Conservation tillage for improving dryland crop yields

Water conservation is essential for successful dryland crop production in semiarid regions. Improved water (also soil) conservation has been achieved in many cases by using conservation tillage, including no-tillage, which is the ultimate type of conservation tillage. The purpose of this article is to review and discuss the principles and practices of conservation tillage and the results of some studies relative to their effect on conserving water for improving crop yields in dryland regions such as those in southern South America. Water and soil conservation is possible by using tillage methods that reduce the amount and/or rate of runoff and improve water infiltration in soil. This is possible even when crop residues are not retained on the soil surface, which is covered by the broad definition of conservation tillage. Improved water and soil conservation, however, usually occurs when crop residues are retained on the soil surface, as covered by the operational definition of conservation tillage. Water and soil conservation usually improves with increasing amounts of residues retained, and results of numerous studies involving conservation tillage, including no-tillage, show that increased water conservation increases the yield of dryland crops. Improved soil conservation resulting from use of conservation tillage helps protect soils for sustained crop productivity. Key words: conservation tillage, dryland regions, soil water.