The response of a birdwood grass - Townsville lucerne pasture to phosphate fertilizers at Katherine, N.T

Abstract

In an experiment at Katherine, N.T., the response of birdwood grass-Townsville lucerne (Cenchrus setigerus Vahl and Stylosanthes hurnilis H.B.K.) pasture sown on virgin land to levels of superphosphate and Christmas Island rock phosphate dust and to levels of superphosphate subsequently applied annually for three years was measured. There were no significant interactions between initial and annual applications. Initial applications of 2 and 4 cwt an acre superphosphate both gave higher forage yields of dry matter and nitrogen than 2 and 4 cwt an acre rock phosphate over the experimental period. Phosphorus yield of forage was a function of rate rather than of type of fertilizer. Annual superphosphate applications up to 1 cwt an acre increased the dry matter and nitrogen yields of the grass, but not those of the legume, and increased the phosphorus yield of both. The higher proportion of grass at high superphosphate levels was interpreted as a difference in responsiveness of the two species. A regime of 2 cwt an acre superphosphate initially and 1/2 cwt an acre annually produced 90 per cent of what was considered to be the maximum yield.