Agroforestry VOLUME 25 I SSUE 3

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pg.4 GIS and Remote 

Sensing for Kansas 

Public Outreach pg.6 Pacific Islands 

Multipurpose 

Windbreaks
2 Inside Agroforestry ] Volume 25, Issue 3

NAC Director's Corner

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

Interest in windbreak assessment, 

renovation and establishment is on the 

rise – and for good reason. When 

designed properly, windbreaks can buffer 

crops from extreme weather and maintain 

or increase crop yields. They can also keep 

soil on the ground, enhance pollinator habitat, produce special 

forest products and provide other sustainable agriculture 

benefits. But wait, there’s more – when planted as living snow 

fences, windbreaks improve highway safety, and, when planted 

around farmsteads, they reduce energy costs. 

In order to maximize the ability of farmers, ranchers and 

communities to access windbreak information and assistance, 

a team of forestry and agriculture professionals from across 

the Great Plains held a Great Plains Windbreak Action 

Plan workshop. Representatives of local, state, federal, 

and non-profit organizations met in Manhattan, Kansas 

to lay the foundation for the advancement of windbreak 

research, outreach, and assistance to support and enhance 

landowner interest in windbreak renovation, maintenance 

and establishment. Workshop participants focused on four 

areas: training for natural resource professionals; outreach 

and education for landowners/producers; programs and 

policies to support windbreaks; and critical research.

The high level of energy among participants at the Manhattan 

workshop, and the stories presented in this newsletter, are 

examples of a renewed recognition that, in the right place 

and at the right time, windbreaks can continue to fill an 

important niche in America’s sustainable agriculture tool kit.

Windbreaks in the Webinar Library

Many organizations use webinars to provide training, share information, and promote agroforestry. Because agroforestry is interdisciplinary, these are archived in many different places. The NAC website contains a webinar library with links to archived 

webinars hosted by its partners. The library has been updated to contain over 75 recorded webinars covering many agroforestry practices 

and has filtering and sorting capabilities to help users access the content in which they are most interested. Please contact Kate MacFarland 

at kdmacfarland@fs.fed.us for more information. 

Selected windbreak webinars: 

Multipurpose Buffers for Poultry Farms and 

Production, by Paul Patterson (2017), hosted by the 

Northeast/Mid-Atlantic Agroforestry Working Group

Snow Control Tools, by Dan Gullickson and David 

Smith (2015), hosted by the University of Minnesota

Shelterbelts, Beef Producers & Behaviors: 

Investigating an Alternative Approach Using Social 

Marketing, by Ryan Canart, Ian Shanghvi, William 

Ashton, and Blair English (2012), hosted by NAC

Pollinator-friendly Multi-functional Windbreak Design, 

by Mark Wonneck (2012), hosted by NAC

Windbreak Economics by Larry D. Godsey (2012), 

hosted by NAC

United States National Windbreak Perspective, by 

Bruce Wight (2012), hosted by NAC
Inside Agroforestry ] Volume 25, Issue 3 3

New Frontiers in Tree Inventory and 

Monitoring for the Central United States

Todd Kellerman, National Agroforestry Center

Dacia Meneguzzo, Northern Research Station, U.S. Forest Service

Greg Liknes, Northern Research Station, U.S. Forest Service

I

n response to the 

devastating dust storms 

of the mid-1930s, more 

than 30,000 shelterbelts were 

planted, covering over 18,000 

miles across the Central U.S. 

through the Prairie States 

Forestry Project/Shelterbelt 

Program (1935-1942). To 

date, this remains one of the 

largest environmental projects 

in U.S. history. The last 

official survey of the original 

shelterbelts planted during this 

program was conducted in 

1954, but the present state of 

windbreaks in the Great Plains 

region is largely unknown. 

