled zeolitic tuffs that were

being quarried in Japan. Subsequently, the Oaxacan rock was shown to consist of about 90

percent clinoptilolite and mordenite. Shortly

thereafter, several similar deposits were discovered in this part of Mexico and Mexican scientists quickly learned to recognize zeolitic tuffs

in the field. One deposit was spotted in a road

cut while driving past it at 50 miles per hour,

suggesting that many more await discovery

with only minimal exploration efforts. As a result of these discoveries, at least three other deposits of sedimentary zeolites have been found

in the northern part of the country by Mexican geologists who are now atune to the existence of zeolites in volcanogenic environments

and to their potential applications in industrial

and agricultural technology.

Similar to Mexico, major parts of the central

Anatolian region of Turkey are covered by

thick sequences of Tertiary volcanic rocks, but,

with the exception of a few minor occurrences

of analcime in saline-lake environments, reports of zeolites in the volcanogenic sedimentary rocks of this country have been rare. The

principal reason for this is simply lack of exploration combined with a lack of knowledge

about the potential applications of such materials in industry. Turkey’s few geologists have

been more occupied with their chrome and

borate resources, which are exported in large

quantities to acquire badly needed currency.

In 1977, however, several low-grade occurrences of erionite and chabazite were uncovered in Turkey’s Cappadocia region, along with

a major deposit of clinoptilolite (7). In 1979, a

second major deposit was discovered by the au-
148

Table 15.— Reported Occurrences of Sedimentary Zeolites

Zeolite . —

Country species

Minable Minor Chances for

deposit occurrence finding deposit

Europe:

Belgium

Bulgaria

Czechoslovakia

Denmark

Finland

France

Germany

Great Britain

Hungary

Italy

Poland

Romania

Soviet Union

Spain

Switzerland

Turkey

Yugoslavia

North America:

Canada

Cuba

Guatemala

Mexico

Panama

West Indies

Africa:

Angola

Botswana

Congo

Egypt

Kenya

Laumontite

Clinoptilolite

Mordenite

Analcime

Clinoptilolite

Clinoptilolite

Laumontite

Clinoptilolite

Chabazite

Phillipsite

Analcime

Analcime

Clinoptilolite

Laumontite

Clinoptilolite

Mordenite

Chabazite

Phillipsite

Analcime

Clinoptilolite

Clinoptilolite

Clinoptilolite

Mordenite

Chabazite

Analcime

Laumontite

Clinoptilolite

Mordenite

Clinoptilolite

Laumontite

Clinoptilolite

Erionite

Chabazite

Analcime

Clinoptilolite

Analcime

Mordenite

Erionite

Laumontite

Clinoptilolite

Clinoptilolite

Mordenite

Clinoptilolite

Clinoptilolite

Mordenite

Analcime

Erionite

Phillipsite

Clinoptilolite

Wairakite

Clinoptilolite

Clinoptilolite

Clinoptilolite

Analcime

Heulandite

Phillipsite

Erionite

xxx

x

x

xx

xx

xx

x

xxx

xxx

xx

xx

xxx

xx

xx

x

xxx

x

x

xx

x

x

xx

xx

x

x

x

x

x

x

x

x

x

xxx

xx

x

x

x

x

x

x

x

x

x

x

xx

xx

xx

x

x

x

x

x

x

x

x

x

x

Poor

Excellent

Excellent

Poor

Good

Poor

Poor

Good

Good

Good

Poor

Poor

Poor

Poor

Excellent

Excellent

Excellent

Excellent

Good

Excellent

Excellent

Excellent

Excellent

Good

Good

Good

Good

Good

Poor

Poor

Excellent

Excellent

Excellent

Excellent

Excellent

Good

Excellent

Good

Poor

Good

Excellent

Excellent

Excellent

Excellent

Excellent

Good

Excellent

Excellent

Excellent

Poor

Excellent

Good

Good

Good

Good

Excellent

Excellent
149

Table 15.— Reported Occurrences of Sedimentary Zeolites—Continued

Zeolite Minable Minor Chances for

Country species deposit occurrence finding deposit

Northwest Africa Analcime

Mordenite

Clinoptilolite

Republic of South Africa Analcime

Clinoptilolite

Tanzania Erionite

Chabazite

Phillipsite

Analcime

Clinoptilolite

x Good

Good

Excellent

Poor

Excellent

Excellent

Excellent

Excellent

Excellent

Excellent

x

x

x

xx

x

x

x

x

x

Asia:

Iran

Israel

Pakistan

Australia

Clinoptilolite

Clinoptilolite

Analcime

Clinoptilolite

Analcime

Clinoptilolite

Laumontite

Analcime

Clinoptilolite

Mordenite

Analcime

Laumontite

Wairakite

Clinoptilolite

Analcime

Clinoptilolite

Mordenite

Laumontite

Erionite

Laumontite

x Excellent

Excellent

Good

Good

Good

Excellent

Poor

Good

Excellent

Excellent

Poor

Poor

Poor

Excellent

Good

Good

Excellent

Good

Good

Poor

xx

x

x

xx

x

China

Formosa x

x

Japan xxx

xx

x

x

x

Korea

New Zealand

xx

x

xx

x

x

x

Oceania

South Africa:

Argentina

x

Clinoptilolite

Analcime

Laumontite

Clinoptilolite

xx

x

Excellent

Excellent

Poor

Excellent

x

Chile x

Antarctica:

Antarctica Laumontite

Phillipsite

x

x

Poor

Poor

thor (59) and R. A. Sheppard of the U.S. Geological Survey, accompanied by a Turkish geologist, with a minimum of field effort. This

indicates a widespread distribution of such materials in volcanogenic sedimentary rocks in

this country.

face deposits overlain by a few to no more than

25 meters of overburden. The zeolite beds are

usually flat-lying and vary only slightly in thickness along the length of the deposit. Shallow

drilling is usually required to outline the areas

of highest grade, but many deposits are mined

by simple projection of the bed behind the outcrop, Commonly, the exposed bed can be broken in the mine by bulldozers or rippers; in

places small amounts of blasting are required.

In thinner deposits, care must be taken to eliminate overlying and underlying clays and volcanic ash from the ore to preserve purity, but

in some of the thicker deposits this poses no

problem,

Mining and Milling

The mining of zeolites in bedded sedimentary deposits is a relatively straightforward

process requiring only a minimum of equipment and trained personnel. Almost all of the

known zeolite deposits being mined are sur-
150

Table 16.—Countries Engaged in Zeolite Mininga

Country Mineral -

—

Mines Remarks

United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cuba . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Korea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bulgaria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hungary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Soviet Union . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Yugoslavia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Italy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

aAs of 1980

Clinoptilolite

Chabazite

Erionite

Mordenite

Mordenite/Clinoptilolite

Clinoptilolite

Clinoptilolite

Mordenite

Clinoptilolite

Clinoptilolite

Clinoptilolite

Mordenite

Clinoptilolite

Mordenite

Clinoptilolite

Clinoptilolite

Chabazite/Phillipsite

Chabazite/Phillipsite

12

4

2

1

1

1

8

5

2

1

1

1

3

1

2

1

Processing the raw ore is dependent on the

envisioned end use. Water-purification applications require a fine-sand fraction that must

be prepared from the ore by crushing and

screening whereas fertilizer and animal nutrition uses will likely make use of finely powdered material. In general, preparation involves only crushing, screening, and bagging.

Where particle size is critical, the screened

product must be washed to remove undersize

material and then dried. More sophisticated apAgronomic Applications

Many more available.

Single deposit, four companies.

Estimated.

Estimated.

Estimated.

Estimated.

Estimated.

Several more available.

Numerous, used for construction.

Several, used for construction.

plications may require that the zeolite he ionexchanged to an ammonium or potassium form

before being shipped to the consumer. In such

cases, the pulverized and screened product

must be subjected to a series of washes with

chloride or sulfate salts of these elements,

washed with water to e1iminate excess salts,

filtered, dried, and bagged. In 1980, crushed

ore could be produced i n the United States for

about $30 to $40/ton.

DISCUSSION

Although zeolites have been used for many

years in Japan as soil amendments, they are

only now becoming the subject of serious investigation in the United States as slow-release

fertilizers, moisture-control additives to lowclay soils, traps for heavy metals, carriers of

pest icicles, fungicides, and herbicides, and decaking agents in fertilizer storage. As soil

amendments they appear to retain moisture

and i reprove the overall ion-exchange capacit y of sandy and volcanic soils. Studies are being carried out on both pure zeolite and on zeolite that has been pretreated with nutritive

elements, such as potassium or ammonium. In

either case, the zeolite appears to act as a slowrelease fertilizer, selectively holding such elements in its structure for long periods of time,

thereby increasing the efficiency of such additives and reducing the total cost of fertilization. Although the data available are not unequivocal, the greatest success appears to have

been with root crops such as sugar beets, carrots, and radishes, where nitrogen is a vital nutrient. The optimum level of application, however, must still be determined for various types

of soils and for the particular crop in question,

as must the frequency and exact mode of application, the optimum particle size of the zeolite, and the nature of chemical pretreatment

of the zeolite.
151

Table 17 lists organizations that have or are

conducting experiments on the use of natural

zeolites in agronomic applications.

Animal Nutrition Applications

Despite the lack of statistical significance, numerous studies strongly suggest that the addition of certain zeolite mincrals to the diets of

swine, poultry, and ruminants results in decided improvement in growth and in feed efficiency (weight gain/pounds of nutritional feed

consumed). In addition, the incidence of intestinal disease among young animals appears to

be less when zeolites are part of the daily diet,

The most dramatic results have been reported

by overseas workers where experiments may

have been conducted under conditions that

were somewhat less sanitary than those generally employed in the United States. Zeolitesupplemented diets appear to be most beneficia1 in swine during the first 30 to 60 days after weaning, although there is some evidence

to suggest that zeolites in the rations of pregnant sows contributc to increased litter weights

and healthier offspring. In Japan, 2 to 5 percent clinoptilolite in the diets of cattle appeared

to result in larger animals and fewer incidences

of diarrhea. One study in the United States

found a 12-percent increase in feed efficiency

for cattle during the first 37 days using only

1.25 percent zeolite.

The exact function of the zeolites in both dietary and antibiotic phenomena are not well understood and await serious ph}’biological and

biochemical investigation. The ammonium selectivity of clinoptilolite suggests that in

ruminants it acts as a reservoir for ammonium

ions produced by the breakdown of vegetable

protein and nonprotein nitrogen in rations, releasing it for a more efficient synthesis into

amino acids, proteins, and other nitrogenous

compounds by micro-organisms in the gastrointestinal (GI) lumen, From the concentration

of ammonia in the portal blood of weanling rats

fed a 5 percent clinoptilolite diet or dosed oral1y with this zeolite, Pond, et al. (71), postulated

that the zeolite bound free ammonia in the GI

tract, thereby preventing its buildup to toxic

levels in the system. Such an antibiotic effect

could indeed be responsible for the larger

growths recorded for zeolite-fed animals.

Table 18 lists organizations that have or are

conducting experiments on the use of natural

zeolites in animal nutrition applications,

Table 17.—Organizations Engaged in Zeolite/Agronomic Investigationsa

Organizations Crop Organization Crop

Department of Horticulture Radishes Agricultural Experiment Station Corn

Colorado State University New Mexico State University Sorghum

Fort Collins, Colorado Las Crucas, New Mexico

Department of Agronomy Sorghum Department of Plant Science Radishes

Colorado State University Corn University of New Hampshire Corn

Fort Collins, Colorado Wheat Durham, New Hampshire

Department of Environmental Chrysanthemums Texas Agricultural Experiment Rice

HorticuIture Station

University of California Texas A&M University

Davis, California Beaumont, Texas

U.S. Sugarcane Field Laboratory Sugarcane Department of Soils, Water Nitrogen

U.S. Department of Agriculture and Engineering retention

Houma, Louisiana Tucson, Arizona in soils

aAs of 1980
152

Table 18.—Organizations Engaged in Animal Nutrition Studies Using Zeolitesa

Organization Animal Organization Animal

Department of Poultry Science

Colorado State University

Fort Collins, Colorado

Department of Animal Science

Colorado State University

Fort Collins, Colorado

Clayton Livestock Research Center

New Mexico State University

Clayton, New Mexico

Department of Poultry Science

Oregon State University

Corvallis, Oregon

Livestock Nutrition Service

Westminster, California

Department of Animal Science

University of Vermont

Burlington, Vermont

U.S. Meat Animal Research Center

U.S. Department of Agriculture

Clay Center, Nebraska

Department of Animal Science

Pennsylvania State University

University Park, Pennsylvania

Chickens

Swine

Beef Cattle

Chickens

Cattle

Ruminants

Rats (swine)

Cattle

Department of Animal Science

Cornell University

Ithaca, New York

Department of Animal Science

Oregon State University

Corvallis, Oregon

Western Washington Research and Extension

Center

Washington State University

Puyallup, Washington

Department of Animal Science

University of Kentucky

Lexington, Kentucky

Food and Animal Research, Inc.

Juneau, Wisconsin

Department of Biology

Cleveland State University

Cleveland, Ohio

Department of Agricultural Engineering

Oregon State University

Corvallis, Oregon

Swine

Swine

Rabbits

Dairy

Cattle

Calves

Calves

Chickens

Swine

Odor control

a

As of 1980.

Excrement Treatment Applications

Although the results are difficult to quantify,

almost all studies of the use of zeolites as dietary supplements in animal rations have reported a noticeable decrease in excrement malodor and have attributed this observation to the

high selectivity of the zeolite in the feces for

the ammonium ion. Similar results were noted

when zeolites were added directly to cattle

feedlots, suggesting that not only can healthier

and less odoriferous environments be achieved

by the addition of zeolites to animal manure,

but that the nitrogen-retention ability of the manure can be improved as well.

Zeolite purification of low-Btu methane produced by the anaerobic fermentation of excrement and other agricultural waste products

may be a means of producing inexpensive energy on individual farms or in small communities, and zeolite ion-exchange processes may

be employed in the removal of ammonium ions

from recirculating or closed aquacultural systems, thereby allowing more fish to be raised

or transported in the same volume of water.

Aquacultural research of this type has been or

is being conducted by Becker Industries, Newport, OR; the U.S. Fish and Wildlife Service,

Fish Cultural Development Center, Bozeman,

MT; Jungle Laboratories, Comfort, TX; the Department of Fisheries and Wildlife, New Mexico State University, Las Crucas, NM; the Narragansett Marine Laboratory, University of

Rhode Island, Kingston, RI; and the Department of Zoology, Southern Illinois University,

Carbondale, IL.

CONCLUSIONS AND RECOMMENDATIONS

Although they have been used locally for sev- tives to animal rations, and in the treatment

eral years in Japan and other parts of the Far of agricultural wastes is still in the experimenEast in small amounts, the use of zeolites as tal stage in the United States. A number of agrisoil amendments, fertilizer supplements, addi- cultural organizations have or are investigat-
153

ing such uses for natural zeolites in this

country. The projects have generally been

sponsored by grants or contracts from companies that themselves are developing applications for zeolites in one or more areas of technology, or they have been funded by the

institutions themselves and make use of zeolite products provided free or at low cost by

the companies. Table 19 summarizes the agricultural research efforts of companies that hold

properties of natural zeolites. In addition,

other, nonproperty holding organizations, such

as International Minerals & Chemical Corp.,

Cargill, Inc., and Lowe’s, Inc., have also been

involved in the development of uses of natural zeolites in agriculture.

Overseas, six to eight agricultural stations in

Japan continue to investigate natural zeolites

as soil amendments and dietary supplements;

Pratley Perlite Mining Co., which owns a large

c1inoptilolite deposit in South Africa, has made

several studies of the use of zeolites in the rations of swine and poultry; and a recent Bulgarian-Soviet symposium on natural zeolites

contained seven papers on animal-nutrition applications and two on soil-amendment uses,

‘Second Bulgaria n-%t’iet Symposium on Natu ra] Zeolites,

Kardzhali, Bulgaria, Oct. 11-14, 1$)79,

Similar projects are in progress in Cuba and

Hungary, where deposits of clinoptilolite and

mordenite are abundant. The intense interest

in the several socialistic countries mentioned

above undoubtedly stems from their efforts to

use their own natural resources and thereby

reduce their dependency on foreign sources of

expensive fertilizers and animal rations. These

same objectives, of course, are desired by each

developing nation—maximum use of local raw

materials and minimal use of imported products that must be purchased with hard currency. Where they can be found within a particular nation or where they can be obtained from

neighboring countries at minimum cost, natural zeolites have the potential to increase the

agricultural productivity of that nation by reducing the need for or increasing the efficiency

of chemical fertilizers and animal feedstuffs.

To convert the agricultural promise of natural zeolites into commercial reality, a concerted

effort must be made in the United States and

elsewhere by both the private sector and by

State and Federal funding organizations. The

studies to date have been mainly of a preliminary nature—radishes have been grown instead

of potatoes, and rats have been raised instead

of beef cattle—or of limited duration or extent.

Table 19.—Zeolite Property Holders and Zeoagricultural Research Efforts

Organization Zeolite Speciesa Research Effort

Anaconda Company Clinoptilolite, Erionite, In-house; sponsored

Chabazite/Erionite, Clinoptilolite, Chabazite, Mordenite, Phillipsite

Colorado Lien Co. Clinoptilolite Sponsored

Double Eagle Petroleum & Mining Co. Clinoptilolite, Clinoptilolite Sponsored

Forminco Clinoptilolite None

Harris & Western Corp. Clinopti/elite/A40rdenite None

Ladd Mountain Mining Co. Erionite/Clinoptilolite None

Leonard Resources Clinoptilolite Sponsored

Letcher Associates Clinoptilolite

Minerals Research

None

Phillipsite None

Minobras, Inc. Erionite None

Mobil Oil Corp. Erionite None

Monolith Portland Cement Co. Clinoptilolite None

NL Industries Clinoptilolite None

Norton Co. Chabazite/Erionite, Ferrierite None

NRG Corp. Chabazite/Erionite None

Occidental Minerals Corp. Clinoptilolite, Clinoptilolite, Erionite In-house; sponsored

Rocky Mountain Energy Co, Clinoptilolite

Union Carbide Corp.

Sponsored

Chabazite/Erionite, Mordenite, Erionite In-house; sponsored

U.S. Energy Corp. Clinoptilolite None

W. R. Grace & Co. Chabazite/Erionite, Ferrierite None

aRoman type = working mines, italics = prospects
154

Little information has been developed to illuminate the long-term benefits or adverse impacts

on food production. Many of the companies

sponsoring this research have considered the

results proprietary, and rightfully so, but workers in the field are therefore unable to obtain

the latest information, a situation that often results in massive duplication of effort. Largescale testing of zeolites under sustained field

conditions and projects involving statistically

significant numbers of animals are greatly

needed at this juncture. Such projects will require continuous funding by State and Federal

agencies, or perhaps, international agencies if

the results are to be applied to developing nations. It would be extremely instructive to carry

out such testing in several developing nations

themselves, where agricultural practices are

not as finely tuned as in the United States.

The actual introduction of natural zeolites

into specific agricultural processes should pose

no major problems. Crushed and sized material could be added to the fields directly or

banded into the soil either alone or with normal fertilizers using standard equipment. Likewise, the zeolite could be mixed as a powder

or fine granules with normal feedstuffs provided for livestock, or be inserted as a bolus

into the stomachs of ruminants. It could also

be sprinkled on or mixed with manure accumulations on a daily basis for nutrient retentivity.

None of these processes would require special machinery; in fact, all could be carried out

by hand, if such were the common practice in

that country. Users would, of course, need to

be instructed as to the correct amount to apply to fields or to mix with normal rations, and

the optimum time to apply it for specific crops,

and considerable educational efforts may be

necessary to convince the small farmer of the

benefits of zeolite additives. In this regard, zeolites are no different than any innovative procedure that many farmers are slow to accept.

Because the use of zeolites in agricultural

processes has not yet reached the proven or

commercial stage, any scenario developed to

introduce this promising technology into developing nations would involve contributions

from both the United States and the developing nations. The contribution of the United

States would be both geological and agricultural expertise in zeolite technology, whereas

the contribution of the developing nations

would be a willingness to search for deposits

of zeolites and a willingness to carry out some

necessary long-term or large-scale testing under field conditions. Any implementation plan

should begin with a series of visits by a team

of zeolite experts from the United States to

selected developing nations in the world where

zeolites are known or have a high probability

of occurring. In addition to a leader who would

have a broad background in zeolite technology,

the team would consist of four to eight geologists, agronomists, animal nutritionists, and

agricultural engineers who are not only experienced in the use of zeolites in agriculture or

in the occurrence of zeolites in volcanogenic

sedimentary formations, but who can incite an

enthusiasm in others for the wonderful things

that zeolites can do. The team would include:

●

●

c

●

a geologist who is not only knowledgeable about the occurrence of zeolites in such

environments, but who is capable of working with local resource people to find and

evaluate potential deposits of zeolites in

these countries;

an agronomist or plant scientist with considerable experience in the use of zeolites

to improve crop productivity;

an animal nutritionist with the necessary

expertise in the use of zeolites as dietary

supplements in animal nutrition; and

an agricultural engineer who has worked

with zeolites in excrement treatment to improve the health of confined livestock or

the ammonium retentivity of animal wastes.

The agricultural engineer would also provide practical experience to the team.

Prior to the first visit to a developing nation,

the team would arm itself with the latest information in the field by visiting the leading experiment stations and research laboratories in

this country and abroad where zeoagricultural

investigations are being carried out, Special

emphasis would be placed on the recent work

in Japan and in countries of Eastern Europe.
It is vital that the introduction of zeoagriculture into a developing nation not end with the

visit of a team of U.S. experts. On the contrary,

the initial visit should be folloed up as soon

as possible with specific plans for implementing the technology into the nation’s agricultural

processes. Although the implementation scenario of all innovative technologies would appear to be similar from this point on, the zeolite scenario would involve a search for these

materials in the developing nation if such materials had not already been reportrd from that

country. Such exploration would probably be

carried out by the local geological survey or

mining agency, but should be assisted in the

field by a geologist familiar with the occurrence of zeolites. If zeolites are known in the

country or if they can be obtained from neighboring regions without difficulty, plans should

be made with the country's agricultural people to field test the technology under optimum

conditions. Such plans and tests should also

be made with the assistance of agronomists or

animal scientists already familiar with the use

of zeolites in these processes.

-1!

2<

3.

4.

5

6.

7.

0.

9.

10.

11.

12

13.

14,

15.

16.

155

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Mumpton, F. A., “Commercial Utilization of

Natural Zeolites, ” In: Industrial Minerals and

Rocks, S. J. Lefond (cd.), Amer. Inst. Mining

MetaII. Petrol, Eng., New York, 1262-1274,

1975.

Mumpton, F. A., “Natural Zeolites—A New Industrial Mineral Commodity.” In: IVatural Zeolites: Occurrence, Properties, Use, L. B, Sand

and F. A. Mumpton (eds.) (Elmsford, NY: Pergamon Press, 1978).

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60

61

62.

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65

66,

67.

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69.

70.

71,

72.

73,

74.

Mumpton, F. A., “A Reconnaissance Study of

the Association of Zeolites With Mesothelioma

Occurrences in Central Turkey, ” U.S. Geol.

Surv. Open-File Rept, 79-954, 1979.

Mumpton, F. A., and Fishman, P. H., “The Application of Natural Zeolites in Animal Science

and Aquiculture, ” J. Anim. Sci. 45, 1188-1203,

1977.

Mumpton, F, A., and Ormsby, W, C., “Morphology of Zeolites in Sedimentary Rocks by Scanning Electron Microscopy, ” clays and Clay

Minerals 24, 1-23, 1976,

Munson, R, A., and Sheppard, R, A., “Natural

Zeolites: Their Properties, Occurrence, and

Use,” Minerals Science Engineering 6, 19-34,

1974.

Nichols, R, A,, Jungle Laboratories, Comfort,

TX (personal communication), 1975.

Nishita, H., and Haug, R. M,, “Influence of Clinoptilolite on SrgO and CS137 Uptake by Plants, ”

Soi~-Sci. 114, 149-157, 1972.

NRG, “NuFuel, A New Source of Energy,” Brochure of NRG NuFuel Co., 1975.

Onagi, T., “Evaluation of Treatment of Chicken

Droppings With Zeolite-Tuff Powder, ” Rept.

Yamagata Stock Raising Inst., 11-22, 1965,

Onagi, T., “Treating Experiments of Chicken

Droppings With Zeolite Tuff Powder. 2. Experimental Use of Zeolite-Tuffs as Dietary Supplements for Chickens, ” Rept. Yamagata Stock

Raising Inst., 7-18, 1966.

Ousterhout, L. E., “Nutritional Effects of Clays

in Feed, ” Feedstuffs 42, 34-36, 1970.

Peters, M. D., and Bose, R. J., “ClinoptiloliteA Physiochemical Approach to Ammonia Removal in Hatchery and Aquiculture Water Reuse Systems, ” Fish Marine Serv. Tech. Rept,

535, 1975.

Pond, W. G., and Mumpton, F. A., “Effect of

Zeolite Supplementation of Early Weaned Pig

Diets on Growth, Feed Utilization, and Diarrhea,” Anim. Sci. Swine Memo 78-2, Cornell

University, 1978.

Pond, W, G., Yen, J. T., and Hill, D. A., “Decreased Absorption of Orally Administered Ammonia by Clinoptilolite in Rats, ” Proc. Soc, Exper. Biol. Med., 1980.

Pratley, G. M., “Internal Research Report,”

Pratley Perlite Mining Co., Kenmare, South

Africa (personal communication), 1978.

Quisenberry, J. H., “The Use of Clay in Poultry

Feed,” Clays and C’]ay Minera]s 16, 267-270,

1968,

Sate, Iwao, “Adsorption of Heavy Metal Ions
158

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75. Savitsky, A. C., “Utilization of Type A Zeolite

as a Laundry Detergent Builder, ” Soap/Cosmetic/Chemical Specialties 53, 29-31, 64, 66, 1977.

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Chapter IX

AgrotechnoIogies Based on

Symbiotic Systems That

Fix Nitrogen
Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

The Biological Nitrogen Fixation (BNF) Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

Agrotechnologies Based on BNF by Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

The Use of Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Inoculant Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Current Use of Legume-Based BNF Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

The Use of Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

Inoculant Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

How BNF by Legumes Increases Crop Yields and Soil Fertility . . . . . . . . . . . . . . . . 169

Future Potential of Legume-Based BNF Technology . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Constraints on Implementation of BNF Technology.. . . . . . . . . . . . . . . . . . . . . . . . . . 173

Scenario for Full Implementation of BNF Technology . . . . . . . . . . . . . . . . . . . . . . . . . 176

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Table

Table No. Page

I. Allocating Funds for a BNF Resource Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Figure

Figure No. Page

l. Pathways for Flow of Nitrogen From Legumes to Other Crops . . . . . . . . . . . . . . . 170
—

Chapter IX

Agrotechnologies Based on

Symbiotic Systems That Fix Nitrogen

When sustained productivity is sought from

low-input farming systems, legume crops are

especially attractive because of their ability to

be self-sufficient for nitrogen supply. Life on

Earth is dependent on transformations of atmospheric nitrogen to a form that can be absorbed from the soil by plants and used in

protein synthesis. The process can be accomplished industrially, but at a very high energy

cost, Biological nitrogen fixation (BNF) by symbiotic associations of plants with micro-organisms is more sound economically and environmentally than using nitrogen fertilizer in

agriculture.

Agrotechnology based on BNF by legumes

has two facets: the use of legumes and the use

of inoculant technology. Currently, legumes

are used in many systems without any specific

attempt to maximize their nitrogen fixation

through inoculant technology. But yields can

be increased and nitrogen fertilizer requirements reduced by using appropriate inoculant

technology. Maximum gains from BNF in

agriculture will arise from innovative use of

legumes in areas and in roles they have not occupied previously, provided that their modulation and nitrogen fixation is assured. Most

legumes in the Tropics “fix” about 100 kg/ha/

year of nitrogen. The common forage tree leucaena fixes around 350 kg/ha/year and the potential for some species is as high as 800 kg/

ha/year. Fertilizer savings represent not only

significant savings in foreign exchange, but

also reduced dependence on the oil-rich nations whose influence over the cost and availability of nitrogen fertilizer is increasing,

The use of legumes involves the management

of legume species in farming systems not only

for direct benefits accruing from the multiple

uses of legume products and the greater stability of mixed-cropping, but also for indirect

benefits arising from their ability in some circumstances to make a net contribution of nitrogen to the soil. This provides nitrogen for

companion or later nonleguminous crops.

The objective of inoculant technology is to

introduce sufficiently high numbers of preselected strains of rhizobia that they have a

competitive advantage over any indigenous soil

strains of lesser nitrogen-fixing ability into the

vicinity of the emerging root. Inoculation technology involves: selecting strains of rhizobia

that are compatible and effective nitrogenfixers with particular legumes; multiplying

selected strains to high population densities

in bulk cultures; incorporating the liquid rhizobial cultures into a carrier material [usually

finely milled peat) for packaging and distribution; and finally, coating the seeds of legumes

with the carrier or implanting the soil with the

inoculant.

Legumes already are used widely and consistently, though as minor crops, in farming

systems of the Tropics. Inoculant technology

is used on a meaningful scale only in a few

countries other than the United States and Australia. Great future potential rests in the development of:

●

●

●

legume-based pastures and viable multiplecropping systems including legumes for

under-used savannahs;

agroforestry systems that combine fastgrowing, nitrogen-fixing trees, legumes,

and other crops to meet the food and fuel

requirements of the rural poor;

fast-growing leguminous trees for reforesting water catchment areas following forest clearance;

161
162

●

●

legume-based cropping systems to give

sustained productivity in cleared jungle

soils which typically exhibit a rapid decline in fertility under conventional cropping; and

selection of deep-rooted, drought-tolerant

leguminous tree-s that can serve as browse

species in the world’s dry lands.

