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.
Footnotes
D. L. Thomas and M. C. Smith are assistant professors with the Agricultural Engineering Department, University of Georgia, Coastal Plain Experiment Station, Tifton, 31793; R. A. Leonard is a soil scientist with the Southeast Watershed Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Tifton; and F. J. K. daSilva is a former research engineer with the Agricultural Engineering Department, University of Georgia, Coastal Plain Experiment Station, Tifton. Work reported was supported by federal Hatch (Regional Project S-211 and others) and state funds and partially by USDA and U.S. Department of Energy funds under Specific Cooperative Agreements No. 58-43YK-5-6 and 19X-91324C.
- Copyright 1990 by the Soil and Water Conservation Society
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