Effects of vegetation cover on phosphorus loss from a hillslope cropland of purple soil under simulated rainfall: a case study in China

Nutrients and sediment lost through runoff to surface and ground water represents a risk to human and environmental health. In order to understand the mechanisms of nutrient and sediment loss under different levels of vegetation cover, we conducted a simulated rainfall experiment on hillslope cropland in the Sichuan Basin of China. The experiment was performed on a 4.5 m long x 1.5 m wide x 0.6 m deep plot to analyze the mechanisms of overland flow, subsurface flow, sediment yield, and P loss for bare soil, and soil with 25, 50, 75, and 90% vegetation coverage. The results showed that total sediment loss and total bioavailable P (BAP) loss by overland flow decreased with increasing coverage; the rate of P release from fertilizer decreased with increasing time during a rain event and increasing coverage; and the growth in vegetation shoots and roots improved soil physical properties around roots, thus increasing P absorbance and the infiltration rate. Hence, we suggest increasing vegetation coverage to conserve soil and reduce BAP loss by sediments, and paying more attention to groundwater affected by pollutant transport through subsurface flows.