The major constraints to full implementation

of legume-based BNF technology in the Tropics relate to the delivery and acceptability of

the technology at the farm level. The constraints are political, cultural, socioeconomic

and, to a lesser extent, scientific. The major

scientific constraint is inadequate understanding of host legume, rhizobial strain, and environment interactions. This results in an inability to predict whether a given legume will

respond to inoculation in a particular region

or not. A constraint on better understanding

of these interactions is the lack of trained personnel to execute legume inoculation trials to

determine the economic benefits. A lack of domestic inoculant production plants also constrains research, development, and production

enterprises.

Legume-based BNF technology would benefit

●

●

●

●

from:

increasing economic and political pressure

for greater energy efficiency in agriculture;

increased recognition by decisionmakers

in funding agencies and in governments

of the potentials for exploiting BNF in developing country agriculture;

an increase in trained professionals and

technicians in tropical countries;

improved integration of legume germ-

●

●

●

concerted application of international funding to establish a BNF Resource Center

(this Center could be staffed, equipped,

and budgeted to provide technical assistance; offer germplasm and information

services; provide professional and technical training; conduct research necessary

to adapt BNF technology to individual developing countries when it is beyond the

capability of local researchers);

improved opportunity to exchange findings from field research programs; and

implementation of a sequence of standardized experiments designed to quantify the

economic yield benefit attributable to legume inoculation under field conditions

and followed by studies to quantify the nitrogen balance in multiple cropping systems that include legumes.

Legume inoculation does not substantially affect the need for farm labor. The inoculation

is accomplished as an integral part of the sowing method whether by hand or mechanized

planter. If fertilizers are normally applied, elimination of the need for nitrogen reduces the

capital cost but no substantial labor saving is

realized as other fertilizers still need to be applied. The use of legumes to benefit companion

or following crops is consistent with the farming systems already prevalent in the Tropics.

To use legume-fixed nitrogen for, as an example, cereal production in the United States

would necessitate adoption of mixed-cropping

systems that are not easily mechanized. Thus,

an increased demand for labor would be an impact. The major positive impacts of BNF technology are indirect through elimination of the

multitude of negative environmental impacts

plasm improvement programs and legume

bacteriology programs;

associated with nitrogen fertilizer production,

distribution, and use in agriculture.

INTRODUCTION

Beans and peas are well-known examples of terns. This is because of their unusual ability

food products from the array of plant species to be self-sufficient for nitrogen supply. “

that belong to the legume family. Legumes are

especially attractive when sustained produc- Nitrogen is an essential component of all life

tivity is sought from low-input farming sys- forms; it is a cornerstone in the chemical struc-
163

ture of proteins, Ironically, nitrogen is abundant in the atmosphere—the air we breathe is

80 percent nitrogen. In its gaseous form, however, nitrogen occurs as dinitrogen molecules,

each having two nitrogen atoms joined by a triple bond. This is among the most stable, inert

molecules known and cannot be used directly,

Thus, life on Earth is totally dependent on

transformations of atmospheric nitrogen to a

form in which it can be use readily by plants,

and subsequently, by animals and man.

This process is referred to as “nitrogen fixation” and involves splitting dinitrogen into

two nitrogen atoms that are then reacted with

hydrogen (generated by splitting water molecules) to form first ammonia and subsequently

a range of nitrogenous compounds. Nitrogen

fixation can be accomplished industrially, but

the process is one of the most energy demanding in today’s agriculture. The energy cost of

fixing nitrogen in the form of urea, ammonium

sulfate, or ammonium nitrate is compounded

by the additional costs involved in transport

and application. Additionally, the rather small

proportion of nitrogen-fertilizer actually taken

up by the crop to which it is applied and the

serious environmental pollution that can be

caused by nitrogen lost from agricultural land

through run-off are incentives for appraising

alternate nitrogen-sources. Self-sufficiency for

nitrogen supply as exemplified by the legumes

is thus a highly desirable trait.

THE BIOLOGICAL NITROGEN FIXATION (BNF) PROCESS

Biological nitrogen fixation (BNF) in legumes

is possibly because of the mutually beneficial

association (symbiosis) that can form between

leguminous plants and certain micro-organisms from a specific family of soil bacteria

known as Rhizobium. Rhizobia can penetrate

the roots of legumes and give rise to highly specialized organs referred to as root nodules.

These are quite different from tumors or other

swellings that commonly occur on plant roots

as a result of infection by disease-causing (pathogenic) organisms. The structure and function

of nodulated legumes is modified in such a way

that carbohydrates (sugars) produced in the

leaves of the plant during photosynthesis are

delivered to the nodulated root where they are

respired to provide energy. In the nodules, this

energy is consumed during nitrogen fixation

and it is used to sustain the growth requirements of the rhizobia.

Gaseous dinitrogen enters the nodule from

the air spaces in the surrounding soil. An enzyme, nitrogenase, that is the unique contribution of the microsymbiont, catalyzes the splitting of dinitrogen molecules and the reaction

of their component atoms to form ammonia.

Neither the sequence of reactions and transformations that follow initial fixation nor the

precise sites in the nodule where the events occur are fully understood. The steps involve very

rapid incorporation of ammonia, which would

ordinarily be toxic to both symbionts, into nitrogenous compounds such as amino acids,

amides, and/or ureides depending on the particular legume species. These are used throughout the ‘plant as building bl

proteins,

ocks for plan

Most farmers in the Tropics do not know that variably include legumes (52,59), Thus, legume

legumes fix nitrogen. Yet, traditional and mod- cultivation happens because farmers over

ern farming systems of the Tropics almost in- many centuries have recognized that legumes
164

are valuable components in farming systems

rather than from intentional exploitation of biological nitrogen fixation per se.

Agrotechnology based on BNF by legumes,

therefore, has two major aspects. One relates

to the deliberate inclusion of legumes in cropping systems to derive benefits from their nitrogen fixation. The other concerns the intentional use of specific practices to maximize

nitrogen fixation by legumes. For convenience

these two facets of BNF technology will be referred to as “use of legumes” and “inoculation

technology. ” The distinction is drawn to emphasize that currently legumes are used widely

with less than maximal benefits because of deficient symbiotic associations. Productivity

could be increased by using appropriate technology to assure effective symbiotic nitrogen

fixation by legumes. Much greater gains in productivity and economies of energy can be

realized from reduced fertilizer requirements

through innovative use of legumes in roles they

have not occupied previously in production

systems (e. g., the use of fast-growing leguminous trees in agroforestry systems). Production

gains will be greatest if the use of legumes is

always complemented by appropriate inoculant technology. This is because legumes can

only benefit fully from biological nitrogen fixation if they encounter rhizobia with which

they are genetically compatible.

THE USE OF LEGUMES

The benefits from BNF through the use of

legumes in farming systems are both direct, because the legume has an intrinsic value, and

indirect, because inclusion of a legume affords

greater yield stability in adverse growth conditions and can benefit companion or following nonleguminous crops.

Direct benefits from BNF by legumes in cropping systems arise from the multiple uses of

plants in the legume family. Though known

primarily for grain, forage, or feed production,

legumes are also cultivated in the Tropics for

timber, fuelwood, green manures, oils, fibers,

gums, drugs, dyes, and resins. Additionally,

they may be used as hedges; ground covers for

weed, insect, and disease control; as soil stabilizers on terraced slopes; or simply for shade

or as ornamental (59).

Indirect benefits accrue from the stability of

performance and assurance of some economic

return for at least one component under unfavorable conditions when legumes are intercropped with other crops. Stability is afforded,

for example, in erratic rainfall zones when the

components in the intercropping system are

separated in time such as with sorghum/pigeon

pea and groundnut/cotton (59,56). When there

is an outbreak of pests or diseases, maize/beans

and other intercrops afford stability of yields

and income (3,32). Other indirect benefits accrue from the ability of legumes to make a net

contribution of nitrogen to the soil under some

circumstances, thereby reducing the nitrogenfertilizer requirements for a companion or following nonleguminous crop.

INOCULANT TECHNOLOGY

There is a commonly held view (2) that trop- without inoculation (49,30). This view is no

ical legumes are much more promiscuous than longer well-founded. Some species and accestemperate legumes—that they nodulate freely sions from genera previously considered to be

with a wide range of tropical rhizobia and that promiscuous (2) require specific strains of

tropical soils are laden with so many bacteria Rhizobium (9,28,26) or form highly effective

that effective modulation is virtually guaranteed symbioses with only a few out of the wide ar-
-

165

ray of strains with which they nodulate (69,

16,22). Recent intensification of interest in the

tropical legumes and their rhizobia is revealing much greater variation in genetic compatibility and nitrogen fixation effectiveness than

has generally been acknowledged (38,23), A

plea has been made for recognition that tropical legumes fall into one of three categories

(23).

c Promiscuous effective (PE) group, where

modulation occurs with a wide array of

rhizobia isolated from many legume genera and the resultant symbioses are predominantly effective in nitrogen fixation.

● Promiscuous ineffective (PI) group, where

modulation occurs with an array of strains

of rhizobia isolated from many legume

genera, but where fully effective symbioses

form with only a few of those strains.

c Specific (S) group, where those strains

from the same genus (or a restricted number of other genera) form effective symbioses.

Just as with the temperate legumes, the likelihood that compatible, effective rhizobia will

not always be present in sufficient numbers in

the soil microflora is the rationale for using inoculation technology for tropical legumes (24).

When a tropical legume seed is sown uninoculated in a tropical soil, a native rhizobial population of strains differing greatly in their symbiotic effectiveness compete for the finite

number of modulation sites on the legume

roots. Many forage legumes bear only 10 to 20

nodules on which they depend for nitrogen

during the first three months of their establishment. Thus it becomes critically important that

each of the nodules that form on the root contain a strain of Rhizobium that is fully effective in fixing nitrogen. The underlying objective in inoculation technology is to introduce

sufficiently high numbers of preselected strains

of rhizobia into the vicinity of the emerging

root that they have a competitive advantage

over any indigenous soil strains of lesser nitrogen-fixing ability in the formation of rootnodules.

Inoculation technology involves:

selecting strains of rhizobia that are compatible and effective nitrogen-fixers with

particular legumes;

multiplying selected strains to high population densities in bulk cultures;

incorporating the liquid rhizobial cultures

into a carrier material (usually finely

milled peat) for packaging and distribution; and

finally, coating the seeds of legumes with

the carrier or implanting the soil with the

inoculant directly into the seed drill (64,

14,25).

An inoculum strain of Rhizobium recommended for a particular host must be able to

form effective nitrogen-fixing nodules with that

host under a wide range of field conditions. Nitrogen fixation effectiveness is only one important criterion for an inoculant strain. Other

criteria include: competitiveness in nodule formation, particularly against less effective

strains; persistence in the soil in the absence

of the host, especially for strains for annual species; promptness to form nodules; ability to fix

nitrogen under a range of soil temperature conditions; tolerance to pesticides; tolerance of low

soil pH; modulation in the presence of high levels of soil nitrogen; and ability to grow and survive in peat inoculants.

The host genotype interacts with the infecting strain of Rhizobium in determining the

level of nitrogen fixation, with the host playing the dominant role. Thus, two sources of

variation (plant and Rhizobium strain) can be

exploited in selection programs, Most commonly, though, the plant is selected independently and a suitable strain sought thereafter,

thus allowing only for exploitation of strain

variability. The range of specificities of host

genotype interactions is well-illustrated by soybean (77) and in the African clovers (51).

Three approaches to select strains for inoculants exist: select numerous inoculants, each

with a highly effective strain for individual species; select “wide-spectrum” strains that vary
166

from good to excellent in nitrogen fixation with

a range of legumes; or select multiple-strain inoculants containing the best strain for each

host species. There may be a conflict between

the option that would be chosen for commercial expediency and that which is scientifically

preferred (25). In Australia, “wide-spectrum”

strains are used when these are available, but

there is increasing use of specialized inoculants

with specific strains for individual hosts. Despite findings that suggest that multi-strain inoculant should be avoided because of possible

antagonistic and competitive effects (46) and

competition in nodule formation from the less

effective strains (17) this is the approach used

successfully by the U.S. inoculant industry.

Strains for testing can be obtained from other

laboratories working with the same species,

from nodules on plants in the native habitat

from which they were originally collected, and

from nodules formed on the legume by native

strains after sowing uninoculated seed in the

region where the new species is expected to

be used. None of these sources is invariably better in screening programs.

Most legume inoculants are prepared by adding liquid cultures of rhizobium to a finely

ground carrier base material such as peat. Although mixtures of peat with soil or compost

mixtures, lignite, coir dust, and some other

organic materials have been used, peat has

proven to be the most acceptable carrier worldwide. Agar, broth, and lyophylized cultures are

not recommended because survival rates for

these forms are poor (20,21,72).

Peat cultures can be prepared in two ways.

Either ground (milled) peat is mixed with a

high viable count (more than 109 rhizobia/ml)

broth culture in sufficient volume to provide

the minimum number of rhizobium acceptable

for use, or sterilized peat is inoculated with a

small volume of culture and incubated to allow

multiplication of the rhizobia. The choice of

method will depend on two factors—the survival of the rhizobia in peat in numbers high

enough to meet a minimum standard of quality,

and the availability of suitable, sterilizable containers and sterilizing facilities. The two factors that most affect survival of rhizobia in peat

are temperature of storage and sterility of the

peat. There are differences among species and

also between strains of the same species of

Rhizobium in their ability to survive well in

peat (63).

Like all biological products, legume inoculants are prone to loss of quality because of variation in the organism and from unforeseen

factors affecting some aspect of growth or survival. It is therefore essential that a quality control system be established. In Australia, largescale manufacture of legume inoculants is by

private enterprise and a separate, official (government) control laboratory is responsible for

maintaining a high-quality product. The control laboratory maintains and supplies recommended strains of Rhizobium to the industry,

checks strains annually for ability to fix nitrogen, assesses quality of cultures during and

after manufacture, and conducts any research

that is necessary to overcome problems associated with production and survival. In the

United States, the industry is free to select its

own strains and official control ensures that

the product can form nodules on the legume

for which it is recommended.

Although control of inoculant quality is primarily in the manufacturer’s interest and therefore his responsibility, control by external bodies provides protection from less scrupulous

operators and genuine failure of a strain outside manufacturer control. Not all countries

back their control labs with legislation. A control group requires suitably qualified and experienced personnel with facilities to permit

normal aseptic culture transfer and plant

growth facilities suitable for legumes from

many environments. Methods of assessment

involve both qualitative and quantitative tests.

The number and extent of these may vary according to competence and experience of manufacturers and the standards desired. In Australia, this control extends to holding stocks of

the strains used in inoculants. This is not the

case in the United States (29,70). In addition

to assessment of quality throughout manufacture, it is important to monitor product quality

in retail outlets. Standards acceptable at this
167

level may vary between countries. It is important that standards be realistic and within the

capability of manufacturers yet ensure that sufficient viable rhizobia are applied to the seed

to provide a satisfactory inoculation. In many

instances this can be as few as 100 rhizobia per

seed but in cases of severe environmental stress

as high as 10,000 or even 500,000 (1 1,12,21),

The prime objective of inoculation of legume

seed with rhizobial inoculants is to induce nodulation of the introduced legume host plant.

Rhizobia introduced into new environments

must live saprophytically in competition with

other rhizobia and soil micro-organisms in an

environment that may be adverse for their

growth and survival until the host seedling

roots provide the ecological niche to which

they are adapted. Thus, steps should be taken

to help inoculant strains: remain viable until

the host seedling is at the susceptible stage for

infection; compete with any natural rhizobia

for infection sites on the roots of the host legume and permit maximum nitrogen fixation;

nodulate its host promptly and effectively over

a range of environmental conditions; and persist in the soil for at least several years in sufficient numbers to maintain modulation of

perennial legumes or to achieve prompt nodulation of regenerating annual species.

The first attempts at inoculation involved

transferring soil from one field to the next, but

when the organisms responsible for nodule formation were isolated, artificial cultures soon

replaced the laborious soil transfer technique,

The usual inoculation technique is to apply the

inoculant to the seed just before sowing either

as a dust or as a slurry with water or adhesive

solution. Adhesives such as gum arabic or cellulose not only ensure that all the inoculum

adheres to the seed but also provides a more

favorable environment for survival of the inoculum. Pelleting of seed with finely ground

coating materials such as lime, bentonite, rock

phosphate, and even bauxite (11,12) have been

used to protect rhizobia during their time on

the seed coat. pelleting is a simple on-farm

technique (11,50) but custom-pelleted (by seedsmen at farmer’s request) and preinoculated

seed is now more popular. This latter procedure is potentially able to provide high populations of rhizobia on the seed for a long period

of time (one growing season to the next) but

has not yet been fully developed or exploited.

Most preinoculation procedures arc based on

multiple coatings, alternately of adhesive and

finely ground pelleting materials as used in

simple pelleting, The peat inoculant is included

as one (or more) of these coating layers. Soaking seeds in a broth suspension and then exposing them to either high pressure or vacuum

to impregnate the rhizobia into or below the

seed coat has not proven successful. Theoretically, rhizobia introduced in this way would

be protected from drying and other adverse environmental conditions, but the quality of products produced commercially has been variable

to very poor (16,10,66). It is, in fact, an indictment of the research workers in this area that

25 years has yielded so little progress in an area

where there is so much potential,

These production techniques are particularly

applicable to less well-developed and inexperienced rural groups, If high-quality and reliable products were marketed by a manufacturer

or seeds distributor, the farmer would not need

to be involved in legume inoculation.

A recent alternative to pelleting and preinoculation has been the use of concentrated

liquid or solid granular peat culture that can

be sprayed or drilled directly into the soil with

the seed during planting. Suspensions of rhizobia either as reconstituted frozen concentrates

or suspensions of peat inoculant can be applied

with conventional equipment. Similarly, granulated peat inoculants can be drilled in from

separate hoppers on the drilling equipment.

These methods have been especially successful

for introducing inoculant strains into situations

where there are large populations of competing

naturally occurring soil rhizobia (6), in cases

of adverse conditions such as hot-dry soils (68),

and where insecticide or fungicide seed treatment precludes direct seed inoculation (67,12).

Solid inoculant, also known as granular or “sod

implant” inoculum, is advantageous also, where

seeding rates for crop legumes of 70 to 100

kg/ha make on-the-farm inoculation logistically

impracticable.
168

CURRENT USE OF LEGUME-BASED BNF TECHNOLOGY

The Use of Legumes

Grain legumes are cultivated widely in a variety of agro-climatic zones in the Tropics and

Subtropics. Total area in grain legumes in 1979

was 175 billion hectares. Dry bean (Phaseolus

vulgaris) is the most important grain legume

in Latin America, groundnut (Arachis hypogaea) in Africa and collectively groundnut,

piegeon pea (Cajanus cajan) and chickpea

(Cicer arietinum) in Asia. These and other

grain legumes have been consistent components of human diet in the Tropics for centuries, yet in quantitative terms they continue to

be minor crops.

The use of legumes in mixed legume/grass

pastures in the Tropics is at present restricted

to northern Australia, the United States (Hawaii, Florida), southern Brazil, and northeastern Argentina. The total area in improved legume/grass pasture is insignificant compared to

the area of native grasslands under grazing.

The use of temperate forage legumes in mixed

pastures at high altitude locations in developing countries is frequent but is outside the

scope of this report.

Production statistics for tropical grain legumes are seldom accurate. Most of the production is on a subsistence scale on small farms

and the yields are seldom included in official

statistics. Thus, a figure of 186 million tons (31)

should be regarded as an understatement.

There are many agencies supporting and

conducting research related to the use of legumes. International agencies such as FAO,

UNDP, IBPGR, and the IARCs all have grain

and forage legume programs. USAID, together

with the governmental agencies of many countries, engaged in foreign agricultural development support research on legumes. The world

Bank and several private and public foundations also support legume research. The author

is not aware of any country in the Tropics that

does not have a legume project within its official agricultural program. Additionally, universities and agricultural colleges in tropical countries usually have legume programs. These

projects cover the physiology, plant nutrition,

agronomy, pathology, entomology, breeding,

and seed production of legume crops. Insofar

as BNF proceeds at a rate governed strongly

by the plant’s ability to deliver carbohydrate

to its root nodules, most technologies that improve overall plant performance are likely to

have a beneficial impact on modulation and nitrogen fixation. Relatively few projects, however, give adequate attention to specific techniques for maximizing BNF by the respective

legume. In fact, some research programs with

legumes are conducted under nitrogen-fertilized conditions or in fertile, nitrogen-rich soils.

Breeding for high-yielding varieties under such

conditions has resulted in plant types that are

only weakly symbiotic and heavily dependent

on soil nitrogen.

Given the important role of grain legumes as

the major dietary protein source for low-income groups in the developing countries, it is

hardly surprising that such a multitude of funding agencies and implementing organizations

give attention to research on legume technology. While it is to be expected that there will

be overall gains in the amount of nitrogen fixed

from improved performance by legumes in the

roles, and on the acreage they currently occupy, the major gains in BNF will follow increases in the total land area where legumes

are grown and especially the innovative use of

hitherto underutilized legumes.

lnoculant Technology

Inoculant technology is used widely on a

commercial scale in the developed countries.

The United States and Australia have substantial industries to produce, distribute, and market legume inoculants. There is also commercial-scale production in Brazil, Uruguay,

Argentina, India, and Egypt, Inoculants are

available commercially in many other countries but they are produced in U.S. or Australian laboratories. Some research centers, such

as CIAT and the University of Hawaii NifTAL

Project, produce inoculants in pilot-scale plants
as a service to researchers and occasionally to

legume growers. Demands for inoculation technology are increasing, primarily because of the

increased use of soybeans.

There are dangers in trying to satisfy this demand by importing inoculants developed in the

United States or elsewhere. This is because present inoculation technology has not proven

transferable. That is, strains of Rhizobium and

inoculation methods developed for conditions

at one location in a particular farming system

do not perform equally well at another location in a different farming system. Furthermore, the viability of rhizobia in legume inoculants is greatly affected by storage

conditions during shipment. Since producers

are unable to control such factors, no guarantee can be given that the inoculants are of merchantable quality on arrival at their destination.

For both these reasons inoculation failures are

a common occurrence and this is harming consumer acceptance of the technology. An ideal

scenario for improved implementation of BNF

technology is described in a later section.

169

The organizations funding research to adapt

inoculant technology to the circumstances

where it will be used in tropical countries include: UNDP by its support to the IARCs

through CGIAR and for a specific research program involving IITA and BTI/Cornell University; UNEP and UNESCO support inoculant

technology under the MIRCEN Project; FAO

is actively considering the role it might play

in the adaptation of inoculant technology for

use in developing country agriculture; USAID

through its contracts with University of Hawaii

(NifTAL Project) and USDA, Beltsville ARC

(World Rhizobium Study and Collection Center) through grants under Section 211(d) to the

U.S. Universities’ Consortium on BNF in the

Tropics, and through a portfolio of small grants

administered by USDA SEA/CR; USAID and

several governmental and nongovernmental

agencies that support the CGIAR are thereby

sponsoring work at CIAT, IITA, ICRISAT, and

ICARDA on the adaptation of inoculant technology for use in the Tropics.

HOW BNF BY LEGUMES INCREASES CROP YIELDS

AND SOIL FERTILITY

Consider the possible pathways to transfer

nitrogen from legumes to other crops (figure

1), The relative importance of the transfer pathways of nitrogen from legumes to other crops

and/or the soil can be estimated. Nitrogen gains

per hectare per year entering the cycle as seeds

(1 to 2 kg) (41) and in acid rainfall (1.5 to 3.5

kg) (78) are small compared to the nitrogen

fixed biologically. About 50 percent of the nitrogen accumulated in legumes in fertile soils

is attributed to BNF (71), though the proportion from fixed nitrogen will be greater in impoverished soils and lesser under nitrogen fertilization. Nitrogen accumulation in legume

monocrops ranges from 50 to 350 kg/ha/year,

It is generally accepted that nitrogen fixation

of around 100 kg/ha can be expected from the

majority of grain and forage legumes. Higher

levels are possible for leucaena and other forage legumes with a 12-month growing season.

Low levels are likely for bad nitrogen fixers

with short growing seasons (e. g., Phaseolus

vulgaris).

As an example, follow the fate of 100 kg of

biologically fixed nitrogen entering the cycle.

Between 60 and 90 percent of the nitrogen accumulated in legumes is removed as grain—

depending on the species, harvest index, and

harvesting practice, or as animal products depending on the intensity and selectivity of grazing. Thus, in an intercropping system only 10

to 40 kg nitrogen could potentially benefit other

crops. Some of the organic nitrogen of the legume residues is mineralized rapidly. The rest

is added to the soil organic matter pool and it
170

Figure

is mineralized slowly over a much longer period, Studies show that 60 percent is probably

the maximum portion of the nitrogen in the organic residue of a legume crop that could be

mineralized in time to benefit a following crop.

If 50 percent of the nitrogen is used in the

initial mineralization, in a cropping system

where the legume fixes 100 kg/ha/year only 5

to 20 kg of nitrogen is likely to benefit the following crop, One practice that could substantially increase the contribution is green manuring. If one year’s production were incorporated

into the soil, it would leave a residual benefit

of 50 kg/ha/year for the following crop. Experience has shown, however, that crops do not

necessarily respond to exaggerated applications of green manures.

There are few farming systems where green

manuring is economically feasible (41,8) since

land is tied up without immediate economic
171

return. Where green manuring is practiced, 5

tons of green matter per hectare is an accepted

application rate (54). This would represent an

addition of only 40 kg/ha of nitrogen to the soil,

of which only about 20 kg would mineralize

to the benefit of the crop. Green gram contributed 22 kg of nitrogen to following crops and

calapo/stylo green manure contributed 15 kg

(l).

The situation is more complex in mixed cropping systems where the legume and nonlegume

are growing concurrently. Legumes usually

take up less soil nitrogen in competition with

nonlegumes and a greater fraction of the nitrogen they accumulate in a mixed crop is from

fixed nitrogen. Somewhat surprisingly, the nitrogen fixation of intercropped beans (PhaseOlUS vulgaris) per hectare is not significantly

different from beans raised in monoculture

(36). This is attributed to competition between

the maize and the bean for light and nutrients

beginning after the decline in nitrogen-fixing

activity in the bean’s root nodules. Not all legumes shut down nodule function as early in

the growth cycle as Phaseolus vulgaris but the

effect of intercropping on nitrogen fixation

may be detrimental in other intercropping

systems.

It is a common misconception that there is

substantial direct transfer of nitrogen from the

legume to a nonlegume companion species in

a mixed cropping system. There is no convincing evidence that actively growing, healthy legumes, whether grain or forage, excrete significant amounts of nitrogen from their roots or

nodules. The hypothesis originally proposed by

Virtanen and coworkers (73,74,75) that surface

excretion of simple amino compounds from

healthy, functioning legume root-nodules resulted in direct transfer of significant quantities

of nitrogen to nonlegume companion species

has found little support from other workers

(45,7,47,80,81).

Subsequent research under carefully controlled conditions using the “fox box” technique (18) indicated that excretion of a wide

range of substances from plant roots does occur, but that the quantities involved are small,

less than 0.5 percent of the plant’s nitrogen (65).

Stated differently, a crop fixing 100 kg of nitrogen a year would excrete only 0.5 kg to the

soil.

Nitrogen benefit to nonleguminous crops

through association with companion legume

species is considered to be of an indirect nature

through loss and decay of shoot, root, and nodule tissue, or by recycling via the grazing animal, rather than by a direct pathway (76,15,

29,79),

Clearly then, mixed cropping systems that

aim to use legume-fixed nitrogen for the benefit of a companion nonlegume species must

match species so that the nonlegume is longerlived than the legume. Nitrogen will be released

in significant amounts only after cessation of

active growth and decomposition of tissues of

the legume. The maize/bean association used

widely in Latin America shows this principal.

Beans fix about 20 to 40 kg of nitrogen per

growing cycle (34). Assuming 70 percent removal of nitrogen as protein in the legume

grain, this leaves only 6 to 12 kg in legume

residues, of which 3 to 6 kg (assuming 50 percent mineralization) will be mineralized in time

to benefit the maize. Some estimates place the

mineralization that can benefit a companion

species as low as 20 percent. Consistent with

this, it is not uncommon for there to be no detectable nitrogen benefit in companion crops

that are intercropped with legumes.

It is evident that the BNF benefit to nonlegumes due to inclusion of legumes in a cropping

system is small compared to the level of nitrogenous fertilizer used in the more intensive cereal production systems of the developed

world. Thus, the principal contribution of BNF

to human nutrition will continue to be via the

protein in legume grains. Any suggestion of

substantial replacement of nitrogen fertilization of cereals and root crops by biologically

fixed nitrogen is unrealistic because these

crops respond to levels of nitrogen fertilizer far

greater than those currently supplied through

BNF by legumes, Thus, there is an urgent need

to devise ways to increase the contribution that

BNF by legumes can make to cropping systems

as a complement to nitrogen fertilizer-based

production, rather than as an alternative to it.
172

Legumes can be managed to increase their

nitrogen contribution. They vary in total nitrogen fixed, the proportion retained in non-harvested residues, the percentage nitrogen level

in residual tissue, and the facility with which

the organic nitrogen is mineralized. Thus,

some species, managed in particular ways, will

give greater residual nitrogen benefits. Given

this, the priority now given in legume breeding

programs to improving their harvest index, i.e.,

maximizing the fraction of each plant’s total

production that is removed as grain, should be

called into question.

In summary, the principal benefits from BNF

through the use of legumes in farming systems

in the Tropics are derived from the dietary protein of the legume grain, the multiple uses that

legumes serve for the subsistence farmer, and

the greater stability of yield and financial return of intercrops over monocrops. The indirect benefits from contribution of biologically

fixed nitrogen to companion or following species are small but are significant in the context of input levels in subsistence farming.

