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TREATMENTS FOR FARMLAND

CONTAMINATED WITH

RADIOACTIVE MATERIAL

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Agriculture Handbook No. 395 nKÍ\0^i'^^A,:i--..^'-j^>:^

PROCüRf-'^"""

Agricultural Research Service /

UNITED STATES DEPARTMENT OF AGRÍCULTURE

Supported in part by the

UNITED STATES ATOMIC ENERGY COMMISSION

IN
CONTENTS

Page

Eeview of research _-^ 2

Removal of crops and crop residues 2

Eemoval of surface soil 3

Decontamination in cold weather ..^ 3

No-tillage management —- 4

Deep placement of contaminated soil . 4

Irrigation and leaching 5

Applications of lime, fertilizers, and other soil amendments 6

Feasibility of treatments for contaminated areas 6

Exposure of workers 8

Removal of crops and mulches 10

Removal of surface soil 11

Decontamination in cold w^eather 12

No-tillage management = 12

Deep placement of contaminated soil 12

Irrigation and leaching 13

Applications of lime, fertilizers, and other soil amendments 13

Alternatives to treating contaminated soil . 14

Conclusions 14

Literature cited 15

Washington, D.O. Issued June 1971

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 204Ö2 — Price 20 cents
TREATMENTS FOR FARMLAND CONTAMINATED

WITH RADIOACTIVE MATERIAL

By B. G, MENZEL and P. B, JAMES "^

This handbook presents information on the effectiveness and feasibility of various treatments

for farmland that has been contaminated with

radioactive material. Two kinds of treatments

are evaluated. The first kind, w^hich may be called

decontamination, includes methods of removing

radioactive material from farm.land. The second

kind includes methods of treating land to reduce

the uptake of radioactive materials by crops without decontaminating. Alternatives to treating

contaminated land are discussed to give a broader

perspective on the techniques of managing contaminated land.

There are many possible sources of radioactive

material that could contaminate farmland, ranging from widespread fallout from the explosion

of nuclear weapons to a very limited spread from

a transportation accident involving radioactive

material. The explosion of nuclear weapons could

result in contamination of thousands of square

miles. Contamination from a very severe reactor

accident might affect several hundred square

miles. In transportation accidents the contaminated area would probably be less than one acre.

A decision to treat the contaminated area will

require consideration of several complex factors,

including (a) the immediate and long-term hazard presented by the location and nature of the

radioactive material, (b) the hazard likely to remain after treatment, (c) other consequences of

the treatment, such as radiation exposures to the

persons carrying out the treatment and changes

in productivity of the treated land, and (d) the

availability of machinerj^ and manpower for

treatment. It may be unnecessary to treat contami-

^ Respectively, sou scientist, Soil and Water Conservation Research Division, and agricultural engineer, Agricultural Engineering Research Division, Agricultural Research Service, Beltsville, Md,, 20705, This study was

supported in part by the U.S. Atomic Energy Commission.

nated land if the radioactive material is shortlived and the area can be isolated until it decays.

If the area of contamination is large, the quantity of readily available resources might be lacking for desirable treatment of all areas at once.

In that case, careful judgment will be required

to recommend which areas should be treated first

and what methods should be used.

Since the choice of treatment may depend on

the objectives of treating any given area of contamination, it is necessary to define the objectives

clearly. These could be one or more of the following: (a) Preventing spread of the radioactive

material to other areas; (b) reducing the radiation hazard to persons who must live or work

in the area; and (c) reducing the entry of the

radioactive material into food products derived

from the contaminated land. Some treatments are

better suited to one objective than to another.

The urgency of treatment would likewise depend on the objectives. Immediate action might

be essential for preventing spread of radioactivity or reducing the radiation hazard, but not

for reducing the radioactivity in crops. Immediate action might increase greatly the radiation

exposures to the persons carrying out the treatment. In each case of contamination, the hazards

of immediate treatment should be balanced

against those of delaying or forgoing treatment.

In many cases, the main objective of treating

contaminated farmland would be to reduce the

entry of radioactive material into food products.

This would be true if relatively long-lived and

biologically active radionuclides, such as calcium-45, zinc-65, strontium-89, or strontium-90,

were present in appreciable quantities. In fallout from nuclear explosions the strontium radionuclides are very important (7).^ Since they

^ Italic numbers in parentheses refer to Literature

Cited, p. 15.
AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

often constitute the main hazard, we evaluated

the effectiveness of some treatments by the reduction in uptake of radiostrontium.

This bulletin describes the effectiveness and

feasibility of many possible treatments of contaminated land under various soil and crop conditions. This information should allow one to

choose a suitable treatment after the objectives

have been decided upon. This decision must take

into account the particular circumstances of each

instance of contamination.

REVIEW OF RESEARCH

There is widely scattered literature concerning

the treatment of radioactive contamination on

land. Some of the publications are not generally

available, and many of the pertinent results have

not been considered in relation to agricultural

areas. In this review, we have attempted to organize information about a wide variety of proposed treatments for contaminated agricultural

land. Eeferences are either to original work or to

critical reviews. The literature citations are selected to give pertinent results for various treatments.

The general problem of managing contaminated

agricultural land has been discussed briefly in

a previous publication (31), Experimental results

that were available in 1963 concerning the removal of crops, crop residues, and surface soil,

the deep placement of contaminated soil, and the

application of fertilizers and soil amendments

were reviewed. A Russian review of the problem

has been translated and is available from the U.S.

Department of Commerce (i). It discusses results with deep plowing, leaching, and the application of lime and fertilizer.

Many tests on the decontamination of land

areas that have been conducted by the U.S. Department of Defense are relevant to agricultural

decontamination. A performance summary of

these tests has been published (^^), and the application of the results in areas contaminated by

fallout has been considered {25), These tests are

particularly valuable for including techniques

of snow removal and the decontamination of

frozen and thawing soil that have not been studied elsewhere.

Removal of Crops and Crop Residues

A number of tests on the removal of contaminated crops and crop residues have been made

by the Agricultural Research Service at Beltsville, Md. (Í5, ^i, W). Radioactive material was

applied as a spray or as simulated dry fallout.

Measurements were made of the amount of radioactive material removed as various crops or crop

residues were removed from the land. The tests

included removal of standing crops at various

stages of maturity, removal of sod, and removal

of grass or straw mulch.

Removal of standing crops from a contaminated area removed only part of the radioactive

material, because much of it fell through the

vegetative cover to the ground. From one-fourth

to one-half of the radioactive material was usually carried on green crops removed by conventional types of forage-harvesting machinery

{21^ 22), Th.ese included a flail-type forage chopper, a direct-cut forage harvester, and a mower,

follow^ed by a side-delivery rake and windrow

pick-up baler. Crops removed by the forage chopper and harvester carried somewhat more contamination than those removed by mowûng, raking, and baling. Crops providing more complete

ground cover usually carried more of the radioactive material when they were removed. When

rain fell or sprinkler irrigation was used after

contamination and before crop removal, the

amounts of contamination removed with the crops

w^ere appreciably lower.

