Characteristics of Phosphate Adsorption and Desorption in Paddy Soils

The characteristics of phosphate adsorption and desorption in relation to soil properties were investigated in different paddy soils under the condition of constant temperature. The results indicated that all phosphate adsorption curves could be well described by Langmuir, Freundlich and Temkin equations with best fitness by Langmuir equation. The maximum amounts of phosphate adsorption by paddy soils were positively correlated with physical clay content. The sequence of maximum phosphate adsorption among paddy soils tested was Yellow mud field Miry soil Well drained paddy soil Loamy sand soil Salinized paddy soil. The maximum desorption rate was found in Salinized paddy soil among the paddy soils tested in this experiment. Based on the bonding energy, the desorption of phosphates adsorbed by soils was divided into 2-3 phases including the rapid, the intermediate and the slow.