Wind erosion is a significant problem for Indiana soils having a sand, loamy-sand, sandy-loam, or muck-surface texture. Although not as extensive as water erosion, wind erosion can lower crop yields and reduce the productivity of the soil. In addition, wind erosion can damage standing crops by a process called "sand blasting."
Some farming methods increase the risk of wind erosion on susceptible soils, especially intensive cropping systems, including tillage methods that leave less than 30% residue cover. The failure to use cover crops or crop rotations can leave a field subject to long-term damage.
Another problem is increased field size. Removal of fences and similar windbreaks during the last 20 to 30 years to make for more efficient field operations has left many areas less protected. However, the most damaging practice is fall tillage with a moldboard or chisel plow that leaves little surface residue in the field. These wind-erodible soils remain unprotected until crop development late in the following spring.
Wind erosion removes finer particles from the soil. Clay and organic matter, the finest and lightest particles, hold on to nutrients and are important for holding moisture. Wind erosion can rob a sandy soil of the very components that are most needed for productivity. Researchers have shown that the windblown sediments can contain twice as much nitrogen and phosphorus and 20% more potassium than the soil left in place. The fertility can be replaced, but the loss of moisture retention due to removal of finer particles is permanent.
Wind erosion can reduce crop yields. Blowing sand can adversely affect young, tender seedlings-especially corn. Abrasive sand, propelled by strong winds, can actually wear away layers of tissue and eventually cut off seedlings. Wind erosion can reduce stands, stunt plant growth and reduce yields. Vegetables and melons are greatly affected in terms of yield, disease susceptibility, and quality.
Wind erosion helps spread weed seeds along with the other sediments. Weed seeds can be moved long distances from unprotected areas.
Wind erosion can help fill roadside and drainage ditches, which is one of the most costly aspects of both water and wind erosion to the general public. The fewer the windbreaks, or other traps, the more likely wind-blown sediments are to end up in ditches. Ditches that drain organic soils can be tilled very rapidly.
Wind erosion can create a safety hazard from the reduced visibility on roads and highways caused by airborne sediments. In Indiana, this problem has been particularly noticeable on I-65 north of Lafayette and along U.S. 41 in southwestern Indiana.
Figure 1 is a map showing the six soil resource areas of Indiana. Table 1 contains the acreage of wind-erodible soils in each area. The majority of the wind-erodible soils are located in Soil Resource Area A, which includes large areas of sandy deposits from glacial outwash as well as from wind-blown sand. Soil Resource Area D also has wind-erodible soils principally along the major rivers.
Table 2 contains a list of Indiana soil series and surface textures that are considered to be wind-erodible. Conservation practices are needed to prevent short- and long-term problems associated with wind erosion on these soils.
Wind erosion is produced by the three types of soil movement illustrated in Figure 2.
Saltation occurs with fine- to medium-size sand particles (0.1 to 0.5 mm). Wind blowing across the ground surface causes these particles to rotate at several hundred revolutions per second, which, in turn, causes them to jump 1-2 ft. into the air. Returning to the ground, they collide with other particles and break down soil aggregates. Saltation accounts for up to 80% of wind-erosion movement. The other forms of wind-erosion movement do not occur without it.
Suspension affects mineral particles of very fine sand, silt, clay (all less than 0.1 mm) and organic matter. Soil particles that move by saltation strike these finer particles and knock them into the air. The fine particles are light and easily carried by strong wind currents, often for miles before being deposited. Suspension-type movement is very damaging because the lost segment of the soil contains the most nutrients, even though the particles moved by suspension are a small percentage of the wind-eroded sediments.
Surface creep is the way in which the coarse sand-size particles (0.5 to 1.0 mm) are moved by wind. These are the largest particles affected by wind erosion. The factors that cause surface creep are much like those that cause saltation; however, the particles are too heavy to become airborne. They are rolled along the surface instead. This type of wind erosion can also damage vegetation.
Soil avalanching refers to the tendency for the number of soil particles in movement to increase downwind. The degree of damage grows with the increased size of an unprotected area. At the protected edge of a susceptible area, wind erosion is near zero, but when moving downwind, the number of particles of all sizes in movement increases almost like a chain reaction. Soil avalanching can be observed most clearly on sand dunes and to a lesser extent on bare fields. The results of soil avalanching can be observed afterwards by the smoothing of the eroded area and the deposition of sediments in an area that traps the wind-blown materials on the downwind side.