Harvester-thresher combines were used for harvesting and threshing mature rye and soybeans.

About one-tenth of the contamination was removed with the straw. The harvested grains contained less than 1 percent of the contamination

in rye and less than 0.1 percent in soybeans {18),

In these experiments, the radioactive material

was carried on tiny glass spheres (20-40 ¡x in

diam.) in order to simulate fallout occurring

under dry conditions.

Cutting and removing sod removed more than

90 percent of radioactive contamination previously sprayed on the surface. The high effective-
TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

ness resulted from the fact that the root mat

and some soil was removed with the sod. A road

grader was also effective in removing contaminated sod. Similar tests with sod-cutting machines have been conducted by the U.S. Department of Defense, with equally effective results

The effectiveness of decontamination by removing mulches differed greatly according to the

type of mulch and method of contaminating it.

Wheat-straw and bermudagrass mulches were

spread evenly on the ground surface at rates

of 2 to 5 tons per acre. Then they were contaminated and afterward removed from the plots

with a side-delivery rake. When radioactive solution was sprayed onto wheat-straw mulch, more

than 90 percent of the contamination was re=

moved with the mulch {21), With dry simulated fallout applied on bermudagrass mulch,

about 30 percent of the contamination was removed with a mulch of 2 tons per acre and

60 percent with a mulch of 5 tons per acre. The

poorer decontamination with dry fallout was attributed partly to inefficient raking of the fine,

short grass and partly to sifting of dry fallout

through the mulch.

Removal of Surface Soil

Many common types of earth-moving equipment have been used in decontamination tests.

These include graders, bulldozers, and rotary,

elevating, and pan-type scrapers. In tests reported by the Agricultural Kesearch Service {18^

21^ 22)^ from 80 to 90 percent of radioactive

surface contamination was usually removed when

2 inches of soil was removed. Although these

tests were conducted at different times, there appeared to be little difference in the effectiveness

of different kinds of scraping equipment.

Eoughness of the soil surface apparently had

some influence on the depth of cut necessary to

achieve this degree of decontamination. However,

the use of rollers to smooth the surface after

contamination and before scraping did not increase the effectiveness of decontamination. The

lack of significant results in this regard may

have been due to difficulties in controlling the

depth of cut, which varied with moisture content and looseness of the surface soil. The depth

of cut was more easily controlled with the rotary

and elevating scrapers and graders than -with

bulldozers and large pan-type scrapers.

Similar tests have been reported by the U.S.

Department of Defense {29). Tilled, hard, or

turf-covered soils in moist or dry condition w^ere

scraped with a pan-type scraper or with a grader

followed by the scraper to pick up windrows

left by the grader. The first grader cut, 2 inches

deep, removed about 90 percent of the surface

contamination from tilled soil, and after a second cut more than 99 percent of the initial contamination had been removed. Decontamination

was even more effective with hard or turf-covered

soil, or when the scraping was done with the pantype scraper making a cut from 2 to 4 inches

deep.

Street sweepers using vacuum or rotary brooms

have been studied for removal of fallout contamination from soil surfaces. A small vacuum

street sweeper was used to remove contamination

from a clipped meadow of Kentucky 31 fescue

and Ladino clover {18). About half of the con=

tamination could be removed by sweeping the

meadow twice, but little decontamination could

be effected by further sweeping. In later experiments at Beltsville, a rotating broom sweeper

with steel bristles removed about 75 percent of

the contamination from a moist soil with a thin

cover of fescue. A second sweeping gave almost

90 percent removal of contamination. A sweeper

with plastic bristles was less effective, apparently

because the plastic bristles did not cut as well

through vegetation.

Some attempts have been made to bind contamination in a coating of asphalt allowed to

harden on the contaminated surface. By peeling

off the asphalt coating, Schulz and others {33) removed 97 percent of a radioactive tracer that

had been sprinkled on the surface of small plots.

When used on a field scale {21) the asphalt emulsion did not improve decontamination because

mechanical scraping methods broke up the asphalt coating instead of peeling it from the

surface.

Decontamination in Cold Weather

The U.S. Army Nuclear Defense Laboratory

has tested methods for decontaminating various

surfaces under cold weather conditions {23),
AGRICULTURAL HANDBOOK 395. U.S. DEPT. OF AGRICULTURE

Treatments for frozen or thawing gToiind and

that covered with snow or ice are of possible

agricultural interest.

Mechanical snow removal was quite effective

in removing radioactivity from areas where a

fallout simulant had been spread on top of loose

snow. Under good operating conditions, a blade

snow plow or motor grader left less than 5 percent of the radioactivity, and a carryall scraper,

bulldozer, or rotary snowblower left less than

15 percent. More effort was required to reach the

same level of decontamination with warm, sticky

loose snow than with cold snow using either a

road grader or rotary snow blower.

Ice or frozen ground surface was effectively

decontaminated by sweeping. Hand sweeping left

less than 5 percent of the radioactivity on ice.

Mechanical sweeping left less than 15 percent on

a frozen ground surface. It made little difference

whether the temperature was just below freezing

or subzero.

Thawing ground was scra]3ed with a carryall

scraper, bulldozer, or motor grader, which left

less than 10 percent of the radioactivity after

one or two passes of the equipment. With additional passes it was possible to leave less than

one percent of the radioactivity on the ground.

About the same effort was required to scrape

either a thawing soil or a warm soil.

No-tillage Management

When radionuclides are left on the soil surface by not cultivating during the planting and

growth of crops, uptake by many crops is less

than would be obtained with normal cultivation.

For example, irrigated barley grown on a silt

loam soil in central Washington (4) took up

half as much radiostrontium when it was left

on the surface as when it was thoroughly mixed

through 4 inches of soil by cultivation (4). Similar trends were shown for wheat, barley, potatoes, and sugar beets grown in field experiments

on several widely varying soil types in England

(^4)- However, shallow-rooted crops such as ryegrass and kale took up twice as much radiostrontium when it was left on the surface as

when it was plowed 4 inches deep.

The relative uptake of radiostrontium from

no tillage, compared with normal cultivation, has

varied widely in our trials at the Agricultural

Research Center (unpublished data). In the notillage treatment, a fescue meadow was killed

with herbicide, and the crops were seeded 21^

or 5 inches deep with a sod planter. On two soil

types and with three crops grown in 1968, the

relative uptakes were roughly as follows (normal cultivation = 1.0) :

Soil type 'Wheat Com Bush Beans

Elkton silt loam 1.5 ^.5(1) 3

Sassafras sandy loam 2 0.2 M).6(0.3)

Although poor weed control was obtained and

crop growth w^as generally unsatisfactory, it appears that no-tillage management reduced radiostrontium uptake only on the sandy loam with

corn and beans. These crops tend to be deeper

rooted than wheat. The sandy loam is better

aerated and thus encourages deeper rooting than

the silt loam. This factor and the minimum disturbance of the soil surface during planting are

probabl)^ most important for reducing the uptake of radionuclides from the soil surface.