Insufficient reliable data exist on the potential benefits from enhancing, through inoculant

technology, the nitrogen fixation in tropical

legumes. It is tempting to recommend rhizobial

inoculation of all legume sowings as an insurance measure against the risk of modulation

failures that would otherwise occur. However,

inoculant technology does represent a cost, albeit small, and does add a degree of complexity to the sowing practice. Thus, inoculant technology should only be advocated when there

is a known need to inoculate and a demonstrable benefit. Additionally, the concept and practice of inoculant technology is so foreign to the

farmer’s normal practices that it should not be

recommended lightly. A subsistence farmer

can be forgiven for not comprehending nor accepting a technology that involves sticking

black powder containing bacteria to his seeds.

This contradicts concepts which he had only

recently learned, namely, that bacteria are bad

and clean seed is important. It is to be questioned whether inoculant technology in this

form will ever be accepted widely among subsistence farmers in the Tropics and Subtropics.

Unfortunately, many trials performed to evaluate inoculant technology with tropical legumes under tropical conditions have been done

with imported inoculants that may not have

contained acceptable levels of viable rhizobia.

Lack of response to inoculation in such trials

does not preclude the possibility that the legume could potentially benefit from inoculation.

More recently, coordinated networks of trials

have been initiated to determine whether there

is an economic yield benefit from inoculation

of legumes or not. INTSOY conducts international Soybean Rhizobium Inoculation Experiments (ISRIE) throughout the Tropics. CIAT

distributes an International Bean Inoculation

Trial (IBIT) throughout Latin America. The

University of Hawaii coordinates an International Network of Legume Inoculation Trials

(INLIT) offered for 13 agriculturally important

legumes and involving a three-stage experimental program where cooperators throughout the Tropics select strains specifically for

their legume variety and local soil conditions,

thereby maximizing the opportunity for a yield

response following inoculation.

FUTURE POTENTIAL OF LEGUME-BASED BNF TECHNOLOGY

Despite their seeming attractiveness for sus- use of nitrogen fixed biologically by legumes?

tained productivity from low-input production A small-scale, subsistence farmer elects to raise

systems, and despite also their consistent stra- those crops that best meet his household’s

tegic use in many farming systems of the Trop- needs but he also chooses one crop, at least,

ics, legumes have remained minor crops in the to sell or exchange for goods or services. Largesystems where they occur (52). Why is this the scale farmers consider the economic return

case, and what factors would lead to greater and ease of management associated with the
crops they plant. A grower preference for cereals over legumes, when the grain is to be marketed, would be understandable. It is usual for

yields of cereal grains to be as much as four

times higher than legumes (typically 3.0 t/ha

vs. 0.7 t/ha), Although the protein content i s

much higher in legumes (30 percent) than in

cereals (6 percent), the market value of legume

grains, albeit higher than for cereals, does not

compensate the grower for their low relative

yield.

Many factors will contribute to an increase

in the use of legumes. Cereals will continue to

be the major source of protein and calories for

human nutrition worldwide, but an increase

in importance of root and tuber crops and plantains over the next two or three decades is anticipated (58). Legumes can be expected to be

one means of complementing the dietary quality of these starchy protein-deficient foods.

Another factor that has already caused a reappraisal of biological nitrogen fixation

through legumes is the cost and availability of

energy to produce nitrogen fertilizers. Already,

20 percent of nitrogen fertilizer production in

the United States is cost-ineffective because of

the cost of energy (in the form of natural gas)

for the process. Producer costs have been calculated as $160/ton (61) whereas the selling

price is in the range of $85 to $105/ton. Thus,

biological nitrogen fixation through the use of

legumes may be resorted to increasingly, not

only to reduce the cost of on-farm inputs, but

also to save foreign exchange and avoid overdependence on foreign powers.

173

But economic pressure alone will not guarantee adoption of BNF-based technology without compelling demonstration of greater benefits from BNF by legumes. The dramatic

increase in interest in BNF since the energy

crises of 1973, 1974, and 1979 has brought it

under the scrutiny of agencies and individuals

whose concern is its viability as a productive

agricultural technology now rather than its

often acclaimed potentials for the future.

The agricultural research community needs

to undertake a comprehensive program of technology development where the relative distribution of funding and manpower investment

is realistically prioritized. Research to stabilize

grain legume yields can increase the contribution of biological nitrogen fixation in tropical

farming systems more than much of the research on the BNF process per se in grain legumes. Similarly, research to select forage legume germplasm that is adapted to the soils and

climates of the world’s underused savannahs,

and development of appropriate legume-based

pasture management technology, can be expected to increase the use of biological nitrogen fixation even without further research on

the BNF process. These statements assume that

effective modulation can be guaranteed. Since

this is not always the case, those specific aspects of BNF research that study the factors

that limit modulation and nitrogen fixation in

tropical soils should be given highest priority.

CONSTRAINTS ON IMPLEMENTATION OF BNF TECHNOLOGY

There are still many unknowns in the scien- ulant technology have been known for many

tific understanding of BNF, and research into years and have already made major contributhe biochemistry and genetics of the process tions to agricultural production—initially in

is particularly intense and competitive. B ut Australia and, more recently, worldwide as

few, if any, of these unknowns are really con- soybean cultivation has been increasing. The

straining the implementation of legume-based real constraints to fuller implementation of

BNF technology. The basic principles of inoc- BNF technology relate to delivery of the tech-
174

nology, both to potential inoculant producers

and to farmers, and acceptability of the technology.

There has not been adequate demonstration,

under realistic conditions in the developing

countries, of the yield increases and/or reduced

fertilizer needs that are repeatedly stated to be

the benefits of BNF technology. In some cases,

inoculation trials have been performed and no

response obtained. But these trials have been

mainly with imported inoculants, the quality

of which at the time of their use was not or

could not be verified. Thus, a related constraint

is the lack of trained personnel with the essential combination of agronomic and microbiological skills for executing production-oriented

research on BNF technology.

Research is necessary to adapt BNF technology and develop appropriate Rhizobium strains

and inoculation procedures for use in the Tropics and Subtropics. Current inoculation technology as used in the United States and Australia is suited to legumes grown under favorable conditions with relatively high complementary agronomic inputs. Transferability of

this technology to situations where the legumes

are grown under marginal conditions with

minimal inputs, and confronted with one or

more soil and climatic stresses, is in some

doubt (37).

It is the genotype of the legume that is to be

inoculated that is the prime determinant of the

strain used in rhizobial inoculants, rather than

the characteristics of the soil where the inoculant will be introduced. This is contrary to

what is expected by many first-time users.

For example, in providing inoculant services

in Latin America and Hawaii, it has been common to receive data from soil analysis together

with requests for inoculants. Farmers expect

the selection of legume inoculant to be made

after consideration of local soil and climate,

just as would be the choice of crop variety. Yet

there are few instances in which an inoculant

strain is recommended in commercial production because of the soil characteristics. Rhizobium strain CB 81 is recommended for Leucaena leucocephala sown in acid soil and NGR

8 for alkaline soils (48).

When soil characteristics are very different,

the response to inoculation and the relative performance of rhizobial strains is also different.

Even apparently similar soils can show different performances. Thus some authors advocate

that simple “need-to-inoculate” trials always

be performed at the local level due to the unpredictability of the response to inoculation

(11,22,23). This suggestion would result in legume inoculation being tested, essentially by

trial-and-error, at every site where legumes are

to be grown. Inoculation technology needs to

be more transferable than this, otherwise its

value as an agrotechnology is questionable.

There are significant differences between

sites in the size of their indigenous rhizobial

populations (42,55) and in the range of strains

of Rhizobium in the indigenous microflora

(43,55). Such differences have been attributed

to the effect of soil factors (43,5) though the possibility of widespread correlations between

specific soil characteristics and rhizobial occurrence in tropical soils has not been critically

examined.

The response by tropical legumes to inoculation with rhizobia also varies from site to site

(11,22,34,35,44,16). Such variation has been attributed to: differences in number, effectiveness, and competitiveness of native strains (40,

27,55,38); variation in quality of the inoculant

at its time of use (14); and variation in soil nitrate levels (57). The possibility that the response to inoculation could be predicted on the

basis of a more thorough description of soil and

environmental characteristics has not been

tested.

The relative performance of strains selected

under optimal conditions for a specific legume

is variable, depending on the site where they

are introduced (16). With inoculants that contain a mixture of strains of Rhizobium, it is

common for one strain to dominate in the resulting nodule population (33,39). The possibility that rhizobial strains might be selected

for adaptation to particular soil and environ-
mental conditions is not now exploited in tropical agriculture.

A serious constraint to fuller implementation

of BNF technology is the lack of domestically

produced, high-quality inoculants in the Tropics and Subtropics, Thus, factors which deter

government organizations or private enterprise

from undertaking inoculant production in a

particular country are also constraining BNF

technology. Among these are: high capital cost

of inoculant production plant (of the type used

in the United States and mistakenly assumed

to be needed in any production plant); high

operational cost associated with retaining a

professional and well-trained staff to run the

plant; operational risks associated with losses

due to such factors as contamination; absence

in most developing countries of an adequate

infrastructure that would permit marketing

and distributing a biological product with notorious vulnerability to high temperatures;

reticence to embark on an enterprise in advance of official control standards being established (compounded by official reticence to set

standards until there is an industry to be controlled); and insufficient demand and uncertain future demand for inoculants.

The present nature of BNF technology meets

considerable farmer resistance, i.e., the coating

of seeds with peat inoculant. In Brazil, packets

of inoculant are included “free” by some seed

distributors with all seed sales. However, the

inoculant is frequently discarded by farmers

not only because of the nuisance associated

with its use, but also in part because of an unfortunate impression that if inoculant is “free”

it is of little value.

The cost of inoculants is not usually a constraint to farmers who outlay capital for seed.

Inoculant will seldom exceed 1 percent of the

seed cost. For subsistence farmers who do not

ordinarily purchase seed, the capital outlay for

inoculant, albeit small, may be a disincentive.

Cost becomes a more important consideration

with granular forms of inoculant because the

rate of application is much greater than with

seed-applied inoculant.

175

BNF technology is a difficult technology to

deliver by normal extension mechanisms.

Thus, a lack of illustrative pamphlets and other

aids both for extension agents and the farmers

is also a constraint on implementation of BNF

technology at the farm level.

Furthermore, few of the senior administrators and decisionmakers who determine agricultural policy in the developing countries are

fully aware of the applications for legumebased BNF technology. Most policy makers are

aware of some of the attributes of legumes,

Relatively few appreciate the role played by

biological nitrogen fixation, and among those

an even smaller number recognizes that it may

be essential to employ specific technologies to

ensure that maximum nitrogen fixation occurs.

Thus, there is a need for educational material,

specifically developed for decisionmakers,

bringing to their attention the need to adapt

available technology to the particular circumstances where it is to be employed.

As BNF technology is being implemented,

new constraints are emerging that are best described as “scientific” and are researchable.

For example, some countries do not have peat

deposits suitable for carrier materials for inoculant production and alternate materials

must be identified and validated. Also, specific

soil and climatological stresses such as extreme

soil acidity and the associated high levels of

toxic elements like aluminum and manganese

may require selection of strains of rhizobia tolerant to those conditions.

The large number of competent researchers

who expend their energies and resources researching aspects of BNF other than limiting

factors such as the examples cited above is also

a constraint on fuller implementation of BNF

technology. Funding agencies do not always

recognize a distinction between applied and

less practical research in the area of biological nitrogen fixation. Biological nitrogen fixation has great pertinence to agriculture production in developing countries, but not all research conducted under the BNF umbrella is

applicable in agriculture.
176

SCENARIO FOR FULL IMPLEMENTATION ON BNF TECHNOLOGY

The constraints on fuller implementation of

BNF technology are not solely scientific, but

include cultural, socio-economic, and political

factors. Thus, the scenario where BNF might

realize its potential would necessarily be multifaceted and comprehensive.

The current trend toward energy-efficient

farming systems to reduce capital outlay for

imported fertilizers can be expected to continue and intensify. Manufacture of nitrogen fertilizers requires high energy consumption, so

their price and availability is influenced increasingly by oil-rich nations. There is added

attractiveness in alternate nitrogen sources to

avoid further dependence on foreign powers.

Legume-based BNF technology is the major option available and is likely to be resorted to

more and more.

The use of legumes and appropriate inoculant technology has the potential to increase

the amount of biologically fixed nitrogen entering agricultural production systems. Given that

the main value of legumes is their high-protein

grain, rather than their nitrogen contribution

to nonleguminous food crops such as cereals

and root crops, the scenario for full realization

of BNF technology’s potential would need to

include a swing in consumer preferences away

from crops that depend so heavily on nitrogen

fertilizer. Thus, in the gambit of BNF research

priorities, attention will need to be given to

learning the cultural and scientific bases for

these preferences and to alleviating the constraints to greater consumer acceptance of

legumes.

The major increases in benefits from legumebased BNF technology will arise through an increase in the total acreage in legume production; innovative use of legumes in roles they

have not previously occupied; and by ensuring that biological nitrogen fixation in legumes

is maximum through appropriate inoculation

technology. Much remains to be done to improve the role now played by biological nitrogen fixation components. There is a wide discrepancy between farmers’ yields and the

known yield potential of grain legumes. Furthermore, it is disconcerting that in the majority of legume trials that include nitrogen fertilizer application, the legumes responded to

nitrogen fertilization. This is disconcerting because it means that even when legumes were

grown under favorable management in experiments, let alone in farmers’ fields, the symbiotic association of the legume with rhizobium

was defective. Therefore, the potential to double or triple the nitrogen benefits described in

this report exists through development of technology that would assure establishment of maximally effective rhizobial symbioses in tropical legumes under tropical conditions.

Greatest future potential would appear to rest

in developing:

●

●

●

●

●

legume-based pastures and viable multiplecropping systems including legumes for

underused savannahs;

agroforestry systems that combine fastgrowing, nitrogen-fixing trees, legumes,

and other crops to meet the food and fuel

requirements of the rural poor;

fast-growing leguminous trees for reforesting water catchment areas following forest clearance;

legume-based cropping systems to give

sustained productivity in tropical soils following jungle clearance; and

selection of deep-rooted, drought-tolerant

leguminous trees that can serve as browse

species in the world’s dry lands.

Reference has already been made to the need

to exploit fully the variation in host plant,

rhizobial strain, and environment interaction

when selecting the optimal BNF package for

each circumstance. Legume programs should

retain the services of a professional microbiologist, but this suggestion is not practical. First,

few legume programs can afford the luxury of

a full-time microbiology position and second,

there is a worldwide shortage of professional

soil microbiologists that is unlikely to be

alleviated significantly for about 10 years. The

world’s major multidisciplinary legume pro-
177

grams should, however, have their own microbiologists. This is already the case with the

IARC programs for beans, cowpeas, pigeon

peas, groundnuts, chickpea, and tropical forages. INTSOY, working with soybean, has its

own soil microbiologist. Also, there are several

national legume programs where microbiological support is integrated through a participating institute with expertise in the BNF area

(e.g., Brazil, India).

The needs of the other legume programs for

BNF expertise could be met through the provision of one (or more) BNF Resource Center(s).

Such centers could provide technical assistance, offer support services (germplasm and

information), provide professional and technical training, and conduct research necessary

to adapt BNF technology to specific local conditions when it is beyond the capability of local

researchers. Such centers would require a critical mass of BNF researchers to be able to carry

out a comprehensive support program and still

retain a capability to respond to technical assistance requests.

The BNF Resource Center(s) would best be

located at universities in developed countries,

and preferably in the Tropics. A university site

would help provide professional training, important if national institutions in developing

countries are to be able to sustain their own

BNF programs. Short-term, non-degree training programs in BNF technology should be offered to key personnel working on research

programs involving the legume/rhizobium symbiosis. This is more effective in the short term

than Ph.D. or M.S. programs which tend to be

a passport out of research into better paid administrative positions for many graduates returning to their home country. The short courses

should be offered in cooperation with developing country institutes to generate a regional

capability for offering such courses. They

should be complemented by on-the-job training tailored to the needs of selected individuals

that would be conducted at the BNF Resource

Center and include visits to pertinent industry facilities.

Such BNF Resource Centers would engage

information specialists to develop communications materials suitable for the many clientele groups. This would range from newsletters for administrators to pamphlets for extension agents and include providing information for developing country researchers, who

often do not have access to libraries.

Agricultural research tends to focus manpower and resources on improvement of single

commodities. Some organizations, like IARCs,

are characterized by multidisciplinary teams

with specific crop and/or geographic mandates. Establishing a BNF Resource Center

would be considered by some as a return to

discipline-oriented research. This author contends that the key element in the success of

commodity programs such as some of those in

the IARCs has been that they are highly focused and actively managed in pursuit of welldefined research priorities rather than attributable to the commodity approach per se. A program investing manpower and financial resources in an actively managed BNF program

that is sharply focused on the constraints to full

implementation can be expected to make real

progress. The specialized and sophisticated nature of rhizobium bacteriological expertise and

the scarcity of experienced manpower is further justification for assembling a critical mass

of rhizobiologists in a single BNF Resource

Center.

An additional advantage in the existence of

such a BNF Resource Center would be a capability to extend BNF technology developed

at a particular place to other crops and regions.

Staff of the BNF Resource Centers would travel

as required and undertake short (1 to 3 months)

or longer (3 months to 3 years) assignments in

support of specific outreach activities when

warranted. Only travel would help the personnel of the BNF Resource Centers focus their

attention on researchable constraints in real

agricultural situations in the developing countries. Additionally, the Resource Centers wouId

work closely with other universities and research organizations where specific research
178 ——————-——

on factors limiting BNF use could be referred

under subcontract.

The BNF Resource Center would need to develop links with commercial inoculant producers to begin appropriate assistance programs

for government organizations or private enterprise in developing countries contemplating inoculant production. Such programs would cover not only technical aspects of the production

of inoculants but also the business aspects of

small enterprise production, marketing, and

distribution of inoculants. The BNF Resource

Center should develop specifications, including

sources of all equipment items, for inoculant

production facilities that would be feasible at

levels of capital investment ranging from

$50,000 to as high as $1 million. The Center

should also advise governments on an appropriate mechanism for quality control.

The Center would also need to develop strong

links with major legume germplasm centers

and those involved in legume improvement to

encourage simultaneous exploitation of host

legume and rhizobial germplasm in selections

for particular soils and climates.

The BNF Resource Center would take a major organizational responsibility for calling

workshops and scientific meetings to coordinate international experimentation and disseminate results.

The major activity to be undertaken by the

BNF Resource Center would be the coordination of competent, standardized experiments

designed to generate the data necessary to

quantify the economic yield benefit attributable

to legume inoculation under field conditions.

Such trials would also serve as local demonstrations of the benefits from legume inoculation.

The core budget for such a BNF Resource

Center should be guaranteed by the host government through its agency responsible for international development. The host institution

(university) cannot realistically be expected to

provide direct financial support for such a Center given that the Center staff will not have conventional instructional responsibility and that

the research will aid mainly foreign nations

with only minor benefits for agriculture where

the Center is located. The mandate of a BNF

Resource Center is international and therefore,

the support should be international.

There is understandable reticence on the part

of international funding agencies to expend resources in a center located in a developed

country. The author contends that it is in the

best interests of the developing countries that

BNF programs be conducted by a Center located in the Tropics but sited in a developed

country where it can receive unimpeded logistic support for its sophisticated operations and

enjoy continuity of service from high calibre

professional staff. Such a Center would be ultimately more cost effective than fragmented

support to a myriad of in-country programs,

an approach that often causes wasteful duplication of effort. Furthermore, support of a BNF

Resource Center, for example in the United

States with funding by USAID, would be prudent use of public funds. A large share of the

budget would be expended in the United States

sustaining employment of U.S. residents and

strengthening a U.S. institution without lessening the support for the developing countries.

Additionally, a greater degree of control could

be exercised over the activities of a U.S.-based

Center than is possible with grants to foreign

institutions.

Agencies that could be anticipated to contribute to a BNF Resource Center would be: FAO,

UNEP, UNESCO, and UNDP. Technical assistance on a continuing basis to any specific

country ought to be funded externally as a

special project with funding arranged by that

country from its national budget and international development assistance grants or loans.

As a hypothetical estimate, the author suggests the following distribution of $10 million

toward the implementation of legume-based

BNF technology (table 1). It is assumed that the

$10 million is additional to current support for

BNF.
179

Table 1 .—Allocating Funds for a BNF Resource Center

(How to Spend $10 million on BNF)

Salaries (6 professional and 12 subprofessionals)

African network of trials/demonstrations

American network of trtals/demonstrations

Asian network of trials/demonstrations

Training programs in technology

Professional (M.S., Ph.D.) training

Information services

Germplasm services

Workshops/conferences (3 regional, 1 global)

Research

Simplification of inoculant production

Innovative inoculation methods , . .

Stress tolerance in inoculant strains

Quantifying N fixation/cycling in cropping

systems in the tropic s

Advisory services

Contingency fund

Indirect cost s

BNF Resource Center

sub-total

$3,000,000

200,000

200,000

200000

500,000

150,000

120,000

100,000

270.000

90,000

90,000

150,000

220,000

200,000

60,000

1,350,000

$7,000,000’

Pilot Inoculant Plants

Zambia (year one) 250,600

Ivory Coast (year one) 100,000

Others (beginning third year) 1,000,000

Nitrogen-Fixing Tree Research (initially in

Haiti/Thailand/Senegal). 500,000

Socio-economic Evaluation of BNF Technology 250,000

Outreach Programs of BNF Resource Center

(beginning year 3)

Zambi a 300,000

Bangko k 300,000

Peru 300,000

GRAND TOTAL $10,000,000

%This figure is low for the level of operations envisioned and IS possible because a center with

appropriate equipment and buildings has already been established and IS operating in the proposed BNF Resource Center mode (I. e. University of Hawaii NifTAL Project)

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182

Acronyms

ARC —Agricultural Research Center

BNF —Biological Nitrogen Fixation

BTI —Boyce Thompson Institute (Cornell University)

CB 81 —CSIRO, Brisbane, Rhizobium

strain 81

CGIAR —Consultative Group on International Agricultural Research

CIAT —Centro International de Agricultural Tropical (Colombia)

CRSP —Cooperative Research Support

Program

FAO -–-Food and Agriculture Organization (of the United Nations)

IARC(s) —International Agricultural Research Center(s)

IBIT —International Bean Inoculation

Trial

IBPGR —International Board for Plant

Genetic Resources

ICARDA —International Center for Agricultural Research in Dry Areas

(Syria)

ICRISAT —International Crops Research Institute for the Semi-Arid Tropics

(India)

IITA —International Institute for Tropical Agriculture (Nigeria)

INLIT —International Network of Legume Inoculation Trials

INTSOY —International Soybean Program

(University of Illinois)

ISRIE —International Soybean Rhizobium Inoculation Experiment

MIRCEN—Microbiological Resources CenNGR 8

NifTAL

OTA

SEA/CR

UNDP

UNEP

ter (UNEP/UNESCO project)

—New Guinea, Rhizobium strain 8

—Nitrogen Fixation by Tropical

Agricultural Legumes (University of Hawaii)

—Office of Technology Assessment (U.S. Congress)

—Science and Education Administration/Cooperative Research

(USDA)

—United Nations Development

Program

—United Nations Environmental

Program

UNESCO—United Nations Educational,

Scientific, and Cultural Organization

USAID —United States Agency for International Development

USDA —United States Department of

Agriculture
Chapter X

Mycorrhiza Agriculture

Technologies

John A. Menge

Associate Professor

Department of Plant Pathology

University of California

Riverside, CA 92521
Contents

Page

Introduction—What Are Mycorrhizal Fungi? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Ectomycorrhizae . . . . . . . . . . . . . . . . . . . . ,,, .,, ,, . . . .,.,.,... . . . . . . . . . . . . . 185

Vesicular-Arbuscular (VA) Mycorrhizae . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . 185

How Do Mycorrhizal Fungi Improve the Growth of Agricultural Plants? . . . . . . . . 187

Mycorrhizae as Substitutes for Fertilizers . . . . . . . . . . . . . . . . . . . . . . . .,.,., ,..,,, 189

Current Commercial Use of Mycorrhizal Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Disturbed Sites ..............,,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Fumigated or Chemically Treated Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Greenhouses .. .,..., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....,.,., . . . . . . . . . . 192

Commercial Production and Inoculation With Mycorrhizal Fungi . . . . . . . . . . . . . . 192

Potential Uses of Mycorrhizal Fungi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

Constraints on the Commercial Use of Mycorrhizal Fungi . . . . . . . . . . . . . . . . . . . . . 197

Effects of Mycorrhizal Fungi on Agriculture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Conclusions and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

Table

Table No. Page

1. Estimated Cost of production of Vesicular-Arbuscular Mycorrhizal Inoculum on

Sudangrass in 4 Inch Pots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

Figures

Figure No. Page

l. Diagram of a Typical Ectomycorrhiza Including the Hartig Net, Fungal Mantle,

and External Hyphae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

2. Diagram of a Typical Vesicular-Arbuscular Mycorrhiza Including Vesicles,

Arbuscules, Spores, and External Hyphae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

3. The Growth of Citrus Seedlings With and Without VA Mycorrhizal Fungi and

at Different Nutrient Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . , 188

4. Dry Weights of Mycorrhizal and Non-Mycorrhizal Brazilian Sour Orange and

Troyer Citrange Seedlings Fertilized With Different Amounts of Phosphorus., . 190

5. Proposed Scheme for the Commercial Production of Vesicular-Arbuscular

Mycorrhizal Inoculum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Chapter X

Mycorrhiza Agriculture Technologies

INTRODUCTION-WHAT ARE MYCORRHIZAL FUNGI?

Mycorrhizal fungi are beneficial fungi that

are associated with plant roots via a symbiotic

association whereby both the host plant and

the fungus benefit. Mycorrhizae are the structures formed by the symbiotic association between plant roots and mycorrhizal fungi. Mycorrhizae contain both plant roots and fungal

tissues. In nature, mycorrhizae are far more

common than non-mycorrhizal roots (24,92,94).

Nearly all plant species are associated with mycorrhizal symbionts. Because of their importance to plants and their widespread distribution, mycorrhizae must be considered in all

aspects of plant ecology, crop science, and agriculture.

Mycorrhizal fungi are divided into four very

different types (66): ectomycorrhiza, vesiculararbuscular mycorrhiza (abbreviated as VA mycorrhiza), ericaceous mycorrhiza, and orchidaceous mycorrhiza. As indicated by their

names, ericaceous mycorrhiza and orchidaceous mycorrhiza are associated with ericaceous plants (blueberries, cranberries, azaleas,

etc.) and orchidaceous plants (orchids), respectively. Because of the relatively low economic

impact of these plants and the small amount

of available data on these types of mycorrhiza,

they will not be discussed further.

Ectomycorrhizae

Ectomycorrhizae are associated primarily

with trees such as pine, hemlock, spruce, fir,

oak, birch, beech, eucalyptus, willow, and poplar, Ectomycorrhizae are formed by hundreds

of different fungal species belonging to the

Basidiomycetes (mushrooms and puffballs) and

Ascomycetes (cup fungi and truffles). These

fungal symbionts are stimulated by root exudates and grow over the surface of host feeder

roots to form a thick fungal layer known as a

fungal mantle (figure 1). Hyphae of ectomycorFigure 1 .—Diagram of a Typical Ectomycorrhiza

Including the Hartig Net, Fungal Mantle, and

External Hyphae (courtesy D. H. Marx)

rhizal fungi penetrate between the cells of the

host root, develop around the root cortical

cells, replace the host middle lamella, and form

what is called the “Hartig net’’—the distinguishing feature of ectomycorrhizae. In response to the fungal invasion, the host roots

usually swell substantially and may branch dichotomously or in a coralloid manner. The root

cells are not injured, however, and function of

the roots is enhanced, as we shall discuss.

Vesicular-Arbuscular (VA)

Mycorrhizae

VA mycorrhizal fungi have the widest host

range and form by far the most common type

of mycorrhizae. VA mycorrhizae occur on

liverworts, mosses, ferns, some conifers, and

most broad-leaved plants. Only 14 families that

are considered primarily non-mycorrhizal (28).

The important crop families that are non-mycorrhizal are Cruciferae (cabbage, broccoli,

mustard, etc.); Chenopodiaceae (spinach, beet,

185
— —

186

etc.); Cyperaceae (sedges); and Caryophyllaceae

(carnation, pinks, etc.). wetland rice also is usually non-my corrhizal. Nearly all other important agronomic crops including wheat,

potatoes, beans, corn, alfalfa, grapes, date

palms, sugar cane, cassava, and dryland rice

are associated with VA mycorrhizal fungi. Although many trees have ectomycorrhizae, most

have VA mycorrhizae. Sixty-three of sixty-six

tropical trees in Nigeria (77) are associated with

VA mycorrhizae. So are most important tree

crops such as cocoa, coffee, rubber, and citrus. Some trees such as juniper, apple, and poplar can have either ectomycorrhizae or VA

mycorrhizae.

The fungi that form VA mycorrhizae, about

80 species, are in a few genera in the Zygomycetes class of fungi. They are so common in

soils that literally any field soil sample from

arctic to tropical regions will contain these

fungi (66).

The hyphae of VA mycorrhizal fungi penetrate directly into the root cortical cells of host

plants. Inside of the host plant cells, VA mycorrhizal fungi form minute coralloid structures

known as arbuscules (figure 2). Arbuscules are

thought to be the site of nutrient transfer between the symbiotic partners. The host plants

obtain fertilizer nutrients from the mycorrhizal

fungus while the fungus obtains sugars or other

food materials from the plant. Although the arbuscule of VA mycorrhizal fungi occurs inside

root cells, they remain covered by the host cell

membrane and so are not in direct contact with

the host cytoplasm. Vesicles are balloon-like

mycorrhizal fungus structures that usually

form inside the host root. These structures are

thought to be storage organs that the fungus

produces to store nutrient materials inside of

the plant host.

