Kinetics of Dissolution of Phosphate Rocks in Soils

Abstract

Abstract A modified Elovich equation in the form of C t = C 0 − (1/β)ln (αβ) − (1/β) ln t was derived to describe the kinetics of dissolution of three phosphate rocks (North Carolina, central Florida, and Tennessee) in three soils (one soil from Florida and two Nigerian soils). The equation fitted the experimental data the best among various models of kinetics. Comparisons of dissolution rates of various phosphate rocks in a given soil or a given phosphate rock in various soils can be made by comparing the values of three parameters— C 0 , α, and β—in the equation where C 0 is the maximum P concentration in the soil solution that a phosphate rock can provide in a soil ( C t is the P concentration at time t ), and α and β are constants. It was found that C 0 increased as α increased and/or β decreased in a given system. Temperature was found to have no significant effect on the dissolution of phosphate rock in the soil. This implies that phosphorus retention by the tropical soils treated with phospate rock may be much less affected by temperature as compared with water‐soluble P fertilizers such as concentrated superphosphate.