Deep Placement of Contaminated Soil

Field plot experiments have usually shown reductions in the uptake of radiostrontium when

it was placed deeper in the soil than it would

be with normal cultivation. Deep placement has

been accomplished in several experiments by excavating and refilling field plots. Placement of

strontium-89 in a layer 15 inches deep in a silt

loam soil at Beltsville, Md, did not reduce uptake

by soybeans compared with rotary tillage into

the top 6 inches of soil {17).

In other experiments, placement treatments

were combined factorially with lime, irrigation,

and potassium fertilizer treatments to test for

effects on root distribution that might increase

tlie benefit from deep placement. No such effects

were found. With various soil types and climatic

conditions in several states, the lowest strontium90 content of corn, soybean, oats, or wheat grain

with deep placement was about 40 percent of that

with normal plowing {8), The reduction in up-

^ Relative uptake values in parentheses are from planting 5 inches deep. Otherwise, uptake was the same from

both depths of planting.
TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

take from deep placement of strontimii-OO varied

considerably with different crops and locations.

In similar experiments carried out in Eussia,

the uptake of mixed fission products was compared from placements 30 and 60 or 70 cm. (12

and 24 or 28 in.) beneath the surface of a soddy

leached soil {10, pp. Wlf-WS). This type of soil

encourages shallow rooting of plants. Several

crops were grown in 3 or 4 successive years on

the same plots. The results with each crop varied

greatly from year to year. In general, the uptakes from the deeper placements were about

one-tenth of those from the shallow placement.

The reduction from deep placement was least

wdth oats and barley, intermediate with peas, and

greatest with vetch.

Field tests with varying depths of plowing to

reduce radiostrontium uptake have been reported

from England (^4) and Eussia (13). Deep plowing to 50 cm. (20 in.) on a leached chernozem

soil in Eussia reduced average uptake of strontium-90 by oats to 60 percent of the uptake after

disking 10 cm. (3.9 in.) deep. The uptake by

individual plants was highly variable, perhaps

because plowing tended to band the surfaceapplied strontium-90. In England, studies on

widely varying soil types showed that, in general, the deepest plowing (12 inches) resulted

in least uptake for shallow-rooted crops such as

ryegrass and a grass-clover pasture. However,

plowing depths to 12 inches had little effect on

the strontium-89 uptake by deep-rooted crops.

Various herbicides and inorganic chemicals

were used in greenhouse and field experiments

to limit uptake from a buried soil layer containing strontium-8ö {19), When sodium carbonate

was placed with the contaminated layer at the

rate of 10 tons per acre, the uptake of strontium-85 was less than one-tenth of that without

sodium carbonate, but crop yields were only

slightly reduced. Seven other inorganic chemicals

and seven herbicides did not reduce strontium-85

uptake as effectively and tended to give greater

yield reductions. But this limited experience

does not establish that sodium carbonate is the

best material to use as a root inhibitor. A longlasting, immobile material that will stop root

growth into the contaminated soil volume without reducing crop yields is needed.

In a subsequent experiment on an irrigated

silty clay loam in Texas, sodium carbonate at

the same rate of application was plowed to a

depth of 3 feet with contaminated surface soil

{20). A 36-inch moldboard plow with an attached grader blade was used to push a 2-inch

layer of topsoil into the furrow behind the moldboard. Nearly all (95 percent) of the contaminated surface soil was placed deeper than 24

inches beneath the plowed surface. The uptake

of strontium-85 by Sudan grass, sugarbeets, soybeans, and cabbage was from one-fourth to onehalf as much as with rotary tillage to a 6-inch

depth. When sodium carbonate was applied with

deep plowing, the uptake of strontium-85 w^as

only one-fifth as much as without sodium carbonate. On this rather tight, deep, fertile soil,

crop yields were increased markedly by deep

plowing. They were not measurably affected by

the application of sodium carbonate.

Heating contaminated soil to immobilize strontium-90 has been tried in conjunction with deep

placement {2). Uptake of strontium-90 with four

soil types that had been heated to 800° C. ranged

from one-eighth to one-half as much as with no

heating. In all cases, the contaminated soil was

placed 25 cm. (10 in.) deep for measuring plant

uptake. Extractability investigations suggested

that less uptake would be obtained if the soil

were heated to 1,000^ C. or higher.

Irrigation and Leaching

Controlled applications of w^ater to contaminated land might be used to leach radionuclides

out of the rooting zone of crops or to modify the

rooting depth of the crops. Until now, the reported attempts to use irrigation have had little

success toward either objective.

Leaching of radioactive strontium through soils

with water of dilute solutions is very slow. When

columns of various soils were leached with 30

inches of water, the maximum penetration of

strontium-89 was 4.3 inches {26). In the same experiment, leaching with 0.005 N CaCU increased

the penetration, but the average strontium-89

movement in one soil was only 3 inches after

application of 16.4 inches of solution. With the

other soils, more solution (up to 250 inches)

was required to give the same average strontium89 movement. Leaching with dilute solutions of
AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

complexing agents, such as ethylenediaminetetraacetic acid, has also shown little advantage for

removing radioactive strontium (27),

Acids and salts also have been applied to contaminated soil surfaces in order to increase the

movement of strontium-90 during leaching (33).

Hydrochloric acid and ferric chloride, at rates

of 15 and 22 tons per acre, respectively, were

most effective. When these treatments were followed by leaching with 5 feet of irrigation water,

about 20 percent of the strontium-90 remained in

the top foot of a fine sandy loam, and about 60

percent in the top foot of a loam. In addition

to being expensive and rather ineffective, the

latter two treatments would leave an infertile

soil.

A series of field experiments have been reported (8) in which irrigation was used in an

attempt to modify the uptake of strontium-90

from deep or shallow placement in the soil. No

modifying effect of irrigation could be detected.

Applications of Lime, Fertilizers,

and Other Soil Amendments

Soil amendments have been used to reduce

the uptake of radionuclides in different ways.

Calcium- and potassium-bearing materials provide cations that compete, respectively, with

strontium and cesium and thus reduce their entry into plants. Soluble phosphates added in

large amounts precipitate strontium so that less

of it may enter plants. Additions of materials

with a high cation exchange capacity, such as

peat, compost, or clay minerals, may also reduce

the amounts of radionuclides taken up by plants.

Many experiments have shown that applications of lime or gypsum to acid soils reduce

the uptake of radioactive strontium by plants

grown on these soils (i, 4j ^^? ^4? ^^5 ^4)- The

reduction depends upon increasing the available

calcium supply of the soil, so that little effect

is seen on soils already well supplied with calcium. Even on very acid soils, application of

lime or gypsum does not usually reduce uptake

of radiostrontium to less than one-third of the

uptake from the untreated soil.

Potassium fertilizers reduce the uptake of radioactive cesium from soils (/, 17). This is similar to the effect of lime on uptake of radioactive

strontium. Potassium also reduces the uptake

of radioactive strontium, but to a much smaller

degree than applications of lime or gypsum (i,

6,8).