VA fungi also produce abundant spores either inside or outside of host roots. These

Figure 2.—Diagram of a Typical Vesicular-Arbuscular Mycorrhiza Including Vesicles, Arbuscules,

Spores, and External Hyphae
187

spores are the survival structures of VA mycorrhizal fungi. They are long-lived and extremely

resistant to most unfavorable soil conditions.

These spores are responsible for the widespread occurrence of VA mycorrhizal fungi in

nearly all soils throughout the world. Despite

the intracellular penetration by VA mycorrhizal fungi, they do not affect the roots’ outward

appearance except by inducing a yellow coloration in some hosts (4). Detection of VA mycorrhizal roots is best done by staining roots

and examining them microscopically for the

presence of hyphae, arbuscules, or vesicles (73).

Arbuscules of VA mycorrhizal fungi are

short-lived and generally survive for less than

2 weeks before they are digested by the host

plant (61,90). Plant roots normally release large

quantities of chemical “exudates” into the root

zone (8). Since the arbuscules are covered by

the host membrane it is thought that the symbiotic association is regulated by the host plant

via the cell membrane. The more nutrient materials released by the plant membrane to the

arbuscule of the mycorrhizal fungus, the more

abundant the mycorrhizal colonization (76). By

restricting nutrients passing through the plant

membrane the plant is capable of restricting

mycorrhizal infection in roots. A similar mechanism can be postulated for the regulation of

ectomycorrhizae by plant roots.

HOW DO MYCORRHIZAL FUNGI IMPROVE GROWTH OF

AGRICULTURAL PLANTS?

The VA mychorrhizal symbiosis results in

marked increase in crop growth and development. For example, inoculation of fumigated

sand or soil with VA mycorrhizal fungi will increase the growth of citrus by as much as 1600

percent (figure 3); (42), grapes by 4,900 percent

(74), soybeans by 122 percent (84), pine by 323

percent (100), and peaches by 80 percent (44).

Growth responses due to VA mycorrhizal fungi

have been observed in cotton (82), tomatoes

(16), corn (27), wheat (41), clover (75), barley

(5), potatoes (7), ornamental plants (99), and in

many other crops.

VA mycorrhizal fungi stimulate plant absorption of phosphorus (85,74,28,62), zinc (44,61),

calcium (84), copper (84,85,60,42), iron (60),

magnesium (36,61), and manganese (84,61). Increased uptake of phosphorus is perhaps the

most important benefit provided by mycorrhizal fungi,

Most researchers agree that the increase in

effective nutrient absorbing surface provided

by mycorrhizal fungi is primarily responsible

for the increase in uptake of soil nutrients by

mycorrhizal plants. Hyphae from figure 3 mycorrhizal plant roots can extend up to 8 cm into

the surrounding soil and transport nutrients

this distance back to the roots (83).

VA mycorrhizal fungi may increase the effective absorbing surface of a host root by as

much as 10 times (6). Nutrient ions such as

phosphorus, zinc, and copper do not diffuse

readily through soil. Because of this poor diffusion, roots deplete these immobile soil nutrients from a zone immediately surrounding

the root. Mycorrhizal hyphae extend into the

soil past the zone of nutrient depletion and can

increase the effectiveness of absorption of immobile elements by as much as 60 times (6).

Others have calculated that approximately 50

cm of mycorrhizal hyphae per cm root is necessary to account for the uptake of phosphorus

by mycorrhizal plants (89), Experimental observations indicate that plant roots can have more

than 80 cm of mycorrhizal hyphae, more than

the amount necessary to account for the observed phosphorus uptake,

Plant uptake of mobile soil nutrients such as

nitrogen and potassium is rarely improved by

mycorrhizal fungi, Normal soil diffusion is adequate to supply roots of plants with these nutrients whether the roots have a large absorbing surface or not. Generally, plants that are

most dependent on mycorrhizal fungi for nutrient uptake are those having roots with a low

surface to volume ratio; that is, plants with

coarse, fleshy roots with few root hairs (2).

38-846 0 - 85 - 7
188

Although some scientists speculate that mycorrhizal fungi can solubilize and absorb nutrients that are unavailable to plant roots, there

is little evidence to support this claim. Sanders

and Tinker (88) showed conclusively with 32plabelled phosphate that mycorrhizal fungi use

the same phosphorus sources as do plant roots

but they are able to absorb from a larger soil

volume and so are responsible for the vast majority of phosphorus absorption by crop plants.

Mycorrhizal fungi can also enhance water

transport in plants (87) and prevent water stress

under some conditions (54). This probably is

not a direct effect of mycorrhizal fungi, but instead is because of the improved nutrient status

provided by the mycorrhizal fungi. Mycorrhizal fungi can endure much dryer soil conditions than can most plants and it is thought that

plants may benefit from mycorrhizal infection

under drought or water-stressed conditions

(66,86). Ectomycorrhizae, in particular, with

their mantle surrounding the roots, may provide a physical barrier against root dessication.

Considerable evidence exists to suggest that

mycorrhizal plants may be better equipped to

withstand the toxic effects of salt. Calcium,

magnesium, and sodium concentrations in

non-mycorrhizal citrus were 41 percent, 36 percent, and 150 percent greater than in mycorrhizal citrus (55). Hirrel and Gerdemann (35)

found that mycorrhizal fungus increased bell

peppers tolerance to salinity. Trappe, et al. (98),

indicated that VA mycorrhizal fungi provided

resistance to the toxic effects of arsenic. Mycorrhizae may also provide tolerance to excessive soil manganese and aluminum (34).

Mycorrhizal fungi also act to increase modulation by symbiotic nitrogen-fixing bacteria
189

such as Rhizobium (64,69). Mycorrhizal fungi

may stimulate other beneficial rhizosphere organisms as well (1)0

Ectomycorrhizal fungi have been reported to

provide resistance to plant disease in many

plants (48). Although mycorrhizae never confer complete immunity, they often appear to

reduce the severity of disease or symptom expression. Resistance of ectomycorrhizae to disease may result from (48):

● mechanical protection by the mantle,

● better plant nutrition,

Q production of antibiotics by the mycorrhizal fungus,

● competition for infection sites,

● formation of phytoalexins, and

● alteration of root exudates.

Evidence is accumulating that VA mycorrhizal fungi exert similar effects on plant pathogens. Schenck, et al, (91), has reported mycorrhizal resistance to root-knot nematodes.

Schonbeck (93) has examined a variety of foliar

and root pathogens on mycorrhizal plants and

concluded that root pathogens (Thielaviopsis,

Fusarium, nematodes, etc.) are usually inhibited by mycorrhizal fungi while foliar pathogens (viruses, rusts, etc.) are often more severe

on mycorrhizal plants. Davis, et al. (21,22), and

Davis and Menge (20) concluded that the VA

mycorrhizal fungus Glomus fasciculatus produced little resistance to Phytophthora root rot

in citrus and indeed increased Phytophthora

root rot in avocado and Verticillium wilt in cotton. VA mycorrhizal effects on disease may result from improved phosphorus nutrition because of the increased absorbing surface of the

mycorrhizal hyphae. This effect is magnified

when the roots’ normal absorbing capacity is

reduced because the roots are partially

decayed.

There have been reports of mycorrhizal fungi

actually reducing growth of some plants (11,

39,13). These parasitic effects are rare and the

reason for them is not understood, but they apparently occur in grasses, cereals, and

tomatoes at or above optimum soil nutrient

levels when the plant is actively regulating

mycorrhizal invasion,

MYCORRHIZAE AS SUBSTITUTES FOR FERTILIZERS

In the past 40 years the use of agricultural

fertilizers has more than doubled. Crop yields

have risen dramatically as a result. However,

because of shortages in some fertilizer supplies

and the high cost of energy, the cost of fertilizers has risen tremendously. Agricultural

economists indicate that as energy costs rise

the most responsive agricultural input is fertilizer. That is, as energy costs rise, fertilizer

use will decrease. This response is a dangerous

one since chemical fertilizers are said to account for one-third to one-half of the current

U.S. agricultural output (47).

Estimates indicate that agriculture uses between 2.6 and 4.4 percent of all U.S. energy

use. Fertilizers and their application comprise

30 to 45 percent of the total agricultural energy

use. Nitrogen is the main energy user, with

phosphorus and potassium accounting for only

16 percent of the fertilizer energy use (47).

Because mycorrhizal fungi increase the efficiency of fertilizer use, they can be thought of

as “biotic fertilizers” and can indeed be substituted for substantial amounts of some fertilizers (53,55). Mosse (61) maintains that 75

percent of all phosphorus applied to crops is

not used during the first year and reverts to

forms unavailable to plants. In soils high in pH,

aluminum, or calcium carbonate, nearly 100

percent of the phosphorus fertilizer can be immobilized to nonusable forms via chemical reactions in the soil. Tropical oxisols and ultisols

are notorious for their capacity to immobilize

phosphorus. Because mycorrhizal plants are

better suited to exploiting soil with low amounts

of available phosphorus, zinc, and copper, the
190

addition of large amounts of these fertilizers

each year may be unnecessary. Menge, et al.

(55), compared mycorrhizal citrus seedlings

with non-my corrhizal seedlings that received

various amounts of phosphorus fertilizer (figure 4).

Mycorrhizal Troyer citrange that received no

fertilizer phosphorus were equal in size to nonmycorrhizal Troyer citrange that received 112

kg phosphorus per hectare, Similarly, mycorrhizal Brazilian sour orange that received no

fertilizer phosphorus were equal in size to nonmycorrhizal plants that received 560 kg phosphorus per hectare. Concentrations of phosphorus in non-mycorrhizal Brazilian sour

orange leaf tissue were never above 0.05 percent (less than 0.9 percent phosphorus indicates phosphorus deficiency) even when

seedlings were fertilized with 1,120 kg

Figure 4.—Dry Weights of Mycorrhizal and

Non-Mycorrhizal Brazilian Sour Orange and

Troyer Citrange Seedlings Fertilized With

Different Amounts of Phosphorus

phosphorus per hectare. Concentrations of

phosphorus in leaves of mycorrhizal Brazilian

sour orange were above deficiency levels in all

seedlings fertilized with more than 56 kg

phosphorus per hectare. Concentration of

phosphorus in leaves of mycorrhizal Troyer

citrange were never in the deficiency range

even when plants were not fertilized with

phosphorus.

Non-mycorrhizal Troyer citrange, on the

other hand, required over 56 kg phosphorus per

hectare before adequate phosphorus concentrations were restored to the leaves. At 1980

retail costs for triple super-phosphate, it appears that use of mycorrhizal fungi could result in savings of $111 to $558/ha ($45 to

$226/acre) in the cost of phosphorus fertilization of citrus in fumigated nursery soil. In one

California citrus nursery, it was found that inoculation with mycorrhizal fungi could reduce

phosphorus fertilization by two-thirds and save

$652/ha ($264/acre). Similar savings in phosphorus fertilizers have been shown by Kormanik, et al. (43), in fumigated forest nurseries

in the production of sweetgum.

Mycorrhizal fungi also can be substituted for

copper fertilizer in the culture of citrus seedlings (97). Other data has shown that mycorrhizal fungi can be substituted for zinc fertilizer

in the greenhouse culture of citrus and even

nitrogen fertilization can be reduced by as

much as 300 percent in the presence of mycorrhizae (Menge, et al., unpublished data). This

nitrogen savings effect is probably due to an

increased efficiency of nitrogen use resulting

from improved phosphorus nutrition of the

plant.

Since mycorrhizal fungi are present in most

soils, their unique fertilizer-absorbing abilities

are normally already being used by most crops.

If mycorrhizal fungi are removed or damaged

in any way, then the amount of fertilizer required by a crop increases enormously. This

is demonstrated by reports that citrus grown

in fumigated soil or in hydroponic solutions

often require massive phosphorus applications

for adequate growth compared to field grown

citrus (55). Citrus in the field can absorb phos-
191

phorus from phosphorus-deficient soils more

efficiently than either corn or tomatoes, and

citrus orchards do not normally require phosphorus fertilization (9), Differences in phosphorus absorption by citrus grown in fumigated

soil and citrus grown in nonfumigated soils can

be reconciled if mycorrhizal fungi, which are

present in nearly all citrus orchards (52), are

the equivalent of 100 to 500 pounds phosphorus

per acre.

When and if the cost of fertilizer becomes exorbitant, we must devise the most efficient fertilizer supply systems possible—to minimize

costs while conserving energy and nonrenewable resources. I submit that mycorrhizal fungi

could be one alternative that might increase

crop yields and yet reduce fertilizer costs and

energy demands.

CURRENT COMMERCIAL USE OF MYCORRHIZAL FUNGI

Although nearly all plants require mycorrhizal fungi for maximum growth, the widespread

occurrence of these fungi in nearly all soils

limits the immediate needs for inoculation with

mycorrhizal fungi. Mycorrhizal fungi are currently commercially usable in only three major agricultural areas: 1) disturbed sites, 2)

fumigated soils, 3) greenhouses.

Disturbed Sites

Mycorrhizal fungi have been conclusively

shown to improve revegetation of coal spoils,

strip mines, waste areas, road sites, and other

disturbed areas (18,19,15,49,81). In these stressed

sites, mycorrhizal fungi are usually lacking and

adding mycorrhizal fungi provides a nutritional advantage to associated plants in addition

to providing possible resistance to low pH,

heavy metal toxicants, and high temperature,

Fumigated or Chemically Treated Sites

Fumigation with biocides or pesticides such

as methyl bromide (56), chloropicrin (72),

dazomet (50), 1,3-D (72), vapam (71), and vorlex

(71) may destroy or inhibit root infection by

mycorrhizal fungi, Application of many soil

fungicides such as arasan (71), banzot (95),

benomyl (96), botran (71), carbofuran (3),

chloramformethane (37), dichlofluanid (37),

ethirimol (37), lanstan (71), mylone (71), PCNB

(96), sodium azide (3), thiabendazole (37),

thiram (96), triademifon (37), tridemorph (37),

and vitavax (96) have also been reported to be

harmful to mycorrhizal development, Flooding, planting non-my corrhizal crops, or removing topsoil, may also reduce the population of

mycorrhizal fungi to a level requiring reinoculation (7,78).

Fumigation with the biocide methyl bromide

to remove soil-borne pests is required by regulation for the production of many nursery

crops. It is also regularly used in many field

agricultural situations. This chemical is extremely toxic to mycorrhizal fungi and most

field fumigations are sufficient to destroy the

native mycorrhizal inoculum (56). Stunting of

crops following fumigation with methyl bromide is common and is due to the destruction

of mycorrhizal fungi. Although a relatively

small amount of land is treated with this chemical, less than 100,000 acres annually in the

United States, stunting following fumigation

with methyl bromide has been reported in the

United States, Africa, Spain, Peru, Venezuela,

and many other countries (52). Crops that are

routinely grown in methyl bromide fumigated

soils include strawberries, tomatoes, tobacco,

nursery crops, tree crop replants, and some

vegetable crops. For many of these crops the

addition of mycorrhizal fungi following fumigation with methyl bromide is not only recommended but is imperative.

It appears that inoculating methyl bromide

fumigated crops is economically possible. The

cost for inoculating nursery-grown citrus with

mycorrhizal fungi is about $288/acre, while the

cost for phosphorus fertilizer alone is $338/

acre. Fumigated tomatoes receive $51 worth
192

of phosphorus per acre while the cost for mycorrhizal inoculation is less than $28/acre. Mycorrhizal fungi can provide additional benefits

to the crop other than just improved phosphorus nutrition.

For nursery plants grown in methyl bromide

fumigated soil, inoculation with mycorrhizal

fungi should be imperative for the following

reasons:

●

●

●

●

●

the plants grow better (prevents stunting

following fumigation);

there is a decreased need for fertilization,

specifically phosphorus, zinc, and copper,

resulting in decreased fertilizer cost and

energy conservation;

there is decreased chance for water stress

and therefore reduced transplant injury;

mycorrhizal plants survive better especially if transplanted to fumigated, poorly fertilized, or disturbed soil;

plants will be inoculated with effective my-

●

corrhizal fungi rather than leaving mycorrhizal infection to chance; and

mycorrhizal plants may be more resistant

or tolerant to some plant diseases.

Greenhouses

Greenhouse culture uses growth media such

as pine bark, vermiculite, perlite, builders sand,

and peat moss and these are devoid of mycorrhizal fungi. In addition, most greenhouse

operators steam, pasteurize, or chemically treat

their mixes to eradicate harmful pathogens.

Nurserymen have compensated for the absence

of beneficial mycorrhizal fungi by applying luxury amounts of fertilizer and water to achieve

desired growth. Inoculation of container

grown plants to reduce irrigation, fertilizer,

and pesticide applications and cost can be done

as demonstrated by Chatfield, et al. (10), Linderman (46), and Crews, et al. (12).

COMMERCIAL PRODUCTION AND INOCULATION WITH

MYCORRHIZAL FUNGI

Many ectomycorrhizal fungi can be readily

cultured on artificial media and inoculum can

be grown under standard laboratory conditions

(49). Experimentally, sterilized vermiculite and

peat moss is frequently saturated with a liquid

nutrient medium (49) and is infested with a desirable ectomycorrhizal fungus. Ectomycorrhizal fungi generally grow quite slowly and may

take several months to colonize the vermiculitepeat moss mixture. This material can be used

on a small scale to inoculate nurseries and

greenhouses with mycorrhizal fungi. Abbott

Laboratories, North Chicago, Illinois, has produced massive amounts of inoculum of the ectomycorrhizal fungus Pisolithus tinctorius (86).

Abbott Laboratories produced the peat mossvermiculite-nutrient solution inoculum under

large-scale commercial conditions using commercial fermenters.

Under the direction of D. H. Marx, the U.S.

Forestry Service has undertaken a massive

testing program using the commercially produced inoculum. The inoculum will be tested

in nearly 100 tree nursery test sites throughout the United States. Results will be available

within 4 years and will indicate the commercial feasibility of producing and using mycorrhizal inoculum in fumigated tree nurseries.

Ectomycorrhizal inoculum can best be applied in the nursery. Once the trees become

infected, the benefits can be transferred to

wherever the trees are grown. In the nursery,

mycorrhizal inoculum can be distributed by

hand and rototilled into the soil before planting seed. Special machinery has already been

built and is being used to incorporate ectomycorrhizal inoculum.

Commercial production of mycorrhizal inoculum for use in sterilized or fumigated soil

is being attempted at several locations in the

United States. Currently, the only way to produce suitable quantities of a mycorrhizal inoculum is on roots of susceptible host plants.
193

The possibility of pathogenic organisms

contaminating mycorrhizal inoculum is an extremely serious problem when growing VA

mycorrhizal inoculum in semi-sterile cultures

in the greenhouse. For this reason, many scientists will consider mass production of VA

mycorrhizal fungi only if it is done axenically

(one organism only).

Realistically, however, not only must these

obligate parasites be grown in vitro, but they

must produce large quantities of spores in

culture which will survive under soil conditions and infect plants in nature. Information

gained from the culture of other formerly

obligate parasites suggests that the possibility

of realizing this goal in the near future is

unlikely. Even if mycorrhizal fungi are cultured

axenically, mycorrhizal inoculum for field use

will probably be produced on the roots of suitable host plants.

With proper safeguards, mycorrhizal inoculum, free of plant pathogens, can be produced

on plants in the greenhouse. Figure 5 illustrates

a proposed scheme for producing mycorrhizal

inoculum [53). VA mycorrhizal fungi can be

isolated by using bits of roots or soil from the

field to inoculate roots of “trap plants” growing in sterilized soil in the greenhouse. Sudangrass (Sorghum vulgare Pers.) is frequently

used, but other plants such as tomato, soybean,

corn, and safflower may be equally suitable.

The soil used throughout is a low nutrient sand

fertilized once per week with one-half the

standard Hoagland’s solution minus phosphorus. After production of VA mycorrhizal spores

in the “pot cultures,” the spores can be
194

removed by wet sieving (29), elutriation (25),

or centrifugation (85). These spores must be

surface disinfested with substances such as

chloroamine T or sodium hypochlorite and

streptomycin to assure that pathogens do not

accompany the spores (68).

These surface disinfested spores are used to

inoculate the roots of plants that were germinated and grown under aseptic conditions

in growth chambers. The containers illustrated

are made from plastic petri plates and filled

with the low nutrient sand. After 1 to 4 weeks

when the mycorrhizal fungi have infected roots

grown under aseptic conditions root pieces can

be removed and stained (73) to observe infection, root pieces are carefully removed and

used to infect suitable host plants grown in

sterilized soil in the greenhouse. Similar root

pieces can be removed, examined, and plated

on agar to observe pathogenic organisms.

If no pathogens are observed, the greenhouse

“pot culture” may be used as a “mother culture” to produce inoculum that will be used in

the field. Inoculum should be produced on selected hosts that have no root diseases in common with the host plant for which the inoculum is intended. For instance, inoculum for

citrus could be produced on sudangrass but

never on citrus. In this way the wide host range

of most VA mycorrhizal fungi can be used. As

another precaution against propagating pathogens along with mycorrhizal inoculum, the

field inoculum should be drenched several

times with pesticides chosen to eliminate pathogens known to infect the host for which the

inoculum is intended. Mycorrhizal inoculum

intended for citrus should be drenched with

a nematicide to control the citrus nematode

and fungicides to control Phytophthora and

Rhizoctonia. Suggested pesticides are Ethazole

and PCNB. PCNB reduces the population of

mycorrhizal spores but the other pesticide can

actually increase spore production (57). Several

other pesticides can be used without harming

mycorrhizal fungi (96).

Horticultural practices also could be used at

this point to maximize spore production. Eliminating fertilization and slowly reducing the

water may be effective in increasing spore production. When spores are mature, plant tops

are removed and roots, soil, and spores can be

ground up and partially dried (7 to 20 percent

moisture content) and stored at 40 C until used.

If concentrated spore suspensions are desired,

spores can be concentrated by wet sieving (38),

elutriation (25), or centrifugation (85) before

storage. VA mycorrhizal inoculum can be

freeze-dried if desired (38). Inoculum produced

in this manner should be consistently infective

and yet pathogen free.

Using the method described above, the estimated costs for producing mycorrhizal inoculum are shown in table 1. These figures are

derived from production costs of a foliage plant

greenhouse and could be reduced considerably

Table 1 .—Estimated Cost of Production of

Vesicular-Arbuscular Mycorrhizal Inoculum

on Sudangrass in 4 Inch Pots

Item Cost/pot

1. Labor:

a. to prepare the soil mix . . . . . . . . . . . . . . . . . . $0.03

b. potting, inoculating, and seeding. . . . . . . . . . 0.05

c. moving pots to growing area . . . . . . . . . . . . . 0.03

d. pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02

e. spraying (insecticides and fungicides) . . . . . 0.03

f. watering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02

g. harvesting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01

h. grinding and packaging . . . . . . . . . . . . . . . . . . 0.03

i. quality control . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02

j. maintenance of mother cultures . . . . . . . . . . 0.05

Labor cost . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Materials:

a. pots 4 ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b. seed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

c. fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

d. shipping containers . . . . . . . . . . . . . . . . . . . . .

e. insecticides and fungicides . . . . . . . . . . . . . .

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. Overhead expenses:

a. heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b. depreciation on greenhouse . . . . . . . . . . . . . .

c. depreciation on boilers . . . . . . . . . . . . . . . . . .

d. maintenance allowance . . . . . . . . . . . . . . . . . .

e. office supplies . . . . . . . . . . . . . . . . . . . . . . . . .

f. management and office work . . . . . . . . . . . . .

g. return on investment . . . . . . . . . . . . . . . . . . . .

h. loss due to undeveloped plants . . . . . . . . . . .

i. taxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

j. laboratory, incubator, etc. . . . . . . . . . . . . . . . .

$0.29

$0.07

0.002

0.02

0.025

0.03

$0.147

$0.08

0.008

0.003

0.006

0.002

0.03

0.01

0.001

0.06

0.04

Total for overhead . . . . . . . . . . . . . . . . . . . . . . $0.24

Total cost ... ... .$0.677

Selling price ... ..$0.90

0.18¢/500 spores
195

since mycorrhizal inoculum quality is of importance and not plant quality, A reasonably

generous estimate of the cost of mycorrhizal

production, including technical labor and

quality control, together with a small margin

of profit, indicates that consumers may pay

about 0.180/500 spores of VA mycorrhizal

fungi. Such a cost could reasonably be borne

by consumers such as greenhouse operators or

nurserymen.

A similar method to that outlined above has

been patented in England and is being perfected for large-scale commercial use (34). In

this method plants are grown in peat blocks

that are standing in a shallow nutrient-flow

culture. After VA mycorrhizal spores are produced in the peat blocks they are ground up,

roots and all, for inoculation. The finished

product is not only excellent mycorrhizal inoculum but is light and easy to ship.

Although many methods have been used to

inoculate plants with VA mycorrhizal fungi in

greenhouse trials, few inoculation methods are

acceptable for large-scale commercial inoculation. Several different methods to inoculate

corn have been studied and layering inoculum

under the seed was superior to seed inoculation or banding the inoculum (38), Hall (30) developed a method for pelleting seed with a mycorrhizal infection and determined that

mycorrhizal fungi could survive up to 28 days

under these conditions. Menge, et al. (53),

found that layering inoculum below the seed

and banding inoculum were superior to seed

inoculations. Crush and Pattison (14) experimented with several means of inoculating

seeds with VA mycorrhizal fungi, but again

found that sowing seed above pelleted mychorrhizal inoculum was the most effective method

for obtaining mycorrhizal infection. Hattingh

and Gerdemann (31) reported growth responses of citrus in a fumigated nursery after

inoculating citrus seed with mycorrhizal inoculum. Gaunt (26) inoculated onion and

tomato seeds with a VA mycorrhizal fungus

and reported that seed inoculated plants grew

as well as plants that were inoculated by mixing VA mycorrhizal inoculum into the soil.

Commercial applications of mycorrhizal inoculum using fertilizer banding machinery

were successfully carried out in citrus

nurseries in California (23).

Commercial VA mycorrhizal inoculum is

produced using the method described above in

two citrus nurseries—Brokaw Nursery, Saticoy

California and the Thermal Ranch, Thermal,

California. Experimental VA mycorrhizal inoculum is being produced and distributed on

a large scale by Abbott Laboratories, North Chicago, Illinois. Other major corporations that

are supporting or carrying out research on VA

mycorrhizal fungi include Dow Chemical Co.,

Rohm & Haas Co., Dupont, Monsanto Co., and

Ceiba-Geigy Chemical Co.

Plants growing in all soils do not respond favorably to VA mycorrhizal inoculum. If soil nutrition is optimum, mycorrhizal fungi will not

enhance growth of plants. A method for detecting which soils require mycorrhizae for maximum production of citrus was devised by

Menge, et al. (58). In soils with less than 34 ppm

available P (Olson analysis), 12 ppm available

Zn, 27 ppm available Mn, or 3 percent organic

matter, citrus trees will probably require mycorrhizal fungi for maximum growth. Mycorrhizal inoculations are recommended only in

soils with these characteristics, It is estimated

that this includes approximately 85 percent of

the southern California citrus soils. Similar

studies could be done with other crops to determine which soils require mycorrhizal infestation.

POTENTIAL USES FOR MYCORRHIZAL FUNGI

Because mycorrhizal fungi occur on most Large-scale field inoculations with mycorrhizal

agronomic crop plants and improve the growth fungi are rare because of limited inoculum, and

of these plants, the potential use of these fungi natural field soils usually contain adequate

as commercial “biotic fertilizers” is enormous. populations of indigenous mycorrhizal fungi.
196

Under these conditions, any growth benefit

due to mycorrhizal inoculation would depend

primarily on the superiority and/or placement

of the mycorrhizal inoculum. Beneficial responses under these conditions would be predicted to be far less than the responses obtained

in fumigated or partially sterilized soil. However, greenhouse and field experiments in

which plants were inoculated with mycorrhizal

fungi in nonfumigated soils have demonstrated

that growth responses due to mycorrhizal fungi

can occur under these circumstances.

In greenhouse experiments, using untreated

soil, Mosse and her colleagues (62,63,65,67,70)

demonstrated that preinoculation with mycorrhizal fungi could provide the following growth

increases:

Crop Growth increase

Centrosema spp. . . . . 34 percent

corn . . . . . . . . . . . . . . . 306 percent

Melinis spp. . . . . . . . . 41-60 percent

onions . . . . . . . . . . . . . 48-3155 percent

strawberries . . . . . . . . 250 percent

Stylosanthes spp. . . . 85-88 percent

sweetgum . . . . . . . . . . 45 percent

Viola spp. . . . . . . . . . . 527 percent

Other studies have noted similar growth increases in untreated

soil:

corn . . . . . . . . . . . . . . . 14 percent (Gerdemann, 1964)

corn . . . . . . . . . . . . . . . . 0-53 percent (Jackson, et al., 1972)

mahogany . . . . . . . . . . 151 percent (Redhead, 1975)

sudangrass . . . . . . . . . . 0-18 percent (Jackson, et a]., 1972)

white clover . . . . . . . . 80-100 percent (Powell, 1977)

In a large-scale field experiment conducted

in nonsterile, virgin, infertile fields, wheat preinoculated with a mycorrhizal fungus produced 220 percent more grain than non-mycorrhizal wheat (41). In a similar experiment (40),

corn inoculated with a mycorrhizal fungus was

122 percent larger than non-mycorrhizal corn.

Hayman (33) reported white clover growth increases in the field due to inoculation with a

mycorrhizal fungus. Black and Tinker, in an

extremely well-documented field experiment,

found that fallow field inoculation with a mycorrhizal fungus increased potato yield 20

percent.

