Using winter cover crops to improve soil and water quality

This article reviews literature about the impacts of cover crops in croppin g systems that affect soil and water quality and presents limited new infor mation to help fill knowledge gaps. Cover crops reduce sedimentation produc tion from cropland by , grow during periods when the soil might otherwise b e fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microrgan isms, while simultaneously increasing evapotranspiration from the soil. Cov er crops reduce sediment production from cropland by intercepting the kinet ic energy of rainfall and by reducing the amount and velocity of runoff. Co ver crops increase soil quality by improving biological, chemical and physi cal properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribu te a nitrogen (N) to subsequent crops. Other cover crops, especially grasse s and brassicas, are better at scavenging residual N before it can leach. B ecause growth of these scavenging cover crops is usually N limited, growing grass/legume mixtures often increases total carbon inputs without sacrific ing N scavenging efficiency. Cover crops are best adapted to warm areas wit h abundant precipitation. Water use by cover crops can adversely impact yie lds of subsequent dryland crops in semiarid areas. Similarly, cooler soil t emperatures under cover crop residues can retard early growth of subsequent crops grown near the cold end of their range of adaptation. Development of systems that reduce the costs of cover crop establishment and overcome sub sequent crop establishment problems will increase cover crop utilization an d improve soil and water quality.