Federal ground surveys of 

sample locations across the 

Central U.S. over the past 

60 years have provided 

some information about the 

windbreak resource. However, 

those surveys provide little detail 

about the spatial arrangement 

of trees on the landscape. In 

addition, datasets providing 

detailed spatial tree cover 

information on the Great Plains 

are severely lacking. Satellitebased land cover products are 

often collected at a spatial 

resolution too coarse (e.g. 30 

meters or roughly the size of the 

infield on a baseball diamond) 

to accurately depict small areas 

of tree cover, such as single 

tree canopies or linear features 

such as windbreaks. Surveys 

based on sample locations are 

generally summarized to a 

larger scale, such as a county, 

and may only provide useful 

information pertaining to larger 

tracts of wooded land. The 

Forest Inventory and Analysis 

(FIA) program of the U.S. 

Forest Service, which inventories 

all forest lands across all 

ownerships, defines forest land 

as having at least 10% live-tree 

canopy cover, and is at least 1.0-

acre in size and 120 feet wide. 

As a result, FIA inventories 

only include ‘forested’ areas, 

which may exclude as much as 

70% of the tree resource in the 

Great Plains region according 

to photo-interpreted estimates. 

In an effort to fill the abovementioned data gap, FIA and 

the National Agroforestry 

Center (NAC) have formed a 

targeted task team to develop 

methods for efficient mapping of 

trees outside forests (TOF) and 

for identifying and quantifying 

their ecosystem functions in 

agricultural landscapes. This 

mission is currently being 

carried out in two phases, across 

four states: North Dakota, 

South Dakota, Nebraska and 

Kansas. In Phase 1, a baseline 

of TOF is created by mapping 

tree cover from high-resolution 

aerial photography resulting 

in geospatial data that provide 

information about the area and 

location of tree cover. Using 

that baseline information, tree 

cover can then be monitored 

over time by repeated mapping. 

In Phase II, an ecosystem 

function is assigned to each 

contiguous patch of tree 

cover with an emphasis 

on identifying windbreaks 

and riparian corridors. 

When data from the two phases 

are combined, the resulting 

information will meet the 

needs of the natural resource 

agencies in the Great Plains and 

support the USDA Agroforestry 

Strategic Framework. 

Furthermore, this image-based 

inventory of tree resources will 

be consistent across the region, 

facilitating comparisons between 

states and counties. Because 

new imagery is collected every 

few years under the National 

Agriculture Imagery Program 

(NAIP), changes to the resource 

can be monitored over time. 

In a similar fashion to what 

the Kansas Forest Service did 

in 2008 (see article on page 4), 

the geospatial datasets resulting 

from this project can be used 

to identify priority areas for 

conservation tree plantings and 

increase the implementation of 

windbreak renovation practices. 

When this effort is fully 

implemented, about 1 trillion 

pixels over more than 300,000 

square miles in North Dakota, 

South Dakota, Nebraska, and 

Kansas will have been mapped. 

Data will describe the extent, 

location and function for nearly 

12 million acres of tree cover, 5 

million acres of which would be 

considered trees outside forests.

This project will 

describe the extent, 

location and 

function for nearly

12 million acres 

of tree cover, 

5 million acres 

of which would be 

considered trees 

outside forests.
4 Inside Agroforestry ] Volume 25, Issue 3

GIS and Remote Sensing for Kansas 

Windbreaks for Public Outreach

Bob Atchison, Kansas Forest Service, Kansas State University

Darci Paull, Kansas Forest Service, Kansas State University

I

dentifying priority landscapes for addressing natural 

resource concerns requires timely, accurate data. Such 

data can also help organizations make efficient use of 

limited resources to more effectively engage landowners. 

Unfortunately when it comes to windbreaks and other 

agroforestry practices, the data has often been missing. 

The U.S. Forest Service Northern Research Station 

(NRS) Forest Inventory and Analysis (FIA) program 

has done a great job tracking the size and condition of 

Kansas forestlands. However, agroforestry practices 

such as windbreaks and riparian forest buffers do not 

generally meet baseline definitions of “forestland” and 

are not inventoried. For this reason, the condition and 

size of windbreaks has not been adequately measured. 