Not all mycorrhizal inoculations in nonsterile soil result in increased growth. Hayman (33)

indicated that mycorrhizal fungi did not stimulate growth of white clover at several locations. Powell (75) obtained significant growth

increases of white clover after inoculation with

mycorrhizal fungi in only three of nine sites.

Jackson, et al. (38), indicated that with certain

mycorrhizal inoculation methods, growth of

corn, sudangrass, and soybeans was not stimulated in nonsterile soil. Mosse (65) obtained

significant growth responses of Stylosanthes

spp. due to mycorrhizae in 6 of 11 nonsterile

soils. Ross and Harper (85) reported no growth

stimulation of soybeans in nonsterile soil.

Mosse (65) indicated that the inoculum potential of indigenous mycorrhizal fungi is the

major determinant governing growth responses

of plants to mycorrhizal fungi in nontreated

soil. Powell (75) indicated that many indigenous mycorrhizal fungi are “inefficient” symbionts, and that inoculation by more efficient

mycorrhizal fungi will result in growth increases even in nonsterile soil that contain high

populations of “inefficient” mycorrhizal fungi.

placement of mycorrhizal inoculum is equally

important in affecting a plant growth response

(38). Certainly, plants infected early in the

growing season by mycorrhizal fungi are better than plants that do not become infected until later (82).

Huge expanses of tropical soils (e.g., the Brazilian Cerrado) are either deficient in phosphorus or immobilize phosphorus fertilizers.

These marginal agricultural lands could be productive if mycorrhizal fungi, with the ability

to efficiently use extremely small quantities of

fertilizer, were developed and added to the soil.

Cheap but readily available rock phosphate

could be added as the phosphorus source. This

phosphorus source is a poor fertilizer but releases small quantities of phosphorus for long

periods of time. Some mycorrhizal fungi use

rock phosphate much better than others and

can tremendously improve growth of plants

growing in poor soils fertilized with this material (59,66).

Mycorrhizal fungi have been proposed as unstable soil or sand dune stabilizers (96). Finally

ectomycorrhizal fungi have been shown to improve rooting of a wide variety of non-host

plants and the possibility of using them as a

commercial root stimulant has been proposed

(45).
197

CONSTRAINTS ON THE COMMERCIAL USE OF

MYCORRHIZAL FUNGI

The current major obstacles to the commercial use of mycorrhizal fungi are:

c the lack of large-scale field experiments

under normal agricultural conditions,

Q the lack of cost-benefit analysis to determine the economics of mycorrhizal applications, and

● the trend toward excessive fertilization to

substitute for the lack of mycorrhizal

fungi.

Perhaps the most important deterrent of commercial use of mycorrhizal fungi is the lack of

large-scale field tests in a variety of agricultural

soils and locations. The program initiated by

D. H. Marx and the U.S. Forest Service will

correct this deficiency for ectomycorrhizal fungi and within 4 years it will be known if these

mycorrhizal fungi will indeed be economically

feasible to use on a wide scale in the production of forest trees.

This type of program remains to be established

for VA mycorrhizal fungi. Without such data

it is difficult to establish a potential market for

mycorrhizal inoculum. Without a market there

is little incentive for industry to initiate the production of commercial inoculum. Without commercial inoculum it is difficult to carry out

large-scale field tests. With the recent establishment of several commercial sources of mycorrhizal inoculum perhaps this cycle will be broken and more field tests will result.

Once large-scale field tests are seen to be successful, light-weight commercial mycorrhizal

formulations will develop and new application

methods will be devised, Most importantly,

from large-scale field tests, cost benefit analysis can be accurately done to determine the

economic benefit derived from the use of mycorrhizal fungi. In the end, this will be the determining factor in the commercial application

of mycorrhizal fungi. Biological scientists are

rarely able to critically assess the economic factors involved in the application of a new technique and I recommend that agricultural economists should be asked to participate in the

cost-benefit assessment of VA mycorrhizal inoculation.

Heavy phosphorus fertilization severely inhibits mycorrhizal infections (17,68). More

recently, it is becoming evident that heavy nitrogen and zinc applications are also inhibitory

to mycorrhizal fungi (32,51). Daily applications

of 100 ppm nitrogen under greenhouse conditions have been shown to completely eliminate

mycorrhizal infections (J.A. Menge, unpublished data). Many commercial greenhouses

add over 200 ppm nitrogen daily to their plants.

In greenhouse and fumigated nursery conditions, growers are using excessive fertilization

to substitute for the lack of mycorrhizal fungi.

Under these conditions, not only do mycorrhizal fungi not benefit their host plants, but it is

difficult to successfully establish mycorrhizal

infections so that the plants will be mycorrhizal

once they leave the supraoptimal fertility

regime. As long as fertilizer is relatively available and not excessively expensive, it will take

a major educational program to convince many

growers to change their standard operating

procedures and use mycorrhizal fungi that will

not only be cheaper but will conserve fertilizer

and energy.

In my opinion, granting agencies such as the

National Science Foundation, Rockefeller

Foundation, USDA competitive grants, and the

Israeli-U.S. granting agency BARD have effectively provided adequate funding for basic mycorrhizal research. The number of scientific

papers on mycorrhizal fungi has quadrupled

since 1960, which is evidence that there is great

interest and money available for basic mycorrhizal research. However, there are few agencies that will fund the final applied steps in a

biological commercialization project. Research

money for large-scale “applied” or “demonstration” experiments is unavailable. Funding for

small-scale pilot projects is also not available.

It remains for private industry to pick up the

projects from this point, but they have been reluctant to do so. The transition is not going

smoothly and seems to be proceeding slowly

if at all,
198

It is very difficult for a scientist to speculate

on the effects of a new procedure on the social

and economic structure of an agricultural society. Frequently good ideas do not receive the

acclaim they deserve because of prejudices, ignorance, religious preferences, social mores,

and other reasons not fully understood by scientists. In my opinion, the effects of mycorrhizal technology would most alter the socioeconomic structure in areas of intensive agriculture. These situations would be more prevalent in agriculture in developed nations.

Mycorrhizal fungi are most useful in reclaiming sites disturbed by heavily mechanized industries or soil fumigation. Mycorrhizal fungi

can reduce energy and fertilizer and increase

the efficiency of crops grown intensively.

Therefore, mycorrhizal fungi can be viewed as

conservation measures or as substitutes for

high energy uses in developed nations.

In less developed nations, growers would

have to be educated to the methods of producing, handling, and inoculating living microorganisms. This may be difficult. In countries

FUNGI ON AGRICULTURE

with a less well-developed agricultural system,

mycorrhizal fungi have not been altered and

are probably functioning effectively and need

not be applied under such conditions. Fertilizer

in most underdeveloped countries is probably

applied sparingly as manure and therefore mycorrhizal fungi will not result in a great savings either of fertilizer or energy.

If superior strains of mycorrhizal fungi are

developed, marginal agricultural land could be

made productive. Huge amounts of marginal

agricultural land exists in Africa and South

America and the proper use of this land may

well decide the future of some countries. Increased use of agricultural land will provide

for a greater economic base, larger agricultural

productivity, and a better way of life for large

populations in underdeveloped countries. Educating agriculturists to the importance of mycorrhizal fungi may allow developing countries

to avoid the excessive use of energy, fumigants,

and fertilizers associated with intensive agriculture.

Mycorrhizal fungi may be one alternative

that can immediately improve revegetation of

disturbed sites, increase crop growth in fumigated soils and greenhouses, and yet reduce

fertilizer costs and energy demands. If superior

strains of mycorrhizal fungi were developed,

they could potentially improve growth of nearly all agronomic crops in a wide variety of soils

throughout the world. Both ectomycorrhizal

fungi and vesicular-arbuscular mycorrhizal

fungi are in commercial production on a small

scale. The greatest obstacles to the commercialization of mycorrhizal fungi appears to be: 1)

the lack of large-scale field tests under typical

agricultural conditions in a variety of locations;

2) adequate cost-benefit analysis to determine

the economics of the utilization of mycorrhizal

fungi; and 3) a reluctance on the part of growers to switch from an energy dependent, heavy

fertilizer system to a new, but cheaper, energy

conservative system using mycorrhizal fungi.

Recommendations that could substantially

increase the commercial use of’ mycorrhizal

fungi (in relative order of importance) are as

follows:

1. Improved availability of grant funds for

large-scale field applications of mycorrhizal fungi in a wide variety of soils throughout the world. It would be useful to establish several pilot projects in various less

developed countries. These pilot projects

could produce and distribute mycorrhizal

inoculum on a variety of crops growing

under different soil conditions. Cost-benefit analysis on such projects could adequately assess the economics of inoculation with mycorrhizal fungi.
199

2.

3.

4.

5.

6.

7.

Funds should be made available to create

a worldwide bank of beneficial mycorrhizal fungi. The establishment of such a

facility is being investigated by the mycorrhizal community and the National Science Foundation has agreed to entertain

a proposal for such a facility. The University of Florida has agreed to supply the facilities as well as substantial operating

costs for such an establishment. A second

idea would be to add the responsibility for

maintaining mycorrhizal cultures to the

already established government facility

called the American Type Culture Collection which maintains many important

fungal cultures.

It would be desirable to establish a USDAsupported vesicular-arbuscular mycorrhizal research center that would be responsible for maintaining and coordinating

U.S. research on mycorrhizal fungi. This

facility would complement the Mycorrhizal Institute in Athens, Georgia, which was

created by the Forest Service to coordinate

mycorrhizal research on forest trees.

A world survey should be conducted to

collect and test as many different vesicuIar-arbuscular mycorrhizal species as possible. The discovery of a superior mycorrhizal strain with a wide host range could

tremendously increase agricultural productivity throughout the world.

Research is necessary to elucidate the exact role of mycorrhizal fungi play in improving plant growth under stress conditions such as drought, salt, toxic soil

materials, or in marginal agricultural

lands.

Research is necessary to elucidate the genetics of mycorrhizal fungi. Virtually

nothing is known on this subject. The

ability to breed these organisms could result in tremendously increased agricultural productivity.

Efforts should be intensified to grow vesicular-arbuscular mycorrhizal fungi in the

laboratory using artificial media. A

breakthrough in this area could improve

the feasibility of attaining all of the above

recommendations, However, since scientists have been trying to artificially culture

VA mycorrhizal fungi since 1900, this objective may be difficult to achieve and incentives to work on such a problem are difficult to justify.

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38-846 0 - 85 - 8
Chapter XI

A Low Fertilizer Use Approach

to Increasing Tropical Food

Production

William C. Liebhardt

Plant Science Department

University of DeIaware

Newark, Delaware
Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .”””.”.”” ““”...”.””””’””... 207

The Tropics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . ..,.””.’” “’””.,... 207

Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ““””””..”.””+ 208

Farming Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .“.”.””” 208

Tropical Food Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....”.”” 209

Soil Fertility Concepts—A General Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Soil Acidity and Liming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Finding the Correct Lime Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..#.........”...””’o” ““.”””. 212

Nitrogen Supply Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

Biological Nitrogen Fixation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Productivity of Improved Grass-Legume Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Nitrogen Release From Organic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Management of Phosphorus Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . + . . . . . . . . . . 215

Sources of Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

Sulfur Deficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ... ... .....$. ... ..””..O 217

Potassium Deficiency. ....< .. .. .+ ... . ~ .......,. ...........~....’” . . . . . . . . . 218

Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .“”. 218

Plants That Tolerate Adverse Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “.””’”.”.. 221
Chapter Xl

A Low Fertilizer Use Approach to

Increasing Tropical Food Production

ABSTRACT

Low fertilizer use in the Tropics appears to

be a desirable goal and it could involve several

strategies aimed at increased crop production

with minimal use of inputs.

According to the general response curve that

shows the effects of added nutrients, the use

of small amounts of an input may result in substantially increased production. The philosophy employed here is to use less than maximum inputs to achieve the highest output:

input ratio or to make maximum use of inputs

rather than to maximize yields. That often requires a much greater use of scarce inputs such

as fertilizer, capital, etc.

Because they have inherent high fertility, limited inputs are needed on the “high base soils”

(18 percent of tropical soils) when there is sufficient water, Small amounts of nitrogen, phosphorus, and/or micronutrients are sufficient.

High yielding varieties should be used on these

soils to take advantage of the naturally high soil

fertility.

On the “low base soils” (51 percent of tropical soils), which have high soil acidity and aluminum and the associated phosphorus deficiency, the production package should be

considerably different. Lime may be necessary

to reduce the availability of toxic aluminum.

This will also increase the availability of phosphorus. However, additional phosphorus and/

or sulfur will probably be necessary to increase

yields.

The use of crops that will tolerate adverse

soil conditions should also be employed on

these soils. This reverses the philosophy of

changing the soil to fit the crop (an expensive

procedure on these soils) to one that takes the

soil as it is (or changes it minimally) and uses

crops that grow well under existing conditions.

Examples of such crops are upland rice, cassava, sweet potatoes, cowpeas, and some grass

and legume pasture crops.

With both high and low base soils, nitrogen

is probably the most limiting element. Low

yields in many tropical areas reflect a low level

of nitrogen availability. Low yields and the lack

of nitrogen result in low levels of protein for

local human consumption, causing malnutrition. An excellent source of protein and nitrogen are leguminous crops. These crops have

the potential to biologically fix nitrogen from

the atmosphere when growing in association

with the correct bacteria. When these crops are

used, the nitrogen input into the cropping system can be increased several fold. This technology is inexpensive, easy to use, and available. Most important, it can substantially

increase the yield of crop plants as well as meat

and milk production to the benefit of the smaII

farmer and the landless poor.

THE TROPICS

The Tropics are that area of the world lo- lion people in 1975) live in this area. Most of

cated between 23.50 north and south of the the world’s developing countries lie in the

Equator. Thirty-eight percent of the Earth’s Tropics, although some areas in the Tropics are

land surface (about 5 billion hectares) and 45 not considered developing and many developpercent of the world’s population (about 1.8 bil- ing countries are outside the zone.

207
208

Because of the proximity to the Equator, the

Tropics experience little change in temperature

during the year. Variation of daylength is also

relatively small compared to temperate zones.

Rainfall is the variable which differentiates

tropical areas. About one-quarter of the Tropics, mostly those near the Equator, have a rainy

climate. Seasonal climates—those with a distinct wet and dry period—cover about one-half

of the Tropics. Dry climates, usually having a

short wet season, cover 16 percent of the Tropics. Tropical deserts comprise the remaining

area, about 11 percent.

In 1960, the world’s population reached 3 billion; by 20006 billion will inhabit the Earth.

Much of this population increase is taking

place in the Tropics, primarily in Asia. This

About 10 percent of the tropics are cultivated

for food production; pastures and meadows account for an additional 20 percent. The President’s Science Advisory Committee estimated

that only 500 million hectares were cropped

in 1967 even though the potential for cultivation was 117 billion hectares. Grazing occupied

1 billion hectares, but the potential was 1.6 billion hectares. These figures indicate that there

Common farming systems in the Tropics are

(56):

1. shifting cultivation, where the land is

cropped and then abandoned when yields

fall, covers 45 percent of the Tropics;

2. settled subsistence farming is practiced on

17 percent of the Tropics;

3. nomadic herding covers 14 percent of the

area;

4. livestock ranching uses 11 percent; and

5. plantation systems, which cover 4 percent

of the tropical area.

population explosion will place a much greater

strain on the resources of the Tropics. Malnutrition, particularly protein deficiency, is widespread throughout the area. Protein deficiency,

a lack of high protein food, is related to a lack

of nitrogen in the soil-plant system.

Protein synthesis in the plant only occurs

when there is sufficient nitrogen in the soils,

therefore, a lack of soil nitrogen decreases the

rate of protein production in plants and hence,

in the food supply. Inexpensive and efficient

means to increase nitrogen in the tropical system are known. Use of these simple technologies could increase protein production and

eliminate much of the misery and suffering in

the Tropics caused by poor nutrition.

USE

is much potential to expand in agricultural production in the Tropics.

The use of land will vary depending on soil

factors, climate, economic, social, and political factors. In general, the farming systems are

vastly different than those practiced in the

United States.

SYSTEMS

If food production is to be increased and the

majority of people benefit, programs must be

aimed at the small farm rural population since

small farms are the most numerous. In tropical Asia, 75 percent of all farms are smaller

than 2 hectares (5 acres) (36). Sixty-nine percent of Central American farms are smaller

than 5 hectares (12 acres) (14). The average

farm size of 20 tropical African countries reporting such data in the 1973 FAO Production

Yearbook was 5.4 hectares. Studies by CATIE

(14) and Pinchinat, et al. (53), showed that about

70 percent of the food consumed in Colombia
209

and Central America is produced on small

farms. Therefore, any strategy dealing with

Common tropical crops are sugarcane, pineapple, bananas, coffee, and tea. These crops,

however, contribute little to the nutrition of

people in the Tropics because they are exported, largely to the temperate zone. The major food crops consumed by tropical people are

rice, cassava (root crop), corn, sweet potatoes,

yams, wheat, sorghum, peanuts, potatoes, and

dry beans (in order of decreasing importance).

The total area cultivated for these 12 crops is

only 300 million hectares compared to 1 billion hectares of pasture and meadow.

food production in the Tropics must deal with

the small farmer.

FOOD CROPS

and likely to remain that way in the near future. But on the positive side, the soils and climate provide a resource base that can expand

production and help meet these food needs.

The introduction of simple technologies could

greatly increase food production, helping to

stabilize these countries in many ways.

Much of this increase must come from a better use and understanding of the tropical soils’

capacity to produce. Therefore, the bottom line

question becomes a question of soil fertility.

The Tropics can be characterized as a region

where population pressures are often highest

SOIL FERTILITY CONCEPTS-A GENERAL STATEMENT

A fertile soil has the capacity to produce a

high yielding and high quality crop. More specifically, it is a soil that does not limit production because of physical, chemical, or biological constraints.

Numerous essential elements are required

for crop production, including carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium,

calcium, magnesium, sulfur, iron, copper, boron, zinc, manganese, and molybdenum. The

first three are obtained from water and the carbon dioxide in the atmosphere. The rest must

be taken up from the soil by the plant’s root

system. Another important element is aluminum. Although not considered essential to

growth, if excessive, it is severely toxic to

plants and can reduce plant growth and crop

yield.

Soil tests attempt to predict crop yield for a

number of elements. These tests determine as

nearly as possible the soil’s capacity to supply

the elements necessary for plant growth.

where the soil’s supply is considered insufficient for a desired yield, additional amendments are supplied to the soil increasing its

“fertility,” or ability to produce.

A typical soil test crop response curve

follows:

The response curve has three general areas.

Area “a” is the part of the curve where small

inputs of nutrients result in increasingly greatRelative soil test value
210

er production, i.e., the output: input ratio is

favorable. Area “b” is a relative plateau where

increasing fertilizer inputs do not result in increasing yields and the output: input ratio is

poor since yield can be maximized at a lessor

input rate. Area “c” represents the portion of

the curve where additional nutrients actually

reduce yield because of excessive or toxic concentrations. Obviously this is a situation to be

avoided. This is the situation with aluminum

in many unlimed soils of the Tropics.

A few simple equations help to explain the

relationship between the soil and plant nutrients. The general relationship between elements in the soil and plants maybe seen in the

following, where E represents an element used

in plant growth.

Soil solid phase(E) Soil solution phase(E)

Plant root(E) Plant top(E)

As the above equation indicates, an element is

taken in by plant roots and moved to the plant

top as a soluble element dissolved in the soil

solution. Elements are generally considered to

be available when they are in the solution phase

of the soil. In many instances an element is unavailable to the plant because it is not in a form

the plant can use, that is, not in solution. Another equation helps to explain the soil fertility-plant nutrition relationship. Again, E represents an element necessary for plant growth.

This simple equation shows the equilibrium in

the soil that determines if the nutrient can be

used by a plant. This equilibrium is controlled

by the soil environment: soil pH, micro-organisms, oxygen, water, temperature.

Soil pH is a term used to delineate the relative acidity or alkalinity of soils. It is important because soil pH affects the availability of

most nutrients. The soil pH scale follows:

123456 7 8 9 10 11 12 13 14

More acid Neutral More alkaline

or basic

Early in history, man learned to cultivate high

base soils (soils high in calcium, magnesium,

and potassium and low in aluminum) because

they are naturally more productive. The majority of cultivated soils of the Tropics are not

acid (56), although the majority of soils of the

humid Tropics are acid. Soils of tropical America are more acid than those of tropical Africa

and Asia.

Liming of acid soils has been a longstanding

practice. For a long time, the practice involved

adding sufficient lime to raise the soil pH to

7 (neutrality). However, in the early 1950s soil

chemists showed that exchangeable aluminum,

toxic to plants, was the predominate element

in acid mineral soils as contrasted to organic

soils (18). Exchangeable elements such as calcium, magnesium, and potassium are positively charged and are held in the soil by negatively

charged sites. Strongly acid soils (pH less than

5.0) favor aluminum availability to plants,

whereas above pH 5.5, calcium, magnesium

and potassium prevail.

High soil solution aluminum, the available

form for plants, causes reduced plant growth

because aluminum is toxic to plants. Evans and

Kamprath (25) found that an exchangeable aluminum saturation of 60 percent was required

before a large amount of aluminum was present in the soil solution. Work in Guyana

showed that an aluminum saturation of less

than 60 percent resulted in less than 1 ppm—

1 part per million—in the soil solution (13). Increasing fertilizer results in an increase of aluminum in the soil solution (34). Therefore, use

of high amounts of fertilizer could increase aluminum toxicity if the soil is sufficiently acid.

Available aluminum in the soil solution decreases with increasing organic matter since

aluminum forms very strong complexes, making it unavailable.
217

Research by Kamprath (42) showed that elim- 10W. Growth of sugarcane was severely deination of all the exchangeable aluminum was pressed on a soil with an exchangeable aluminot necessary to obtain maximum yield in field num saturation of 70 percent. Addition of lime

and greenhouse studies. Maximum yields of to reduce the aluminum saturation to 30 percorn, soybeans, and cotton were achieved with cent resulted in a four-fold increase in sugaraluminum saturation values of less than 45, 20 cane growth (l).

and 10 percent respectively where soil pH was

FINDING THE CORRECT LIME LEVEL

The work cited above, plus other work, has

shown that lime should be added to reduce the

toxic levels of aluminum. This results in a

much lower soil pH and the use of much less

lime than the traditional approach of liming to

neutrality. Liming beyond this point has resulted in reduced yields on soils of the Tropics because of deficiencies of manganese, zinc,

and/or iron. Like aluminum, manganese becomes available as the soil becomes more acid

(7). Some soils are low in aluminum but high

in manganese. In either case, liming will reduce the availability of manganese. However,

since manganese is an essential element, liming must not be so high as to make the element

unavailable and reduce the soils productivity.

A wise liming philosophy, therefore, should

be to add sufficient lime to decrease the availability of aluminum without limiting manganese to the point of deficiency. The factors to

be considered are: 1) the amount of lime needed

to decrease the percent of aluminum saturation to a level where the particular crop and

variety will grow well, 2) the quality of lime,

and 3) the placement method (56). Kamprath

(42) suggests that lime recommendations be

based on the amount of exchangeable aluminum and that lime rates be calculated by multiplying the milliequivalents (meq) of aluminum

by 1.5, to find the meq of calcium needed as

lime. Lime rates calculated by this method neutralize 85 to 90 percent of the exchangeable aluminum in soils with 2 to 7 percent organic matter, which includes the majority of soils.

This method has been successfully used in

Brazil since 1965 and is employed in most

American countries. The application of this

formula has reduced rates of liming substantially, particularly in acid, highly leached soils

low in cation exchange capacity (this term refers to the amount of negatively charged sites

in the soil). In most cases where 1 to 3 meq of

exchangeable aluminum is present, lime applications are now on the order of 1.6 to 5 tons

per hectare. In the past, rates of 10 to 30 tons

per hectare were frequently used with mixed

results.

Different crops tolerate different levels of aluminum. Crops such as cotton, sorghum, and

alfalfa are susceptible to levels of 10 to 20 percent aluminum saturation, therefore, liming

should be aimed at zero aluminum for these

crops. Corn is sensitive to 40 to 60 percent aluminum saturation, therefore, 20 percent aluminum saturation could be more economical

for corn. Other crops such as rice and cowpeas

are more tolerant than corn. Coffee, pineapple,

and some pasture species seldom respond to

lime, even in soils with high aluminum saturation.

Sources of lime are difficult to find in the

Tropics. If possible, lime should contain both

calcium and magnesium. The coarseness of the

lime also affects its usefulness. Coarse lime,

that which does not pass through a 20 mesh

sieve, will have very little reactivity; lime that

passes through a 60 mesh sieve will react very

slowly. Fine lime, which passes a 100 mesh

sieve, will react quickly. Generally, a good

grade of fineness is more than 60 mesh; a better grade is 100 mesh. Lime is commonly mixed

in the top 6 to 8 inches of soil. In Puerto Rico,
212

Abruna, et al. (z), observed no differences in cases, plants suffer from water stress during

pasture yields between surface-applied and short-term droughts even though the subsoil is

soil-incorporated lime. still moist. Studies show that deep placement

When very acid leached soils are limed to pH of lime resulted in deeper root development,

diminished water stress during drought, and 5.5, most of the root development occurs in the

topsoil. The highly toxic aluminum in the sub- increased corn yield of 20 to 25 percent (56).

soil prevents deeper root development. In such

NITROGEN

Nitrogen, too, is very crucial to crop production and the availability of protein to tropical

people. Acid soils contribute to that problem

largely because soil acidity reduces nitrogen

fixation by leguminous plants. In nitrogen fixation, the nitrogen of the atmosphere is made

available to plants. Next to water, nitrogen is

the most limiting factor in crop production in

the Tropics. It is necessary for protein synthesis and production. Plant-available nitrogen is

derived from organic matter, leguminous nitrogen fixation, fertilizers, and animal manure.

The main source of nitrogen in the Tropics is

the decomposition of organic matter. Therefore, practices that maintain organic matter in

the soil are essential. Organic matter not only

provides nitrogen, but it improves the soil’s

physical condition and water-holding capacity, increasing water to plants and decreasing

the soil temperature.

NITROGEN SUPPLY PROCESS

Nature has provided the nitrogen for crop

production since the beginning of time through

natural processes. However, seldom has it provided an abundance of nitrogen for long and

sustained periods of crop production on the

same piece of land. Moreover, natural processes at their best have seldom provided

enough plant-available nitrogen to achieve the

level of food and fiber production needed to

meet the demands of present day crop production. Natural nitrogen-supplying processes include: 1) mineralization of nitrogen from soil

organic matter and from crop residues; 2) the

reverse process of immobilization in the decomposition of plant and animal debris and soil

organic matter; 3) fixation of nitrogen from the

atmosphere, largely through biological processes; 4) addition of nitrogen through rain and

other forms of precipitation (5).

The nitrogen in soil organic matter is important for crop production, However, soil nitrogen is not inexhaustible; it declines in quantity in the soil as it is used by crops grown,

harvested, and consumed. Nitrogen in soil is

largely organic, replenished by periodic additions of fresh plant or animal residues.

Under normal conditions, nitrogen is added

to the organic supply in soil each year through

crop residues (immobilization), but it is unavailable to plants. Also through biological decomposition, organic nitrogen in the soil is continuously converted to the inorganic form (mineralization), which is available to plants. Under

any sustained system of crop and soil management, these two processes tend to approach

each other in magnitude so that mineralization

balances immobilization (9). When this balance

is attained, the system is considered to be in

equilibrium.

The implications and consequences of an

equilibrium in the soil’s organic nitrogen need

to be emphasized. At equilibrium, the amount

added to the supply of organic nitrogen is essentially balanced by a like amount of decomposition. The total quantity of soil nitrogen re-
213

mains unchanged and the net amount that can

be and is supplied to a crop is zero (5). During

periods of virgin or noncultivated conditions,

such as a forest, certain soils tend to build up

organic matter, accumulating as much as

10,000 kg/ha of nitrogen under virgin conditions. During the first years of cultivation, these

same soils may supply as much as 400 kg/ha

of available nitrogen per year to crops (59). As

cultivation continues and the organic nitrogen

declines, the quantity of nitrogen becoming

available each year also declines. After long

periods of cultivation, the soil’s organic matter becomes exhausted unless legumes are grown

or the soil fertilized with nitrogen. A minimal

amount of nitrogen is supplied by rainwater

and nonsymbiotic nitrogen fixation.

Many of the major land areas of the Tropics

have now been cropped for extended periods

and the organic matter stored under virgin conditions has been dissipated. With little or no

use of nitrogen fertilizer, tropical crop yields

reflect the paucity of the natural nitrogen supply from rainwater and nonsymbiotic nitrogen

fixation.

Yields of corn of 600 to 1200 kg/ha and of

wheat of 400 to 800 kg/ha require a nitrogen

supply only a little larger than could be expected from rain and from nonsymbiotic fixation. Yields this poor remove no more than 15

kg/ha of nitrogen from the land in the harvested

grain products. Such minimal yields can be

sustained for a long period of time without fertilizer or legumes, but do little to sustain the

protein needs of animals or humans.

However, with inclusion of legumes in the

rotation either as a primary food crop or as a

green manure, the nitrogen supply in the soilplant system can be increased substantially.

This will result in increased crop and protein

production, helping to meet the primary malnutrition problem of the Tropics.

BIOLOGICAL NITROGEN FIXATION

Despite the great use of chemical fertilizer

today, biological nitrogen fixation processes

have been responsible for providing most of the

nitrogen currently used by and tied up in plants

and animals and in the decomposed residues

found in soil. It supplies the major part of the

nitrogen for crop production in world agriculture.

According to reviews by Henzell and Norris

(37) and Jones (4)), Rhizobium bacteria fixation

accounts for 100 to 300 kg of nitrogen per hectare and year. Whitney (67), however, reports

an annual range of 47 to 905 kg of nitrogen per

hectare for pure stands of an improved variety of Leucaena leucocephala.