Nitrogen fertilizers tend slightly to increase

the uptake of radioactive strontium and cesium

from soils (i).

Phosphate fertilizers added to soils at the

usual agronomic rates have shown little effect

on uptake of radionuclides (10^ pp, 197-200),

However, large additions of soluble phosphates

have resulted in very striking reduction in the

uptake of radioactive strontium (16). When diammonium or tripotassium phosphates were

added in amounts equivalent to the cation exchange capacity of the soil (4 to 12 metric tons

per hectare, or 2.2 to 6.5 avdp. tons per acre),

the uptake of radioactive strontium was reduced

to one-tenth of that without these materials.

The treatment was more effective in soils with a

higher pH value. At the higher rates of application, some difficulty with plant growth w^as

noted.

Materials with a high cation exchange capacity have reduced uptake of radioactive strontium when they were added to soils. Decomposing organic materials or compost have reduced uptake as much as a factor of five when

mixed with mineral soils in amounts greater than

2 parts per 100 of soil {10, pp, 170-180; 17),

Clay minerals such as kaolinite and montmorillonite have also reduced uptake of radioactive

strontium when added to a sand culture {11) or

soils {ß8).

FEASIBILITY OF TREATMENTS FOR CONTAMINATED AREAS

Treatments for land areas that are contaminated with radioactive materials will not be feasible unless the following requirements are met.

First, the treatment must make a significant reduction in the radiation hazard, either by removing the radioactive material or by reducing its

uptake into crops. Second, it must leave the land

in a productive state for agricultural use. Third,

equipment and materials for the treatment must

be available. Finally, the treatment should meet
TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL

the other requirements with no more than a reasonable effort. Treatments that are feasible in

one situation may not be in another.

In some cases it may be impractical, or even

impossible, to treat contaminated land because

of the condition of the land. An obvious limitation would exist if the radiation level w^ere

high enough to endanger workers in the field.

The existence of heavy vegetative or snow cover,

or of a frozen surface soil, would preclude the

use of most kinds of scraping equipment. Soil

characteristics such as surface roughness, shallowness of fertile soil, or the presence of stones

might greatly increase the effort needed to reach

the desired effectiveness, or even prevent some

treatments.

In order to compare the feasibility of various

treatments, their important characteristics are

given in tables 1, 2, 3, and 4. These characteristics include the effectiveness of the treatment,

the effort required for treatment and for disposal

of contaminated material, and the productivity of

treated land. Because soil and crop conditions

vary so widely, we attempt only the qualitative

evaluation of these characteristics. For example,

the effectiveness of a treatment is judged good

if test results generally showed more than 95

percent of surface contamination was removed,

poor if less than 75 percent was removed, and

fair if the amount removed WSLS intermediate.

Few data are available for estimating effort required for treatment or disposal, or predicting

the productivity of treated land. Evaluations of

these characteristics are based on existing data,

supplemented by qualitative observations of test

procedures and general agricultural experience.

We found that machinery must be operated

with care to obtain clean removal of contamiTABLE 1.—Ä comparison of 7nethods for removing contaminated crops or mulches from land

Type of

vegetation

Implement Removal of

radioactivity ^

BfCort reqniredFor

removal ^

For

disposal ^

Soybeans, 12" high ^ „ .. =.Mower __= Poor Poor __ Fair.

Soybeans, 12" high ___„_„___„__„_. Flail harvester Poor Fair Good.

Soybeans, full growth Flail harvester Poor Poor to fair Good.

Soybeans, full growth .__ Forage harvester Poor Poor to fair Good.

Soybeans, mature Combine, straw removed Poor Poor Fair.

Peseue-clover meadow Forage harvester Poor Poor to fair Good.

Sudan grass, 12" high Mower Poor Poor Fair.

Sudan grass, 12" high Flail harvester Poor Fair Good.

Rye, full growth . Mow, rake and bale Poor___ Poor Good.

Rye, full growth Forage harvester Poor Poor to fair Good.

Rye, mature ___ „ . Combine, straw^ removed ^.Poor Poor . Fair.

Wheat, mature Combine, straw removed Poor Poor Fair.

Corn, full growth , Forage harvester Poor Poor Fair.

Mulch, 5 tons wheat straw/acre _. Side-delivery rake Good Poor Fair.

Mulch, 5 tons bermudagrass hay/acre Rake and bale Poor______ Poor ____Good.

^Rating of removal of radioactivity: Good—>95 percent removal.

Fair—75 to 95 percent removal.

Poor—<;75 percent removal.

^ Rating of removal effort : Good— >5 acres per hour.

Fair—1 to 5 acres per hour.

Poor—<1 acre per hour,

^Rating of disposal effort: Good—additional loading and hauling effort minimal.

Fair—considerable effort in loading and hauling.

Poor—very great loading and hauling effort
8 AGEIOULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

nated soil or vegetation. This means that more

effort may be required than in normal operations

with the same types of machinery.

Exposure of Workers

It is doubtful whether the treatment of agricultural land would be so urgent as to justify

exposing workers to possibly disabling amounts

of radiation. Disabling illnesses are not likely

to occur if radiation doses to humans are limited to less than 100 rems (5, p. 591), Different

ways may be used to limit radiation doses, depending on whether intense local contamination

or widespread fallout are present.

In cases of localized contamination, it should

be possible to limit exposures by evacuating residents and using teams of workers to remove the

contamination. Each team might work only a

short time in areas of high radiation intensity.

Specially shielded or radio-controlled equipment could be brought to the contaminated area

to reduce further the exposure of workers. Concentrated effort would be needed to remove conTABLE 2.—A comparison of methods for remov ing soil surface contamination in loarm toeather

Effort required—

Condition of

surface

Implement Removal of

radioactivity ^

For

removal ^

For

disposal ^

Effect on

soil

productivity *

Bluegrass sod Sod cutter 12" wide Good to fair Poor Fair Good to fair.

Fescue-clover meadow Vaeuumized sweeper „_Poor ..Poor Good Good.

Fescue meadow Rotating-broom sweeper . Fair Fair Good Good.

Fescue-clover meadow Motor grader Fair Poor Poor Good to fair.

Fescue-clover 12" high Motor grader Good to fair Poor Poor Good to fair.

Soybean stubble Motor grader Fair Poor Poor Good to fair.

Soybean stubble —Constant-draft scraper î'air Poor Poor Good to fair.

Wheat stubble Vaeuumized sweeper Poor __Poor Good Good.

Corn stubble Motor grader Poor Poor Poor Good to fair.

Plowed Motor grader Fair Poor Poor Good to fair.

Plowed Bulldozer ___^ Good Poor Poor Good to fair.

Plowed Self-loading scraper, 1 cu. yd Fair to good . Poor Fair Good to fair.

Plowed Pan-type scraper, 8 cu. yd. Good Poor Fair Fair.

Disked Motor grader __ Fair to poor Poor Poor Good to fair.

Disked Rotary scraper Pair to good Poor Fair Good to fair.

Disked Elevating scraper Fair . Poor Fair Good to fair.

