Effects of hydrological conditions on soil erosion and nutrient loss at purple soil hillslope

This paper quantitatively studied effects of hydrological conditions on soil erosion,nitrogen and phosphorus losses at purple soil hillslope by using of rainfall simulator.Experimental treatments included two levels of fertilizer input(low and high input) and four near-surface soil hydrological conditions(free infiltration;water saturation;subsurface flow without rainfall;and subsurface flow with rainfall).Rainfall intensity of 60 mm/h was simulated for 60 min.The results showed that soil loss of subsurface flow with rainfall and water saturation treatments is 3.1 and 1.7 times higher than that of free infiltration.The concentrations and losses of the NO3-N and HPO4-P in surface runoff of subsurface flow without rainfall,subsurface flow with rainfall,and water saturation are much higher than those of free infiltration.Under the low fertilizer input,the NO3-N concentrations in surface runoff from free infiltration,water saturation,subsurface flow without rainfall and subsurface flow with rainfall are 0.88,58.90,698.41,and 87.80 mg/L,respectively;HPO4-P concentrations from free infiltration,water saturation,subsurface flow without rainfall and subsurface flow with rainfall are 0.252,0.322,0.811 and 0.383 mg/L,respectively.Similar trends are observed for the concentrations of NO3-N and HPO4-P under the high fertilizer treatment.NO3-N and HPO4-P loadings from water saturation and subsurface flow with rainfall are 27-39 and 100-114 times higher than those from free infiltration;and HPO4-P loadings from water saturation and subsurface flow with rainfall are 1.3 and 1.5-1.7 times higher than those from free infiltration.Meanwhile,the losses of the NO3-N and HPO4-P in sediment from subsurface flow with rainfall and water saturation are higher than those from free infiltration.