The effect of time of application of superphosphate on seasonal yield of dry matter from annual pasture

Abstract

The effect of time of application of superphosphate on the dry matter produced from a subterranean clover (Trifolium subterraneum)annual grass pasture was studied. Treatments involved an annual topdressing of superphosphate, at 125 kg ha-1, in a particular month of the year, for each of the twelve months ; there was also an unfertilized control. In winter, dry matter yield was increased by 350-1190 kg ha-1 when superphosphate was applied at any time of the year. Winter yields were higher after application in January to May (mean 1570 kg ha-1) than in October to December (mean 1190 kg ha-1) or in June-July (mean 1230 kg ha-1). In spring, the greatest increases in dry matter yield were from topdressing in August or September (1600 and 1210 kg ha-1 respectively). Spring yields following application in other months were smaller but usually significantly greater than the yield of unfertilized pasture. The response to autumn application of superphosphate was much greater in winter than in spring. This was not due to a lower phosphorus requirement by the pasture in spring than in winter.