| In recent years,as the growth of the economy,the amount of chemical fertilizer inputed in agricultural production in our country is gradually increasing,as a result,it has located in the first place around the world.The overcommitment of fertilizer result in considerable amount of chemical fertilizer accumulation in soil.Rainfall can result in a massive loss of the nitrogen and phosphorus in the soil through surface runoff water and soil permeate water and it is the main reason of non-point source pollution.Non-point source pollution is widely distributed in our country,but its prevention and treatment is very difficult.Therefore,the control and prevention of agricultural non-point source pollution has become a hot spot.In this paper,the status quo of agricultural non-point source pollution at home and abroad was studied.It was found that the excessive loss of nutrients caused by excessive application of chemical fertilizers was the most important factor in many factors that caused agricultural non-point source pollution.Based on the current research hotspots,this paper selected the three indicators of total phosphorus,soluble total phosphorus and soluble phosphate in water,and studied the characteristics of phosphorus loss in different agricultural non-point source pollution under different chemical fertilizers and different rainfall intensities.The following conclusions were drawn.(1)Study on the characteristics of phosphorus loss in the process of non-point source pollution in the case of different dosage of fertilizer:In the case of moderate rainfall intensity,this paper set up four experimental groups with different fertilization levels(no fertilizer,less fertilizer,moderate fertilizer,high dosage fertilizer;no fertilizer is the blank control group)and collect and analyse the surface runoff water and Soil infiltration water in the depth of 25cm,50cm.The data of the experiments concluded that:the total phosphorus,soluble total phosphorus,soluble phosphate concentration of four fertilizer levels experimental group in surface runoff water and soil infiltration water show up that,high dosage fertilizer>moderate fertilizer group>less fertilizer group>no fertilizer group.In the case of moderate rainfall intensity,it is found that the concentration of total phosphorus in the surface runoff get the peak the eleventh day(2.76mg/L、3.0 mg/L、3.17 mg/L、3.26 mg/L).Therefore the output concentration of phosphorus is positively correlated with the amount of fertilizer applied,that is,when the amount of fertilizer was increased,the concentration should be higher.(2)Study on the characteristics of phosphorus loss in the process of non-point source pollution in the case of different intensity of rainfall:In the case of moderate level fertilizer,this paper set up there experimental groups with different rainfall intensity(strong rain intensity R3,moderate rain intensity R2,light rain intensity R1)and collect and analyse the surface runoff water and Soil infiltration water in the depth of 25cm,50cm.The data of the experiments concluded that:the total phosphorus,soluble total phosphorus,soluble phosphate concentration of three different rainfall intensity experimental group in surface runoff water and soil infiltration water show up that,R3>R2>R1.In the case of moderate level fertilizer,it is found that the concentration of total phosphorus in the surface runoff get the peak in the eleventh day(2.51mg/L、3.19mg/L、7.6mg/L).Therefore the output concentration of phosphorus is positively correlated with the intensity of rainfall,that is,when the intensity of rainfall was increased,the concentration should be higher.The output concentration of phosphorus along with the deepening of the depth of the soil,C0>C25>C50(the figure is the behalf of the depth of the soil,cm).As a result,it is shown that the output of phosphorus in the vertical direction of the soil is decreasing by the effect of soil adsorption,which indicates that a large amount of phosphorus is fixed by soil adsorption and avoids penetrating into the deep soil and groundwater through soil permeation.The result of this paper can give acetain degree support for the source treatment of non-point source pollution. |
