Laboratory experiments of soil nutrient transfer in the loess slope with surface runoff during simulated rainfall

The release and transfer of soil chemicals in surface runoff during the rainfall is not only an agricultural issue, but also a water environmental problem. The characteristics of soil nitrogen, phosphorus and potassium transfer with surface runoff were studied by simulated rainfall. Results indicated that, when the slope increased within the range from 5° to 25° for the given slope length, time to runoff commencement decreased first, and then increased with increasing slope. The magnitude of runoff first increased fiercely and then became stable within 15 min after the beginning of the runoff. Losses of soil and water became drastic and solute concentration in runoff enhanced with increasing slope, and the effect of the soil erosion on the solute concentration in runoff enhanced as well. Compared with the exponential function, the power function can be more suitable for fitting the changes of chemicals concentrations in runoff under unsaturated conditions from the loss slope, and for the description of the mass loss of phosphorus and potassium in runoff as well, but not for the initial phase. The study provided a reference for improving the model of soil nutrient transfer in runoff on the loess slope.