Emergency Tillage to Control Wind Erosion

DS-25-97, June 1997

Vern Hofman , Agricultural Engineer, retired
Dave Franzen, Soil Science Specialist

Causes of Wind Erosion

Bare, unprotected soil is extremely vulnerable to wind erosion. Erosion occurs with strong, turbulent winds blowing across a soil surface that is smooth, loose, dry and finely granulated. Very fine particles are suspended in the air stream and carried long distances. Slightly larger soil particles bounce or roll along the soil surface. Loose particles drift along, bombarding and dislodging still more particles with the same effect on clods or growing plants as sandblasting.

Unprotected soil surfaces occur with removal or covering of plant material after harvest of crops. Land that has been recently leveled is especially vulnerable to wind erosion, as is overgrazed rangeland. Removal of crop residue for feed, by tillage operations, or by burning can lead to serious wind erosion in problem areas. Marginal cropland areas that produce little residue in low rainfall regions contribute to conditions ideal for wind erosion.

Preventing Wind Erosion

The most effective wind erosion control measure is to maintain cover on the soil surface throughout the year. As a rule, residue cover adequate for wind erosion control also effectively controls water erosion. In North Dakota, land is most susceptible to wind erosion in the fall following harvest, over winter while the ground is frozen, and in the spring until seeded crops provide protective cover. This period also includes seasons when rapidly moving weather fronts, accompanied by high winds, are most common. Usually, wind erosion is the most serious in the spring because freeze-thaw cycles detach small soil particles from clods.

Direct seeding of the next year's crop into the previous year's residue is an excellent way of maintaining cover on the land. This will usually keep enough cover (30 percent or more) on the surface to prevent excessive erosion. Air seeders designed for heavy crop residue are available commercially and are extensively used in North Dakota for seeding. Also, some no-till drills are available which cause very little reduction in cover on the soil. Direct seeding is a way to save as much moisture as possible, complete tillage for weed control, warm the soil surface and place the seed in direct contact with moist soil. This will allow the crop to emerge as soon as possible. During dry spells when the stand is being established, this will allow the least amount of stored soil moisture loss as possible.

Increased surface roughness and clods left on the soil surface of cultivated land are only a temporary measure for wind erosion control. More permanent measures include establishing windbreaks, strip-cropping, or maintaining a year-around cover with plant residue or growing crops. Using stubble mulch, reduced tillage and other high residue management methods minimizes wind erosion.

Each tillage operation causes some soil moisture and crop residue loss. Need for weed control sometimes causes farmers to overtill fields until most of the residue is gone. Under dry soil conditions and in low rainfall areas, using sweep tillage tools and other reduced tillage practices can control most weeds without destroying a large amount of residue. However, under wet and cool conditions, weed control can be difficult with shallow subsurface tillage operations. If these conditions exist, most weeds can be controlled with a timely application of herbicide. Broadleaf weeds are often controlled with chemicals at a cost equal or less than tillage costs.

Strip-cropping, employing narrow strips, is an effective measure to control wind erosion. Strips should be at a right angle to prevailing winds and alternative strips must have a protective cover at all times. Width of strips depends on soil type, strip direction in relation to erosive wind direction and wind speed. Light sandy soils require narrower strips.

The best protection against wind erosion is a good protective cover of growing plants or residue. If no cover exists, farmers have no practical choice except emergency control by using tillage or mulching.

Temporary Control

Once soil drifting has started, it is difficult to stop damage. Prompt action may prevent a small blow spot from spreading to the entire field or other fields. Choosing the specific emergency measures depends on the seriousness of the erosion, susceptibility of the particular soil to erosion, and the duration of the needed protection.

Mulching -- Mulching is an effective tool for preventing erosion damage spread. Erosion usually starts at the same spot in fields each year. Protecting these sites may prevent more widespread damage. You can control wind erosion by mulching with manure or plant material such as straw, hay or corn stalks. About 2,300 to 2,500 pounds per acre of plant residue is needed to control areas which already have considerable wind erosion.

Residue can be spread by hand or manure spreader. Small rectangular bales of straw 15 to 20 feet apart and spread over about a 40-foot distance will give adequate residue coverage. A mulch treader or rotary hoe will help anchor and spread the residue uniformly. Straw residue can also be anchored with a disc run straight or by using a chisel plow with chisels spaced about 30 inches apart. Residue should be anchored at right angles to the prevailing winds. Heavy wet manure will usually hold without any additional anchoring.

Pounds of Residue to Control Wind Erosion on Various Soil Textures
Soil Texture	Pounds Residue
Sand	2,300
Loamy Sand	1,800
Sandy Loam	1,400
Loam/Sandy Clay Loam	1,150
Silt Loam/Clay Loam	1,050
Silty Clay Loam	950

Emergency tillage -- Emergency tillage is a last resort, though it can be effective if carried out properly. Emergency tillage provides a roughened, cloddy surface resistant to wind erosion. Surface roughness reduces the wind velocity at the surface and provides traps to catch the windblown soil particles. Ridges should be formed at right angles to prevailing winds.

Chisels are the most common tool used to roughen the soil and bring clods to the surface. In growing wheat, 2-inch chisels spaced 3 feet apart and operated 4 to 6 inches deep will usually bring sufficient clods to the surface to reduce wind erosion. This operation frequently saves the wheat. However, if the wheat is already destroyed and the ground is bare, a chisel with 4- to 6-inch wide sweeps spaced 30 inches apart and operated at a depth of 4 to 5 inches is more effective in stopping erosion. If erosion persists, a second chiseling operation may be needed.

Loose, sandy soils require a different type of tillage. More drastic or more frequent measures are needed and the resulting surface roughness is short lived. A moldboard lister spaced 40 to 50 inches apart may be necessary to obtain sufficient clods and surface roughness. The first listing should be shallow -- not more than 4 to 5 inches deep. Later listings, if necessary, should be progressively deeper. With a lister, one can split the middle or work in the old furrows.

Some Additional Pointers:

• A sufficient area upwind should be tilled -- not just the area presently blowing.
• The direction of emergency tillage should always be at a right angle to the wind for maximum protection.
• For row crops, it may be necessary to compromise by following the row pattern instead of the prevailing winds. If old crop stubble remains, the emergency tillage tool should run between rows, leaving as much upright stubble in the rows as possible.
• Tractor speed and tillage depth should be varied as needed to bring clods to the surface. The best, most effective clods come from moist soil. Slower travel speeds with tillage implements will build higher ridges and more protection.

Remember, prevention is the best method of controlling wind erosion. The best prevention is maintaining continuous protective cover of crop residue or growing plants on the soil surface.