Seedbed _ Motor grader -Good to fair Poor .__Poor Good to fair.

Seedbed Bulldozer „__Good to fair Poor Poor Good to fair.

Seedbed Self-loading scraper _„_ Fair Poor Fair Good to fair.

Seedbed Pan-type scraper ._Good Poor Fair Fair.

^Rating of removal of radioactivity: Good—> 95 percent removal.

Pair—75-95 percent removal.

Poor—< 75 percent removal.

^Rating of removal effort: Good—> 5 acres per hour.

Fair—1 to 5 acres per hour.

Poor—< 1 acre per hour.

^ Rating of disposal effort : Good—additional loading and hauling effort minimal.

Fair—considerable effort in loading and hauling.

Poor—very great loading and hauling effort.

* Rating of effect on soil productivity : Good—Increases or does not change productivity.

Fair—^Reduces productivity < 20 percent.

Poor—Reduces productivity > 20 percent.
TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 9

tamination quickly or prevent its spreading to come primarily from external gamma radiation,

other areas. Fallout on sparsely populated farmland would

In case of widespread contamination after a contribute relatively little external gamma radinuclear attack, decontamination effort should be ation to the whole population. It would conconcentrated in densely populated areas. For tribute more radiation internally through the

the population as a whole, this would give the entry of strontium-90 and other fission prodgreatest reduction in radiation dose, which would ucts into the food chain. Thus, the probable purTABLE 3.—A GompaHson of methods for removing soil surface contamination in cold weather

Effort required— Effect on

Condition of Implement Removal of For For soil

surface radioactivity^ removal^ disposal productivity*

Loose snow 2 to 7" deep Motor grader „ Poor to good Fair Fair Good.

Do. . Carryall scraper „ Fair Fair Good Good.

Do. Bulldozer „_ .__.___ Fair Fair Fair Good.

Do. -Rotary snow blower Fair Poor Fair Good.

Loose snow 7 to 12" deep Snow plow .Good Good Poor Good.

Do. Motor grader Good Fair Poor Good.

Do. . Carryall scraper Fair _^ _»_Fair Fair Good.

Do. Rotary snow blower Poor to good Poor Poor Good.

Packed snow Motor grader Fair Fair to poor Fair Good.

Do. . Rotary-broom sweeper Fair _, Fair to poor Good Good.

Do, „_„ Vacuumized sweeper Poor to fair _^ Poor —Good Good.

Loose snow on Motor grader .-Poor to fair Poor Fair Good.

packed snow.

Frozen loose snow Snow plow Poor «_^ __Good Fair Good.

on packed snow.

Frozen ground Motor grader Poor Poor B^air Good.

Do. Rotary-broom sweeper Fair to good Poor to fair Good Good,

Do. Vacuumized sweeper Poor to fair Poor to fair Good „Good.

Thawing ground Motor grader Good Poor Poor Good to

fair.

Do. . Carryall sweeper . -Good Poor Fair Good to

fair.

Do. . Bulldozer . Good Poor Poor Good to

fair.

Do. Rotary-broom sweeper Poor Fair Good Good.

^Rating of removal of radioactivity: Good—> 95 percent removal.

Fair—75 to 95 percent removal.

Poor—<^ 75 percent removal.

^Rating of removal effort: Good—> 5 acres per hour.

Fair—1 to 5 acres per hour.

Poor—<; 1 acre per hour.

^ Rating of disposal effort : Good—additional loading and hauling effort minimal.

Fair—considerable effort in loading and hauling.

Poor—very great loading and hauling effort

^Rating of effect on soil productivity: Good—Increases or does not change productivity.

Fair—Reduces productivity < 20 percent.

Poor—Reduces productivity > 20 percent.
10 AGRICULTURAL HANDBOOK 895, U.S. DBPT. OF AGRICULTURE

pose of treating farmland after contamination

with widespread fallout w^ould be to reduce uptake of fission products by plants.

Removal of Crops and Mulches

The presence of a crop would affect the choice

of treatments for a contaminated area. A heavy

crop would intercept part of any contaminating

material that was deposited from the air, such

as fallout. Thus, removal of the crop would

partly decontaminate a land area. However, crop

removal would generally be inadequate. In some

cases, crops might have to be removed before

other, more effective treatments could be carried

out.

The feasibility ratings of methods for removing crops and mulches are summarized in table 1.

Most common types of crop-harvesting machinery

are compared on crops ranging from meadow to

full-grown corn.

With one exception, none of the methods removed more than 75 percent of simulated fallout

from a contaminated area. The exception is that

taking off a heavy mulch of wheat straw gave

good decontamination. This test was run with

liquid droplet contamination, which apparently

adhered to the straw. Dry fallout contamination

TABLE 4.—Ä comparison of soil management methods for reducing strontium-90 uptake from

contaminated soils.

Method Reduction in

gr-9Ô uptake ^

Effort

required ^

Effect on soil

productivity*

Minimum tiUage

Plowing, 7" deep __ ___

Plowing, 12" deep _

Plowing, 36'' deep

Plowing, 36'' deep with

root inhibition.

Irrigation

Leaching _ .

Lime application, 2 to 10

tons/acre.

Nitrogen fertilizers,

100# N/acre.

Phosphate fertilizers,

100# P/acre.

Potassium fertilizers,

500# K/acre.

Organic compost,

5 to 20 tons/acre.

Clay minerals,

5 to 20 tons/acre.

Ammonium or potassium

phosphates, 2 to 5 tons/acre.

Poor to fair . »Good

Poor ^____ Good

Poor .__»» ___-.__„«_ Fair .

Fair to poor . Poor

Good to fair _»«_— _ Poor

Poor _--._ Fair to good

Poor ^ —Fair ^-.

Poor to fair __„__=_ Good

Poor

Poor

Poor

Poor

Poor

.Good

.Good

.Good

.Fair

.Fair .

Fair =_-_» -__ - Fair

-Good to poor.

-Good.

-Good.

-Good to poor.

-Good to poor.

.Good.

-Poor.

-Good.

-Good.

-Good.

-Good.

-Good.

-Good to fair.

-Fair to poor.

^Rating of reduction in Sr-90 uptake: Good—> 95 percent reduction.

Fair—75 to 95 percent reduction.

Poor—< 75 percent reduction.

"* Rating of effort required : Good—Not significantly more than normal field practices.

Fair—Extra equipment, materials, or labor required.

Poor—Very great requirement of equipment, materials, or labor.

^ Rating of effect on soil productivity : Good—Increases or does not change productivity.

Fair—Reduces productivity < 20 percent.

Poor—Reduces productivity > 20 percent.
TREATMEÏNTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 11

might sift through the straw, resulting in poor

decontamination as was achieved with the bermudagrass hay mulch.

In view of the rather poor removal of radioactivity, crop removal would probably be used

only as a necessary preliminary to some soil treatment that would be more effective. For example,

a bulky crop would interfere with the loading of

scrapers, and cause excessive spillage from the

blades of graders or bulldozers. Such crops would

have to be removed before the land could be

decontaminated by scraping. Even then, roots

that could not be cut might decrease the effectiveness of scraping. Areas with trees probably

could not be decontaminated effectively.

