Agroforestry VOLUME 27 ISSUE 1

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Creating Healthy Soils

The agricultural community is paying more attention to the importance of soil health in moving toward 

supporting our individual and collective ecological and economic goals. For decades soil conservation 

has largely focused on keeping soil in place, a very important step. More recently, increasing soil 

organic matter and biological activity have taken center stage. Agroforestry practices can help improve 

soil health in a variety of ways. Learn how people are improving soil health through agroforestry.
2 Inside Agroforestry ] Volume 27, Issue 1

NAC Director's Corner

A commentary on the status of agroforestry by Susan Stein, NAC Director

 As world populations rise and acres 

under agriculture increase, so does 

the need to keep our soils healthy 

and productive. It is exciting to 

learn about the different approaches that farmers are 

using to enhance soil health, including no-till, cover 

cropping, diverse rotations, and, as discussed here, 

agroforestry. Farmers in the United States and beyond 

are taking deliberate steps to improve soil health in 

order to increase crop yields or decrease input costs, as 

well as to enhance water quality and quantity, crop 

resilience, climate change adaptation, and wildlife 

habitat, among other priorities. 

Soil conservation has been viewed as an important 

benefit of agroforestry since the Dust Bowl days, with 

the establishment of windbreaks and shelterbelts. 

This benefit continues to be a focus of agroforestry 

research and adoption today. Both research and 

practice point to the compatibility of agroforestry with 

the other conservation practices mentioned above 

— cover crops, no or low till, and crop rotation. 

In fact, by providing year-round perennial vegetation, 

agroforestry can provide a risk-reducing backstop 

for those times of the year when annual crops 

and cover crops aren’t yet established or those 

years when extreme weather events prevent the 

establishment of other soil health practices.

This issue of "Inside Agroforestry" provides 

insights on how people are using agroforestry to 

meet their soil health needs and long-term goals. 

The National Agroforestry Center also has other 

publications available on soil health. Check out 

our soil health w soil health webpage at http://fs.usda.gov/

nac/topics/soil-health.php and our “Working 

Trees” information sheets: “Can alley cropping 

support soil health?” and “Can windbreaks 

benefit your soil health management system?”

New Faces at NAC

The USDA National Agroforestry Center welcomes two new staff members: Matthew Smith, research program lead, and 

Lord Ameyaw, NRCS agroforester, a shared position with the Nebraska Forest Service.

Matthew Smith 

Research Program Lead

Mathew.Smith4@usda.gov

Lord Ameyaw 

NRCS Agroforester

Lord.Ameyaw@usda.gov
Inside Agroforestry ] Volume 27, Issue 1 3

Soil Health on a Farm in Hawaii

Richard Straight, USDA National Agroforestry Center

Consultant Sam Knowlten discusses high carbon 

mulching during a training session at HAPI. 

Photo by Adam Lottig.

A core tenet of the Haiku Aina Permaculture Initiative (HAPI) on Maui is that renewal of the soil begins 

with a new relationship between people and the soil. 

Francis Spalluto explains that humans’ relationship with 

nature should be one of respect, harmony, and adherence 

to natural law, and not a relationship of people being 

outside of nature, manipulating it only for personal gain. 

However, Spalluto notes that the historical relationship 

with this 13.5-acre plot of land has been very different. 

Steep slopes, plenty of precipitation, year-long growing 

seasons, and annual cropping systems led to leached soils. 

In fact at HAPI, past agricultural uses of the land had left 

the soil leached of calcium, leaving high levels of aluminum 

near the surface and low levels of organic matter.

But that began to change when Jeffrey Bronfman acquired 

the property with the intent to develop a business on 

the north side of Maui and a vision to model diversity 

that could someday be applied at scale. His desire was 

to use restoration principles he had learned from an 

ongoing project in Brazil. With teaching and direction 

from Mauricio Hoffman, agroforestry specialist with 

Dagrofloresta, and hiring Spalluto to manage the property, 

Bronfman began the process of restoring this 13.5-acre 

parcel. The restoration process began with the soil.

The HAPI experience began in 2011 with the first project 

carried out on a portion of the land. In the following years, 

Hoffman traveled to HAPI twice a year. During the first 

visit each year, he would provide training and discuss issues 

and ideas for the next project. In his absence, Spalluto and 

interns would discuss and develop plans for the project. 

During the second trip, Hoffman would help fine tune the 

plan and direct its implementation. Different approaches 

were used throughout the HAPI land because of the 

many changes in soil, aspect, and existing plant cover.

