Changes in Soil Phosphorus Forms Due to Application of Phosphorus Saturated Gypsum.

Gypsum filters designed to remove phosphorus (P) from agricultural drainage are currently being evaluated in Maryland (USA). A laboratory incubation study was performed to determine how land-application of the P saturated gypsum would affect soil P forms and availability and to evaluate the effectiveness of P saturated gypsum as a fertilizer material. Gypsum was saturated at two levels on a mass basis of P, and applied to two soil types, a silt loam and a sandy loam at both a high and low rate. The treated soils were incubated at 25° C and samples were collected 0, 1, 7, 28, 63, 91 and 119 days after amendment. Changes in chemically defined P forms in the soil will be discussed.