Protecting Fields With Windbreaks
F-1054, August 1993
Vernon Quam, Forestry Specialist, NDSU Extension Service
Bruce Wight, National Windbreak Forester, USDA-Soil Conservation Service
Field windbreaks complement the farm operation by protecting crops and soil from wind
damage. Winds move up and over the windbreak producing an area of protection extending out
on the leeward side. The maximum area of protection extends from 15 to 20 times the height
of the windbreak. The area of protection occurs in the shape of a bell.
This area of protection can be extended when supplemented with another windbreak
planting perpendicular to the original planting (see Figure 1).
Figure 1. (14KB b&w
image) The zone of wind protection provided by A) a two row windbreak on
one side of the field and B) two two row windbreaks on two sides of the field. C) A cross
section view of wind protection where percentages of open field velocity are indicated by
distance from the windbreak.
The wind protection provided by windbreaks provides several benefits in cropland
production.
- Soils are protected from wind exposure and erosion. Soil is the single most
valuable natural resource to agriculture. When wind protection is provided,
evapo-transpiration is reduced, soil moisture is retained longer and soils tend to blow
less.
Table 1. Relative responsiveness of various crops to shelter*.
No. of Weighted mean
Crop Field Years yield increase
(%)
---------------------------------------------------------
Spring wheat 190 8
Winter wheat 131 23
Barley 30 25
Oats 48 6
Rye 39 19
Millet 18 44
Corn 209 12
Alfalfa 3 99
Hay 14 20
(mixed grasses
and legumes)
--------------------------------------------------------
* Based on 50 studies compiled by John Kort, Agriculture
Canada, Saskatchewan, Canada. Research locations were
in U.S.A. (North Dakota, South Dakota, Nebraska,
Kansas, Wyoming, Wisconsin), U.S.S.R., Denmark, Canada
(Manitoba, Saskatchewan), Germany, Argentina, Japan,
Italy, India, Netherlands, Pakistan, New Zealand,
Nigeria, Poland, 1932-1985.
- Crop protection is provided from winds that physically injure standing crops,
including lodging of the stem and sand blasting the crop. Sand blasting can wound the crop
and allow disease pests to infect. Evaporation is reduced from exposed soil, allowing more
moisture for crop uptake. Many crops have a very low tolerance level to wind and wind
blown soil. These crops include beans, soybeans, sugarbeets, potatoes, muskmelons, and
alfalfa.
- Crop production is increased in the protected zone. A unique area of protection
or a microclimate is created. The various changes in crop yield and microenvironment are
presented in Figure 2.
Figure 2. (11KB b&w image) The
generalized response of crop yield and microenvironment factors due to windspeed reduction
on windward and leeward side of field windbreaks.
Soil moisture (b), daytime air (c) and soil temperature (d) and relative humidity (e) are
higher near the windbreak and tapper off at a distance of 8 to 10 times the height of the
windbreak. Night air temperature (g), and evaporation (h), are lower ducts decreased
windspeeds (f) are lower near the windbreak. These factors contribute to the increase of
crop yield (a) in this protected zone except for the area next to the windbreak. About 1
to 2 times the windbreak height distance from the windbreak edge, crop yields are reduced
due to competition with tree roots. Yields level off at about 12 to 15 times the windbreak
height to average yield, but some wind protection continues out to 40 times height. Single
row belts will have a smaller protection zone. Total crop production is higher in a
protected field than one not protected.
Figure 3. (8KB b&w image) Often
crop yields are lowest next to a tree windbreak. A common mistake is to observe only this
area – the greatest gains are out a few more rods.
Windbreaks should be designed for protection from prevailing winds. Crops that have a high
moisture requirement may need protection from hot, dry winds during the growing season.
These sensitive crops, such as soybeans, produce higher yields with southern protection
during the growing season (Figure 4).
Figure 4. (18KB b&w image) Average
soybean yields in relation to windbreak protection at Ridgetown, Ontario, Canada (Baldwin
and Johnston, Ridgetown University 1984).
- Snow collection is important in designing your field windbreak. It is desirable
to provide adequate crop protection during the growing season yet remain open enough to
allow winter snows to spread evenly across the field. Spreading of collected snow will
allow closer cultivation to the windbreak planting in the spring.
