Effect of nitrogen fertilizer on a kangaroo grass (Themeda australis) grassland

Abstract

Three rates of nitrogen fertilizer and a standard superphosphate dressing were applied to a Themeda australis grassland with and without broadcast seed of Dactylis glomerata. Two cutting frequencies were imposed and dry matter yields and botanical composition were measured. T. australis responded to nitrogen, but the response was not sufficient for it to predominate over other species, particularly Poa labillardieri, as it had done under low fertility conditions. P. labillardieri yields increased markedly with increasing nitrogen rate. D. glomerata, which established only where nitrogen fertilizer was applied, substantially reduced the increase in P. labillardieri at the high level of nitrogen. Cutting frequency affected botanical composition in degree but not in kind. Both P. labillardieri and D. glomerata yielded less, but T. australis yielded more under more frequent cutting. For pasture improvement in wetter parts of the southern tablelands of New South Wales, it is important to establish a perennial grass at the beginning of the programme to reduce the growth of the undesirable tussock. P. labillardieri.