Effect of Phosphorus Fertilizer Application Rates on the Loss of Colloidal Phosphorus on Purple Soil Slopes
[Objective]The risk of phosphorus loss from farmland is closely related to the amount of phosphorus fertilizer.Given the important role of soil colloids in the process of phosphorus transport and transformation at the soil-water interface,the effect of phosphorus fertilizer application on the loss of phosphorus from colloidal state on purple soil slopes and its relationship with runoff and sand production were explored,in order to provide the scientific basis for the understanding of phosphorus transport mechanism from the soil colloid point of view.[Method]Combining artificial simulated rainfall with laboratory analysis,the experiment was conducted to study the characteristics of abortion sediment production and colloid phosphorus loss on purple soil slope under the dosage of phosphorus fertilizer 0(P0),20(P20),40(P40)and 100(P1 00)mg·kg-1.[Result]Surface runoff was less affected by phosphorus fertilizer application,and erosion sand production was more affected by phosphorus fertilizer application.The initial sand production of the slope was significantly reduced by 49.3％-68.7％after phosphorus application,and the cumulative sand production was significantly reduced by 26.5％-30.9％under P100 treatment compared to the other phosphorus treatments.Surface runoff was the main loss pathway of water-dispersible total phosphorus(WTP)and colloidal phosphorus(CP)from purple soil slopes,which accounted for 57.5％-93.9 and 62.3％-94.8％of the total loss,respectively;CP was the main form of WTP loss from surface runoff,which accounted for 72.1％-80.7％of the WTP loss.Phosphorus application significantly increased the risk of phosphorus loss.Compared with P0 treatment,the cumulative loss loads of surface runoff WTP,CP,and DP(dissolved phosphorus)under phosphorus fertilizer application treatments were increased by 2.56-20.97,2.72-22.21,and 1.17-10.40 times after phosphorus application,respectively,and the cumulative loss loads of eroded sediment WTP,CP,and DP were increased by 0.24-0.92 times,0.05-1.09 times,0.47-0.76 times,respectively.[Conclusion]The main pathway of colloidal phosphorus loss from purple soil slopes was surface runoff,and the characteristics of concentration change were closely related to the flow production process,while the loss load mainly depended on the phosphorus content of slope soil and the amount of phosphorus fertilizer applied.Total water dispersible phosphorus and colloidal phosphorus showed a highly significant correlation,colloidal phosphorus was the main form of phosphorus loss on purple soil slopes,and CP loss on slopes could be reduced by regulating surface runoff and reducing the amount of phosphorus fertilizer.
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