Obviously, the potential to increase the nitrogen in a cropping system several fold (15

kg/ha v. several hundred kg) using legumes in

crops or pastures is possible. Differences

among adapted species within a specific environment seem to be closely related to dry matter production (total growth) (40). This suggests

that there is little difference in the capacity of

legumes to fix nitrogen as long as they are

adapted to the environment. Factors affecting

dry matter production, such as moisture or nutrient stress, solar radiation, diseases, and other

factors will determine nitrogen fixation.

pastures and meadows make up the greatest

portion of the land that is managed for food

consumption, therefore, potential increases in

food are large if this segment of tropical production could be increased. Another important

factor to consider is that production from pastures and meadows results in increased meat

and milk, both high in quality proteins.

Some individuals consider cattle to be a very

inefficient source of protein for humans in the

food chain. This is true when animals and humans compete for grain. It is not true when cattle convert forage from pasture and meadow

lands into meat and milk. The determining factor will be how much and what kind of land

is available for cultivation.
214

Beef production will normally increase by a

factor of 2 to 4 due to establishment of grasslegume mixtures (40). Few experiments provide

long-term data. Sanchez (56) cites a study of

a legume, Stylosanthes humilis introduced into

a Queensland pasture and followed beef production for 7 years. The following table summarizes the results:

Beef Production Systems in the Tropics

Treatment Beef kg/ha

Grass alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Grass & fertilization* . . . . . . . . . . . . . . . . . . . . . . . 62

Grass & legume . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Grass & legume & fertilization* . . . . . . . . . . . . . . 148

● Annual application 10 kg P/ha as0O-20-0 and 40 kg K/ha plus Mo.

It is interesting to note that the grass-legume

treatment produced more beef than did the fertilizer treatment. The grass-legume mixture

plus fertilizer more than doubled the beef produced by grass alone plus fertilizer, demonstrating the effect of adding nitrogen to the system via the legume.

Another plant, a fern, Azolla, grows in association with rice, the major crop of Asia. Azolla

does not fix nitrogen itself, however, it grows

in symbiotic association with blue-green algae

Anabaena azollae (16). About 10 percent of

China’s rice (3.2 million acres) are grown with

Azolla. He states that yields of rice of 6 tons

per acre have been reported along with 60 tons

of Azolla. Rice with conventional fertilizers

yields about 4 tons per acre. Preliminary experiments indicate that Azolla will produce so

to 180 pounds of nitrogen per acre, making it

highly attractive as a natural nitrogen source.

Another nitrogen fixing system has been reported by Dobereiner and her associates in Brazil (20,22). Their work has focused on nitrogen

fixation by nonleguminous plants. This work

has a great potential if efficient strains of bacteria can be found. At present, this rate of

asymbiotic fixation contributes only about 10

kg of nitrogen per hectare per year.

Recent evidence suggests that symbiotic nitrogen fixation takes place in some tropical

grasses (22). The nitrogen fixation takes place

in the rhizosphere (soil close to root), however,

since this nitrogen is taken up directly by

plants, it is considered symbiosis. Laboratory

experiments suggest that the magnitude of this

mechanism may be on the order of 1 kg of nitrogen per hectare per day. This system needs

to be taken out into the field to determine nitrogen fixation under more realistic conditions.

Field beans, Phaseolus vulgaris, a staple in

many Latin American countries, appear to fix

little nitrogen (56). This is attributed to poor

modulation characteristics that may be due to

low phosphorus or high aluminum which inhibit Rhizobium activity. When these legumes

are grown, they contribute nitrogen to the

system. It eventually becomes available via

mineralization or the breakdown of complex

nitrogen compounds into simpler nitrogen

compounds.

Plant-available inorganic nitrogen in most

tropical areas shows a marked seasonal fluctuation (56). This is characterized by a slow nitrate (available form to plants) buildup during

dry season. There is a large, but short-lived, increase at the beginning of the rainy season, and

a rapid decrease during the rest of the rainy

season because of leaching.

Since the level of plant-available nitrogen in

many tropical soils is low, the use of extra nitrogen (green manure, animal waste, or fertilizer) will almost always increase yields of crops

if these crops can make use of the extra nitrogen. Therefore, if nitrogen fertilizer is to be added, it should be at rates that can be justified

economically.
215

Since most nitrogen fertilizer is very transitory due to its soluble nature, the use of nitrogen should be timed to the needs of the plant,

This will avoid excessive loss due to leaching

rain or denitrification, the loss of nitrogen as

a gas. Numerous experiments in both temperate and tropical climates have shown that the

application of nitrogen soon after planting,

when demand is highest, will result in higher

yields and more efficient use of the applied nitrogen,

Nitrogen loss is not a serious problem with

organic nitrogen from legumes or animal waste

since these complex organic materials are not

subject to leaching like the more soluble inorganic fertilizers. This suggests that organic

forms of nitrogen have a greater efficiency in

high rainfall areas. In some cases, nitrogen addition alone will not increase productivity substantially because other elements may be deficient or toxic. This is the case with acid soils,

Lime will promote legume establishment and

growth by reducing aluminum availability and

increasing the availability of phosphorus. Phosphorus deficiency is a serious problem in many

tropical soils and must be considered in the fertility regime,

PHOSPHORUS

Following water and nitrogen, phosphorus

is probably the most limiting nutrient in the

Tropics. This is particularly true in the acid

soils of the humid tropics since the high aluminum and iron concentrations render phosphorus unavailable to plants. The term used to

denote this is phosphorus fixation. When phosphorus is added as soluble monocalcium phosphate (Ca(H2C9PO4

)2) the soil pH is reduced to

1 to 1.5 (very acid). The acid dissolves aluminum, iron, potassium, and magnesium compounds and unsoluble phosphates of iron and

aluminum are formed. The higher the phosphorus-fixing capacity of the soil, the higher the

content of iron and aluminum oxides (56).

Higher exchangeable aluminum also increases

the soil’s phosphorus fixation ability. Because

of the fixation process, higher rates of phosphorus must be added to achieve the same level

of plant-available phosphorus compared to a

soil that does not fix phosphorus. The amount

of phosphorus added to a soil to get 0,2 ppm

phosphorus (adequate level) in the soil solution

can vary from 20 to 30 pounds per acre to as

much as 1,500 pounds per acre. A general recommendation for corn and rice in Latin America is 100 to 150 of kg P2O5 per hectare for corn

and from O to 60 kg for upland rice. In many

cases, soils respond only slightly to phosphorus unless they are first limed (15). In an experiment, limed corn plots showed a marked

response to 50 kg P2O5 per hectare with a yield

increase from 0.8 to 3.2 tons per hectare. In

limed plots, rice did not respond to phosphorus.

MANAGEMENT OF PHOSPHORUS FERTILIZER

Phosphorus responses are common in many In soils with high phosphorus fixation capactropical soils. Well-calibrated soil tests can ity, economically sound phosphorus manageidentify the soils with a high probability of ment involves several approaches (56). Two

phosphorus response. Phosphorus manage- general approaches are used to deal with high

ment in soils with moderate fixation capacity phosphorus fixing soils. One is to apply small

is usually a simple procedure: small annual to moderate amounts in bands near the plant.

rates of superphosphate can be broadcast The other is to apply a large amount at one time

(spread over top of soil) and incorporated or saturating the soil’s fixation capacity, eliminatbanded (placed in a band near the seed). ing the problem right away. However, this has

38-846 0 - 85 - 9
216

a disadvantage because it requires a high initial investment and adequate financing. In a

high-fixing soil from North Carolina, Kamprath

(41) studied the residual effect of massive initial applications versus small annual maintenance rates applied in bands. In that study, the

small annual banded application is superior to

the massive single dose.

Applying phosphorus fertilizers in bands is

a simple practice that satisfies the phosphorus

fixation capacity of a small soil volume, making the fertilizer directly available to plants. In

using a system of minimal inputs, banding is

very appropriate since the goal is to increase

crop production with minimal inputs without

changing the inherent fertility of the entire soil

volume. Sanchez (56) cites an example of

banded versus broadcast applications in a high

phosphorus-fixing soil in Brazil. The results

showed that broadcast-incorporated applications were superior to banded applications in

the first crop. Banded applications concentrated corn root development around the band.

When a temporary drought struck, these plants

suffered more than those of the broadcast plots

because those had a more extensive root system. In time, however, the effectiveness of the

banded treatments increased while the broadcast treatments decreased. Annually banded

treatments began

treatments as the

in the soil.

to approach the broadcast

phosphorus became mixed

SOURCES OF PHOSPHORUS

Research in temperate regions indicates that application without testing. These are largely

phosphorus fertilizers should have at least 40

to 50 percent phosphorus in water-soluble form

to ensure an adequate supply at early growth

stages (23). Ordinary and triple superphosphate

and monoammonium and diammonium phosphates meet this requirement and can be used

effectively in soils with low to moderate fixation capacities.

In acid soils that fix large quantities of phosphorus, application of less soluble phosphorus

sources such as rock phosphate may be more

effective and economical than the slightly soluble forms. Rock phosphates are more reactive

in acid soils and usually cost one-third to onefifth as much as superphosphate per unit of

phosphorus (56).

The literature on tropical agriculture is full

of research indicating the desirability of highquality rock phosphate sources over superphosphate in acid soils (46,4,23) and the poor performance of low-citrate-volubility rock phosphate sources in acid soils (3,50,66). Studies at

TVA by Lehr and McClellan (45) indicate that

when rock phosphate deposits (North Carolina

and Tunisia) are given an index of 100, rock

phosphates with a volubility index of 70 percent or greater can be recommended for direct

concentrated in North Africa, the Soviet ‘Union, and the Southeastern United States.

The effects of rock phosphates of varying citrate volubility on flooded rice yields in an acid

sulfate soil from Thailand was studied by Englestad, et al. (24). The initial and residual effects of the rock phosphates were highly dependent on their absolute citrate solubilities.

The yield responses of the North Carolina and

Florida rocks approximated those of triple superphosphate.

In the Tropics, high-citrate volubility deposits are limited to relatively small areas in Peru

and India (56). The majority of the deposits in

most tropical areas, including significant ones

in Brazil, Colombia, Venezuela, Togo, and India have relative solubilities lower than 40 percent. Most are unsuitable for direct applications, but their reactivity can be increased by

fine grinding or by thermal alteration and fusion with silica sand, sodium, or magnesium

carbonates. These silicophosphates, called

“Rhenenia” or thermophosphates, appear to

have promise for acid soils that fix large quantities of phosphorus because of the blocking effect of silicon on phosphorus fixation sites

(52,27).
217

The potential effectiveness of these cheaper

forms of phosphorus in acid soils is illustrated

in the following table:

Behavior of Different Fertilizer Sources on

Wheat Grown in Oxisols of Southern Brazil

Phosphorus Relative yield

source 5-year average

No phosphorus . . . . . . . . . . . . . . . . . . . . . 100

Olinda rock phosphate* . . . . . . . . . . . . . . 179

Simple superphosphate . . . . . . . . . . . . . . 206

Thermophosphate. . . . . . . . . . . . . . . . . . . . 218

‘Low citrate solubility.

SOURCE W.J. Goedert (personal communication) as cited by Sanchez (1976),

The low citrate volubility Olinda rock phosphate was inferior to ordinary superphosphate;

but when thermally treated with silicates and

carbonates to produce a thermophosphate, its

effectiveness was superior to that of ordinary

superphosphate. In view of the substantially

lower costs of the rock phosphates and some

thermophosphates, both seem desirable alternatives for soils with high fixation capacities.

An additional strategy, sometimes feasible

for managing soils with high phosphorus fixation capacities, is to reduce their fixation

through amendments that will block some of

the fixing sites in the soil. This can be accomplished in some soils through liming or silicate

additions (56).

Liming soils to pH 5.5 generally increases the

availability of phosphorus by precipitating exchangeable aluminum and hydroxy aluminum.

This has also been observed by Fox, et al. (29),

in high fixing Hawaiian soils.

Applications of silicon or sand (an unessential element), usually as calcium silicate, sodium silicate, or basic slag, are known to decrease phosphorus fixation and increase phosphorus uptake by crops. In one study, grass

yields increased from 2 to 7.6 tons per hectare

and phosphorus uptake rose from 4 to 15 kg

phosphorus per hectare when 1 ton of silicon

per hectare was applied without added phosphorus (62),

Silicon is generally not considered to be essential to plant growth, however, positive yield

responses have been achieved on highly leached

soils of the Tropics under intense cultivation

of sugarcane or rice. Soils having low contents

of soluble silicon are most likely to show response to silicon applications. Fox, et al. (32),

suggested that the critical level is 0.9 ppm silicon in water extracts. Responses have been obtained on the leached soils of Hawaii, Maurituis, and the rice soils in Japan, Korea, and Sri

Lanka,

In these rice soils, silicon applications increased yields because of a more erect leaf habit, greater tolerance against insects and disease

attacks, lower uptake of iron and manganese

when present in toxic

soil, and perhaps a rise

of rice roots.

SULFUR Deficiency

An element with plant requirements very found in sub-Saharan

concentrations in the

in the oxidizing power

Africa and the sandy

similar to phosphorus is sulfur. Sulfur deficiency results in a reduction of growth and protein deficiency, often resembling nitrogen deficiency. widespread sulfur deficiencies and

responses have been reported all over the Tropics. McClung, et al. (48), observed sulfur responses in the Brazilian Cerrado in both savannas and recently cleared forests. In Central

America, sulfur deficiencies are also widespread (5 I ,28), Sulfur deficiency has also been

soils of central Africa (8). They have been reported in Asia (52) and in Australia and Hawaii (68,30). Sulfur-deficient soils are generally

high in allophane or oxides, low in organic

matter, and often sandy. Soils subject to repeated annual burning are often sulfur deficient since about 74 percent of the sulfur is

volatilized (goes off as a gas) by fire. Sulfurdeficient soils occur in unpolluted, inland areas

where the atmosphere is low in sulfur.
218

Sulfur requirements are similar to phosphorus in tropical conditions ranging from 0.1 to

0.3 percent of plant tissue. A sulfur deficiency

at early growth stages may disappear later

when the roots come in contact with the sulfurbearing subsoil.

POTASSIUM

The last major element to be considered, of

less importance than the other nutrients considered here, is potassium. Potassium deficiencies do occur in the Tropics, however, lack of

potassium is not nearly as widespread as nitrogen and phosphorus deficiencies. Boyer (10)

in a review article suggests that the absolute

minimum requirement of exchangeable potassium—the amount considered to be available

to the plant—is close to 0.10 meq/100 g of soil

but that this may vary between 0.07 and 0.20

meq/l00 g depending on the kind of crops

grown and the soils.

In Africa, the most severe potassium deficiency appears in the savanna on sandy soils.

In the lower Ivory Coast, potassium application resulted in very substantial yield increase

In general, small rates of sulfur (10 to 40

kg/ha) will overcome sulfur deficiencies. Sulfur as part of either nitrogen or phosphorus fertilizer is usually sufficient to take care of sulfur problems. If not, any soluble source

containing sulfate will work.

DEFICIENCY

with oil palm (9). Potassium deficiencies have

occurred in the southwestern Cameroon (64)

in Madagascar (65) and in Brazil on sandy soils.

Laudelot (45) in the Congo (Zaire) showed that

the exchangeable potassium increased from

0.067 meq/100 g to 0.325 meq/100 after burning a forest. Thus, clearing a forest by burning substantially increases the potassium content of soils. Busch (12) found that the increases

in bases (calcium, magnesium, and potassium)

persists for a number of years after burning.

When soils are potassium deficient, fertilization with moderate amounts of potassium

usually corrects the problem. High yield crops

that contain high carbohydrates such as potatoes have a higher potassium requirement than

a grain crop such as wheat or rice.

RICE

Since rice culture differs from other crops

because it demands flooding, it must be considered separately. Regardless of their original

pH values, most rice soils reach a pH of 6.5 to

7.2 within a month after flooding and remain

at that level until dried (56). This increase in

soil pH is a result of the release of OH. (base)

ion when Fe(OH)3 is reduced. Consequently,

liming is of little value in flooded rice production. If low pH is a problem, flooding 2 to 3

weeks prior to transplanting may eliminate this

danger.

Oxygen is consumed in flooded soils; therefore, nitrates will be lost via denitrification.

Since ammonium is already reduced, it is stable in flooded environments. Organic matter

decomposition proceeds at a slower rate without oxygen, however, materials such as rice

straw (which has a high carbon to nitrogen ratio) may mineralize more rapidly under these

anaerobic conditions, thus providing a source

of plant-available nitrogen. Soil solution phosphorus increases upon flooding, explaining

why additional phosphorus in flooded conditions is rarely needed.

Nitrogen use in rice is very critical. An ammonium source is generally used when fertilizer is used. It is incorporated in the soil before seeding or transplanting, or broadcast at

different stages of growth. Incorporations of

2 inches are usually sufficient for constant

flooding conditions. This places the nitrogen

below the oxidized layer, a necessary condition to prevent denitrifiction (49). Nitrogen up-
219

take proceeds throughout the growth cycle of

the rice plant but it is particularly critical during two physiological stages: at the beginning

of tillering and at the panicle (grain head) initiation stage (47). Adequate nitrogen at tillering increases tillers, which is closely correlated

with yield in short varieties. However, excessive nitrogen after maximum tillering and before panicle initiation may result in a large proportion of unproductive tillers and premature

lodging in tall varieties. Excessive nitrogen after flowering may extend growth duration and

increase susceptibility to some diseases.

The efficient use of nitrogen is very important economically. Scientists at the International Rice Research Institute (38) have almost doubled the efficiency of nitrogen fertilizer by

either mixing it in mudballs or making urea briquettes. Fifty pounds of nitrogen per acre in

this fashion was equal to 100 pounds per acre

applied on the surface.

Rice rarely responds to phosphorus fertilizer

except in highly weathered leached soils (57).

Traditional soil tests for phosphorus do a poor

job in predicting the need for phosphorus under flooded conditions.

Zinc deficiency is probably the most widespread micronutrient disorder in tropical rice,

occurring in parts of India, Pakistan, the Philippines, and Colombia under low lowland conditions (63,69,15,39). It also occurs throughout

the Cerrado of Brazil under upland conditions

(19). In lowland rice, zinc deficiency is associated with calcareous (high base) soils and is

accentuated by prolonged flooding. Deficiency

can be corrected by applications of 5 to 15 kg

of zinc per hectare as the sulfate or oxide incorporated into soil before seeding (35). An alternative is dipping the transplant seedlings in

a 1 percent zinc oxide suspension before transplanting and mixing zinc oxide with pre-soaked

rice seeds before direct seeding (69,15). Yield

increase of 2 to 3 tons/ha have been achieved

with 1 to 2 kg of zinc oxide per hectare (11).

This again is an example of fertilizing the plant

and not the soil, a much more economical and

easy approach than treating the whole soil.

Potassium deficiency is rare in lowland rice

as these soils are usually adequate in exchangeable potassium and receive potassium in the

irrigation water when flooded. Soil tests are

good for estimating potassium-deficient soils

(56).

PLANTS THAT TOLERATE ADVERSE CONDITIONS

Up to this point this paper has concentrated

on soil modification as a way to increase crop

production. Another approach is to select or

breed crops that will tolerate and produce well

under natural, though sometimes hostile, conditions,

Certain crops grown exclusively in the Tropics normally grow at pH levels that would kill

corn or soybeans (56). Pineapple is perhaps the

best known example, but coffee, tea, rubber,

and cassava also tolerate very high levels of exchangeable aluminum. Among the pasture species, several grasses and legumes are apparently very well adapted to acid soil conditions,

Tropical grasses such as guinea grass, Panicum

maximum; jaragua, Hyparrhanea rufa; molasses grass, Melinia multiflora, and several species of the genera Paspalum and Brachiaria

grow well in very acid soils.

Legumes are considered very susceptible to

soil acidity because of their high calcium requirements for modulation. However, several

tropical pasture legumes are strikingly well

adapted to acid conditions. Stylosanthes spp.,

Desmodium spp., Centrosema spp., Calopogonium spp., and tropical Kudzu, Pueraria phaseoloides are the principal ones (56), Among the

grain legumes, cowpeas and pigeon peas are

more tolerant of acidity than field beans and

soybeans. Many of these species have evolved

in acid soils and have genetic properties that

tolerate conditions associated with high aluminum levels.
220

On the basis of research, Spain, et al. (61),

have produced a list of species adapted to high

soil acidity and aluminum:

Crops and Pasture Species Suitable for

Acid Soils With Minimum Lime Requirements

Lime Al Crops

requirement saturation (using tolerant

(tons/ha) (percent) pH varieties

0.25 to 0.5 68 to 75 4.5 to 4.7 Upland rice, cassava, mango, cashew, citrus, pineapple, Stylosanthes,

Desmodium, kudzu,

Centrosema, molasses,

grass, jaragua, Brichiaria decumbens, Paspalum

plicatulum

0.5 to 1.0 45 to 58 4.7 to 5.0 Cowpeas, plantains

1.0 to 2.0 31 to 45 5.0 to 5.3 Corn, black beans

In a review of tolerance to aluminum, Foy

(1974) concluded:

1.

2.

3.

4.

5.

6.

Some aluminum-tolerant varieties keep developing and are not injured.

Some aluminum-tolerant varieties increase

the pH of growth medium which reduces

the availability of aluminum; sensitive

ones decrease soil pH, compounding the

problem.

Some tolerant species accumulate aluminum in their roots or translocate (transport) aluminum at a slower rate to the top.

Aluminum in roots does not inhibit the uptake and translocation of calcium, magnesium, and potassium in tolerant varieties,

whereas it does so in sensitive varieties.

High plant silicon is associated with aluminum tolerance in certain rice varieties.

Aluminum tolerant varieties do not inhibit

phosphorus uptake and translocation as

much as susceptible varieties or species.

Also, many aluminum-tolerant species or

varieties are very tolerant of low phosphorus levels.

Cassava Manihot spp., a tropical root crop

growing widely on infertile soils that are frequently acid, has acquired the reputation for

being a crop that yields well under very low

fertility conditions (17). Cassava tolerates low

soil pH and high levels of aluminum and manganese as well as low levels of soil calcium, nitrogen, and potassium better than many other

species. While it has a high phosphorus requirement for maximum growth, it can use

phosphorus sources that are relatively unavailable to other plants. It is highly tolerant of uncertain rainfall patterns and is an extremely efficient carbohydrate source on low fertility,

acid soils with low levels of fertilizer applications. Cassava yields of 36 metric tons per hectare per year have been obtained under conditions that are suboptimal for many crops.

An estimated 1.57 million people live in the

Tropics and this number is likely to expand to

5 billion in 50 years (55). This rapidly growing

population will have to rely increasingly on

plants as sources of both energy and protein.

In the semiarid to subhumid climates, twothirds of dietary calories come from cereals,

while in the humid tropics the bulk of dietary

carbohydrate comes from roots and tubers. The

production of starchy root and tuber crops is

inherently more efficient than the production

of cereals, especially on marginal lands and/or

land with minimal external inputs. It is estimated that with roots and tubers, at least two

to three times more caloric energy can be produced per unit of land and time and with only

one-third to one-half the production cost of

cereals. It is, therefore, suggested that an increasing proportion of human energy needs

will be derived from starch roots and tubers.

The Tropics have a large amount of infertile

lands, ill-suited for many crops with moderate

to high nutrient requirements. One of the most

serious problems of some tropical soils is phosphorus deficiency that seriously limits crop

production.

Sweet potatoes (Ipomoea batatas (L.) Lam.),

long associated with poor people and less productive soils, may be one solution (54). There

is good reason that the sweet potato is grown

so widely under such difficult conditions.

Sweet potato had one of the lowest phosphorus

requirements of the crops studied (Lettuce,

Lactuca sativa; corn, Zea mays; and Chinese

cabbage, Brassica pekinesis) (31).

The International Rice Research Institute

(39), classified varieties of rice that are tolerant or sensitive to low phosphorus. They are
221

also selecting varieties for tolerance to iron deficiency or toxicity and the presence of toxic

soil reduction products.

In summary, it is apparent that high production can be achieved on rather hostile soils as

long as tolerant species or varieties of plants

are selected, This would be a strategy that relies on no or minimal inputs and yet can increase food production substantially,

1,

2,

3.

4.

5.

6.

7.

8.

9.

10.

11.

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. ., “

- ,- ---
Chapter XII

The Gene Revolution:

Maximizing Yields in the

Tropical Moist Forest Biome

James A. Duke

U.S. Department of Agriculture

Beltsville, MD 20705
Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Economic Botany Laboratory ...,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

The Quest for Tolerant Germplasm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Intercropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Legumes. ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

Azolla as Fertilizer. , . . . . . . . . . . . . . ,....., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

Heat or Meat... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Sewage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

Oil Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Allelopathy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

Drug Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

Essential Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Fiber Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Gums, Resins, and Balsams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

Wax Crops. ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,..., . . . . . . . . . . . . . . . . 238

Weeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Tropical Moist Forest Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

References, . . . ., ......,, ,...., . . . . . . . . . . . . . . . . . . . . ...,, . . . . . . . . . . . . . . 242

Appendix A–Magic Mountain: 2000 AD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. 243

List of Tables

Table No. Page

l. Estimates of Net Primary Production in Tropical Forests. . . . . . . . , . . . . . . . . . . . 240

2. Tropical Root Crops, .....,, ,, .,..,, ., . . . , , , ..., , , , ., . . . . . . . . . . . . . . . . . . . 240

3, Tropical Vegetables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

4. Tropical Spices, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

5. Net Primary Productivity . . .+.,.. . . . . . . . . . . . . . . . ..,+. . . . . . . . . . . . . . . . . . . . 241
Chapter XII

The Gene Revolution:

Maximizing Yields in the

Tropical Moist Forest Biome

It is the skills of plant geneticists, rather than record after another in crop yields in , . . both

large amounts of artificial additives such as temperate and tropical zones (Norman Meyers,

pesticides and fertilizers, that have led to one The Sinking Art, 1980).

Should there be a Gene Revolution, based on

low-input multiuse extensive agroecosystems,

to supplant the Green Revolution, based on

high input intensive agriculture? Genes best

adapted to the marginal environments found

in the humid tropics should be pooled, combined, and recombined to produce moderateyielding, well-adapted, multipurpose species.

These gene combinations and recombination

should be tested, not for their yields in monocultural situations, but in well-planned, multitiered intercropped agroecosystems.

The search for appropriate genes can be

scientifically directed by a computerized catalog of the varieties, cultivars, and species of

potentially economic native and introduced

species. Technologies that would be part of

such a multiple-use agroecosystem would include small-scale biomass- and alcohol-fueled

and solar plant-extraction equipment, as well

as fermentation and distilling apparatus, designed to run on some of the products of the

agroecosystem. In summary, the Gene Revolution should be directed toward a multitiered,

multiuse, polygenic, low-input agroecosystem,

fueled and fertilized from within. The Gene

Revolution should pull together the five major

ingredients important in marginal environments: 1) tolerant germplasm, 2) multiple and

intercropping scenarios, 3) organic gardening

(recycling animal and plant residues), 4) biological control of pests (including allelopathy),

and 5) whole plant fractionation and utilization

for such integrated agroecosystems. Such systems should be developed from existing farms,

not from the forests.

INTRODUCTION

... Plant germplasm can be selected and su- long periods without a high level of inputs. But

perior cultivars developed on the basis of their such inputs are rarely affordable to developadaptation to problem soils. Although we have ing tropical countries. If these countries canmoved slowly to capitalize on this information, not afford the inputs required for high-level

it offers great promise in reducing energy in- production of conventional food crops, per- puts and improving the reliability of crop haps they should aim instead for a moderate yields in both developed and developing countries (A. A. Hanson, 1976). production of nonconventional crops with

moderate inputs. The Green Revolution, which

The highly weathered soils of the humid trop- called for maximum inputs, has pretty well run

ics will rarely support conventional crops for its course, maximizing productivity where high

227
228

inputs are possible. It is time for the Gene Revolution, to tailor existing plant types to maximize output with minimal input. The genes exist in nature, but they are disappearing fast. It

is up to the Gene Revolutionists to get the genes

together in the most meaningful manner, to

maximize productivity under various low input scenarios.

With the end of the cheap energy era, developed and developing countries must reassess

their imports and exports, their agricultural inputs and outputs, and their needs, often with

a view toward substituting botanochemical

fibers, fuels, and pharmaceuticals for those

derived from petrochemicals.

Energy-hungry developing countries should

closely watch developments at the Northern

Regional Research Laboratory in Peoria, Illinois. If the botanochemical approach is practical today or tomorrow in an energy-rich country like the United States, then it will be all the

more practical in the energy-poor countries of

the humid tropics because:

1. Natural (and agricultural) productivity per

unit area is higher in tropical than temperate zones, other things being equal.

Hence, there should be much more biomass for a total-utilization scheme. The

Gene Revolutionist is charged with finding the best genes and combining them in

the best plants for maximizing output in

the marginal low-input farm scenario.

2. The diversity of useful species on which

to draw for our total-utilization concept is

perhaps 10 times as high in the Tropics as

in the temperate zone. Hence, the array of

combinations for the recommended intercropping approach is staggeringly complex. The multitiered, intercropping agroecosystem being studied seems to be one

of the most highly productive terrestrial

agroecosystems, competing with the highly

productive aquatic ecosystems of the Tropics. Yields of either of these systems can

be improved vastly by the addition of ameliorated sewage sludge or other natural fertilizers in lieu of artificial fertilizer inputs.

However, sewage sludge is recommended

for biomass and chemurgic crops, not food

crops.

