TILLAGE EFFECTS ON SEDIMENT AND SOLUBLE NUTRIENT LOSSES FROM A MAURY SILT LOAM SOIL

As the role of nonpoint-source contamination of surface waters becomes more evident, increasingly more attention is focused on the effects of agricultural practices on soil erosion and water quality. Tillage systems are known to affect the amount of water moving over the surface and through the soil. This study compared the contributions of three tillage systems used in corn (Zea mays L.) production with (i) sediment losses and surface runoff and (ii) the potential for nonpoint-source surface water pollution from N and P fertilizers and triazine herbicides. Tillage treatments were no-tillage, chisel-plow tillage, and conventional tillage (moldboard plow plus secondary tillage). The study site was on a Maury silt loam (Typic Paleudalfs). Over the 4-yr period, conventional tillage runoff volume was 576.7 kL ha-1, chisel-plow 205.7 kL ha-1, and no-tillage 239.9 kL ha-1. Total soil loss from conventional tillage was 19.79 Mg ha-1, chisel plow 0.71 Mg ha-1, and no-tillage 0.55 Mg ha-1. Amounts of NO3-, soluble P, and atrazine leaving the plots in surface runoff were greatest from conventional tillage and about equal from chisel-plow and no-tillage. The magnitudes of the losses in surface runoff water were small for all chemicals measured.