Protecting the soil from rain drop impact and leaching 

were the primary concerns. Simple mulching seemed 

to stop the leaching process. “In order to feed the soil 

biome, we often put down 20 to 50 kinds of biomass 

onto the soil,” Spalluto said. “We are trying to move 

toward a fungal dominance in the soil biome.” Along 

with a diversity of biomass from various plant sources, 

biologic teas were often added to the soil. The mulch also 

shaded the soil and helped keep soil temperatures below 

73 degrees Fahrenheit. The goal of these activities was 

to enhance the biological activity in the soil, which can 

help plants access the minerals and nutrients in the soil.

Plant diversity and pruning were the driving forces of the 

system. About one-third of HAPI’s plants are for biomass, 

one-third for timber (to be utilized and sold), and one-third 

are food-producing plants (both above and below ground). 

The biomass plants are planted densely and are dropped and 

chopped onto the ground for mulch. HAPI often overplants 

bananas as biomass. They provide a water sugar supply to 

feed both macro-and micro-organisms. Some plants serve 

dual purposes, like an edible hibiscus. “It is one of the fastest 

growing plants we have,” Spalluto said. “It produces more 

than we can eat, so the rest of the plant becomes mulch.”

By using so many perennial food plants, the soil is host 

to living plants all year long. Trees are especially good for 

serving multiple uses (food, timber, and biomass) and have 

been an important contributor to the success of the systems. 

For example, one of the early sites was planted with bananas. 

The first plants were small and produced small racks, so 

they were cut down and incorporated into the soil. The 

subsequent banana planting was much more successful. 

Over time the soil color became much darker, and now 

more water is held in the rooting zone. An abundance of 

worms and evidence of fungal growth have also appeared. 

In 2016 HAPI began a multistory cropping system with help 

from the USDA Natural Resources Conservation Service. 

They removed a small stand of eucalyptus trees, along 

with about 200 invasive Christmas berry and fiddlewood 

trees, to create a clearing to grow food. Among the many 

crops planted were banana, papaya, cassava, sweet potato, 

taro, jackfruit, soursop, mango, and gliricidia. They also 

milled about 1,000 board feet of mango and 3,000 board 

feet of eucalyptus for sale and use on the property. 

When asked about how well these systems are accepted 

by other producers, Spalluto noted, “At first people are 

overwhelmed by what appears to be this random mass of green 

plants. But once they see that what we have is a vibrant system, 

not random at all, with no real pest problems, they become 

enthused. In fact, one large farmer in the area is considering 

adopting some of these methods onto 200 acres.” e
4 Inside Agroforestry ] Volume 27, Issue 1

Hazelnuts and Soil Health: Managing for 

Multiple Outcomes at My Brothers’ Farm

Kate MacFarland, USDA National Agroforestry Center

For Taylor Larson and his brothers, their goals for theirland and their land’s soil are intertwined. As they use 

ecological restoration and sustainable agriculture methods 

to transform their farm, they are creating systems and 

using practices that support many soil health principles.

Taylor manages My Brothers’ Farm with his two younger 

brothers, along with help from their partners and parents. Their 

main products are organic hazelnuts, apples, bison, and pigs. 

The 320-acre home farm has historically grown grass seed. 

They have been incrementally converting the farm to orchards 

and pastures. They also lease a 32-acre hazelnut orchard down 

the road and manage another 26-acre hazelnut orchard on a 

custom basis. In addition to 140 acres of pasture, they graze 

pigs in some of the farm’s oak stands and in the orchard. Their 

"big picture" goal has been to perennialize the landscape 

and move away from systems that require annual tillage.

My Brothers’ Farm includes a wide range of production 

systems that incorporate trees and shrubs to varying 

degrees. Along with the orchards, they also have 80 acres 

in riparian restoration projects. With support from the 

Oregon Watershed Enhancement Board and the Meyer 

Memorial Trust, as well as the USDA Conservation 

Reserve Enhancement Program, they have planted 

80,000 native trees and shrubs in these riparian areas.

While the perennialization effort supports a number of soil 

health principles, two systems of note demonstrate how 

the Larsons achieve soil health goals while supporting the 

operation in an agroforestry context. When starting to plant 

their hazelnut orchards, Taylor and his brothers knew they 

weren’t interested in using the typical method for harvesting 

hazelnuts in the Willamette Valley: waiting for the hazelnuts 

to ripen and fall to the ground, driving a machine through 

the orchard to blow and sweep the hazelnuts into a windrow, 

and driving a harvester over the pile to separate the nuts. This 

method requires dry conditions and a flat, well-manicured 

orchard floor without woody debris or vegetation.