Cloddiness of surface. Soil clods and aggregates, particularly those resulting from tillage, help a soil resist the damaging effects of wind erosion. Clods or aggregates on the surface are too large to be moved by the wind, thereby protecting the component particles. But clods made up of sand, loamy sand, or sandy loam, which are the most wind-erodible soils, break down much more quickly than do soils of finer texture. Conversely, soils with more clay are held together in much stronger aggregates. Lack of strong aggregates is a major contributing cause to increased wind erosion from coarser soils.
Roughness of surface. An irregular surface from ridge-till or chisel tillage does much to reduce wind damage by absorbing and deflecting the erosive energy of the wind. An irregular surface can slow down and alter the movement of particles involved in saltation and soil creep.
The one disadvantage is that formation of ridges by tillage exposes the top of the ridge increasing the potential for erosion, particularly if the ridge is much higher than 5 in. This is not a great concern if crop residues are left in place as is the case with ridge-till.
Wind velocity. Soil particles do not start to blow until wind velocity reaches 12-13 mi. per hr. 1 ft. above the surface. The effectiveness of the wind to erode soil is related to the wind velocity. When wind velocity doubles, the effectiveness of the wind to erode is not doubled, but rather increased eight times.
Soil moisture. In general, wind erosion increases as soil moisture decreases. Mathematically stated, if soil moisture is reduced by half, then soil movement is increased by four times.
Field length. The efficiency of the wind to erode increases directly with distance from a protected edge as the wind moves across an unprotected field. Soil movement by wind reaches a limit for a given wind velocity with certain soil and roughness conditions. Most fields in the Midwest are too small to see what researchers believe to be the maximum effect of a wind. However, the recommendations for strip cropping provide clues as to the critical length (limited to 100 ft.) where soil movement by wind becomes important. The 100 ft. limit has been shown to be a critical distance on many soils. In another example, windbreaks are considered to provide effective protection downwind 10 to 12 times the height of the windbreaks. For trees approximately 40 ft. tall this would mean 400 to 500 ft., which appears to be on the upper limits of open fields.
Soil resource Total area Wind erodible area 1000 acres 1000 acres % --------------------------------------------------- A 3,957.0 1937.0 49 B 3,264.6 104.9 3 C 7,267.5 101.5 1 D 3,187.9 203.0 6 E 3,935.3 15.0 <1 F 1,535.7 28.2 2 ------------------------------------------ Total 23,148.0 2,389.6 10
Vegetative/residue cover. Cover on the surface is the most effective way to control wind erosion. There are three aspects of cover that can be used to evaluate effectiveness. They are quantity, kind, and orientation. In general, the more residue, the less soil is eroded by wind. Although a variety of factors must be considered, a 30% cover is probably a good estimate of the amount needed for adequate protection. Crop residues have been shown to have different abilities to limit wind erosion. For example, wheat stubble is, pound for pound, more effective than corn stubble; however, corn stubble is more effective than soybean residue. The orientation (flat or standing) and condition of the residue is important. Small-grain stubble standing is 2.5 times as effective as the same residue when it is flat on the ground.
Knoll effects. The topography of northeastern Indiana includes a number of sandy ridges. The ridges are a combination of beach and dune deposits developed during glaciation. Oak trees are the natural vegetation; and the trees, if present, make these land forms easy to identify. When these trees are removed, however, the soils are very susceptible to erosion, not only because of the sandy surface texture, but also because of slope. The wind velocity increases as it blows across a knoll, and when it does, the compressed air flow at the top of the knoll creates wind erosion that is much greater on the upper third of a slope than on the lower parts. Erosion on the downwind side of the knoll can increase because eroding particles coming from the top of the hill can start the saltation process on the lower parts of the slope.
Researchers have developed a formula to estimate wind erosion on a field. Soil conservationists use this formula for developing a conservation plan. The amount of soil eroded by wind can be calculated using the following equation:
E = f (I, K, C, L, V)
The average annual soil loss in tons-per-acre by wind erosion (E) from a given field is determined by interaction of these five factors:
I, the soil-erodibility index, is related to the amount of sand-size soil aggregates and further influenced by soil slope.
K, the soil-roughness factor, is determined by the height and spacing of ridges or clods.
