Effects of natural rainfall on soil and nutrient erosion on sloping cropland in a small watershed of the Dan River, China

Soil erosion and nutrient loss are two important aspects influencing crop production and water quality in the Dan River. In this study, a field experiment was conducted in the Yingwugou Watershed. A corn field of slope 23° with an area of 243 m2 was selected to study the spatial variability of soil properties for cropland and to determine the loss amounts of soil total nitrogen (STN), soil total phosphorus (STP), soil organic carbon (SOC) and silt-clay under natural rainfall. Geostatistical analysis indicated that generally STN, STP, SOC and silt-clay had strong spatial dependence (with nugget ratio <25%) primarily induced by structural factors. Kriging successfully interpolated the studied soil properties. There were some intrinsic relationships among STN, STP, SOC and silt-clay. The effect of rainfall on the spatial autocorrelation for STN and STP was more significant than that for SOC and silt-clay. Natural rainfall had a weak effect on SOC. The total loss of STN, STP and silt-clay in the sloping corn field decreased by 348.7 g, 2640.4 g, and 0.47% during the study period, respectively. The results provide useful information for understanding the nutrient loss and soil erosion on sloping cropland.