水稻土对磷的吸附及吸附态磷的释放特征

Characteristics of phosphate sorption and sorbed-P release in paddy soils

采用等温吸附法和离子交换树脂法研究水稻土对磷的吸附及吸附态磷的释放规律．磷的等温吸附研究表明：Langmuir方程能较好地拟合浙江金华市的20个代表性水稻土对磷的吸附特征，相关系数在0．970～0．999之间；Langmuir等温方程的参数与土壤的理化性质有关，发育于第四纪红色粘土的水稻土的参数Xm、K、MBC和X0.2值都明显高于其他发育于冲积物的水稻土；在淹水条件下，溶液中P可能较易得到土壤固相P的补偿，和旱地作物相比，水稻生长所需要的平衡磷浓度（EPC）可能远低于0．2mg．L-1．磷的解吸研究表明：离子交换树脂提取的磷量与土壤吸附态P总量成正比，不管是冲积型水稻土还是红壤性水稻土，这种直线关系都成立（r=0．941～0．999）；在淹水条件下土壤磷的释放与土壤对磷酸根的吸附饱和度，即土壤对磷酸根的吸附能大小紧密相关．在水稻土的P肥管理实践中，维持适当水平的土壤总P量与维持适当水平的土壤有效P含量同样值得重视．

Characteristics of phosphate sorption and sorbed-P release in paddy soils were studied using adsorption isotherm and ion exchange resin method. The results show that phosphate adsorption isotherm of 20 rice soils of Jinhua City of Zhejiang Province fitted in with Langmuir equation very well. The correlation coefficients were from 0. 970 to 0. 999. Parameters of Xm, X0.2, K and MBC （maximum buffer capacity） of the Langmuir equation might correlate with soil properties. The highest values of Xm, K, MBC and Xo.z were found in red earth derived rice soils, which might relate to their high content of clay and Fe, AI oxides. Comparing with upland crops, which equilibrium P concentration of 0.2 mg. L 1 may satisfy P demand for most crops, irrigated rice might need a less equilibrium P concentration in solution for its growth because the solution P could be more easily compensated through P release from soil particles in rice soils. It was found that the resin extractable P was proportional to soil adsorbed P （sum of soil Resin-P and newly adsorbed P from solution）. The linear relationship was valid for all the soils studied, that is RAQ P=A-？BX, where A and B are constants （r=0. 941 to 0. 999）. It seemed that under water submerged condition, phosphate adsorbing saturation controlled the rate and quantity of P released from soil pay our attention to maintain an soil available P. to the resin sink adequate level of total soil P P fertilizer management in paddy soils, it content or to maintain an adequate level of soll available P.