C, the climatic-factor, takes into account the anticipated wind velocity and surface-soil moisture.
L, the length-factor, is the unobstructed distance across a field along the direction of the prevailing wind.
V, the vegetation-factor, is related to the present crop, its quantity and orientation.
Components of this wind-erosion equation are specific to a given field and not suitable for general calculations. County soil and water conservation districts have the information needed to complete calculation of wind-caused soil loss on specific fields. This equation is currently being reviewed. It has been very useful on the Great Plains, but some feel that it under estimates wind erosion in the humid Midwest.
Wind-erosion control techniques can be grouped into two general categories: practices that cover the soil and practices that slow or disrupt the wind.
Conservation tillage. This is the practice most easily applied, and most effective, for soils where wind erosion is a problem. There are several types of conservation tillage. One helpful publication, AY-210, Adaptability of Various Tillage-Planting Systems to Indiana Soils, discusses each rather thoroughly, and then rates them as to suitability on a given soil series. Before selecting any method for controlling wind erosion, consult AY-210 and your county soil survey to be sure the method selected is the best fit for all the soils on the landscape.
It is best to delay tillage to leave as much residue in place for as long as possible. Row direction should be at right angles to the prevailing wind, usually from the southwest. Unfortunately, this is difficult with the field orientation common to Indiana.
Cover crops. Cover crops of wheat rye or oats planted in the fall can prevent serious wind erosion by covering the soil surface and providing plant roots to hold the soil together. Fortunately, cover crops are well-adapted on the soils that most need them. In the spring, these crops can be plowed under or chemically controlled and then used as a mulch for no-till planting.
Soil series Erodible surface Soil series Erodible surface texture* texture* ------------------------------------------------------------------------------------------------ Abscota FSL, LFS, S Fox FSL, SL Ackerman MU Genesee FSL, SL Ade FSL, LFS Gilford FSL, SL Adrian MU Granby FSL, LFS, LS Algansee FSL, LS, LFS Gravelton LS Alida FSL, LFS Grovecity FSL Alvin FSL, LFS, SL Hanna SL Aubbeenaubbee FSL, SL Haymond LS Ayr FSL, LFS, LS Hillsdale FSL, SL Ayrmount LFS Homer FSL, SL Ayrshire FSL, SL Hononegah LS, FSL Barry FSL Hoopeston FSL Belleville LS Houghton MU Belmore FSL Huntington FSL Berrien LFS Iroquois FSL Billett FSL, SL Jasper FSL Bloomfield FS, LFS, LS, S Junius LS Bobtown LFS Kalamazoo SL Boots MU Kentland FS Bourbon SL Kosciusko SL Boyer LS, SL Landes FSL, SL, LS Brady FSL, LES, SL Linkville SL Branch LS Linwood MU Brems FS, S, LFS, LS, FSL Lyles FSL, SL Bronson LS, SL Markton LS, S Bruno FSL Martinsville FSL, SL Carlisle MU Martisco MU Carmi SL Maumee FSL, LFS, LS, S Casco SL Metamora FSL Celina FSL Metea LFS, LS Ceresco FSL, SL Miami FSL, SL Chatterton FSL, SL, LS Montmorenci FSL Cheektowaga FSL Morley SL Chelsea FS, LFS, LS Morocco FSL, LFS, LS Cohoctah FSL, SL Moundhaven FSL, SL Coloma FS, LFS, S Mudlavia SL Conotton SL Muskego MU Conrad FS, LFS Mussey SL Corwin FSL Napoleon MU Craigmile FSL, SL Nesius FS, LS, LFS Crosby FSL Newton FSL, LFS, LS Crosier FSL Nineveh SL Darroch FSL Oakville FS, LFS, S Desker SL Ockley SL Dickinson SL Octagon FSL Edwards MU Onarga FSL Elston FSL, SL Ormas LFS, LS, S Foresman FSL -----------------------------------------------------------------------------------------------
Soil series Erodible surface Soil series Erodible surface texture* texture* ------------------------------------------------------------------------------------------- Oshtemo CSL, FSL, LFS, LS, SL Zadog LS Ouiatenon FSL, LS, SL Zipp SL Owosso FSL, SL Palms MU Papineau FSL, SL *CSL - Coarse Sandy Loam Parr FSL FS - Fine Sand Piankeshaw SL FSL - Fine Sandy Loam Pinevillage SL LFS - Loamy Fine Sand Pinhook SL LS - Loamy Sand Pipestone LFS MU - Muck Plainfield FS, S, LS, LFS S - Sand Princeton FSL SL - Sandy Loam Prochaska LS VFSL - Very Fine Sandy Loam Rawson FSL, SL Rensselaer FSL, SL Riddles FSL, SL Ridgeville FSL Riverdale LS Roby SL Rockton FSL Rodman CSL, SL Ruark SL Saugatuck LFS Seafield FSL Sebewa SL Selfridge LFS Selma FSL Seward LFS Shipshe SL Simonin LS Sparta FS, LS, S, LFS Spinks S, FS Stockland SL Stonelick FSL, LFS, SL Tawas MU Tedrow FS, LS, LFS Toto MU Tracy SL Tyner LFS, LS Warners FSL Warsaw SL Watseka LFS, LS Wauseon FSL Wawasee FSL, SL Wesley FSL Wheeling FSL Whitaker FSL, SL Willette MU Wirt FSL,VFSL Zaborsky FS -------------------------------------------------------------------------------------
