The effects of nitrogenous fertilizers on the winter growth of pastures in a tablelands environment

Abstract

Second-year grass swards near Canberra, A.C.T., responded well in August and September to nitrogen (urea or ammonium sulphate) applied in June or July, with increases in yield of up to 17 lb of dry matter for each lb of nitrogen applied. Mixed grass-clover swards showed smaller responses in total dry matter after applications of urea in July, but applications of urea in April produced no significant response. In 1961, when the grass component of the mixed swards responded to urea applied in April, there was a concurrent clover suppression before the early September harvest, which eliminated any potential increase in total yield. Seasonal differences and the date of nitrogen application influenced the extent of August-September responses more than the particular grass species. The grasses differed greatly in their mean yields, irrespective of the nitrogen treatment, and also in their influence on the yield of the associated clover, but the response to nitrogen by the grass component was essentially similar for Wimmera ryegrass (Lolium rigidum Gaud.), Clunes perennial ryegrass (Lolium perenne L.), Phalaris (Phalaris tuberosa L.), and Demeter fescue (Festuca arundinacea Schreb.).