Tillage and stubble management
1991
Bolton, F. (Oregon State Univ., Corvallis (USA). Department of Crop Science)
Conventional or clean tillage has a long traditional and historical basis in rainfed cropping areas of the world. Exploitation of the organic matter to mineralize nitrogen and other plant nutrients was used for many decades before yield levels began to drop. When fertilizer materials became available, the tradition of clean tillage was strongly ingrained and is still widely used today. In the past, stubble residues were used for feed, fuel, and if in excess, were burned. In developing countries, crop residues are still used for animal feed and fuel. Rapid declines in organic nitrogen and carbon are often the result of removing all crop residues. When residues are returned to the soil, even by turning under, this decline is reduced. Conservation tillage, which requires that stubble residues remain on or near the soil surface, is becoming more widely used. A general rule for erosion control is to leave 30 of the surface covered for water erosion and/or 1120 kg/ha of stubble on the surface for wind erosion control. Minimum and no-till cropping systems, which leave most of the stubble residues on the soil surface, have not been entirely successful in semi-arid regions. In humid regions where spring-planted crops (corn, soybeans) are grown in wide rows, these systems are being widely adopted. Research is being conducted on stand establishment, fertilizer placement, weed control, and stubble management for better adaptation to semi-arid conditions. The ultimate cropping systems will probably be a compromise between clean tillage, minimum tillage, and no-tillage, with each being used as circumstances permit
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