Environmental Threshold of Phosphorus Infiltration in Red Soil under Different Land Use Patterns

摘要

The risk of soil phosphorus leaching increases in basin regions in light of large-scale use of phosphorus fertilizers because of agricultural modernization. In this study, we conducted an earth pillar simulation test on the infiltration threshold of red soil, Vaseline-coated PVC pipe, intact soil core, fine sand , and nylon filter was used for Penetration test, which covers the largest area of the Dianchi Lake Basin in China. Results showed that : 1) The contents of the total available phosphorus in algae (NaOH-P) and dissolved labile phosphorus (CaCl_(2)-P) in red soil were consistent with the content of available phosphorus (Olsen-P) under different use patterns manifested by the law of greenhouse > open field > grassland. Grassland had the highest phosphorus sorption index (PSI), followed by the greenhouse and then by the open field. 2) The leachate under the same use pattern had the characteristics of total phosphorus (TP) > particle phosphorus (PP) > total dissolved phosphorus (TDP) > dissolved organic phosphorus (DOP) > molybdate reactive phosphorus (MRP). T he TP contents in the leachates of grassland, greenhouse, and open field were 0.46, 0.61, and 0.49 mg/L, respectively. DOP, TDP, PP, and MRP had similar contents, and their distributions in the three land types were consistent with that of TP. 3) Olsen-P had a significant correlation with TP, TDP, PP, and DOP in the leachates. Olsen-P of 50 slightly influenced eutrophication. Moreover, Olsen-P of >40 and 40 had minimal influence on the environment. Olsen-P of >70.90 mg/kg and PSI of 26.09 mg/kg, the TP content in the leachate increased sharply.