A comparison of dicalcium phosphate and single superphosphate as phosphate sources for pasture

Abstract

Abstract The effect of commercially available dicalcium phosphate (DCP) and single superphosphate on pasture production was evaluated in glasshouse and field trials. When compared on a unit-P basis, DCP (5.6% P) was slightly inferior (up to 10%) to superphosphate (8.6% P) in a glasshouse trial with ryegrass as the indicator plant; on a unit weight basis, DCP was only 60–70% as effective as superphosphate. No differences were obtained in the P concentration of the herbage obtained using the two materials. In a field trial on a P-responsive site, DCP and superphosphate gave similar increases in pasture production. Marked treatment differences were obtained for the P concentrations in ryegrass and clover in the field trial, particularly in the first harvest and with ryegrass. No difference was obtained in the short-term residual effect of the two materials. The data obtained are interpreted in terms of the chemical and mineralogical composition, and water solubility of DCP.