Crop removal requires considerable time. The

most rapid methods will clear little more than

one acre per hour.

The problem of disposal of contaminated plant

material has received little attention. It consists

of reducing bulk of the material, hauling it, and

storing it in a safe manner. For the ratings in

table 1, it was considered that crop disposal

w^ould be easier than disposal of surface soil,

since the weight of material to be hauled would

be much less. Methods that remove and load the

plant material for hauling in one operation are

generally less time consuming than those that

do not. Disposal might be in pits or isolated

stacks or buildings.

The removal of crops and mulches would have

no detrimental effect on soil productivity.

Removal of Surface Soil

Decontamination of farmland is easier if the

contaminated surface soil can be removed before

the soil has been cultivated. Penetration of surface contamination into soil by leaching or erosion is minor compared to that in cultivation.

Thus, removal of a few centimeters of surface

soil will give a high degree of decontamination

unless the soil has been disturbed by cultivation

or the surface is so rough that some of the exposed soil is not i^emoved by shallow scraping.

Feasibility ratings are summarized in table 2

for various methods of removing unfrozen contaminated surface soil. The equipment ranges

from sweepers, which would remove a minimal

thickness of soil, to heavy earth-moving equipment. Soil conditions vary from a rough plowed

surface to light vegetative covers, which are not

expected to interfere with soil removal.

Scraping operations usually remove more than

T5 percent of the radioactive contamination on a

soil surface. The removal of radioactivity is

likely to be better from a smooth seedbed than

from a corn stubble or other rough soil surface.

Decontamination with scrapers is ineffective

on stony soils. Scrapers cannot cut at shallow

depths when large stones lie at the soil surface.

Even small stones, a few centimeters in diameter, may cause the scraper blade to roll over

considerable quantities of fine soil containing the

radioactive material. Thus, it would be necessary to scrape repeatedly, or to greater depth,

to achieve a high degree of decontamination.

Eough soil surfaces are common in pastures

and cultivated fields. Freshly plowed surfaces

and row-crop ridges often have differences in

elevation of several inches between the highest

and lowest surface. Land that has been bedded

for furrow irrigation presents even greater extremes. Since a greater amount of soil would have

to be removed for effective decontamination,

rough surface areas would require extra effort

for soil removal and disposal.

Measurements of the time required for soil removal and disposal were made in the U.S. Department of Defense tests {29) and iu some of

our unpublished studies. Bulldozers, road graders, and scrapers required more than one hour

of equipment time per acre of surface soil removed. It usually required more time to haul the

soil to a disposal pit or pile than it did to scrape

the surface.

Feasibility ratings for disposal (table 2) are

based on the mass of soil to be moved and the

loading effort required after decontamination.

After scraping with a motor grader or bulldozer,

the removed soil must be loaded for hauling to a

disposal area. The sweepers and other scrapers

are loaded during decontamination. The mass

of soil to be hauled is much greater with the

scrapers than with sweepers.

Studies on removal of surface soil have often

shown some loss in soil productivity (^, SIf),

The loss in productivity will vary according to

the depth of fertile soil originally present, and

the amount of soil removed. Eestoring the pro-
12 AGRICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE

ductivity of the treated area requires improvements in the physical structure and in the nutrient supply of the remaining soil. Additions

of lime, fertilizers, manure, and mulches help to

restore productivity.

Decontamination in Cold Weather

Subfreezing weather and the possibility of

snow cover exist for part of the year on large

acreages of farmland in the united States. In

cold weather, the removal of surface contamination would usually be more difficult than in warm

weather. If the soil surface w^ere frozen, it could

not be removed by scraping. Vacuum or sweeping machines might be useful unless the contaminant had been frozen into the surface.

A snow cover would present different problems,

depending on whether the contaminant was beneath it, mixed with it, or deposited on top of it.

In the first case, the snow cover would have to

be removed before the contaminant on the soil

surface could be treated. If additional hazard

w^ould be created by contaminant carried in the

runoff from melted snow, it might be desirable

to remove the snow cover in spite of the extra

effort required. In case the contaminant was in

or on top of the snow, the area could be decontaminated by removing only the snow. However,

the presence of crop residues in the snow cover

would interfere with snow removal and could

seriously reduce the effectiveness of decontamination.

Studies on the decontamination of land that

was frozen or covered with ice or snow have been

made by the U.S. Army Nuclear Defense Laboratory (ßS). Feasibility ratings derived from

their data are given in table 3 for methods that

may be applicable under some farmland conditions.

Several methods removed 75 percent or even

95 percent of the contaminant that had been

deposited on the snow or ground surface. Since

tests were carried out at varying temperatures

and textures of the snow, differences betw^een implements in effectiveness of removal of radioactivity may not be significant. The texture of

the snow, which varied with the recent temperature history, affected the removal of radioactivity.

The effort required for removal of radioactive

contaminants in cold weather was not excessive

under the conditions of the tests, which were

run on paved or smooth ground areas. On rough

land areas, the rate of travel would be much

slower. A longer time would be required for

decontamination in such circumstances, even assuming that the snow cover permitted effective

decontamination.

Ratings for disposal effort are based on the

weight of materials to be moved, and whether

or not an extra loading operation would be necessary. However, the disposal of contaminated

snow could be very difficult because of its great

bulk. It should be piled so that the contaminant

would not spread by wind, rain, or runoff from

melting snow. If one could let the snow melt

while retaining the contaminant, there would

be much less material for disposal.

No effect on soil productivity would be expected from snow removal, and removal of thawing ground should have an effect comparable to

that of removal of surface soil.

No-tillage Management

Where the soil surface contains most of the

radioactive contamination, its uptake by crops

could be lessened by growing deep-rooted crops

under conditions of no-tillage. The feasibility

of no-tillage management has been established

for economic production of certain crops (5),

but its possible usefulness as a treatment for contaminated land has not been established. It would

have the advantage of keeping the radioactive

material mostly on the surface, where it could

later be removed or otherwise treated. Estimated

feasibility ratings for no-tillage management are

given in table 4.

Deep Placement of Contaminated Soil

Contaminated surface soil may be buried by

plowing. With common farm tractors and plows,

the depth of plowing is limited to about 12 inches.
TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 13

Large moldboard or disk plows are available in

limited numbers. Some of these plows might not

give efficient burial of contaminated soil {15),

The uptake of radioactivity is much less w^hen

sodium carbonate is placed on the contaminated

soil before deep plowing.

Feasibility ratings for plowing treatments are

summarized in table 4. Plowing to 7 or 12 inches

deep could be carried out with common farm

plows, but it has little effect on uptake of radioactive strontium. If the hazard were from external gamma radiation from uptake of radioactivity into plants, plowing would reduce the

hazard very greatly. Plowing 36 inches deep requires special machinery, and the effects on strontium uptake may vary greatly with different soils

and crops. Only by using some material or technique to stop root growth into the contaminated

soil volume can a highly effective reduction in

uptake be achieved.

