Simulated effects of rapeseed production alternatives on pollution potential in the Georgia Coastal Plain

ABSTRACT:

Long-term model simulations have the potential for economical evaluation of alternative management practice effects on pollutant yields for new crops. The CREAMS and GLEAMS models were used to evaluate alternative planting dates, nitrogen (N) applications, soil types, and soil slopes (typical of the Georgia Coastal Plain) planted to rapeseed for the potential effects of these four variables on sediment, nutrient, and pesticide losses. Planting dates significantly affected runoff; total N leached; soluble and sediment-bound f sulfoxide (in runoff); soluble, sediment-bound, and leached f. sulfone (metabolites of the nematicide fenamiphos); and soluble and leached metalaxil (fungicide). The first planting date, October 12, showed a significant reduction in losses compared to the third planting date, November 9. An evaluation of split N applications indicated a significant reduction in leached N as the number of splits increased for the same total N applied. Several of the sediment-bound pollutants in runoff increased significantly as slope increased. There is potential for reducing runoff losses by selecting soils with less slope or by using alternative management practices. The soil type influenced the pollutant losses in most cases. Greenville sandy clay loam had the greater losses of runoff-based pollutants, and Tifton loamy sand showed higher losses due to leaching for most parameters. Depending on the soil type and slope, careful selection of management practices can reduce the potential yield in rapeseed production.