Study on the phosphorus sorption-desorption characteristics of red soils and its environmental impact

The characteristics of phosphorus(P) sorption-desorption and its environmental impact were investigated in red soils(field with tillage practices for a long time and field with tillage practices for 2～3 years).The results indicated that the two soils had strong capacity to adsorb phosphorus.This capacity with the concentration of phosphorus increased.field with tillage practices for a long time released more phosphorus than that of tillage practices for 2～3 years.The content of phosphorus desorption of two soils was enhanced with the increasing of phosphorus adsorption,in other words,release of phosphorus depended on phosphorus saturation degree.Phosphorus adsorption curves could be well described by Langmuir equation.Field with tillage practices for a long time had phosphorus saturation degree lower 1.5% than 25%,an environmentally sensitive threshold.field with tillage practices for a long time should be applied in accordance with the expected demand for phosphate fertilizer.field with tillage practices for 2～3 years had phosphorus saturation only 9.6%.In order to achieve high-yield,soil use more phosphorus fertilizer.