| The soil available phosphorus (P) plays an important role on crop growth and the safety of waterenvironment, excessive application of P fertilizers to agricultural land can cause various ecologicalproblems, such as entrophication. How to establish the relationship between soil availiable P, the cropyield and the evaluation index of water environment, which have a great significance for the agricultureproduction and water environment protection. Two typical agriculture planting patterns were chose asthe research regions, which were the Southern semi-humid region of Hubei province and the NorthernHuang-huai-hai semi-humid region of Beijing, and in combination with two long-term monitor test,which were paddy-upland rotation and wheat-maize rotation, respectively. The research was based onthe field monitor test and combined with the indoor simulation experiment. Through the differentdosage of P fertilizer applicating to the field, analysising the relationship between soil availiable P, thecrop yield and the evaluation index of water environment. The threshold value of agronomy andenvironmental was identified, which was based on ensure the crop yield and the security of waterenvironment quality. According to analysising the relationship between the initial concentration of soil P,P application, crop yield and the Olsen-P accumulation by residual P, and based on environmentalthreshold, then present the calculation model of soil P application to the field. The model was expectedto provide a kind of management thought concerning the agricultural product and water environmentprotect. The main results were as follows:1. In the paddy-upland rotation of the Southern semi-humid region, the runoff loss of soil P wasmainly composed of PP, in the P leaching process with different treatments, TDP was accounted for9.5-85.6%of the TP, with average of47.8%; TDP was accounted for29.3%of TP in the dry periodwhile TDP was accounted for50.0%of TP in the rice season. The leaching of TP with differenttreatments was ranged from3.9to5.7kg P hm-2and the soil available P was accounted for above80%.The average value of soil Papparent turnover was1.5%.2. In the wheat-maize rotation of the Northern Huang-huai-hai semi-humid region, the leaching lossof soil P was mainly composed of TDPin120cm of soil profile, in the Pleaching process with differenttreatments, TDP was accounted for48.2-91.7%of the TP, with average of69.1%. The leaching of TPwith different treatments was ranged from0.035to0.096kg P hm-2. The average value of soil Papparent turnover was0.065%.3. When excessive application P fertilizer to the soil, soil Olsen-P content was increased withprolonged. In the wheat-maize rotation of the Haplic Luvisol soil in Beijing area, soil Olsen-P contentincreased0.019mg kg1with NPK treatment when1kg P fertilizer was remained in soil. Meanwhile,soil Olsen-P content increased an average of0.054mg kg1with NPKM1and NPKM2treatments when1kg P fertilizer was remained in soil, which was about three times than the NPK treatment. In addition,in the paddy-upland rotation of the Paddy soil in Hubei province, soil Olsen-P content increased0.086mg Pkg-1with NPK treatment when1kg Pfertilizer was remained in soil. 4. The results showed that the line-line and line-platform model was fitted to simulate relationshipbetween soil Olsen-P content and crop yield in the wheat-maize rotation of the Huang-huai-haisemi-humid region, the agronomy threshold of soil Olsen P was15mg Pkg1; Meanwhile conbinatingwith the indoor cultivation and monitoring experiments in the situ, analysising the relationship betweensoil Olsen-P content and the index of the water environment. Results showed that the non-point sourcepollution in this regions was mainly conposed of P leaching and the environmental threshold of soilOlsen P was30mg P kg1. Finally, the threshold of Olsen P in Haplic Luvisol soil was ranged from15to30mg P kg-1in the wheat-maize rotation of the Northern Huang-huai-hai semi-humid region.5. The results showed that the line-line and line-platform model was fitted to simulate relationshipbetween soil Olsen-P content and crop yield in the paddy-upland rotation of the semi-humid region, theagronomy threshold of soil Olsen P was15mg P kg1; Meanwhile conbinating with the indoorcultivation and monitoring experiments in the situ, analysising the relationship between soil Olsen-Pcontent and the index of the water environment. Results showed that the non-point source pollution inthis regions was mainly conposed of running off of P. Furthermore, in combination with the Pconcentration limit in different waters refering to the Environmental Quality Standards for SurfaceWater (GB3838-2002), the environmental threshold of soil Olsen-P was25mg P kg-1when aiming atthe waters of lake or reservoir; the environmental threshold of soil Olsen-P was75mg P kg-1whenaiming at the waters of river. Finally, in the paddy-upland rotation of the Southern semi-humid region,the threshold of Olsen P in Paddy soil was ranged from15to25mg P kg-1mg P kg-1in the waters oflake or reservoir while in the waters of river, the values was ranged from15to75mg P kg-1mg Pkg-1.6. In this study, we built a threshold model of soil P input to the field in the first time, it was basedon the balance of soil phosphorus black-box theory, and analyzed the soil Olsen-P accumulationnP t characteristic, which th P0f (P i Ci Yi L i) te model wasi1. We took the wheat and maize rotation asexample in this study. The soil Olsen-Pinitial content was15mg P kg-1, and the average of chemical Papplication amount was65kg P hm-2a-1. The result calculated by the model indicated that the soilOlsen-P would reach the environmental threshold in25years. However, if the input amount was35kg Phm-2a-1, it could guarantee the soil Olsen-P did not accumulate, and could ensure the crop yield and thesafety of water environment. This method could provide a management idea for the agriculturalproduction and water environment protection. |