This method, although common, was incompatible with 

the goals that My Brothers’ Farm had for soil health and 

biological diversity, so they had to find new ways to grow 

and harvest. They looked for options that allowed for 

more plant diversity, less soil disturbance, and kept the soil 

covered as much as possible. While they currently hand 

harvest, they are also working to learn more about shakeand-catch methods through a Western SARE Farmer/

Rancher grant. This shake-and-catch system is more 

compatible with their orchard management goals. 

My Brothers’ Farm has worked to create diverse orchard 

ecosystems that resemble woodlands, which incorporate diverse 

cover crop mixes, woodchips, and other elements to enhance the 

fungal biology of the system. This species diversity changes the 

orchard floor and would be incompatible with harvest methods 

that require vegetation to be short or manicured. My Brothers’ 

Farm also has integrated animals into its orchard system to 

enhance nutrient cycling, reduce fertilizer needs, and prevent 

My Brothers' Farm integrates hogs into their hazelnut 

orchards. Photo by Taylor Larson.
Inside Agroforestry ] Volume 27, Issue 1 5

pests. However, if you apply manure to an orchard and harvest 

off the ground, there is a very long return interval required 

between manure applications and harvesting. Harvesting 

directly from the tree allows for more flexibility in grazing. 

In its first year, the shake-and-catch system yielded mixed 

results. Hazelnuts ripen over three weeks, so identifying 

the correct timing was challenging. A big wind event 

the day before harvest also knocked many nuts to the 

ground. They are continuing to prototype the equipment 

to gain efficiency. That said, they have a higher tolerance 

for missed nuts because of their integration of pigs – 

livestock integration is another soil health principle. 

Taylor is also interested in increasing plant diversity within 

the orchard by adding apples, alders, cottonwoods, and 

other trees and shrubs. This diversity provides another 

challenge to the usual drop-and-sweep method of harvesting 

hazelnuts: apples or other crops in the windrows prevent 

using typical equipment. The brothers’ goal is to figure out 

how to manage diverse systems instead of monocultures, 

and do the homework up front on how to be successful.

In addition to investigating innovative harvesting techniques, 

Taylor has taken other measures to improve hazelnut production 

without sacrificing soil health. Grazing is an important tool in 

both enhancing ecological function (including soil health) and 

finding economic efficiencies. The farm’s interest in grazing 

oak woodlands is not just to gain the benefits expected from 

silvopasture systems or simply to have extra pasture available 

for the pigs. It also helps overcome an important economic 

threat to organic hazelnut production: the filbert worm.

The filbert worm lives part of its life in the acorns of Oregon 

white oak (Quercus garryana). This means that oak woodlands are 

often home for filbert worms that invade hazelnut orchards. As 

a result, the typical practice on hazelnut farms is to remove oak 

woodlands in the area. This is a conservation challenge because 

oak woodlands are one of the most threatened ecosystems in 

Oregon’s Willamette Valley; only 5% of the habitat remains 

today. Taylor and his research partners are studying whether 

grazing acorns will reduce filbert worm populations. 

Before grazing their oak woodlands, Taylor was a little worried 

about impacts to understory vegetation and soils. However, so 

far it’s been working great. “The pigs are only in the woodlands 

for a short period of time – right after acorn fall,” he said. 

Paddocks in the woodlands are usually about two acres, and 

the pigs are only in there for three or four days out of the entire 

year. The time of year that the pigs are in the woodlands is 

also fairly dry, so erosion, compaction, and wallowing are less 

of an issue. “They have such a strong preference for acorns 

(or hazelnuts in the orchards) that they don’t root,” he said. 

The pigs are monitored one to two times a day to see when 

they’ve made it through the available nuts. “There’s stiff 

competition for the nuts among the pigs,” Taylor said. ”They 

aren’t going after anything else until the nuts are gone.”

Still, to better understand potential understory impacts, My 

Brothers’ Farm worked with an undergraduate researcher 

from the University of Oregon to compare oak woodlands 

that were grazed and ungrazed. This research found no 

impact on the understory vegetation. While this project 

only collected one year of data, it provides a baseline for 

the future. My Brothers’ Farm plans to use the research 

design to look for changes in vegetation and soil health 

over time. They will continue collecting data this season. 

Research is ongoing as to whether filbert worm numbers 

and nut harvest are improved through grazing.

