Author
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UNGER, PAUL - Retired ARS Employee |
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Submitted to: Water Resources Impact
Publication Type: Popular Publication Publication Acceptance Date: 12/15/2010 Publication Date: 11/1/2011 Citation: Unger, P.W. 2011. Tillage methods for conserving soil water-Then and now. Water Resources Impact. 13(6):12-14. Interpretive Summary: The need to conserve water for producing crop has long been recognized. It has become increasingly important because more food production is needed for the increasing population in the world. In addition, there is increasing competition for fresh water among agricultural, urban, industrial, and recreational users. Early settlers in the eastern United States used clean tillage to bury crop residues and to control weeds, and there generally was little concern for conserving soil water. In the early 1900s, deep and frequent plowing was promoted to conserve water. Clean tillage, including such deep tillage, left the soils bare and subject to the impact of raindrops, which caused soil aggregates to disperse and thereby caused the soil surface to seal, which increased runoff and soil erosion. When the value of keeping crop residues on the surface for avoiding these problems was recognized, their value for conserving soil water soon was recognized also. Clean tillage is still used under many conditions, but some tillage methods now used (conservation tillage) keep some crop residues on the surface with the most being kept when the no-tillage method is used. For no-tillage, weeds are controlled with herbicides and the soil usually is not disturbed between crops, except to open a narrow slit to plant the next crop. Where a dense subsurface layer is present, no-tillage soils may be loosened with a subsoiler that does not greatly disturb the residues on the surface. Keeping residues on the surface minimizes surface sealing, thereby reducing runoff, improving water infiltration, and reducing the potential for erosion; reduces water losses from soil due to evaporation; and conserves soil water, all being important for achieving greater crop production. Certainly, tillage methods now suitable for conserving soil water are drastically different than methods used in the 1800's or early 1900's. Technical Abstract: The importance of conserving water for producing crop has long been recognized and has become increasingly important because greater food production is needed for the world's increasing population and because of increasing competition for fresh water among agricultural, urban, industrial, and recreational users. Early settlers in the eastern United States used clean tillage to turn under surface residues and control weeds, generally with little concern for conserving soil water. In the early 1900's, deep and frequent plowing was promoted to conserve water. Clean tillage, including such deep tillage, left the soil surface bare and subject to the impact of raindrops, which resulted in soil aggregate dispersion, surface sealing, increased runoff, and the potential for soil erosion. When the value of surface residues for avoiding these problems was recognized, their value for conserving soil water soon was recognized also. Although clean tillage is still used under many conditions, some tillage methods now used (conservation tillage) result in retaining some crop residues on the surface with the greatest retention being achieved by using the no-tillage method. For no-tillage, weeds are controlled with herbicides and there is usually no soil disturbance between crops, except for opening a narrow slit in the soil for planting the next crop. Where a dense subsurface layer is present, no-tillage soils may be loosened with a subsoiler that causes little disturbance of the residues. Retaining residues on the surface minimizes surface sealing, thereby reducing runoff, improving water infiltration, and reducing the potential for erosion; reduces evaporative water losses from soil; and conserves soil water, all being important for achieving greater agricultural crop production. Certainly, tillage methods now suitable for conserving soil water are drastically different than methods used in the 1800's or early 1900's. |
