Characteristics and influencing factors of phosphorus loss from fluvo-aquic soil under simulated rainfall conditions

Fluvo-aquic soil is an important cultivated soil in China.The loss of phosphorus not only affects soil fertility and crop yield, but also increases the pollution load of surface water environment.In this paper, an artificial rainfall simulation was conducted to study the dynamic changes of phosphorus and the characteristics of phosphorus loss in fluvo-aquic soil runoff under different rainfall intensities and slope gradients.The aim was to provide theoretical basis for controlling non-point source pollution of runoff in fluvo-aquic soil area.The results showed that: (1) total phosphorus(TP) and particulate phosphorus(PP) in runoff changed greatly, while total dissolved phosphorus(TDP) changed little during the whole rainfall process.When the rainfall intensity was 30 mm·h^-1, the concentrations of TP and PP in the fluvo-aquic soil with different slopes fluctuated throughout the rainfall process; when the rainfall intensity was 60 mm·h^-1, the concentrations of TP and PP in the runoff increased first and then decreased; when the rainfall intensity was 90 mm·h^-1, the TP and PP concentrations increased first and then decreased under the condition of slope 8°, while the concentrations of TP and PP decreased with fluctuation under the condition of slope 15°.(2) The concentration of TP ranged from 0.323 to 2.315 mg·L^-1, TDP from 0.083 to 0.163 mg·L^-1, and PP from 0.240 to 2.152 mg·L^-1 in fluvo-aquic soil runoff; the concentration of various forms of phosphorus in fluvo-aquic soil increased with increasing rainfall intensity and slope gradient.(3) TP and PP losses in fluvo-aquic soil in runoff increased with increasing rainfall intensity and slope, while TDP losses increased first and then decreased with increasing rainfall intensity under the condition of slope 8°, and kept an increasing trend under the condition of slope 15°.PP was the main form of phosphorus loss in the fluvo-aquic soil runoff.(4) There was an obvious linear relationship between the loss of TP and PP in the fluvo-aquic soil runoff and the rainfall intensity, slope and runoff quality(Q) under simulated rainfall conditions.The results provided a simple calculation method and scientific basis for predicting the loss of TP and PP per unit area in the runoff of the fluvo-aquic soil area under certain conditions.