Using soil health principles to further the farm’s goals has been 

an effective approach for My Brothers’ Farm. By integrating 

concepts of ecological restoration with sustainable agriculture, 

they are able to meet their economic and ecological goals. e

Taylor Larson is testing a shake-and-catch 

harvesting system for the hazelnuts at My Brothers' 

Farm. This work is supported by a Western SARE 

Farmer/Rancher grant. Photo by Taylor Larson.
6 Inside Agroforestry ] Volume 27, Issue 1

Soil Nitrogen in Honeylocust Silvopasture 

Gabriel J. Pent, Virginia Tech University

John H. Fike, Virginia Tech University

Minimizing competitive interactions between trees and forages is often 

a primary consideration in silvopasture 

design. However, potential exists for 

facilitating beneficial interactions 

between the plants in a silvopasture. For 

example, some trees (e.g., black locust 

(Robinia pseudoacacia L.)) or forages (e.g., 

clovers (Trifolium spp.)) can convert 

atmospheric nitrogen into a biologically 

usable form that can promote the 

growth of other non-nitrogen fixing 

plants within the silvopasture.

Although honeylocust (Gleditsia triacanthos

L.) trees are in the legume family, they do 

not form nodules, which are swellings on 

the roots that typically host the rhizobial 

bacteria responsible for nitrogen fixation. 

Recent evidence suggests that some 

Rhizobium species may be associated 

with the honeylocust rhizosphere and 

support some level of nitrogen fixation 

(Ahrenhoerster et al., 2017). This is 

supported by the observation that foliar 

nitrogen concentrations of honeylocust 

trees are intermediate between levels 

found in nodulating legumes, such 

as black locust, and nonleguminous 

trees, such as buttonbush (Cephalanthus 

occidentalis L.) (Van Sambeek et al., 2008).

Well-functioning silvopasture systems 

can be designed and managed to take 

advantage of biological pathways that 

reduce the need for external inputs, such 

as fertilizers, but little research exists for 

leguminous trees in temperate zones. 

Whether these trees can fix atmospheric 

nitrogen to support both their growth 

and that of forages remains a question. 

A 25-year-old silvopasture research 

site in Blacksburg, Virginia, provides 

some indication that honeylocust trees 

are indeed associated with additional 

nitrogen in the soil, but the mechanism 

by which this happens is not clear.

At the Whitethorne Agroforestry 

Research and Demonstration Center at 

Kentland Farm, two types of silvopasture 

have been compared to open (treeless) 

pastures. Black walnut (Juglans nigra

L.) trees were planted in one set of 

paddocks for their nuts and timber, while 

honeylocust trees (cv. Millwood) were 

established in other paddocks for their 

nutritious pods. Both species are “warm 

season species” and have compound 

leaves with diffuse canopies. The trees 

were initially planted in 1995 with 40 feet 

between tree rows and 8 feet between 

trees within rows. Over time, trees have 

been thinned to a 40 by 40-foot spacing.

performed on all pastures throughout 

three summers (2014-2016). The 

main grass species were tall fescue 

(Schedonorus arundinaceous (Schreb.) 

Dumort.) and orchardgrass (Dactylis 

glomerata L.), although the black walnut 

silvopastures had less tall fescue and 

more orchardgrass compared to the 

other pastures. Forage legumes, such as 

red (T. pratense L.) and white (T. repens L.) 

clover, can provide substantial amounts 

of nitrogen to pastures when they are 

consumed by livestock and any excess 

nitrogen is excreted by the animal 

back onto the pasture. Honeylocust 

silvopastures had about twice as much 

clover as the open pastures in 2014 

and 2015 (table 2). The presence of 

the trees in these pastures markedly 

changed the species composition of 

the forage sward (figure 1), and it may 

be that the honeylocust trees provided 

an environment more suitable for the 

growth of clovers than open pastures 

or black walnut silvopastures.

In 2015, a small set of soil samples were 

collected from the silvopastures and open 

pasture. (Each system was replicated 

three times.) Soil samples were analyzed 

for inorganic nitrogen (i.e., nitrate and 

ammonium). Total inorganic nitrogen was 

nominally, but not statistically, greater in 

honeylocust silvopastures (table 1). It will 

be interesting to more thoroughly sample 

and analyze soils in these systems to 

truly determine if the honeylocust trees 

do, in fact, confer a positive nitrogen 

status to these silvopasture soils.

