Chapter 12 Cover Crops in No-till Systems

mer months when temperatures are high and rain-fall is highly variable. Cover crops may be cheap, and if legumes are used, they may reduce nitrogen fertilizer costs for the following crop. Cover crops contribute a variety of conserva-tion benefits. For water conservation, they offer a triple bonus. A living cover crop traps surface water. When killed and left on the surface, cover crop resi-due increases water infiltration, lessens erosion, and reduces evaporation. Green manure cover crops in-volve incorporation for the purpose of soil improve-ment. Water storage efficiencies in traditional clean-till fallow systems usually are around 20 percent, while water storage efficiency in no-till systems is near 40 percent, but seldom exceeds this amount (Greb, 1983; Unger, 1984). This means 60 percent of the precipitation received during fallow is lost to evaporation. In a no-till system, incorporation of residues is not possible, which makes it difficult to determine nutrient contribution from these crops. A cover crop is any crop grown to provide soil cover, regardless of whether it is incorporated later. Cover crops are grown primarily to prevent soil erosion by wind and water. Cover crops and green manures can be annual, biennial, or perennial herbaceous plant