Consequently, the 

common perception of 

a decline in windbreaks 

throughout the Great 

Plains is based on anecdotal 

evidence or limited and 

local inventories.

To fill the gap in data on 

trees outside of forests, State 

forestry agencies, the U.S. 

Forest Service, and others 

have worked together to 

develop efficient assessment 

tools. Some of these are 

described here, focusing 

on work in Kansas.

In 2008, the Great Plains Initiative (GPI I) was organized 

to assess trees outside of forests across the Great Plains. 

This assessment documented 5.1 million acres of trees 

outside of forests (TOF) across the Northern Great Plains 

(ND, SD, NE, and KS), including windbreaks, riparian 

forests and other treed resources. That’s almost as much 

area as the 6.4 million acres of forestland in these states. 

Testing Methods in Kansas

Using GIS and an object-based software (initially 

ENVI-Zoom 4.5) to analyze 4-band NAIP imagery, the 

Kansas Forest Service was able to identify windbreak 

locations and estimate their acreage. The software is 

“trained’ to classify objects into a variety of land use 

covers including windbreaks. Windbreak condition is 

estimated using a normalized difference vegetation index, 

NDVI, which measures live-green vegetation. When 

combined with ground truth sampling (comparing the 

accuracy of remote sensing with on-the-ground inventory) 

windbreaks are placed into one of three condition 

classes (good, fair or poor). The criteria used to assign 

condition classes is the same criteria used by NRCS 

Forestry Technical Note KS-11. Windbreaks in fair to 

poor condition were identified as a “resource concern” 

and are eligible for windbreak renovation through 

EQIP (Environmental Quality Incentives Program).

Next the Kansas Forest Service identified the owners 

of windbreaks in poor or fair condition, using data on 

land ownership and parcel data acquired from County 

Appraisers’ offices. Working through trusted County 

Conservation Districts, the Kansas Forest Service 

then mailed letters to landowners with windbreaks 

in fair or poor condition, inviting them to consider 

renovating their windbreaks through EQIP.

The most recent outreach efforts focused on Wallace, 

Logan and Gove counties in northwest Kansas. Nearly 

350 letters were sent to landowners with a response rate of 

over 10%. Due to this outreach, 44 properties were visited 

and 53 windbreaks were serviced, including creating 33 

renovation plans and 5 new windbreak establishment plans. 

Ninety-two percent of the windbreaks qualified for EQIP 

and 95% of the EQIP allocation for the Forestland Health 

category were spent in this 3-county area that same year.

Continued Efforts to Assess Trees 

Outside of Forests in 

Kansas and Beyond

While the approach described above has been effective 

in locating and estimating area of windbreaks, 

there were some challenges. The process used for 

estimating condition was effective, but required the 

use of “ground-truthed” windbreaks as references. 

The Kansas Forest Service is now using eCognition, 

a much more powerful object-based remote sensing 

software. Thanks to the U.S. Forest Service, NRS, 

FIA, and the National Agroforestry Center, the Kansas 

Forest Service just completed and published the rural 

tree canopy of Kansas using 2015 NAIP imagery 

...the condition 

and size of 

windbreaks 

has not been 

adequately 

measured.
Inside Agroforestry ] Volume 25, Issue 3 5

Windbreak 

Condition

Good

Fair

Poor

Wallace County, KS

Windbreaks in Wallace County, Kansas were identified and their condition was 

estimated using GIS and object-based software. This analysis helped identify 

windbreaks that need renovation. Staff and other resources targeted for windbreak 

renovation could then be directed to where they were most needed.

at a 1-meter resolution. This automated process was 

completed in a three-month period and can now be used 

as the initial analysis of windbreak location. Effectively 

assigning windbreak condition remains a challenge.

