Adsorption and Desorption Characteristics of Phosphorus on Cropland Soils in the Hilly Area of Sichuan Basin,China

Adsorption and desorption characteristics of cropland soils at different pH in the hilly area of Sichuan Basin to phosphorus were studied,and the effect of soil physicochemical properties on adsorption and desorption parameters was discussed.The results showed that the adsorption characteristics of the tested soil to phosphorus could be well described by Langmuir,Freundlich,and Temkin equations.Adsorption and desorption of the cropland soils at different pH to phosphorus indicated significant differences.The adsorption capacity showed an order of neutral,acidic and calcarous for the purple soil and paddy soil from high to low,and neutral soil was beneficial to phosphorus adsorption.The Maximum adsorption capacity(Qm) and maximum buffer capacity(MBC) of the paddy soil to phosphorus were higher than that of the purple soil,while the equilibrium concentration of phosphorus at zero sorption(EPC0) and desorption rate(b) in an inverse order.The adsorption and desorption parameters were influenced by the physicochemical properties of soil.Qm and MBC showed a positive relationship with the contents of organic matter and Fe-ox(P0.01,n=6),while b showed a negative relationship with the content of Fe-ox(P0.05,n=6) significantly.Adsorption constant(K) showed a negative relationship with the content of organic phosphate(P0.05,n=6) significantly.EPC0 showed negative relationship with pH and CaCO3 content(P0.05,n=6) while a positive relationship with the content of organic phosphate(P0.05,n=6) significantly.Therefore,the suitable countermeasures should be put forward for phosphorus managements in farmland,e.g.,promote the activation of phosphorus for the paddy soil and control the usage of phosphorus fertilizers for the purple soil.