In this talk, I will try to respond to the central issue: the highly weathered soils of the hot,

wet tropics. These soils are rich in aluminum,

silica, and iron, and poor in the common plant

nutrients. What could USDA’s Economic

Botany Laboratory (EBL) do to improve “biological productivity of such soils without using

much or any chemical fertilizer?” That is the

charge put to me by the Office of Technology

Assessment. Let’s analyze that a bit before proceeding. Is it rare that we can improve natural biological productivity? Nature does a good

job maximizing biological productivity under

nature’s constraints. If I compared productivity, I would only be comparing usable with

total productivity. And if we are talking about

the maximum Usability Concept, then we are

not talking conventional agriculture at all.

Before laying out my plans for any country,

I would analyze their import tables, especially

the energy columns. Then I would plan a

multitiered agroecosystem that would maximize benefits to the countries, import-export

situation, seeking the best genes to maximize

output for a modicum of inputs, under the

ecological conditions prevailing. Geneticists

could maximize the yields while American

technology could maximize the extraction of

useful products from the total yield.

Humid tropics has been variously defined.

Most of my examples relate to what is called

the Tropical Moist Forest (TMF), where annual

biotemperatures are greater than 24° C and annual rainfall is between 2,000 and 4,000 mm.

I have spent years in the Tropical Moist Forests

of Latin America, and am still awed by the

diversity of economic products endemic to the

area. There are even more exogenous economic species from similar ecological zones

outside Latin America. Unlike others in this

workshop, I do not stress using native species,

but I share the belief that we should not introduce exotics that are ill-adapted to an area.

EBL’s computer system helps find the right

germplasm for a given tropical ecosystem.
229

Drawing on these tropical gene pools, the

Gene Revolutionist has perhaps more than 75

percent of the world’s species to consider, perhaps 250,000 species. Each is a unique chemical factory, manufacturing biomass that we

may need to draw upon as a source of energy.

As the preface of the National Research Council’s book, Conversion of Tropical Moist

Forests, begins: “The tropical moist forest

biome is biologically the richest, and least well

known portion of the earth’s surface.”

Unfortunately, much of TMF is underlain by

femalsols (strongly weathered soils of tropical

regions, consisting mainly of kaolinite, quartz,

and hydrated oxides, and having a low base exchange capacity). Dudal (6) summarizes the

mineral stress phenomena in such soils:

1. Deficiency in bases (Ca, Mg, K) and incapability to retain bases applied as fertilizers or amendments.

2. Presence (pH < 5.2) of exchangeable Al,

toxic to many species and active in binding phosphates.

3.

4.

5.

6.

Presence (acid soils) of free Mn, also toxic.

Fixation of phosphate

Deficiency of molybdenum, especially for

legumes.

Fe and Mn toxicity shown by paddy rice.

Such soils are said to occupy more than a billion hectares, more than 8 percent of the

world’s soil.

There are those who say that conversion of

TMF to agriculture will lead only to the socalled “red desert. ” Ewel (8) says, however:

The red desert view of mature tropical ecosystem destruction is incorrect. Nature abhors

a vacuum, so sites laid bare by human activity are quickly covered by some kind of community, although not usually the original one.

We must face the fact that successional communities are going to be the dominant tropical ecosystems of the future.

ECONOMIC BOTANY LABORATORY

I am still awed by the diversity of the Tropical Moist Forest. Working at the Economic

Botany Laboratory, I have begun to try to

organize the information pertinent to the Tropical Moist Forest. There is already so much information that we depend on computers to

assimilate the information. We are primarily

concerned with the medicinal plants of the

world, especially those with anticancer activity. secondly, we are concerned with cataloging agronomic, ecological, geographical, and

utilitarian information on economic plants of

any description. From his studies alone,

Schultes (23) compiled a list of more than 1,300

species employed by natives of the northwest

Amazon as medicines, poisons, or narcotics.

Our computer files already contain entries on

more than 4,000 folk medicinal species, some

of which double as food plants, fiber plants,

dye plants, etc. We have yield data on some of

these, under various ecological regimes in the

Tropical Moist Forest.

With careful expansion, such a data base

could catalog information on ecology, utility,

and yields of all economic plants, and guide

the Gene Revolutionists in their search for the

right genes or germplasm. Details of some strategies that should be employed in the quest of

tolerant germplasm are explored in Duke (7).

Ecological data on more than 500 species suitable for exploitation in the Tropical Moist Forest are tabulated. I will not relate all those data

here, but will present a few examples.

We know the conventional yield figures for

only a fraction of tropical crops. Biomass or

residue figures are even rarer, although such

numbers are necessary for systems analysis of

the yield potential of a multiuse agroecosystern.

According to Westlake (29), conversion factors

range from 1.3 to 4.0 for estimating aerial

biomass from conventional yield units. I called

all the experts I could find, in vain, in my

search for the biomass figures for the temperate
230

lentil. Who would I call for such figures on the

myriads of tropical products? The numbers do

not exist. “The accuracy of productivity measurements is the lowest for tropical areas. The

key to future refinement of our understanding

the global productivity capacity lies, therefore,

in the study of tropical primary productivity”

(16). If biomass is a viable competitor in the

energy field, it is time pertinent numbers were

generated by baseline research program.

If I were Secretary of State, determining

what strings were tied to AID funds overseas,

I would see to it that funds went to carefully

distributed research plots in developing countries. These plots would be funded to generate

the numbers needed to support Maximum Utilization Concepts. How much biomass can we

grow and harvest under various scenarios?

Which scenario gives us the greatest net usable

returns? I would fund no studies that did not

give biomass yields related to climatic and

edaphic data, and I would fund no country that

did not make a commitment to preserve their

current forests, and concentrate on increasing

the productivity of current croplands.

Why should the remaining forests not be converted into agroecosystems? If they are lost,

thousands of undescribed species will disappear forever before they have been named.

Thousands of others will disappear with no

studies of their economic potential. It is difficult to put a price on their heads. One in ten

species studied shows anticancer activity; but

only about 15 of the first 30,000 species studied in our anticancer program are of sufficient

interest to have reached preclinical testing.

Only one of those has resulted in thousands of

remissions in cancer. This superstar, Catharanthus roseus, the Madagascar periwinkle, is a

pantropical ornamental and folk medicine in

Tropical Moist and Dry Forests. There are

probably nine more superstars awaiting discovery (if they do not fall victim to the tropical

axe). Can we afford to extinguish them?

THE QUEST FOR TOLERANT GERMPLASM

Elsewhere, I have advocated and outlined is cheaper to increase yields by finding a

measures for seeking out the genes we need for cultivar that will tolerate the acidity, and its

marginal environments in the Tropics (7). complications, than to increase the yields by

Other research backs this idea: importing 6 tons of lime per acre. This is just

The correction of Al and Mn toxicities by the first step in the Gene Revolution. Incorliming is not always economically feasible, porating the appropriate genetically tailored

especially Al toxicity in strongly acid subsoils. species, varieties, races, and cultivars in a

However, plant species and varieties with spe- multitiered, multiple cropping system requires

cies differ widely in their tolerance to both even further genetic selection, manipulation,

factors, and some of these differences are and experimentation.

genetically controlled (10,25).

It is such differences we hope to capitalize on

in the EBL Quest for Tolerant Germplasm. It

INTERCROPPING

Work on multitiered agroecosystems is pro- trees, are common. Thousands of combinations

ceeding most rapidly in Asia, but temperate are possible in a tropical three-tiered system.

systems are familiar to us all. Two-tiered sys- In one, pineapple was planted as the ground

tems, with hay, legume, or cereal crops alter- crop, cocoa as the first story, and pepper as the

nating or intercropped with rows of fruit or nut second story. Total harvestable crops and
231

residues from such systems usually exceed significantly the expected crops of the individual

species, had they been planted in monoculture.

Advocating agroecosystems that simulate the

natural ecosystem it replaces Hart (12) says:

The replacement of weeds by analogous

crops and an increase in crop diversity will

usually reduce the amount of energy used by

weeds and pests.

Those systems of tropical forestry and agriculture that have been successfully employed

for the longest periods are those that favor the

maintenance of large mycorrhizal fungus population. Traditional shifting agriculture in

small forest-enclosed plots probably attains

mycorrhizal homeostasis. Mycorrhizae seem

to minimize the expense to the host of seekingout minerals. Cultivation of annual crops may

lead to increased prominence of nonmycorrhizal species and grasses in weed communities. Soil sterilization can eliminate mycorrhizal fungi, and fungicides used against

pathogens may adversely affect mycorrhizal

fungi as well. Monoculture of crops that are

probably nonmycorrhizal, such as grain amaranths and chenopods, might markedly lower

mycorrhizal fungus populations and jeopardize subsequent mycotrophic crops (14).

LEGUMES

Even the nitrogen fixed by legumes is not

free. Under conventional farming, there is a

price to pay for the nitrogen contribution of

the legume. In an unpublished paper, I pulled,

at random, biomass yields for pure stands of

C-4 grasses, C-3 grasses, and legumes. Though

relatively higher in nitrogen and protein, the

legumes yielded only half as much total biomass as the C-3 grasses, which in turn yielded

only about half as much total biomass as the

C-4 grasses. These are the biological costs (1)

for nitrogen fixation and (2) excessive photorespiration. Although no one seems to have accepted my simple 1:2:4 ratio, I believe it. So

called super-yield targets in the United States

are 100 bushels of soybeans; the target for corn

is 400 bushels.

Appropriate combinations of legumes and

grasses seem to give the best yields for forage

or hay, and probably for maximum utilizable

biomass under renewable situations where

water is not the limiting factor. The C-4 grass

might give highest yields for a while, but it

seems doubtful that such yields would be sustainable without the help of added N, be it from

legume, crop residues, manure (green or

brown), or sewage sludge. For high-quality leaf

protein, the legume seems indispensable for

most scenarios (without the sewage increment)

whether the protein is for animal food, human

food, or chemurgic use.

The amount of N fixed by legumes varies of

course, but some of our economic legumes play

a larger role than making beans and fixing nitrogen. According to Nigmator, et al. (1978),

the cultivation of the legume licorice (Glycyrrhiza glabra) showed a marked ameliorative effect on saline soil in Uzbekistan, Russia. The

licorice, in pure stands, did not form a complete soil cover during the first 1 to 2 years, but

this was achieved by sowing it in mixture with

sudan grass, cowpea, and lablab. The mixture

decreased the evaporation and the rise of salts

to the upper soil layers. Haines, et al. (11), reported that undersowing sycamore (Platanus

occidentals) with clovers and vetch in a discultivated, z-year-old plantation suppressed

weed growth to the point where height and volume increments of the young trees were increased significantly.

According to Felker (9):

Leguminous trees have a unique advantage

over annual legumes in dealing with the inhibitory effect of drought stress on nitrogen

fixation because the deep-rooted leguminous

trees may reach moisture, and thus relieve the

plant of water stress for a longer time in the

year than is possible with annuals.

An illustration of the ability of leguminous

trees in semiarid climates to increase soil fertility more than annual legumes can be found
232

in West Africa, where yields of peanuts are increased if grown beneath Acacia albida trees.

The work on “teaching the grasses to fix nitrogen” goes on, but does not generate as many

headlines as in the past. Nitrogen-fixation is

being reported in more and more nonlegumes.

Just this month, I noted an abstract dealing

with nitrogen fixation in blackberries. Becking

(z) assayed nitrogenase activity by acetylene

reduction in detached Rubus ellipticus root

nodules. It was similar to that in several nonlegume N2 fixing nodules. The endophyte was

an actinomycete.

AZOLLA AS FERTILIZER

While legumes are one source of fertilizer for

our multitiered agroforestry units, tropical

azollas might be another. Azolla, an aquatic

fern, is a source of nitrogen. Clark (5), reviewing Azolla use in China, notes that Azolla

“seed” are started in nurseries, then the seed

ferns are introduced directly into rice paddies.

In some areas, two rows of rice are planted

with the Azolla growing in larger rows on either side of the double rice rows. Yields of 15

MT/ha of rice and 150 MT of Azolla have been

reported for this simultaneous cultivation

method. Rice grown with conventional fertilizers averages only 10 MT/ha (5). No mention is made of fish biomass harvested from

such ecosystems. Could they also harvest 15

MT/ha catfish as have been reported from wellaerated Louisiana fishponds (21)? Grass carp

(Ctenopharyngodon idella) and Tilapia mossambica are said to relish azolla, which has also

been fed to cattle, chickens, ducks, and even

has been suggested for human consumption.

Typically, yields of grass carp are 10 times

higher in the Tropics (l,500 kg/ha) than in the

temperate zone (164 kg/ha).

Unfortunately, we do not know that Clark’s

150 MT of Azolla is dry weight or wet weight;

if dry weight, we have our fertilizer factory producing biomass equivalent to some of the highest reported, while increasing the yields of the

rice crop, almost incredible. Here let me point

out serious conflicts facing USDA officials:

there are potent advocates and opponents of

the introduction of many of the biomass

wonders of the world (Acacia, Azolla, Leucaena, Prosopis, etc.) and the opponents hope

that the advocates are willing to foot the bill

should these wonders become the major weed

of the 21st century.

I mention Azolla first because it is being

championed as a free fertilizer, one producing

150 MT of biomass, while increasing the yield

of rice by I% times. These are the “facts”

hailed by the advocates. Azolla pinnata can

double its biomass in 3 to 5 days, maybe 5 to

10 days in the field. Some claim that Azolla will

suppress other weeds in rice, if not the rice

itself. Other reports indicate the Azolla can either prevent mosquitoes from laying their eggs

of their larvae from surfacing. Some say it releases nitrogen while alive, others only after

death. Vietnam reports 1 MT/ha N fixed per

year; China 0.7 to 1.8 MT N (13).

But there is a weed potential lurking there.

Weeds cost the United States about $16 billion

in 1979. Would Azolla introduce increase

yields or would it clutter up more ponds than

it helps. Responsible weed scientists as loudly

and justly proclaim their fears as responsible

forward-lookers champion this “free” fertilizer.

There is no cut and dry answer.

On the negative side of the Azolla equation:

● In Japan, there have been complaints

about Azolla covering the rice seedlings.

● In the Philippines, Azolla is called a weed

in rice.

● In New Jersey, it has clogged up water

channels to boat traffic.

● In South Africa, farmers claim it killed

fish, prevented cattle from drinking the

water, and clogged pipes.
233

MEAT OR MEAT

The Tropics may not face the heat or meat

decision that temperate countries will face if

there are no energy breakthroughs soon. According to some estimates, more than 90 percent of U.S. cereals and legumes are destined

for animal food. If Americans went vegetarian

tomorrow, and quit exporting grain, more than

95 percent of our agricultural biomass could

go into ethanol production here. Some of us

would rather be warm and do without meat,

than be cold and eat meat regularly; others

would say an emphatic “no.” According to

Meyers (19), much TMF biomass goes into

cheap hamburger for the United States. Would

it be better converted to fuel for the people of

the TMF?

I have been a human guinea pig on three

human nutrition studies at USDA, all involving high fiber and/or vegetarian diets. In one,

20 male subjects, none vegetarian or particularly sympathetic with vegetarianism, were fed

soy protein in lieu of meat protein. None suffered from the soy as opposed to meat. On the

contrary, there were no significant changes in

the health of the subjects, at least by the standards investigated. From 40 to 50 percent of the

human subjects preferred each soy analog to

its meat counterpart.

Thanks to coal, America need not face the

heat or meat crisis immediately. Thanks to the

temperature of the humid tropics, the TMF

might not face that choice either. But they

might need to decide whether their biomass

residues go into animal production or fuels for

their machinery.

WOOD

Even today in the United States, wood is said

to provide more energy than hydroelectric or

nuclear power. Wood is a valuable byproduct

of the multitiered agroecosystem, and the Gene

Revolutionist should remember that in tailoring species for TMF.

The growth rate of tropical weed trees characteristic of the humid lowlands are quite

remarkable. I have measured naturally regenerated Trema micrantha in Costa Rica’s OSA

Peninsula, which were 9 m tall at one year,

and more than 30 m tall at 8 years. It is these

fast-growing, low-density trees which will

constitute the wood resource of the future as

mature tropical forests are felled and regenerate (8).

Ewel’s figures for 13-month-old regrowth in various life zones are TWF, 12 MT/ha; TDF, 10

MT/ha; SWF, 6 MT/ha; SDFA, 5 MT/ha; and

Tropical Montane Rain Forest, 1 MT/ha.

I do not advocate replacement of wood as a

source of energy for cooking and heat in the

TMF. I do advocate the production of cheap

wood-burning devices for distribution to the

poor. Most of the timbers of the Tropics go up

in smoke, much of it wasted. With energyconserving wood stoves, there would be more

biomass available for the production and distillation of alcohol and other uses.

Liquid fuels for use in cars, trucks, and

vehicles should be produced by all but the

smallest farms in cheap mass-produced stills

provided by the technologically well-off,
234

SEWAGE

There is justifiable concern that maximum

use will strip the soils of organic matter. If we

only use the above-ground biomass, we leave

the below-ground biomass. According to Van

Dyne, et al. (28):

Below-ground production is more than

twice above-ground in annual grasslands, but

standing crops of biomass below-ground

maybe five to ten times as much as above-

-ground standing crops.

The humid tropics do not lack water like the

arid tropics, but they do need organic fertilizers, especially if continuously harvested.

Here I take the opportunity to introduce into

the tropical scenario an idea that I think should

be exploited in the United States: piping

sewage sludge out of the cities of the world and

into energy farm areas. The pipeline routes

could parallel proposed coal-slurry lines, natural gaslines, or petroleum pipelines. Oil shale

mines, strip mines, any type of old mine site

could be partially or totally reclaimed or improved with sludge-planted areas. The highest

biomass yield reports I find are from The

wealth of India, where such yields as 160 MT/

ha for Pennisetum purpureum are reported for

fields irrigated with sewage. Westlake (29)

reports unusually high yields even in the temperate zone. With sewage irrigation and intercropping, he reported DM yields of mixed

alfalfa-orchardgrass at 26 to 39 MT/ha, at least

five times greater than the expected yield of

alfalfa alone, without sewage irrigation. This

compares with 40 MT for Phragmites australis,

which Westlake describes as the most productive temperate community.

City planners should adopt the Design With

Nature Concept, building above the productive

alluvial plains, clearly the most productive

lands in any biome, with nothing but natural

inputs. Alluvial plains and energy sumps

should occupy the fertile lowlands, while no

more building on the floodplains should be

permitted. These most fertile lands are being

gobbled-up by suburban creep, here and

elsewhere.

I decry the cancellation of plans to barge

sludge to Haiti, because I believe sewage sludge

could play a big role in the greening of Haiti

or the Sonoran or Negev deserts for that matter. We could concomitantly alleviate the shortage of water and organic matter in the desert,

with its low real-estate values, while alleviating

the waste disposal problem in the cities, with

their high real-estate values.

Water-borne sludge could prove a boon to the

humid tropics. If sewage sludge can double

yields in the humid tropics, the reverse pipeline could be shipping ethanol out, still leaving a positive balance in organic matter in the

humid tropics. Once the pipelines were established, the sludge could be a free input, doubling outputs. Hence, I see this untried concept

as one way to double the productivity of the

humid tropics, or treble the productivity of the

arid tropics, with a free input. The excess

yields could be devoted to production of alcohol, for internal or external energy use.

Such an area might appropriately be called

an energy sump, and would not be an attractive place to live, but the products of the energy

sump could make jobs there, and a higher

standard of living elsewhere.

Here, as much as anywhere, the talents of the

Gene Revolutionists will be called into play.

The genes for maximizing productivity in the

energy sump will be very different from those

for maximizing productivity in the unaltered

humid tropics. Planting, cultivating, weeding,

and harvesting technologies, even the recommended varieties, if not species, will be different for the two scenarios.
235

OIL

Back in April 1977, I suggested that palm oil

might someday be competitive with petroleum.

Today, foreign palm oil in New York is still

higher than domestic petroleum at the pump,

but at the rate the gap has closed since my paper. Palm oil will be as cheap as petroleum by

the year 2000.

Oil palm is one of many species with varieties tolerant of the allic soils of the humid tropics. Oil palm is currently growing in countries

that show deficits in both edible oils and

energy. It has already been shown that simply

growing legumes between the oils palms can

increase oil yields by 2 MT/ha/yr (3) or the

equivalent of 6 barrels of oil per hectare, simply

by the selection of proper legume for intercropping. These legumes (Centrosema pubescens,

Pueraria phaseoloides), in addition to increasing our energy budget, at little or no cost following planting, can provide food, conventional or unconventional. I am sure, based on

temperate figures, that more protein per hectare will be produced if the whole aerial biomass of the legume is harvested, thrown into

our energy vat, the leaf protein extracted for

human consumption, the carbohydrates for

ethanol production, the residues for return to

the soil.

We have spoken only of the oil yields of the

oil palm, There is still a lot of unused biomass,

which could go, depending on the outcomes

of our systems analysis, into ethanol production, internal or external combustion devices

and/or soil amendments.

Not all, but most palms, survive or thrive in

the humid tropics. Like the oil palm, they are

multiple-use plants, prime candidates for the

upper or intermediate stories in the multitiered

agroecosystem for the humid tropics. Could we

not multiply the yields of these unstudied

palms by 10 as we have done with the Hevea

rubber plant. Let’s look briefly at one mentioned by Amazonian expert R. E. Shultes (23):

Orbignya martiana: One palm may produce

a ton of nuts a year, 198 pounds of which is

kernel . . . with up to 72 percent of an almost

SEEDS

colorless oil very similar in composition to

coconut oil. The seed cake remaining, containing 27 percent protein, is an excellent animal feed. I read this as a ton of biomass per

year, more than 100 pounds of which is oil.

I don’t know that these figures are more or

less reliable than those with which Calvin

derived 50 barrels of diesel per acre. Conservatively, it would take four of these productive palms to produce one barrel of oil per

year, or 200 trees to produce 50 barrels, From

my experience in Latin America, I would pin

my 50 barrels/acre hope on the palm before

I would Calvin’s Diesel Tree. Calvin figured

at least 100 trees per acre, but his trees were

1 m in diameter. I don’t know any palms that

big. Thin canopied palms would permit intercropping of food crops, which I speculate

would be impossible in the shade of “diesel

trees.”

Note that with our hypothetical Orbignya,

with no genetic research, we are getting 50 barrels of palm oil per acre, with a residue of 1,900

pounds per tree. We have assumed a tree producing 2,000 pounds of fruit, 100 pounds of

which is oil (3,300 pounds are reported, with

an oil yield in excess of 200 pounds oil per tree).

Assume 300 to 350 pounds per barrel of oil. We

can further assume after the extraction of our

100 pounds of oil, we have 1,900 pounds of

biomass in the pot, 900 pounds of which might,

conservatively, be water. Of the remaining

1,000 pounds, perhaps there is another 100

pounds of protein, per tree, and 900 pounds

of carbohydrates, etc., 400 pounds of which

might give us another barrel of ethanol per hectare. So, hypothetically we have 100 pounds of

protein and 2 barrels of ethanol as byproduct

from our 1 barrel

The technology

scenario:

1. oil extraction

2. carbohydrate

tion; and

of palm oil.

needed for this oil palm

(available for oil palm);

fermentation and distilla3. protein purification and sanitation, for

human or animal production.

There are palms for the arid tropics, for the

humid tropics, for brackish swamps, for fresh-
236

water swamp situations, and for our sewage

sump, all potentially intercroppable with other

food/energy/chemurgic crops. But the Gene

Revolutionist has not started to tailor these species to specific environments and to increase

their yields. And we have not even talked about

the waxes, steroids, leaf-proteins, and ethanol

that could be produced by the leaves. Some

palms will disappear before we have studied

their potential.

Production of conventional palm oil (from

Elaeis) was expected to total 4.3 million MT

in 1979-80, compared to 3.9 million MT in

1978-79 [1). Whether or not these are viewed

handled in the U.S. market. Residues could be

used for alcohol or methane generation, or as

a soil amendment.

Some prices quoted in the Chemical Marketing Reporter for various tropical oilseeds during 1979 are avocado ($ S. IS/lb), castor oil

($0.40/lb), coconut ($0.57/lb), corn ($0.50/lb),

cottonseed ($0.18/lb), oiticica ($0.60/lb), palm

($0.33/ lb), palm kernel ($0.42 /lb), and soybean

($0.48/lb). The newly generated market for jojoba “oil” has a cult of followers, but this socalled oil is a liquid wax, unique to the jojoba

among plants. Soy oil, peanut oil, and sunflower oil have been used as diesel substitutes.

as petroleum alternatives, many oilseeds are

ALLELOPATHY

Allelopathy has not yet been developed to be

an alternative to herbicides. But if different

chemurgic species are selectively herbicidal,

as one gathers from reading the allelopathic

literature, then all these herbicidal activities

should be cataloged. Residues of the allelopathic species might then be returned to the

intercropped agroecosystem where its herbicidal effects will do the most good and least

harm. One can even suggest how coumarincontaining residues (Melilotus, Trigonella, etc.)

can be used to stimulate rooting in the softwood cuttings used for propagation in our tropical agroecosystem (17). Steenhagen and Zimdahl (26) show that the hydrocarbon-producing

Euphorbia esula reduces the frequency of

quackgrass and ragweed, but also reduces the

growth of tomato seedlings. Dry leaves of the

medicinal species, Parthenium hysterophorus,

inhibit growth and modulation in legumes,

branching in tomato and plant height in ragi

(Eleusine coracana) and reduce the yield of

bean, tomato, and ragi. On the other hand, the

leaves stimulate the growth of Pennisetum

americanum (15). Such data are being generated rapidly, but there seems to be no computerized catalog to enable us to evaluate and

use these data effectively in planning multiuse

agroecosystems.

DRUG CROPS

The Economic Botany Laboratory specializes

in medicinal plants. We have found that there

are often huge residues of biomass following

drug extraction. It takes 11/2 MT of dry stem

and bark of Maytenus to yield a gram of

maytansine, one of the anticancer superstars

of the last decade.

Bruceine, cassia, caffeine, cocaine, heliotropic, ipecac, papain, pilocarpine, quinine,

quinidine, reserpine, rutin, steroids, and theophylline: these are a few drugs that can be

harvested in the humid tropics. Many of these

are million dollar items that could be extracted

on-site as income producers, leaving behind 99

percent of the biomass for food and/or fuel production. Some drugs might be byproducts from

conventional foods, e.g., caffeine from coffee

and tea, theophylline from tea, steroids from

legumes, rutin from buckwheats. The steroids

once derived from tropical dioscoreas (“barbasco”) are now largely derived as byproducts

of legumes and agaves.
237

ESSENTIAL OIL

The United States imports nearly 10,000 MT

of essential oils at close to $100 million per

year. This probably represents the distillation

of about one million MT of biomass, 99 percent of which could have been funnelled into

food and fuel production as byproducts. By no

means all of these essential oils are humid tropical species, but I list a few that are from the

humid tropics:

● Trees: bay, bergamot, camphor, cassia,

cinnamon, clove, copaiba, grapefruit,

guaiac, lemon, lime, linaloe, nutmeg, petitgrain, ylang-ylang

● Forbs: cardamon, citronella, ginger, lemongrass, palmarosa, patchouli, vetiver.

The trees might be considered as alternating

trees or strata with other trees, like palms, in

the upper strata of our multitiered agroecosystem. The forbs might be considered for the

ground layer. Our Gene Revolutionists should

already be looking for tolerance to shade and

root competition in our lower tier, and tolerance to root competition in candidates for the

upper tier.

FIBER CROPS

On the last day of October 1980, an official steriods, waxes, leaf protein and alcohol, even

called from the Strategic Materials Department tequila, could be produced. Many natural fibers

to ask where in our 50 States we could grow can be produced in the humid tropics, among

several strategic materials. Among them were them abaca, baobob, coir, cotton, ensete, hemp,

two tropical fibers, abaca and sisal, the former henequen, jute, kenaf, remaie, roselle, sisal,

adapted more to the humid tropics, the latter snakeplant, sunn hemp, etc. As the cost of pemore to the arid tropics. With sisal, fiber yields trochemicals rise, some economists predict a

are only 3 percent of the leaves. From the re- return to natural fibers instead of synthetics.

maining 97 percent biomass, I am certain that

Some chemicals in this group approach the

classical petrochemical or “neoclassical”

botanochemicals. Swedish and Finnish firms

are reported to have developed an efficient

turpentine car engine that runs on turpentine

produced from the oleoresin of scotch pine.

High road mileage is claimed for turpentine

(20). Presumably, yields of tropical pines may

be higher than the temperate pines. The Gene

Revolutionist would be charged with increasing both the nut (pinyon) and turpentine for

specified intercropping stratagems under specified ecological conditions.

Copaiba oil, traded at over $2.00 per kilo,

may or may not be the same as the oil from

Melvin Calvin’s tropical “diesel tree” Copaifera

langsdorfii. According to Dr. Calvin, (4) 11/2

inch holes drilled halfway through large trees

about 2 feet above the ground yield about 20

liters of “diesel” (mostly 2 or 3 main C-15 sesquiterpenes and 30 or 40 minor C-15 sesquiterpenes) in two hours. The holes are bunged and

retapped again in about 6 months, and said to

yield another 20 liters of diesel, or 40 liters of

diesel per year per tree. This is exactly the same

yield reported in Grieve’s Modern Herbal,

1931. Dr. Calvin, perhaps optimistically, calculates that we can get 25 barrels of diesel per

acre per year on a sustainable basis from the

copaiba tree (18). Unfortunately, the tree seems

to be intolerant of frost. I will be getting resin

from an equally productive timber species of

Copaifera during my next trip to Panama.
238

Gum arabic, guar, karaya, locust, myrrh, ported with a value of $608,346. More than 23

olibanum, and tragacanth are among some of million pounds of guar gum were imported in

the vegetable gums now traded. With problems that same month. Acacia, Tamarinds, and

in Iran, a major producer of tragacanth, prices Sterculia are major tropical sources of gums

of tragacanth have risen considerably. In April that can provide renewable harvests in inter1979, 56,900 pounds of tragacanth- were im- cropping- strategies.

