Dissolution of granulated CuZn-superphosphate in soils

Granules and pressed pellets of ordinary superphosphate and CuZn superphosphate were drilled and surface applied to two moist soils in the field. Residues were collected at intervals up to 1 year and chemically analyzed. The water-soluble P, Cu and Zn fractions dissolved within 7 days. Dissolution of S, Ca, remaining Cu and citratesoluble P was slow with approximately half the initial contents remaining in pellets and large granules after 1 year.All constituents dissolved more rapidly from small granules and in the heavier-textured soil. Crystalline dicalcium phosphate was not detected in residues despite its reported formation in analogous laboratory studies.