The disappearance of phosphate from soil solution results from a fast initial sorption reaction followed by a much slower transformation of phosphate to amorphous and crystalline precipitates of iron, aluminum, and calcium. The kinetics of the transformation have been determined at a phenomenological level and often shown to follow Elovich or first-order equations. Kinetic models are applied to laboratory data to describe step response of phosphorus and quasi-steady state response of phosphorus in soil columns. Results indicate a first-order kinetic equation gives an adequate description of phosphorus movement in soil columns when the water velocity is known.