Continuing inventory of the Kansas tree canopy is part of a 

larger effort throughout the Northern Great Plains known 

as the Great Plains Initiative 2. The goal is to map the 

vitally important and often underreported ‘trees outside of 

forests’ including windbreaks and riparian forests. Another 

inventory advancement in the Great Plains is the use of 

linear intersect tool developed by the U.S. Forest Service 

Northern Research Station, Forest Inventory and Analysis 

and the National Agroforestry Center. This tool will help 

calculate the change in windbreak acreage over time by 

sampling windbreaks that intersect series of lines laid over 

the top of the satellite imagery. Two students are currently 

mapping windbreaks using this tool. The results will be a 

more accurate representation of windbreak location and 

acreage and how the resource has changed over time. 

Further GIS work is planned to train software to scan 

imagery and classify groups of trees as either windbreaks or 

riparian forests. This will improve our ability to inventory 

and assess the value and benefits of trees outside of forests. 

By using new GIS techniques and outreach, Kansas Forest 

Service and other Plains states are using limited resources 

more effectively to engage farmers on management of 

windbreaks to conserve soil and enjoy the other benefits 

windbreaks provide. This is especially important in an 

age of increased drought and temperature when no-till 

and residue management may not be as effective. 

For more information, see: 

Ghimire, K., Dulin, M.W., Atchison, R.L., Goodin, D, Hutchinson, J. (2014). Identification 

of windbreaks in Kansas using object-based image analysis, GIS techniques and 

field survey. Agroforestry Systems. 88. 1-11. 10.1007/s10457-014-9731-4. 
6 Inside Agroforestry ] Volume 25, Issue 3

Pacific Islands Multipurpose Windbreaks

Richard Straight, National Agroforestry Center

Michael Constantinides, NRCS Hawaii

"THEY'RE NOT MAKING 

ANY MORE LAND!"

The truth of this statement is amplified when living on an island. Farmers and ranchers living on the Pacific islands 

are acutely aware of both the need to produce and the necessity 

to conserve soil and water. Here are just three examples of how 

producers are accomplishing both by growing crops in their 

windbreaks in Hawaii and the U.S.-Affiliated Pacific Islands.

Photographs by Michael Constantinides

Sapanaria is one of the plants that the Ms. Bello planted to 

support native pollinators.

Ms. Bello chose many different species for the windbreak in 

order to provide a variety of benefits. In this image African 

mahogany, soursop and gliricidia can be seen.

Poohala Farms, LLC|Ms. Mary Bello

Wahiawa, Oahu

Six miles away from the town of Wahiawa, Oahu, Ms. Mary 

Bello and her family operate a goat dairy on approximately 100 

acres of land that was formerly in pineapples. Strong trade winds 

occur on this central plateau. Ms. Bello contacted the NRCS for 

assistance in designing and installing a windbreak along the two 

windward property boundaries, covering a distance of 3,250 feet.

The windbreak is comprised of four rows. Short-statured trees/

shrubs are in the windward row, medium height trees in the 

second row, tall trees in the third row, and medium or tall 

trees in the leeward row. The windbreak rows are divided into 

43 segments ranging from 200 to 1,750 feet long, with each 

segment containing only one species.

Ms. Bello sought to address a tremendous variety of 

resource concerns and create benefits in this highly 

diverse design:

Mitigate dust and odor drift from a neighboring 

commercial composting operation. The approach here 

included a wider design with four windbreak rows, coupled 

with plant selections that have a high leaf surface area and/

or species that produce pleasant scents.

Produce fodder from nitrogen fixing Gliricidia sepium trees 

planted in the first row. While this species can grow to be a 

medium sized tree, it is also very tolerant of complete crown 

removal and is easily maintained via coppice management. 

While serving as a short hedge in the first row, the tree tops 

are also removed once every few years to provide a cut-andcarry source of nutritious fodder for the dairy goats – they 

love it!

Enhance views by creating a visual barrier for the 

commercial operation on the windward side, and installing 

trees with beautiful flowers or bark along the leeward side, 

which also faces the farmstead.

