PHOSPHORUS SORPTION CHARACTERISTICS OF SELECTED SOILS OF LOUISIANA

Investigations were conducted on phosphorus (P) sorption in ten selected soils of Louisiana. Soil samples were incubated with 0.005M calcium nitrate [Ca(NO3)2] solution containing P from 0 to 200 mg/kg at 25 degrees C and at a soil to solution ratio of 1:10 for 1 to 14 days. Concentration of solution P at all rates of P application was found to decrease linearly with time. The first order kinetic model fitted well to the P sorption data in all soils with exception to one. Linear regression equations were developed for predicting solution P at 1 to 14 days with the eight different rates of P application. Phosphorus sorption isotherms constructed by plotting log of P sorbed against the log of P remaining in solution, showed straight line relationships in all soils, except the Crowley silt loam. Therefore, simple linear regression equations were developed to estimate the parameters of the Freundlich equation for predicting sorbed P for desired levels of Pin solution.