Effect of Incorporation of Fall-Applied Fertilizer on Runoff Losses of Nutrients and Soil from Soybean Ground

摘要

Plot measurements of soil and nutrient runoff concentrations and losses were made for two simulated rains in the fall after soybean harvest and fertilization (N, P and K at 31, 35 and 80 kg/ha, respectively). The five treatments were: fertilizer surface-applied, no incorporation; fertilizer point-injected into the soil; fertilizer incorporated by chisel plowing; fertilizer incorporated by disking; and no fertilizer applied, no tillage. Chisel plowing reduced surface residue coverage from 82% (before tillage and the first rain) to 48%; disking reduced coverage to 31%. About half the residue buried by tillage was uncovered by the first rain. Sediment concentrations in runoff from the tillage plots were about three times higher than from the no-tillage plots. Chemical concentrations from the surface application without incorporation treatment were significantly higher than from all other treatments, particularly for the first rain.