Produce timber for the Bellos’ custom millwork operation. 

Inclusion of kou, koaia, kamani, cocobolo, three species of 

mahogany, pheasantwood, and four species of eucalyptus 

allows for a diversity of timber production.

Enhance native insect pollinator habitat. This was 

addressed by including ten native tree and shrub species.

Support managed hives on the farm by using several species 

known to provide desirable forage for honey bees.
Inside Agroforestry ] Volume 25, Issue 3 7

Mr. Juan Lizama 

Kagman, Saipan CNMI

Mr. Lizama manages a farm, on 

approximately 3.5 acres of land leased 

from the Division of Agriculture, 

Commonwealth of the Northern Mariana 

Islands, near the community of Kagman, 

in southeast Saipan. He grows a variety of 

crops including sweet corn, cucumbers, 

and peas.

The land has a relatively gently slope 

with substantial precipitation (Kagman 

receives about 80 inches of annual rainfall). 

However, as with many tropical islands, 

the year round heat and sunny conditions 

combine with steady trade winds to create 

high evapotranspiration potential and 

soil water loss. Consequently good water 

conservation practices are necessary. 

For many farmers, the risk of not having a 

lease renewed often acts as a deterrent for 

long-term investments such as windbreaks. 

However, the Division of Agriculture 

policy ensures that a farmer can keep their 

lease as long as the lease payments are kept 

current. As a result, Mr. Lizama decided to 

plant windbreaks. 

On the northeast side of the field is a 

two-row windbreak with mango in the 

windward row and citrus trees in the 

leeward. The mango trees can easily grow to 

30 or 40 feet tall which will provide wind 

protection for the entire field and provide 

additional fruit to sell at the farmers market. 

The southeast side of the field has two rows 

of mango trees planted on a 15’x15’ spacing. 

SN Farms, LLC|Mr. Andy Nguyen

Kunia, Oahu

Mr. Andy Nguyen of SN Farms, LLC 

has a diversified agriculture operation on 

approximately 10 acres of land in Kunia, 

Oahu. The farm is among thousands of 

acres in Central Oahu that were historically 

in pineapple cultivation. The climate is 

favorable for year-round cropping, but 

farming is challenged by high winds that 

buffet the farm throughout the year, 

limited natural rainfall limited to the point 

that acute drought conditions are common, 

and only intermittent access to irrigation.

Mr. Nguyen primarily grows Thai basil 

and taro for both leaf and corm (similar to 

a tuber); but also produces some vegetables 

such as eggplant. Through NRCS 

technical and financial assistance, Mr. 

Nguyen installed his primary/windward 

windbreak, comprised of banana trees, 

in 2012. Individual stump sprouts were 

planted along the 1,000 foot windbreak 

alignment, reaching a mature height of 

12-15 feet within 18 months while also 

rapidly expanding into clumps.

In 2014, Mr. Nguyen opted to add a 

second row of taller trees to his windbreak 

to extend the zone of leeward protection 

farther into his cropped fields. For this 

second row he chose primarily jackfruit, 

but also included occasional mango, 

avocado, lychee and citrus trees.

Here an important theme emerges – in 

addition to protecting his annual and 

perennial field crops from mechanical 

damage and minimizing evaporation losses 

of scarce irrigation water, Mr. Nguyen 

pursued an important secondary objective 

in maximizing the quantity and diversity 

of production from his small farm by 

selecting only fruit trees for his windbreak.

A ten-year old double row of mango helps protect sweet corn and a variety of other vegetable crops on Mr. Nyugen’s farm plot.

Newly planted cucurbits and sweet 

corn are protected from southeast 

trade winds by a double row 

windbreak of mango and citrus trees.

A windbreak consisting of banana and 

jackfruit protect a crop of taro on the 

island of Oahu.

