Seasonal changes in the nitrogen content of three warm-climate pasture grasses

Abstract

The nitrogen content of three pasture grasses was measured under irrigation at Samford, south-east Queensland, during the period February-September 1962. The grasses were Paspalum plicatulum, Sefaria sphacelata, and Chloris gayana. Two nitrogen treatments were used-nil, and a high rate. The high rate comprised frequent nitrogen fertilizer dressings in amounts chosen to match the shape of the plant growth curve. Addition of nitrogen fertilizer caused a marked increase in the nitrogen content of all parts of the plant and maintained a higher nitrogen content in mature grass samples. Flowering had relatively less effect on the nitrogen content of the grasses than nitrogen supply. Frost had very little effect on the nitrogen content of these grasses. It is suggested that warm-climate pasture grasses generally are subjected to a greater degree of nitrogen deficiency than their temperate counterparts, and that this accounts, at least in part, for their comparatively low nitrogen content. In the nil nitrogen treatment, Setaria sphacelata and Chloris gayana consistently exhibited a higher nitrogen content than Paspalum plicatulum. The differences were greatest in the leaf blades and least in the stems. The relative influences of nitrogen supply and stage of development on the nitrogen content of pasture grasses are discussed.