Strip cropping. Just as strip cropping disrupts water runoff, it also disrupts wind-current flow. For wind-erosion control, use long, narrow strips, oriented at right angles to the prevailing wind. Crops of varying heights are planted in each narrow strip. Both row orientation and crop-height difference disrupts wind currents. One limitation of this method is that small grains and hay may not be tall enough to completely protect the soil during the growing season.
A variation of the above technique can be used after corn harvest if some fall plowing is desired. For each 40 rows of cornstalks plowed under, leave eight rows unplowed. This usually disrupts wind currents enough to reduce wind erosion under most Indiana conditions. Again, corn rows need to be at right angles to the prevailing wind
Windbreaks. In extensive areas of wind-erodible soils, tree or grass windbreaks at right angles to the prevailing wind are useful. Although it removes some land from production, the long-term productivity is saved on the protected land, and the yield benefit of enhanced moisture collection through increased snow collection should offset this loss.
In general, the effectiveness of a windbreak extends in distance ten to twelve times the height of the windbreak, depending somewhat on climate, soils, and the other practices used. Spacing should take into account equipment size. If irrigation is present, windbreak designs and plantings are available which do not interfere with established patterns. Windbreaks are most effective when used over fairly large areas and when used in combination with other wind erosion-control practices. Windbreaks can be designed to serve a variety of purposes in addition to erosion control, such as wildlife habitats and livestock protection.
Snow has a tendency to collect around windbreaks, and may delay some spring tillage near the windbreak, but part of this area may actually have a higher yield because of moisture collection. Lower yields are likely to occur very close to the windbreak because of trees competing with crops for moisture and nutrients.
Emergency tillage. The primary means of controlling wind erosion are conservation tillage, cover crops, stop cropping, and windbreaks. If because of intense wind, very dry conditions or some other reason these should fail, emergency tillage may be needed. The purpose of emergency tillage is to produce a cloddy surface and thus break-up wind patterns near the surface.
A heavy-duty chisel plow is the implement best suited. The chisel points may be a variety of types, but the important thing is that they leave a rough surface. Speed of operation is important. If you drive too slow, not enough clods are raised. If you drive too fast, the soil is pulverized. A speed of 3.5 to 4 mi. per hr. is usually about right. Begin on the windward side of the field and chisel occasional strips every 100 ft. or so. The entire field may need to be chisel plowed.
The sandier the soil, the more difficult it is to stop the erosion of soil by emergency tillage. Thus the importance of improving the soil over the long-term by cover crops, rotational sod crops and good residue management cannot be over emphasized.
Precise estimates of wind erosion are difficult. It is clear from the Indiana soil map that wind erosion is a significant problem in the northwestern part of Indiana. This publication has discussed some of the principles of controlling wind erosion, but the ultimate decision rests with the farmer.
An important first step is to check the county soil survey report and compare the soils with those listed in Table 2. If there are a number of soils subject to serious wind erosion in a field, then a plan should be developed. Fortunately, wind erosion can usually be controlled by minor changes in current practices. If more extensive changes are needed, your local soil and water conservation district has the expertise to develop such programs.
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to our programs and facilities.