RUBBER

The first Hevea plantation set out in the Far

East yielded about 450 pounds dry rubber per

acre, while currently available clones yield

about 3,000 lbs/acre (<10 barrels). New chemical treatments applicable during tapping can

increase the figure to 6,000 lbs an improvement

of 13.3 times. These yields are available while

leaving the biomass intact. Other options might

be to grow whole plants for rubber extraction

between our upper story palms in the humid

tropics. The Petroleum Plant from which

Calvin once projected 50 barrels per acre could

be grown in the humid tropics as well as the

arid tropics. Detractors from Calvin say yields

would be closer to two barrels than 50 barrels

from the “Petroleum Plant.”

Calvin’s plant has received other headlines

under the name of gopherweed (Euphorbia

lathyris):

Melvin Calvin, Nobel Laureate in Chemistry, believes that the U.S. could produce

more than 2 million barrels a day of gopheroil

by 1995, The Department of Energy has

granted Calvin $250,000 to continue his research. Marvin Bagby, head of the Agriculture

Departments hydrocarbon-plant research

project, thinks that gopherweed is the leader

among 45 hydrocarbon-bearing plants that

have commercial promise (l).

Other species of Euphorbiaceae are better

adapted to and more productive in TMF than

the headliners Calvin promoted. The latex of

milkweeds could more appropriately be funnelled into rubber production. Be it spurge or

milkweed as hydrocarbon sources, the whole

plant would be thrown into the extraction vat,

with waxes, drugs, rubber, leaf-protein and

ethanol as feasible byproducts, all grown between our upper-story palm trees. Whether

Calvin gets 2, 10, 25, or 50 barrels/acre of petroleum or rubber from the “petroleum plant,”

gopherweed,” or “diesel plants,” I maintain

that the ethanol potential from the residues has

more energy content than what he obtains.

WAX CROPS

Waxes tend to be more frequently derived

from arid land plants than humid tropical species. But if the wax can be taken as byproduct,

like ethanol, following extraction of edible leaf

protein, humid tropical waxes might become

export money-makers. In the Chemical Marketing Report, one finds such waxes as the

temperate bayberry wax ($3.00/kg), the arid

lands candelilla wax ($3.()()/kg), and the subtropical carnauba wax ($4.00/kg). Yields rarely

exceed 1 percent of the plant, leaving 99 percent of the biomass as waste, or better as leafprotein or energy stock. One second-growth

“weed,” Calathea lutea, of the humid tropics,

could serve as source for food, wax, and biomass, as could members of the banana family.

The Calathea is easily propagated with as many

as 30,000 plants per hectare, yielding up to 70

pounds of wax per acre (23). I project that

would leave at least 29,700 pounds dry weight

of biomass in the vat for leaf protein and

ethanol production. This leaves the underground roots untapped. Aerial biomass yields

of 18 MT/ha might complement the edible-
239

rooted Calthea allouia (12 MT root/ha). Here other tropical plants, now all but unexploited,

we must remember that increases in the below- can yield food, fiber, fuel, and residue for the

ground yields will usually be compensated for energy farm of the humid tropics.

by losses in above-ground yields. Calathea and

Neither the Weed Science Society of America (WSSA) nor the oil companies have loudly

advocated the use of biomass as an energy

alternative in the past. I find it interesting that

there were five items in the October 1980

Newsletter of the WSSA hinting at plants as

a source of energy. Not necessarily believing

the figures myself, I summarize the estimates

from that WSSA newsletter:

●

●

●

●

●

It

Euphorbia: 50-125 bbls/ha,

Salsola: Arizona grant to make fuel from

the Russian thistle, a serious weed.

Asclepias: Improved variety of milkweed

could be source of biomass for synthetic

fuels and chemical feedstocks and a source

of fat, protein, oil and fiber. Lab estimate

of 60 bbls/ha crude oil.

Parthenium: Guayule provides a latex that

can be used for fuel, petrochemicals, and

rubbers.

Simmondsia: Speculation holds that

mature jojobas might produce the equivalent of 50 bbls/ha.

might be added that these optimistic estimates are based on marginal weed species in

areas of marginal inputs. But these are gross

energy outputs. Whether it would take 100 to

250 bbls/ha input to obtain the 50 to 125 bbls/ha

output is speculative. No one has analyzed the

energy inputs required to obtain these optiTROPICAL MOIST

Do energy farms produce more biomass than

the pristine moist forest produces? Those who

speak of highly productive TMF mention great

quantities of biomass. The climax forest is in

equilibrium, metabolizing as much as it synthesizes, so that although gross production may

mistic outputs. Research should provide these

numbers.

A more pessimistic note comes from Shell’s

“Ecolibrium” 9(4):1980:

According to the Gold Kist plant officials,

a good peanut crop can reap 142 gallons an

acre. And, unlike alcohol from grain, you

don’t have to distill peanuts to get oil, you just

squeeze them. The peanut oil costs about

$3.00 a gallon.

The 142 gallons an acre is equivalent to less

than 10 barrels per hectare.

This shows the wide disparity in figures used

by optimists and pessimists. Scientific research

should rectify this disparity.

It seems doubtful that the herbicide industry would encourage hand harvesting of weeds

and their conversion into alcohol and/or protein. I advocate just that in TMF countries with

unemployed hungry people. Almost all studies

show that hand weeding, though using human

labor, results in better yields than herbicide

controls. In some cultivated communities,

weeds constitute 8 to 27 percent of the shoot

biomass. This 25 percent might represent 2.5

MT on a tropical hectare, which could be

harvested and converted to fuel, at the same

time increasing the yield of the crops the weeds

were competing with.

FOREST BIOMASS

be extremely high, metabolism erases the

profit, leaving no net biomass increase. Do

agroecosystems produce more total biomass

than native forest ecosystems? I cannot say

categorically. The optimist figures on arid land

weeds yielding 50 to 125 barrels of oil per hec-
240

tare; the pessimist peanut prospectus lies at less

than 10 barrels per hectare. And we see estimates of up to 150 MT dry weight from some

tropical grasses under sewage irrigation. These

figures suggest to net that agroforestry is more

productive of biomass than the climax forest.

Estimates of the net primary production of

tropical forests (table 1) presented by UNESCO

(27) range from 9 to 32.

For comparison, I list in tables 2 through 4

some examples of yields of tropical crops that

can be grown in the lands occupied by the

forests mentioned in table 1. These data,

gathered from a variety of sources, do not consistently represent maximums, minimums, or

means, nor are such data available. Hence,

these numbers cannot be compared.

Today the biomass data bank at the Economic Botany Laboratory has close to a thousand entries in it. EBL is probably the best

equipped lab in the USDA to compare biomass

potential of different monocultural, polycultural,

and natural ecosystems. Consequently, I have

brought my computer to this workshop so you

can check it out on the spot. Incidentally, EBL

is probably the best equipped lab in the USDA

to give you the ecological amplitudes, nutritional analyses, and folk-medicinal attributes

of the little known economic plants of TMF,

some of which now extant, may soon be

extinct.

Table 2.—Tropical Root Crops (yields in MT/ha)

Arrowroot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Canna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Cassava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

GalIan , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Ginger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Groundnut (bambarra) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Leren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Lotus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Peanut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Sweet Potato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Taro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Turmeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Yambean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Yautia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 3.—Tropical Vegetables (yields in MT/ha)

Banana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 M

Cantaloupe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 M

Eggplant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......24 M

Garlic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......10 M

Okra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23M

Onion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29M

Pepper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14M

Pigeonpea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13M

Plantain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45M

Pumpkin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23M

Squash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23M

Tomato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22M

Tomatillo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36M

Yardlona bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 M

T

T

T

T

T

T

T

T

T

T

T

T

T

T

Watermelon . . . . . . . . . . . . . . . . . . . . . . . .. ... ... ...20MT

Table 1 .—Estimates of Net Primary Production (MT/ha/yr) in Tropical Forests

(UNESCO,1978)

Forest type Location Net production

Equatorial Yangambi, Zaire 32

Equatorial Khao Chong, Thailand 29

Secondary forest 40 years old Kade, Chana 24

Lowland dipterocarp Pasoh, Malaysia 22

Bamboo in monsoon forest Burma 20a

Subequatorial (Banco plateau) Ivory Coast 17

Bamboo in rain forest Burma 16a

Dry deciduous Varanasi India 16

Lower montane El Verde, Puerto Rico 16

Subequatorial (Yapo plateau) Ivory Coast 15

Seasonal rain Anguededou, coastal 13

Ivory Coast

Mangrove Puerto Rico 9

aEstlrnate does not include roots.
241

Table 4.—Tropical Spices Table 5 presents estimates of standing phytoTrees:

mass and net primary productivity for some

Allspice . . . . . . .

Bayrum tree . . .

Camphor . . . . . .

Cassia . . . . . . . .

Cinnamon . . . . .

Mace . . . . . . . . .

Pimenta dioica of the various vegetation types that might be

Pimenta racemosa expected in a tropical country. I believe, but

Cinnamomum camphora

Cinnamonmum aromaticum

Cinnamomum verum

Myristica fragrans

cannot prove, that intensively- managed agroecosystems used in places formerly occupied

by these forest types could produce two to five

Herbs and vines: times as much (except for the alluvial swamp

Lemon grass: Cymbopogon citratus 95 MT WM forests). I do not advocate replacement of for- Patchouli . . . . . . Pogostemon cablin 36 MT WM

Pepper, black . . Piper nigrum 6 MT (fr) est with agroecosystem, but better management

Vanilla . . . . . . . . Vanilla fragrans 1 MT (sol) of existing agroecosystems.

Vetiver . . . . . . . . Vetiveria zizaniodes 2.5 MT (rt)

Table 5.—Net Primary Productivity

Republic of Panama Republic of Panama

Phytomass NPP Phytomass NPP

MT/ha MT/ha MT/ha MT/ha

Tropical:

Humid tropics:

Bright Ferrallitic Evergreen . . . . .

Swamp Forest . . . . . . . . . . . . . . . .

Bogs . . . . . . . . . . . . . . . . . . . . . . . .

Monsoon Forest (Savanna) Red .

Monsoon (Dark Soil) . . . . . . . . . . .

Alluvial Forests . . . . . . . . . . . . . . .

Mangrove . . . . . . . . . . . . . . . . . . . .

Submontane Evergreen . . . . . . . .

Submontane Monsoon . . . . . . . . .

240

440

650

500

300

200

80

250

130

700

450

18

29

27

25

150

16

15

70

10

35

29

Semiarid tropics: 107 14

Xerophytic Forest (Ferrallitic) . . .

Grass Shrub Savanna

(Redbrown) . . . . . . . . . . . . . . . . .

Grass Shrub Savanna (Black) . . .

Grass Shrub Savanna

(Solonets) . . . . . . . . . . . . . . . . . .

Swamp Savanna . . . . . . . . . . . . . .

Alluvial Gallery . . . . . . . . . . . . . . .

Sub montane Xerophytic

Forest . . . . . . . . . . . . . . . . . . . . .

Sub montane Savanna . . . . . . . . .

250

40

30

20

60

200

200

40

17

12

11

7

14

60

15

12

Arid tropics: 7 2

Savanna (red-brown soils) . . . . . . 15 4

Alluvial Gallery . . . . . . . . . . . . . . . 150 40

Tropical Desert . . . . . . . . . . . . . . . 1.5 1

Psammonphyte on sand . . . . . . . 1.0 0.1

Desert (Coalessed soil) . . . . . . . . 1.0 0.2

Halophytes (solanchaks) . . . . . . . 1.0 0.1

Submontane Desert . . . . . . . . . . . 7.0 2.0

SOURCE Rodln and Brazil in Lieth. 1978

Subtropical: 133 14

Humid subtropical: 366 25

Bright ferrallitic Evergreen . . . . . 450 20

Rendaina Evergreen . . . . . . . . . . . 380 16

Prairie . . . . . . . . . . . . . . . . . . . . . . . 30 13

Swamp Forest . . . . . . . . . . . . . . . . 400 22

Meadow Bog . . . . . . . . . . . . . . . . . 200 130

Gallery Forest . . . . . . . . . . . . . . . . 250 40

Submontane Forest . . . . . . . . . . . 410 18

Semiarid subtropics: 99 14

Xerophytic Forests . . . . . . . . . . . . 170 16

Shrub-steppe (Gray-Brown soil) . 35 10

Shrub-steppe (Soloneta) . . . . . . . . 20 6

Shrub-steppe (Chernoaenoid) . . . 25 8

Psammophyte on sand. . . . . . . . . 20 5

Halophytes on Glanchak . . . . . . . 1.5 0.5

Gallery Forest . . . . . . . . . . . . . . . . 250 40

Submontane Forest . . . . . . . . . . . 120 13

Submontane Shrub-steppe . . . . . 99 14

Arid Subtropics: 14 7

Steppe desert (Serozem) . . . . . . . 12

Desert (sub-desert soil) . . . . . . . . 2

Psammonphytes on sand . . . . . . 3

Desert on takyrs . . . . . . . . . . . . . . 1

Halophyte on solonchak . . . . . . . 1

Gallery Forest . . . . . . . . . . . . . . . . 200

Submontane Desert (Serozem) . . 15

Submontane Desert (Desert

soil) . . . . . . . . . . . . . . . . . . . . . . . 3

10

1

0.1

0.5

0.2

90

12

1
.

242

1.

2.

3,

4.

5.

6.

7.

8.

9,

10.

11.

12.

13.

14.

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243

APPENDIX A-MAGIC MOUNTAIN: 2000 AD

by James A. Duke1

Twas the year 2000 on Magic Mountain, in the

Tropical Moist Forest Life Zone. None of the natives lived by the river anymore. After the last flood

they abandoned the last alluvial homesite and

moved up on top of Old Magic. This freed 100 of

their most productive hectares for agriculture. Untended slopes yield 30 MT/ha biomass each year

and the ridges where they now have their residences yield only 15. The bottomland they abandoned, fertilized by the floods that used to destroy

their homes periodically, yields 150 MT/ha. With

the help of leaf-protein extraction equipment, they

are getting 3 MT protein per bottomland hectare,

but the bulk of their bottomland biomass goes into

barrels, as ethanol. Lo and behold, they are getting

2 barrels of alcohol for every MT of biomass, using

firewood and residues to fuel the distillation, applying the ashes back to the farm. That’s big money

these days with ethanol at $100 a barrel, oil at $200.

Instead of sending them arms, powdered milk, peanut butter, and fertilizer, the United States sent

them LP (leaf protein) extractors, seeds (computerselected for this ecosystem), inoculum, stills, and

energy-producing portajohns.

Back in the 1990s some of the donors from the

overdeveloped countries realized that they could

nitrogenate more acres in the tropical backwoods

with a kilo of inoculated legume seed than a kilo

of nitrogen. Adventist Missionaries made their

point back in 1990 when they showed the natives

that they could get 10 to 20 times as much protein

from leaves if they did the conversion themselves

rather than let the cattle do it. So now, each hectare gives 3 tons of protein instead of 300 kg. As

a byproduct they have 100 barrels of ethanol, worth

$10,000. With their tropical climate, conducive to

higher productivity, they are now exporting ethanol

to the United States at $100 a barrel, while the

Arabs are having trouble finding buyers for their

oil at $200 a barrel, Instead of bananas at 5¢ a finger or coffee at one clam per kilo, the barge that

chugs up the river hauls ethanol out for those profligate spenders up in the United States who are still

sitting on their coal, to give them the energetic upper hand in case the Russians don’t get out of Poland, Afghanistan, Syria, and Iran (all of whose oil

had been burned up by saboteurs).

1

This is a fictional presentation created by Jim Duke for the

Office of Technology Assessment. It reflects the personal opinions of the author.

Neophytes to the Tropics thought that Magic

Mountain was Virgin Rain Forest, but those of us

in the know knew that nearly all of Magic Mountain was a multitiered, multiuse agroecosystem.

The Virgin Rain Forest was the next ridge over, by

Rocky Rapid River, i.e., Meyers Mountain. Rocky

Rapid River still provides cold clear water and the

electricity consumed on Magic Mountain. Meyers

Mountain, now a State Park, has several endemic

species that are being studied by the Natural Products people looking for better contraceptives and

cancer cures, Neophytes thought this was Virgin

Forest because it had more than 100 tree species

per hectare in at least two tiers. Palms and legumes

stuck out on top, with coffee and cacao in the lower

tiers of some, leguminous vines in others, lemongrass in others, yams in others, and zingiberacous

spices in the shade of others.

Finding forest on magic mountain surprised a lot

of armchair botanists, who, back in the 1980s predicted that the forest would be reduced to savannoid “red desert, ” But there were at least three

strikes against the “red desert” hypothesis: 1) the

Secretary of State convinced the President that

trees alleviated rather than aggravated the pollution

problem, so Americans were not running a “Down

With Trees” campaign, 2) natives had experienced

fewer bug and disease problems in their multitiered

agroecosystems than in their brief monocultural experiments, and 3) Americans had encouraged a forest “barrier” between the hoof-and-mouth disease

of Colombia and the Hamburger Farms in Central

America. The Neophytes thought that the Americans had taught the Indians this multitiered approach, but, in fact, the Indians had taught the

Americans. Even in temperate America, the Indians were intercropping when Columbus got here,

with beans fixing a little nitrogen to supplement

that left by the decaying fish they placed with their

C-4 corn seed. The C-3 pumpkins we used for our

Thanksgiving pie were used by the Indians as well.

But they knew that the cucurbits smothered weeds

long before young Dr. Duke discovered that cucurbits not only smothered the weeds, but allelochemically discouraged them.

The standard of living was almost as high on

Magic Mountain as it was in New York City. A few

hippies and naturalists thought it was even better.

It seems that in spite of marvelous inventions in

solar energy and energy conservation (halving the

consumption of individual appliances), the Amer-
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icans were still energy guzzlers. They now had electric nail clippers, electric combs, and electric toothpicks, and they had to recharge their electric cars

in offpeak hours with their palm oil and ethanolfueled generators. These were located on offshore

barges for the receipt of the barrels of ethanol and

palm oil flowing in from the neotropics. The gringo

still heats his home 6 months of the year to 72° F

and cools it 6 months of the year to 62° F, wearing

short sleeves in the wintertime around the house

and coat and tie during his air-conditioned summer, Jim Duke said you could fuel America with

sewage-irrigated biomass (if Americans went vegetarian) and Melvin Calvin said Arizona planted to

the petroleum plant (Euphorbia lathyris) could

satisfy the energy needs of the United States. Szego

and Kemp said you could do it with Btu bushes. But

America went on and paved its bottomlands, its

most productive farmland, which now sells at

$200,000 per hectare. No one really knew who was

right, Should they have believed Vergara and Pimentel who said that all the biomass in the United

States would support only 21/2 percent of their energy needs (while in 1980 concluded that biomass

already supplied 2 percent of U.S. energy consumption and could supply up to 20 percent by 2000),

or estimates of 10 percent (like Dugas came up within California), or those who said U.S. consumption

about equals the net annual storage of solar energy

in U.S. biomass, or Vietmeyer who accepts Calvin’s

suggestion that Arizona planted with petroleum

plants could fuel all the United States?

There aren’t too many animals on Magic Mountain and these are there more for biocontrol than

for meat. Sam Swindell has a bunch of pigs that are

rotated from one alluvial farm to another when the

nutgrass gets out of control. Seems that the nutgrass

was evolving just as fast as the herbicides. The last

generation of nutgrass herbicides reduced yields of

the crop by 50 percent. One group of hippies down

in Guyana had started making a beverage (Chufa

Cola) out of the nutgrass tubers, using the aerial biomass to generate the energy to run their operation.

But nutgrass got so rare that Chufa Cola is barely

competitive with Coca Cola anymore. Tommy Tucker intercrops turkeys with the legumes in his orchards, largely to control weeds as suggested by

Surguladze. Joe Groats has a few goats he stakes

out whenever the tropical Rubus the gringos introduced for nitrogen fixation gets out of hand.

The Rice-Azolla farmers let the geese help the

Azolla keep down the other weeds, while the grass

carp keeps down the Azolla and finishes off the zeolite-treated human refuse. They’re returning the residues from the essential oil still provided by AID

to the soil. But not just any residue anywhere.

Seems that back in 1985, Duke quit talking and

computerized all that data showing which plants

(and their residues) had positive effects like alfalfa

on crop yields and which had negative effects on

crops and weeds. Getting 3 MT of leaf protein from

alfalfa left a lot of spent residue around, even after

ethanol generation. Some of the triacontinol persisted even in these second generation residues,

enough to boost the yields of tomatoes by 10 percent, beans by 15 percent. With the computerized

systems analysis of the allelochemic insecticides

and fungicidal, as well as insect-regulatory aspects

of spent residues, there was real planning as to distribution of the allelopathic residues. The locals

went all out on Vietmeyer’s winged bean when they

found germplasm for seeds resistant to bruchids.

In the past, bruchids had consumed half of their

stored grain. This minor discovery had the effect

of doubling their yields of dry beans. Besides, they

got more nitrogen fixed than from the haricot bean,

and edible roots instead of poisonous roots.

Following up on McKell’s suggestion back in

1980, the Magic Mountaineers are using native species in their multitiered agroecosystems. Ipecac,

here, like ginseng to the north, only grows in the

shade. The natives are using byproducts from their

overstory tonka bean (coumarin producer Dipteryx

odorata) to stimulate rooting of new cuttings of

ipecac (Cephaelis ipecacuanha) as they harvest

roots of the older ipecac. Coumarin has been shown

to stimulate cuttings. Both these species, like shadeloving Piper dariense (used for toothache and fish

poison), are adapted to the cooler, higher slopes of

the Subtropical Montane Forests.

Gradually, tonka beans and oil-producing palms

and diesel trees are being introduced into the forest canopy as other species are felled or die. Magic

Mountaineers still don’t believe Calvin’s estimates

that they can get 125 barrels of “diesel” per hectare from their “diesel trees,” Copaifera spp., but

the resin is now selling for $10 a kilo and they can

harvest renewably a few hundred dollars worth a

year as they are harvesting ipecac, chicle, rubber,

ivory palm, quinine, and tonka beans from TMF

species over on Meyer’s Mountain. The nature lovers still prefer to gather their items renewably from

Meyer’s Mountain National Forest, while the homebodies are transplanting their species as moneymaking trees for the upper story of their agroforestry enterprises.

One of the Magic Mountaineers was raising crocodiles for the export market in his water chestnut

patch. If harvested young, they did not thrash

around too much and mess up his water chestnuts.
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However, the crocodiles did cut his fish and prawn

yield by 50 percent. He had trouble getting his hides

shipped directly to the United States Endangered

species authorities thought that cultivating crocodiles might endanger them in the wild. Another

Magic Mountaineer had been exporting butterflies

to the United States until the endangered species

people shut off the port. When the farmer abandoned his operation, two species went extinct, as

far as Magic Mountain was concerned. Perhaps

they still exist over on Meyer’s Mountain. Another

farmer was exporting amaranth seed to the U.S.

health food market until the regulators stopped

him, trying to avoid the importation of another

weed, Boy Scouts back in the United States quietly

filled this market by harvesting the amaranth seeds

from weedy cornfields.

On the gravelly limestone ridge, where the 4 m

annual rainfall quickly percolated through, some

of Felker’s Prosopis was doing well, but the natives

still preferred the tamarinds (Dialium, Tamarindus). They tend to vary their diets with other legumes, some mentioned by Felker; Cassia, Enterolobium, Hymenaea, Inga, Parkia, Prosopis, The

Prosopis yield of 12 MT/ha did not carry so much

weight here in the humid tropics as it did back on

the Chilean desert. One Chilean tree was reported

to yield at the rate of 12,700 kg fruit/ha, clearly a

good yield for the desert. But none of the Arid Tropical species compete well in the Humid Tropics and

vice versa,

A cord of mesquite will yield 30 million Btu compared to 25 million Btu from a ton of coal. Arizona

pinon-juniper yields 18 million Btu. And Magic

Mountaineers, still cooking with wood, were impressed by Vietmeyer’s statement that a hectare of

Leucaena would yield 10 times as much wood as

a well-managed pine plantation. The new fuel-efficient stoves the Swedes sent cut down on firewood

consumption, leaving them with less ash to fertilize their vegetable plots.

Some of the natives of Magic Mountain are not

fond of Leucaena, some of them even lamenting

that they had sown it for cover on the old landslide.

Its seeds were coming up everywhere, but it only

seems to be a real weed on the scarp. Nitrogen is,

after water, the most frequent limiting factor in the

Tropics, so Leucaena is viewed by some as a good

N source. Our Magic Mountaineers were impressed with Halliday’s statement that biological nitrogen fixation is “economically more sound and

environmentally more acceptable than nitrogen fertilizer use in agriculture” and his statistics; most

legumes fix 100 kg/ha, with Leucaena at 350 kg/ha,

and a potential of 800 kg/ha, Bill Liebhardt estimated Rhizobial Nitrogen fixation of pure strands

of Leucaena at 50 to 900 kg/ha. Still, certain government agencies sent millions of dollars worth of

N to the Third World, when appropriately inoculated legumes, cheaper to distribute, would have

done the job renewably. Efficiency was the excuse,

it takes less paperwork to spend $100 million at one

fell swoop than to make 100 separate million dollar investments.

The Chinese on the steep slopes of the wet side

of the mountain are intercropping azolla, rice, fish

and duck, in their intricately terraced rice paddies.

They were getting 15 MT rice per hectare as Clark

had reported in 1980. They were not getting 150

MT dry weight of Azolla as suggested by Clark, but

they had devised a system for raking off the bulk

of the Azolla every 10 days, after it doubled its biomass, and adding the biomass as a mulch to truck

gardens on the ferralsols. And they sell a lot of

azolla-fed fish and ducks off their rice terraces.

There is a persistent rumor that they are adding

night soil to their rice-azolla farms. But their terraced slopes are as productive as the alluvial bottomland,

Duke had always pushed the sunchoke (sunflower

X artichoke) as a biomass candidate for the temperate zone. The Chinese have squeezed it, like so

many other temperate species, into the humid tropics. Sunchoke accomplished some of the things enthusiasts for perennial corn were pushing back in

the 1980s. The roots are perennial and produce at

least 20 MT/ha edible root, leaving behind more

than enough to reseed itself and feed the last of the

wild peccaries. The annual sunflower parent would

have to be replanted but not the artichoke, it kept

coming back like a song, more like a weed. One

farmer who wishes to go into a different agrotechnology had to borrow the biocontrol pigs to clear

his land of sunchokes. Chinese learned to add the

raw artichoke to Chinese dishes to substitute for

water chestnut. It also turns out that the aerial biomass, cut three or four times a year, was good for

leaf protein and ethanol synthesis, Still this sunchoke did not yield as highly as some of the other

scenarios. Some of the Magic Mountaineers accused Johnny Sunchokeseed of introducing a weed

to the Tropics, Take it home, yankee.

Down in the swamps, the natives were producing closer to the lower than the upper predictions

of DOE back in 1980, 60 to 270 barrels of ethanol

per hectare from cattails. They were getting higher

yields from some of the native swamp species Acrostichum, Dieffenbachia, Gynerium, Erythrina,
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Montrichardia, Panicum and Pennisetum, species

that DOE had not even considered.

Before Panama took over the canal, U.S. germplasm specialists provided many useful palms for

trial on Magic Mountain. Finally the Orbignya from

Brazil was bearing seed, but the smuggled seed had

triggered an incident. Brazil broke relations with

Panama and the United States for collecting germplasm without a permit. Back in the 1980s at a congressional OTA workshop, Duke had wondered

about some of Schultes’ optimistic numbers for Orbignya martiana: trees reported to yield more than

a MT of fruit per year, 10 percent of which was kernel, 50 percent of which was oil for a yield of 40

kg oil per tree or a barrel of oil for every 4 trees,

accompanied by 40 kg protein per tree and perhaps

350 kg carbohydrate per tree. Duke feared these

projections were optimistic, like Melvin Calvin’s

estimates of gopherweed oil. Still he recommended

that OTA urge investigation of all palms because

many are adapted to marginal tropical habitats.

Some of the Magic Mountaineers did get yields almost that high with trees at 100 to 200 trees per hectare. Above this, per-tree yields dropped off. Still,

some of our Magic Mountaineers are getting 100

barrels of palm oil per hectare on marginal soils.

There was almost as much protein, and more carbohydrates for ethanol production.

Magic Mountaineers had really been impressed

with Mumpton’s zeolites. Zeolites increased their

fish biomass by 10 percent with 5 percent clinoptilolite, chicken feed efficiencies by 20 percent with

10 percent zeolite, beef profitability by 20 percent,

calf growth by 20 percent with 5 percent zeolite,

and swine growth by 25 to 30 percent with 5 percent clinoptilolite. They are using the clinoptilolite

to treat feces in their portajohns, lessening the odor.

Zeolites have made a big difference in farming,

too. The nitrogen is held longer after the zeolite is

applied to the soil. Near Panama City, the zeolites

were being imported from the interior to slowdown plant uptake of heavy metals in the sewage

sludge energy farms and in the purification of lowBtu methane produced by anaerobic fermentation

of beef excrement in the Hamburger Farm.

One oilpalm farmer with several dozen hectares

persisted in grazing beef and milk cows in the partial shade of his oil palms and coconuts. He heard

that he could increase his oil yields by 2 MT (about

6 barrels) per hectare simply by interplanting with

tropical kudzu and butterfly pea. He found that by

limited grazing, he could maintain his oil production. When asked what he was doing with his oil

and cattle he said, “Those carnivorous Americans

are still after our cheap hamburgers. Why at some

joints you can get a centigrammer (centigram hamburger) for $2.00. Some people hint that it’s laced

with palm protein, one of our byproducts here. And

the Americans are running their soybean farms

with diesel tractors fueled with palmoil. That is

considerably cheaper than soyoil.” “And what

about your milk?””Oh, we dehydrate that and send

it to the Americans too. ”

o