The effort required for plowing increases

sharply with increasing depth of plowing. Two

large crawler tractors were required to pull the

plow 36 inches deep in Pullman silty clay loam

{12), About one acre was plowed per hour of

operating time. Two tractor drivers and one man

at the controls of the plow were used. During

large field operations, the rear tractor driver

could possibly control the plow. However, it was

convenient to station an extra man on the front

tractor to warn its driver in case of equipment

breakdown. Thus, from 2 to 4 man-hours were

required per acre plowed.

Many soils would produce poor crops after

deep plowing. This could result from low fertility,

high acidity, soluble salts, or poor texture or

structure of the soil brought to the surface. Fertility and acidity problems could be corrected by

mixing fertilizers and lime into the new tppsoil.

Correcting poor soil structure is more difficult

since it may require large additions of sand, compost, or manure, and long periods of time for the

improvement of structure. These measures would

add to the already great effort of deep plowing.

Soils with deep, fertile subsoils would be most

likely to produce good crops after deep plowing.

Some impervious soils are benefited by improved

water infiltration after deep plowing {30^ 3§).

Irrigation and Leaching

The effectiveness, effort, and productivity ratings of irrigation and leaching treatments for

contaminated land are listed in table 4. Irrigation

does not reduce uptake of radioactive strontium.

Leaching removes little radioactive strontium

from the soil profile unless large quantities of

chemicals are added to increase the movement of

strontium. Therefore, irrigation and leaching

would not be feasible treatments for contaminated soils, even though little extra effort might

be needed in some irrigated areas to change the

frequency of irrigation or to leach with large

amounts of water. Soil productivity would be

lowered by leaching because essential nutrient

elements would be removed with the strontium.

Applications of Lime, Fertilizers,

and Other Soil Amendments

The effectiveness, effort, and productivity

ratings of various soil amendments are also given

in table 4. Unfortunately, none of the soil amendments are highly effective in reducing uptake of

radioactive strontium. Large applications of

ammonium or potassium phosphates and, on very

acid soils, the application of lime, will reduce the

uptake of radioactive strontium by 75 percent.

With lime, this is about the maximum reduction

that can be achieved, and it has been observed

only on soils that were initially very low in exchangeable calcium. With the phosphates, reductions in the range of 76 to 95 percent have

been observed on a number of soil types in the

greenhouse, but phosphates are much less readily

obtainable than lime, and detrimental effects on

plant growth have been observed. Field tests have

not been made with the phosphates.

Applications of soil amendments could be made

more easily than most other treatments for contaminated land. They would be limited mainly

by the availability of the materials, the effort

required to spread them on the land, and response

of the soil to the amendment. Optimum use of

lime and fertilizers for economic crop production

gives nearly as much reduction in radiostrontium

uptake as can be achieved with heavier applications of these materials.
14 AGRIOULTUBAL HANDBOOK 395, U.S. DBPT. OF AGRICULTURE

ALTERNATIVES TO TREATING CONTAMINATED SOIL

In the event of widespread radioactive contamination^ such as after a nuclear attack, much

of the contaminated farmland could be needed

for crop production before it could be treated.

Since the major hazard from farmland contamination arises from the entry of radionuclides,

especially strontium, into human food, some

alternatives to soil treatment have been suggested.

Among these are using contaminated land to

grow crops that contribute lesser amounts of

radionuclides to the human diet; using contaminated pastures for beef or mutton instead of

dairy production; and removing radionuclides

from milk and other products by treatment in

processing. The main characteristics and limitations of these alternatives are important in

determining the feasibility of treating contaminated soil.

Some crops would contribute little or no radioactive material to the human diet, even if they

were grown on highly contaminated soils. Fiber

crops, such as cotton and flax, are obvious examples. Sugar and oil crops would have most of

the radioactive materials removed from the refined products that are part of the human diet.

However, in case byproducts, such as cottonseed

meal or sugarbeet pulp, are fed to animals, the

indirect contribution of radionuclides to the human diet would have to be considered. Since corn

has one of the lowest mineral contents of any

grain, its content of radionuclides such as strontium is very low. Other essential food crops, especially those that contribute important minerals

to the diet, would have to be grown on land with

lesser amounts of contamination. Such crops

would include most fruits and vegetables.

Meat and eggs would contribute little radioactive strontium to the human diet. Thus, when

the most hazardous contaminating material was

strontium, using the land for beef, pork, mutton,

or poultry production would be advantageous.

This may not be true when other radionuclides

constitute the main hazard. For example, meat

contributes almost as much cesium-137 to the diet

as does milk (36).

Ion-exchange treatment of milk could reduce

its strontium-90 content perhaps more effectively

than decontamination or soil management treatments on hay and pasture land. In full-scale tests

of ion-exchange treatment in a milk-processing

plant, from 90 to 97 percent of the strontium-90

was removed from the milk (S5). Similar treatment may be possible with vegetable and fruit

juices and purees, but experimental tests have not

been made.

If the alternatives to treating contaminated

soil were used fully, land for nutritionally critical crops could be treated preferentially. Critical

crops might vary, depending on what crops were

normally produced in the highly contaminated

areas and the possibility of transporting substitutes from other areas. In subsequent years, more

land could be treated for producing critical crops.

In some situations, it might be possible to use

very highly contaminated land by treating the

soil and then using one of the above alternatives.

CONCLUSIONS

Land that has been contafininated with radioactive materials may be treated to remove the

contamdnant or to reduce its entry into food

products. Because these treatments usually require great effort, the objectives and feasibility

of various treatments need to be carefully evaluated for each contamination incident. Indiscriminate use of ineffective treatments could be very

costly without much reduction in the radiation

hazard to the population.

Treatment objectives may vary according to

the type and extent of contamination. If accidental contamination is confined to a limited area,

it may be removed to prevent its spread to other

areas. In such cases, an existing or potential

radiation hazard may be removed without undue

hazard to the decontamination workers. If the

contamination is widespread radioactive fallout,

it may be physically impossible to remove the

entire hazard, ^nevertheless, the proper choice of

treatments and land areas to be treated could

reduce significantly the entry of radionuclides

into the human food chain.

Scraping off the surface soil is the most ef-
TEEATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 15

fective method of removing a surface deposit of

radioactive material. More than 95 percent may

be removed if scraping is carefully done. Scraping should be done before the contaminated soil

has been cultivated. Even in favorable circumstances, about one hour of equipment time per

acre is required for soil removal and disposal.

Scraping rough or stony soil, or that covered by

coarse vegetation, is less effective and requires

more effort. Various kinds of scraping machinery

could be used, but those providing easy depth

control and self-loading reduce the effort of soil

removal and disposal. Scraping treatments may

also be effective for contaminated snow surfaces.

A TotaTy-hrush street sweeper removes more

than 75 percent of radioactive particles that have

heen deposited on a relatively hard^ smooth soil

surface. Two or three passages of the sweeper

remove additional contamination, and the amount

of soil to be disposed of is much smaller than

with scraping equipment. This treatment may

also be effective on ice or frozen soil surfaces.

