Effects of cover crops on surface water quality

The current emphasis on sustainable agricultural systems has led to a renewed interest in the use of cover crops to reduce soil erosion losses and retain soluble nutrients during the dormant season. Cover crop choices include a broad range of plant material, such as ryegrass (Secufe cereale L.), winter wheat (Triticum aestivum L.), forage grasses, and legumes. Historically, cover crops were used to fix atmospheric nitrogen (N), improve soil structure and tilth, and minimize runoff and erosion. As a result, much information is available on the agronomic and economic effects of cover crops under different management systems and regions of the country (9, 10, 35, 42). Less attention, however, has been given to the effect of cover crops on nutrient losses in surface runoff. While it is generally recognized that cover crops can be very effective in reducing nutrient losses associated with sediment transport (i.e., sediment-bound or particulate nutrients), information regarding soluble nutrient losses in surface runoff is sparse. An increased public perception of the role of agriculture in nonpoint-source pollution has stimulated need for information on the effect of current and proposed agricultural management practices on surface water quality (40). Because of easier identification and control of point sources of pollution, agricultural nonpoint sources now account for a larger share of all discharges than a decade ago. Consequently, more attention will be directed toward developing models that simulate nutrient transport in runoff to help select management systems that can minimize associated water quality problems. In this chapter, we consider surface water quality impacts