Figure 5. (8KB b&w image) Snow
collection and spread of a single row windbreak planting of green ash. Light shaded area
represents a spacing between trees of 5 to 6 feet and dark shaded area represents spacing
between trees 9-14 feet.
- Field windbreaks are excellent wildlife habitat cover and travel lanes to and
from sources of water, feeding areas, and activity. Game and song birds make nests and
feed on tree seeds and fruits. Many of these birds feed on insects that are potential crop
pests.
Windbreak Design
There are two main designs used in field windbreaks -- single row or multirow designs
(two to three rows). The single row takes less land out of production and allows more snow
movement out over the field. The multirow (two to three rows) windbreak allows the use of
several tree or shrub species. This design gives more diversity in case loss to a pest
invasion similar to Dutch elm disease. Multirow windbreaks are denser than the single row
and provide more wind protection to crops.
Center Pivot Irrigation Systems
Field windbreaks decrease water evaporation from irrigation systems by decreasing
exposure to drying winds. This ensures more water delivery to the crop. Evaporation from
the crop is decreased within the area of wind protection. Taller trees in single or twin
row designs are used outside of the pivot system. Shrub rows can be used as needed under
the pivot arms. The corners are opportunities for wildlife planting or other harvestable
crops. (Christmas trees, fence posts, fruit trees and shrubs.)
Figure 6. (16KB b&w
image) Potential field windbreak design patterns A and B are dryland sites
and C and D are fields under center pivot irrigation. A and B have a twin row windbreak on
the field margins where the fall and winter prevailing winds in combination with a series
of single row belts perpendicular to most prevalent winds. B represents an option of
planting around a lake or slough area. Tree planting around wetland and river systems can
reduce soil and chemical runoff. C and D show a twin row wind break on the field margins
where the summer prevailing winds are present. Shrub rows can be used within the field to
extend wind protection and allow spaces for the wheel tracks to pass. Access to fields
should be designed downwind from protected areas.
Custom Designs
Field windbreaks can be designed to fit any size or shape of field or farming
operations. Utilizing the basic single and multirow designs will provide the benefits
desired for the site.
Figures 7-10 should help in determining the type of windbreak protection required for
certain crops. These figures show the area of crop protection from wind damage and
windblown soil along with yield increase due to protection. A list of crops with various
tolerances to wind injury and wind blown soil is provided. Your local Soil Conservation
District can assist you in designing, planning, and planting your field windbreaks. For
more information contact your county office of the NDSU Extension Service, USDA Soil
Conservation Service, or local Soil Conservation District.
Figure 7. (7KB b&w image)
Risk and yield guide for tolerant crops. Tolerant crops include: barley,
buckwheat, flax, millet, oats, rye and spring wheat.
(Source: USDA Soil Conservation Service)
Figure 8. (7KB b&w image)
Risk and yield guide for moderate tolerance crops. Moderate tolerance crops
include: corn, grain sorghum, sunflower and sweet corn.
(Source: USDA Soil Conservation Service)
Figure 9. (8KB b&w image)
Risk and yield guide for low tolerance crops. Low tolerance crops include:
apples, cherries, grapes, peaches, plums and pears.
(Source: USDA Soil Conservation Service)
Figure 10. (9KB b&w
image) Risk and yield guide for very low tolerance crops. Very low
tolerance crops include: alfalfa, asparagus, beans, table beets, sugarbeet, broccoli,
cabbage, carrots, celery, cucumbers, egg plant, flowers (seed production and cut green
peas, lettuce, muskmelons, onions, peppers, potatoes, soybeans, strawberries, tomatoes,
watermelons and young orchards (apples, sandcherries, plums and pears). (Source: USDA Soil Conservation Service)
F-1054, August 1993
NDSU Extension Service, North Dakota State University of Agriculture and Applied
Science, and U.S. Department of Agriculture cooperating. Sharon D. Anderson, Director,
Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June
30, 1914. We offer our programs and facilities to all persons regardless of race, color,
national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual
orientation; and are an equal opportunity employer.
This publication will be made available in alternative formats for people with
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