Nitrogen fertilizer responses and seasonal production of temperate and warm climate grasses on the Northern Tablelands of New South Wales

Abstract

The seasonal patterns of herbage production and the nitrogen responses by two temperate (Lolium perenne and Phalaris tuberosa) and two tropical grasses (Digitaria macroglossa and Paspalum dilatatum) were compared in the field at Armidale, New South Wales from January 1969 to March 1971 with and without irrigation. Growth and nitrogen recovery of the grasses were affected by temperature, moisture and nitrogen rate. Temperate grasses produced little herbage at mean weekly temperatures below 6¦C. Maximum growth rates were measured in October when mean weekly temperatures were approximately 14¦C; growth rate declined markedly over summer. Digitaria was the highest yielding species during the first summer but failed to survive in winter. Paspalum was tolerant of winter temperatures as low as -8¦C mean weekly minimum; growth commenced when mean weekly temperatures exceeded 13¦C and maximum growth occurred in summer when the highest mean weekly temperature was 20¦C. Phalaris and Paspalum were very tolerant of dry conditions but Lolium declined in sward density and subsequent productivity. Response to nitrogen was directly related to seasonal conditions. Highest responses were coincident with the highest growth rates and declined as a result of moisture stress and low temperatures. Splitting nitrogen rates into a number of smaller applications had little effect on total herbage yield or distribution of dry matter production compared with a single topdressing. In the first year of the study the per cent nitrogen recovery by the temperate grasses ranged from 72.5 to 81.9 per cent compared with 25.3 (dryland) and 39.4 per cent (irrigated) for Paspalum. Under dry conditions the apparent percentage nitrogen recovery was increased by irrigation but over the first 48 weeks of the experiment there was little difference in the recovery between irrigated and dryland swards of the temperate grasses.