If these results were found to be 

statistically significant with additional 

sampling, another mechanism may be at 

work contributing to this phenomenon 

beyond the nitrogen fixation associated 

with honeylocust trees. Detailed forage 

species composition analyses were 

Regardless of the mechanism, 

honeylocust trees may provide more 

than just aboveground benefits to the 

silvopastoral system. Clovers have long 

been valued by livestock producers 

for their nutritional contributions to 

livestock and their nutrient contributions 

Table 1

Total

Pasture Nitrate Ammonium inorganic nitrogen

Black Walnut 20.9 2.2 23.2

Honeylocust 24.9 3.9 28.4

Open 

Honeylocust 17.9 4 22.0

P-value 0.4422 0.4103 0.5198

Soil nitrogen concentrations were not significantly different 

(P-value≥0.05) between treatments, but sample numbers were 

limited. Nitrate concentrations were numerically greatest in the 

honeylocust silvopastures.
Inside Agroforestry ] Volume 27, Issue 1 7

Table 2

Red clover White clover

Pasture 2014 2015 2016 2014 2015 2016

Black Walnut 4.8 1.1 4.7 4.9 3.8 2.1

Honeylocust 13.6 1.6 1.2 8.6 7.6 1.2

Open 7.3 0.7 2.6 4.4 3.1 1.3

SE* 1.1 1.1 1.1 0.9 0.9 0.9

*SE = standard error

The percent cover of clover declined in all pastures, but was greatest in the honeylocust 

silvopastures in 2014 (red clover and white clover; P-value<0.05) and 2015 (white clover; 

P-value<0.05). (SE = standard error.)

to pasture soils. Although more work is 

needed to fully understand and verify 

these relationships, honeylocust trees 

may prove to have similar “nitrifying” 

effects as clovers, or they may facilitate 

the establishment or growth of clovers 

in pastures — or both. Regardless, 

better understanding of the interactions 

among trees, forages, and livestock 

can lead to more deliberate facilitation 

of these factors to maximize the 

benefits derived from silvopastures.

Clover is evident in the 

honeylocust silvopastures 

(foreground) in this picture from 

June 2014, while it is less evident 

in the black walnut silvopasture 

paddocks (middle) and open 

pasture paddocks (background). 

Photo by Gabriel J. Pent.

Clover was abundant in the 

honeylocust silvopastures in 

2014. Photo by Gabriel J. Pent.

References:

Ahrenhoerster, C., G. Prasad, & B. 

Martinez-Vaz. 2017. Metagenomic 

analysis of bacterial communities in the 

rhizosphere of leguminous crops and 

trees. FASEB Journal 31(Suppl 1): 623.2.

Van Sambeek, J. W., NavarreteTindall, N. E., & Hunt, K. L. (2008, 

April). Growth and foliar nitrogen 

concentrations of interplanted 

native woody legumes and pecan. 

In Proceedings, 16th Central 

Hardwood Forest Conference. Gen. 

Tech. Rep. NRS-P-24. Newtown 

Square, PA: US Department of 

Agriculture, Forest Service, Northern 

Research Station (pp. 580-588).
8 Inside Agroforestry ] Volume 27, Issue 1

Inside Agroforestry VOLUME 27, ISSUE 1

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Upcoming Events

January 30, 2020

Center for Agroforestry Symposium: 

Value-Added Processing

Columbia, MO and online:

http://www.centerforagroforestry.

org/events/symposia.php

February 5-8, 2020

Pennsylvania Association for 

Sustainable Agriculture Conference

Lancaster, PA

For more information, visit: 

https://pasafarming.org/conference/

March 17-19, 2020

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and Best Practice Solutions

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For more information, email: 

swagroforestry@gmail.com

“Inside Agroforestry” is published by the USDA National 

Agroforestry Center: www.fs.usda.gov/nac

Phone: 402-437-5178 

Fax: 402-437-5712

• Susan Stein, NAC Director

• Matthew Smith, FS Research Lead (ext. 4021)

• Richard Straight, FS Lead Agroforester (ext. 4024)

• Lord Ameyaw, NRCS Agroforester (ext. 4012)

• Kate MacFarland, FS Agroforester

• Information Assistant - Vacant 

NAC Mission

The USDA National Agroforestry Center (NAC) is a partnership of the Forest Service (Research & Development and State & Private Forestry) 

and the Natural Resources Conservation Service. NAC’s staff is located at the University of Nebraska in Lincoln. NAC’s purpose is to accelerate 

the development and application of agroforestry technologies to attain more economically, environmentally, and socially sustainable land 

use systems by working with a national network of partners and cooperators to conduct research, develop technologies and tools, establish 

demonstrations, and provide useful information to natural resource professionals.

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