Along with the banana windbreak in 

the background, Mr. Nyugen included 

a windbreak of citrus part way across 

the field to ensure wind protection 

and produce another crop.
8 Inside Agroforestry ] Volume 25, Issue 3

Vegetative Environmental Buffers for 

Mid-Atlantic Poultry Farms

Shawn Belt, NRCS Norman A. Berg National Plant Materials Center

Mid-Atlantic poultry producers are leading the country in implementing conservation practices that decrease 

environmental impacts and increase the efficiency of producing 

poultry meat and eggs for a growing population. 

More than ten years ago, producers began strategically planting 

trees, shrubs and grasses as vegetative environmental buffers 

(VEBs) around their farms. These buffers can improve the 

environment for poultry farms and their neighbors (Figure 1).

The NRCS National Plant Materials Center is expanding the 

variety of plants available to create successful VEBs. Forty 

species of new plants were tested from 2009 – 2015, including 

9 grasses, 27 deciduous shrubs/trees and 4 evergreens. Fifteen 

of the 40 different plants tested (38%) had survival percentages 

above 60% over a two year period (for grasses) or over a three 

year period (for trees and shrubs)(Table 1). Eight of the forty 

species tested (20%) had survival percentages below 60% and 

are intolerant of poultry farm emissions. Seventeen plants 

(43%) require further testing to determine emission tolerance.

Poultry producers are working with NRCS to adopt this 

agroforestry practice that benefits their operations while at 

the same time enhancing the environment. From 2014 – 2017 

Maryland and Delaware NRCS assisted producers with over 

$180,000 in cost share funds to install more than 100 VEBs. 

Figure 1

Vegetative 

Filter

Windbreak

Visual Screen

Shade

Animal 

Housing

Wind
Inside Agroforestry ] Volume 25, Issue 3 9

Vegetative Environmental Buffers have a number of functions

• Filter and trap dust, odor and viruses from poultry 

house exhaust fans.

• Reduce the solar heat loads on barns, thus lowering 

energy expenditures.

• Protect poultry from winter winds.

• Shelter buildings, feed bins, access roads, and 

doors from drifting snow.

• Slow and buffer water from poultry house roofs, 

roads and barnyards

• Filter nutrients and sediment.

• Produce renewable bedding, replacing pine 

shavings traditionally used for bedding, with 

switchgrass straw, chopped willow, or poplar 

shavings (the spent litter can be used as a 

renewable, carbon-neutral fuel to replace fossil fuels 

like propane). 

• Screen poultry management activities from 

neighbors.

• Beautify the barns and farm at the urban/rural 

interface. 

• Sequester carbon

Research and outreach on VEBs 

has been carried out by NRCS and 

a number of partners through the 

years. Such efforts include:

• The University of Delaware and the USDA Agricultural 

Research Service have worked to quantify VEB 

effectiveness through a NRCS Conservation Innovation 

Grant (CIG). 

• Penn State has conducted research on harvesting VEBs for 

biofuel, litter, and heat.

• The Delmarva Poultry Industry association has worked to 

encourage producer adoption of this practice. 

• USDA’s Natural Resources Conservation Service (NRCS) 

offers farmers cost share incentives to plant VEBs through 

the Environmental Quality Incentive Program (EQIP). 

However, the challenging conditions near poultry house 

exhaust fans hinder or kill some plants while stimulating 

growth in others. 

Table 1. Plants with best survival results

Common Name

Survival 

Percentage

Coastal panicgrass 100

Switchgrass var. Timber 100

Switchgrass var. Northwind 100

Switchgrass var. Thundercload 91

Prairie Cordgrass var. Southampton 100

Red Maple 100

Chinkapin var. Golden 100

Netleaf Hackberry 100

Common Hackberry 100

Dwarf Hackberry 100

Spreading Euonymus var. Manhattan 100

Honeylocust 100

Eastern Redcedar 75

Additional Information:

Plants Tolerant of Poultry Farm Emissions in the Chesapeake Bay Watershed

https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/mdpmcsr12671.pdf

Pennsylvania State University Vegetative Buffers

http://extension.psu.edu/animals/poultry/nutrient-management/vegetative-buffers
10 Inside Agroforestry ] Volume 25, Issue 3

In Brief...

