Agronomic value of Calciphos, Phospal, and red phosphorus

In a long-term experiment on a yellow-brown loam of medium P status, the efficiencies of Calciphos, Phospal, and red phosphorus were compared with superphosphate. Calciphos and its 1:1 mixture with superphosphate (equal-P basis) proved to be an efficient source of phosphate for pasture. Though the initial efficiency of Calciphos was low it improved with time and by the fifth year was 84% as efficient as superphosphate on an equal-phosphorus basis. Calciphos was quicker acting and maintained higher yields than Phospal, but the efficiency of Phospal also improved with time. Annual applications of Calciphos and Phospal were less effective than the same total amount in a single application, but annual applications of superphosphate yielded more than a single dressing. Highest seasonal responses from all fertilisers, applied in spring, were obtained in summer seasons (37% of total), irrespective of whether these were applied annually or in single applications.