Transport of Inorganic Phosphorus in an Alfisol

Adsorption, desorption, and movement of phosphorus in an Alfisol soil were characterized by miscible‐displacement and batch‐type experiments. The influence of pore‐water velocity, aggregate size, and pretreatment of the soil with P was evaluated. A model which considers the interaction of P with soil as an equilibrium kinetic process was utilized to differentiate between instantaneous and time‐dependent reactions which appear to govern the adsorption‐desorption process during displacement. Pore‐water velocity has a greater influence on the adsorption rather than the desorption process which appeared to be more chemically controlled. Aggregate size affected the time‐dependent more than the instantaneous processes of soil‐P interaction. Instantaneous reactions between P and soil were shown to be mitigated by pretreatment of the soil with P in contrast to time‐dependent reactions. A pore model was hypothesized to explain the differential uptake and release of P during displacement.