A periodic summary of agroforestry-related journal articles

John S. Weedon, Stark (OH) Soil & Water Conservation District

Living Snows Fences 

Provide Quick Impact

Living snow fences (LSF) are windbreaks that capture 

snow before it blows or drifts onto roads. The economic, 

environmental, and aesthetic benefits of LSF are well 

documented, but their effectiveness throughout their life 

cycle is poorly understood. Researchers in New York State 

investigated 18 willow and conifer LSF sites to see how they 

functioned at different ages. Willows increased in height and 

decreased in porosity over time, while conifer height and 

porosity remained constant. However, these growth factors 

appear to make little difference on their effectiveness as LSF. 

Three years after planting, both willow and conifer LSF had 

capacities to trap more snow than the estimated quantity of 

blowing snow transported by wind towards the road. From 

four to eleven years after planting, the ratio of capacity to 

transported snow for both types of LSF jumped to at least 

3:1 and as much as 110:1, indicating a large capacity to 

handle massive snowfalls fairly quickly after establishment. 

Moreover, drift length was consistently less than 10 meters 

once the capacity to transported snow ratio hits 15:1, which 

occurred as soon as five years after planting. The shorter drift 

length should permit shorter setback distances from roads. 

Take Home Message: In less than four years after planting, 

willow and conifer LSF effectively capture drifting snow, 

and by the fifth year the drift length is less than 10 meters, 

which expands the number of locations suitable for LSFs.

Heavey JP, Volk TA. 2014. Living snow fences show 

potential for large storage capacity and reduced drift length 

shortly after planting. Agroforest Syst. 88:803-814.

Windbreaks Are Climate 

Smart For Crop Yields

Smart farmers consider predicting seasonal rainfall a 

fool’s errand, especially given the anticipated rainfall 

intensification under climate change. Instead, they hedge 

their bets by preparing for high and low amounts of 

precipitation. According to multiple scientific studies, 

one way they can do this is by planting windbreaks. 

One early study reported increased net crop yields for fields 

with windbreaks during years with little rain (Kort 1988). 

Although yields were lower adjacent to the tree rows, due to 

above and below ground competition for resources between 

trees and crops, there was much higher production in the 

sheltered zone (from two to twenty-four times tree height), 

resulting in a higher overall yield. The increased shelterbelt 

yields were attributed to creation of favorable microclimates 

from the reduction of wind speed and turbulent air mixing. 

Unchecked, both of these factors can cause tearing, 

shearing and other physical damage to plants. They can also 

reduce available soil moisture by increasing evaporation. 

More recent research in southern Québec indicated that 

windbreaks minimally impact yields during years of 

normal or above normal rainfall (Rivest and Vézina 2015). 

In this study, researchers investigated maize yields on the 

leeward side of mature (average age of 30) single tree row 

windbreaks on four sites over three growing seasons. In 

seven out of nine cases, the net effect of windbreaks on 

production was negligible with the yield variation in the 

shelterbelt zone generally decreasing in wetter years. 

Take Home Message: Windbreaks increase 

crop yields in parched seasons while doing 

no harm in normal and wet years.

Kort J. 1988. Benefits of windbreaks to field and forage 

crops. Agric Ecosyst Environ. 122(23):165-191.

