EFFECTS OF COMBINATIONS OF TRIPLE SUPERPHOSPHATE AND A REACTIVE PHOSPHATE ROCK ON YIELD AND PHOSPHORUS UPTAKE BY CORN

A combination of finely ground phosphate rock (PR) and triple superphosphate (TSP) represents a method that can improve the agronomic value of PR at a lower cost than would be required to manufacture the conventional, fully acidulated fertilizers from that same rock. A reactive PR from North Carolina was evaluated for its effectiveness as a P source when used in conjunction with TSP at P rates up to 266 mg P kg** minus **1 in a short-term (6-week) greenhouse experiment. The soil used was a limed Mountview silt loam (Typic Paleudult) with pH 6. 2. As measured by dry-matter yield and P uptake, P availability from PR appeared to increase with increases in the proportions of TSP to PR in the TSP-PR mixtures.