Abstract:Freezing-thawing cycles have important effects on physical and chemical properties of soil, which affect adsorption and desorption characteristics of phosphorus in soil. A laboratory experiment was conducted to determine the effects of freezing-thawing on phosphorus adsorption and desorption characteristic of black soil. The results showed that, the trend of phosphorus adsorption in freezing-thawing treatment was that all the phosphorus adsorption capacity increased with the increasing of phosphorus concentration, and there was obvious turning point when the exogenous phosphorus concentration was 120 mg/L. Compared to the no freezing-thawing treatment samples, black soil adsorbed more phosphorus and had higher adsorption rate after freezing-thawing cycles. At low exogenous phosphorus concentration, freezing-thawing cycles have relatively large influence on phosphorus adsorption quantity, on the contrary, at high exogenous phosphorus concentration, the influence reduced. In the condition of freezing-thawing, phosphorus adsorption curves could be well fitted by Langmuir equation. Under the condition of successive freezing-thawing cycles, maximum adsorption capacity Pmax, combining ability between soil and phosphorus and phosphorus adsorption maximum buffer capacity has the same trend of gradual increase.