Vegetative cover would intercept part of a

deposit of radioactive material^ and removing the

vegetation might remove up to half of the radioactive material, Kemoval of vegetation might be

a necessary preliminary to a more effective treatment such as scraping. Conventional forageharvesting machinery could be used to remove

vegetation.

Lime^ fertilisers or other amendments Tnay reduce the entry of radionuclides from, contaminated soils into crops. Use of lime and fertilizers

for optimum economic return often gives the best

reduction in radionuclide uptake. Hence, although

the reduced uptake may be 70 or 80 percent of

that with no treatment, it can be obtained at no

cost. Some other amendments, including large

applications of ammonium phosphate or sodium

carbonate (the latter plow^ed deeply with the

contaminated soil), may reduce radionuclide uptake much more effectively. However, the reduction in uptake is less than would be obtained by

scraping a suitable soil surface, and the treatments would probably be more costly than scraping.

Alternatives to decontamination and soil management treatments should he considered^ especially if the radioactive material is widespread,^

hecause of the great effort requifred for effective

treatment of contaminated land. Some alternatives are growing crops that take up small

amounts of radionuclides and removing radionuclides from milk and other products by treatment

during processing. The treatment of contaminated

land might then be limited to those areas needed

for the production of certain vegetable or fruit

crops.

LITERATURE CITED

(1) ALEKSAKHIN, R. M.

1965. [RADIOACTIVE CONTAMINATION OF SOIL AND

PLANTS]. Translated from Russian by the

U.S. Atomic Energy Oomn., AEC-tr-6631,

pp. 68-86.

(2) ANDERSEN, A. J.

1967. REDUCTION OF THE STRONTIUM-90 UPTAKE

BY BARLEY THROUGH HIGH-TEMPERATURE

TREATMENT AND DEEP PLACEMENT OP THE

CONTAMINATED SOIL LAYER. In Radioecological Concentration Processes, pp. 421-

427. Ed. by B. Aberg and F. P. Hungate,

Pergamon, Oxford.

(3) BACHTELL, M. A., WILLARD, C. J., and TAYLOR,

G. S.

1956. BUILDING FERTILITY IN EXPOSED SUBSOIL.

Ohio Agr. Expt. Sta. Res. Bui. 782, 35 pp.

(4) CLINE, J. F., and HUNGATE, F. P.

1956. EFFECT OF STRONTIUM AND CALCIUM IN SOIL

ON UPTAKE OP SR-90 BY BARLEY PLANTS.

U.S. Atomic Energy Comn. HW 41500:

81-84.

(5) DEERING, R. E.

1967. LOW-COST FARMING WITHOUT A MOLDBOARD.

Farm Quarterly 22 (1) : 92-95, 132-138.

(6) EVANS, E. J., and DEKKER, A. J.

1963. THE EFFECT OF POTASSIUM FERTILIZATION

ON THE STRONTIUM-90 CONTENT OF CROPS.

Canad. Jour. Soil Sei. 43: 309-315.

(7) FRERE, M. H., LARSON, K. H., MENZEL, R. G., and

others.

1963. THE BEHAVIOR OF RADIOACTIVE FALLOUT IN

SOILS AND PLANTS. Nati. Acad. Sei. Nati.

Res. Council Pub. 1092, Washington, D.O.,

32 pp.
16 AGRICULTURAL HANDBOOK 395. U.S. DEPT. OF AGRICULTURE

(g) , MENZEL, R. G., ROBERTS, H., JR. and others.

1967. REDUCTION IN THE PLANT UPTAKE OF SR-90

BY SOIL MANAGEMENT TREATMENTS. U.S.

Dept. Agr. Tech. Bui. 1378, 38 pp.

(9) GLASSTONE, S. (Ed.)

1962. THE EFFECTS OF NUCLEAR WEAPONS (reV.

ed.) U.S. Atomic Energy Comn., 730 pp.

(10) GULYAKIN, L V., and YUDINTSEVA, YE. V.

1962. [RADIOACTIVE FISSION PRODUCTS IN SOILS

AND PLANTS.] (In Russian.) Gosatomizdat. MOSCOW. 276 pp.

(11) __ YUDINTSEVA, E. V., and LEVINA, E. M.

1966. [EFFECT OF SOIL-FORMING MINERALS ON THE

AVAILABILITY OF SR-90 TO PLANTS.] (In

Russian.) Agrokhimiya, No. 3, pp. 111-

120.

(12) JAMES, P. E., and WILKINS, D. E.

1969. DEEP PLOWING: AN ENGINEERING APPRAISAL.

ASAE Paper No. 69-152. (Presented at

American Society of Agricultural Engineers, Lafayette, Ind., June 22-25, 1969).

(13) KACHANOVA, G. R.

1962. [ SR-90 UPTAKE FROM SOIL INTO PLANTS

GROWN UNDER FIELD CONDITIONS.] (In RUSsian) Izv. Timiryazev. S. Kh. Akad. 4:

105-110.

(14) KLECHKOVSKII, V. M., (Ed.)

1955. [ON THE BEHAVIOR OF RADIOACTIVE FISSION

PRODUCTS IN SOIL, THEIR ABSORPTION BY

PLANTS AND THEIR ACCUMULATION IN CROPS.]

Translated from Russian by the U.S.

Atomic Energy Comn., AEC-tr-2867,

227 pp.

(15) LYLES, LEON, HEILMAN, M. D., and THOMAS, J. R.

1963. SOIL-MIXING CHARACTERISTICS OF THREE

DEEP-TILLAGE PLOWS. Jour. Soil and Water

Conserv. 18: 150-151.

(16) MEL'NIKOVA, M. K,, and KUDELYA, A. D.

1966. [REACTION IN THE SOIL OF MICROQUANTITIES

OF STRONTIUM WITH PHOSPHATES OF ALKALI

METALS AND ITS UPTAKE BY PLANTS,] (In

Russian.) In [Radioactivity of Soils and

Its Determination] pp. 133-154, ed. by

I. N. Antipov-Karataev, V. I. Baranov,

and Yu. A. Polyakov, Vsesoyuz. Obshch.

Pochvoved. Akad. Nauk. SSR, Moscow.

(17) MENZEL, R. G.

1960. RADIOISOTOPES IN SOILS : EFFECTS OF AMENDMENTS ON AVAILABILITY. In "Radioisotopes in the Biosphere", pp. 37-46, ed. by

R. S. Caldecott and L. A. Snyder. Univ.

Minn. Center for Continuing Study.

(19) ECK, H. V., and CHAMPION, D. F.

(18)

1962. DECONTAMINATION OF SOILS.

Review 8 (2) : 8-12.

Plant Food

1967. EFFECT OF PLACEMENT DEPTH AND ROOTINHIBITING CHEMICALS ON UPTAKE OF STRONTIUM-85 BY FIELD CROPS. AgTOn. JOUr.

59: 70-72.

(20) ECK, H. V., JAMES, P. B., and WILKINS,

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