SURFACE AND INCORPORATED WHEAT STRAW EFFECTS ON INTERRILL RUNOFF AND SOIL EROSION

ABSTRACT A laboratory study was conducted on a Grenada silt loam soil to quantify the effect of various rate combinations of incorporated and surface applied wheat straw on interrill runoff and soil loss. Simulated rainfall, at a rate of 64 mm/h, was applied to a soil pan oriented on a 2.5% slope. There was no significant effect on interrill runoff or soil loss for either dry, wet, or very wet runs for increasing rates of recently incorporated straw (1, 3, 5, and 7 t/ha) over two levels (1 and 3 t/ha) of surface straw. The increase in surface straw from 1 to 3 t/ha produced significant decreases in soil loss in dry, wet, and very wet runs. The sum of soil losses from the 60-minute dry, 30-minute wet, and 30-minute very wet runs with a surface straw application of 3 t/ha over all rates of incorporated straw (1, 3, 5, and 7 t/ha) averaged only 289 g/m^ as compared to 572 g/m^ for a surface straw application rate of 1 t/ha. Relationships for interrill runoff and soil loss as a function of weight of surface straw were derived using observations of runoff and soil loss in this study combined with observations from closely related laboratory studies.