Bioavailable phosphorus transport from a hillslope cropland of purple soil under natural and simulated rainfall.

To further understand the mechanism of bioavailable total P (BAP) and bioavailable dissolved P (BDP) transport by overland and subsurface flow, we exposed a runoff plot 4.5 m long × 1.5 m wide × 0.6 m deep to simulated and natural rainfall in order to study the effects of rainfall type, rainfall intensity, and vegetation cover on BAP and BDP transport. The results showed that vegetation cover could alleviate the discharge of overland flow and sediment transport and enhance subsurface flow. BAP transport significantly increased with elevated rainfall intensity. Vegetation cover reduced the BAP transport by overland flow and increased it by subsurface flow. BDP transport showed no significant relationship with vegetation cover and rainfall type. The bioavailable particulate P (BPP) transport by overland flow contributed to no less than 90% by weight of total BAP, and the BPP transport by subsurface flow contributed to no less than 60% by weight of total BAP. Short-time heavy rainfall caused more BAP transport and accelerated non-point source pollution.