Soluble potassium transport in agricultural runoff water |
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| Institution: | 1. Universidad Politécnica de Madrid, Departamento de Matemática Aplicada, E.T.S.I. Agrónomos, Avda. Puerta de Hierro 2, 28040 Madrid, Spain;2. Universidad Politécnica de Madrid, Departamento de Edafología, E.T.S.I. Agrónomos, Avda. Puerta de Hierro 2, 28040 Madrid, Spain |
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| Abstract: | Potassium transport in runoff from three agricultural soils was investigated in laboratory and field experiments using a kinetic equation describing soil K desorption. In the laboratory, this equation was used to study the effect of rainfall intensity and soil slope, cover, and residue incorporation on the effective depth of interaction between surface soil and runoff (edi), an important parameter in the kinetic equation. Using simulated rainfall, edi increased linearly (from 1.6 to 22.0 mm) with an increase in rainfall intensity (50 to 160 mm h−1) and soil slope (2 to 20%). edi was reduced an average 82% following incorporation of 5.0 t ha−1 of wheat straw (Triticum aestivum L. sp.) and 44% by a 0.5-mm2 mesh screen, simulating crop cover, compared to the control (4.5 mm). This reduction was attributed to a decreased turbulent mixing of water at the soil surface brought about by an increased physical protection of soil. For all soils and treatments, edi was logarithmically related to soil loss (r2 = 0.80), allowing estimation of edi under variable rainfall intensity, soil slope, type, and cover conditions from measured or estimated soil loss. The values of edi, thus estimated were used in the kinetic equation to predict solution K transport in runoff from eight agricultural watersheds in Oklahoma, U.S.A. Measured and predicted mean annual flow-weighted concentrations of solution K were not significantly different and were strongly correlated (r2 = 0.92). These results improve our capability to predict K transport in runoff under field conditions. These methods could also be applied to other agricultural chemicals transported in runoff and results used to improve management of soil and water. |
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