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

Abstract

The risk of soil phosphorus leaching increases in basin regions in light \nof large-scale use of phosphorus fertilizers because of agricultural \nmodernization. In this study, we conducted an earth pillar simulation test on \nthe infiltration threshold of red soil, Vaseline-coated PVC pipe, intact soil \ncore, fine sand, and \nnylon filter was used for Penetration test, which covers the largest area of \nthe Dianchi Lake Basin in China. Results showed that: 1) The contents of the total available phosphorus \nin algae (NaOH-P) and dissolved labile phosphorus (CaCl2-P) in red \nsoil were consistent with the content of available phosphorus (Olsen-P) under \ndifferent use patterns manifested by the law of greenhouse > open field > \ngrassland. Grassland had the highest phosphorus sorption index (PSI), followed \nby the greenhouse and then by the open field. 2) The leachate under the \nsame use pattern had the characteristics of total phosphorus (TP) > particle \nphosphorus (PP) > total dissolved phosphorus (TDP) > dissolved organic \nphosphorus (DOP) > molybdate reactive phosphorus (MRP). The TP \ncontents in the leachates of grassland, greenhouse, and open field were 0.46, \n0.61, and 0.49 mg/L, respectively. DOP, TDP, PP, and MRP had similar contents, \nand their distributions in the three land types were consistent with that of \nTP. 3) Olsen-P had a significant correlation with TP, TDP, PP, and DOP in the \nleachates. Olsen-P of 50 slightly influenced \neutrophication. Moreover, Olsen-P of >40 and 40 had minimal influence on the environment. Olsen-P of >70.90 mg/kg and \nPSI of 26.09 mg/kg, the TP content in the leachate increased \nsharply.