LAND-USE AND MANAGEMENT EFFECTS ON NONPOINT LOADING FROM MIAMIAN SOIL

Land use greatly affects soil and hydrological processes, which have major implications for environmental quality and agricultural sustainability. The objective of this study was to determine the effects of four land use systems - continuous alfalfa, forest, ridge-till corn (Zea mays L.) and conventional-till corn - on runoff, soil loss, and nutrient transport in runoff and sediment. Eight field plots (18.5 by 21 m), equipped with 0.3-m H-flumes and FW-1 water-level recorders, were established on Miamian silty clay loam soil (fine, mixed, mesic Typic Hapludalf) at the Ohio State University Agronomy Farm, Columbus, OH. Runoff samples, collected after erosive storms during the growing season in 1990, were analyzed for sediment concentration, NO3-N, NH4-N, PO4-P, and dissolved organic C. Sediment collected from the flume base was analyzed for total Kjeldahl N and available P. A critical period was identified as the early stages of crop growth during which the soil was particularly vulnerable to erosion due to excessive runoff. Soil and nutrient losses were typically higher during the critical than during the noncritical period. Both N and P losses in runoff and sediment were higher for cropped treatments than for alfalfa (Medicago sativa L.) and forest. Losses observed for conventional tillage were, however, several orders of magnitude larger than uncropped treatments.