Rivest D, Vézina A. 2015. Maize yield patterns on the leeward 

side of tree windbreaks are site-specific and depend on rainfall 

conditions in eastern Canada. Agroforest Syst. 89:237-246.
Inside Agroforestry ] Volume 25, Issue 3 11

Conserving the Dust Bowl:

The New Deal’s Prairie States 

Forestry Project

The Prairie States Forestry Project was an innovative approach to 

conservation initiated by President 

Franklin D. Roosevelt in 1933 with 

the goal of creating a “Great Wall of 

Trees” across the Great Plains. Sarah 

Thomas Karle and David Karle recently 

published a book describing this 

innovative time and the agroforestry 

efforts carried out throughout the 

region titled Conserving the Dust 

Bowl: The New Deal’s Prairie States 

Forestry Project, published by the 

Louisiana State University Press. 

This book describes the economic, 

environmental, and social factors 

that led to the Dust Bowl and Great 

Depression and how conservationfocused projects, such as the Prairie 

States Forestry Project were used to 

create jobs and reduce soil erosion. 

More Windbreak 

Resources from NAC

Are you interested in learning more about windbreaks or providing materials about windbreaks to your community? NAC has a variety of windbreak 

publications and other resources that you can read online or order for use at 

workshops and events. These include Working Trees Information Sheets titled 

“Can windbreaks do more than slow the wind?” and “Can windbreaks help 

with organic farming?”, as well as a new sheet titled “Can windbreaks benefit 

your soil health management system?” NAC also has a special 12 brochure 

series on windbreaks, covering everything from How Windbreaks Work to 

Windbreaks and Wildlife to Windbreaks for Fruit and Vegetable Crops. 

To learn more, visit https://nac.unl.edu/practices/windbreaks.htm
12 Inside Agroforestry ] Volume 25, Issue 3

Inside Agroforestry VOLUME 25, ISSUE 3

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Upcoming Events

November 3, 2017

Using the NTFP Calculator

Webinar

www.nemaagroforestry.org/webinars

November 15th, 2017

Agroforestry Technical Tour - SAF

Albuquerque, NM

http://bit.ly/2gIjHhG

November 28-29, 2017

Green Lands, Blue Waters

Madison, WI

https://greenlandsbluewaters.net

For more upcoming events, visit our website calendar: nac.unl.edu/events

“Inside Agroforestry” is published by the USDA National 

Agroforestry Center. 

Phone: 402-437-5178 

Fax: 402-437-5712

• Susan Stein, NAC Director

• Gary Bentrup FS Research Lead (ext. 4018)

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

• Kate MacFarland, FS Assistant Agroforester (ext. 4012)

• Joseph Banegas, Information Assistant/ 

 “Inside Agroforestry” Designer (ext. 4014)

https://nac.unl.edu

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, Lincoln, NE. 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.

USDA Non-Discrimination Policy

In accordance with Federal civil rights law and U.S. Department of 

Agriculture (USDA) civil rights regulations and policies, the USDA, 

its Agencies, offices, and employees, and institutions participating in 

or administering USDA programs are prohibited from discriminating 

based on race, color, national origin, religion, sex, gender identity 

(including gender expression), sexual orientation, disability, age, 

marital status, family/parental status, income derived from a public 

assistance program, political beliefs, or reprisal or retaliation for prior 

civil rights activity, in any program or activity conducted or funded by 

USDA (not all bases apply to all programs). Remedies and complaint 

filing deadlines vary by program or incident. 

Persons with disabilities who require alternative means of 

communication for program information (e.g., Braille, large print, 

audiotape, American Sign Language, etc.) should contact the 

responsible Agency or USDA’s TARGET Center at (202) 720-2600 

(voice and TTY) or contact USDA through the Federal Relay Service 

at (800) 877-8339. Additionally, program information may be made 

available in languages other than English.

To file a program discrimination complaint, complete the USDA 

Program Discrimination Complaint Form, AD-3027, found online 

at https://www.ascr.usda.gov/complaint_filing_cust.html and at any 

USDA office or write a letter addressed to USDA and provide in the 

letter all of the information requested in the form. To request a copy of 

the complaint form, call (866) 632-9992. Submit your completed form 

or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office 

of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, 

SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) 

email: program.intake@usda.gov.

USDA is an equal opportunity provider, employer, and lender.