Adsorption-Desorption Behaviors of Phosphorus under Different Silicon Concentrations in Paddy Soils

Silicon(Si) and phosphorus(P) are very important elements for the growth of crops. The interactions between them have great effects on their bioavailability. In this paper, effect of Si on adsorption and desorption behaviors of P was studied in paddy soil from ShangYu, Zhejiang Province. The results showed that addition of Si into the soil decreased the amount of adsorption of P. The amount of adsorption of P decreased with the increase of Si concentration in soils. The isotherm of P could be well described by Freundlich and liner equation(P0.001) for any Si treatments. K value in Freundlich equation decreased when Si were added into soil, which indicated that Si decreased adsorption capacity of P in soil. Addition of Si into soil increased amounts of desorption of P in soil. The amounts of adsorption and desorption of P increased rapidly at first phase of adsorption-desorption and then increased slowly and maintain steady. The addition of Si into soil reduced the adsorption rate of P and increased the desorption rate of P. It can be known from the present study that addition of Si into soil increases the mobilization and bioavailability of P.