Effect of time of tiller emergence and nitrogen fertiliser on seed yield components of Digitaria eriantha cv. Premier

Abstract

The effect of fertiliser nitrogen (N) and season (spring or autumn seed harvests) on tiller appearance, development and survival, and seed production in D. eriantha was investigated in a trial in south-east Queensland. In both spring and autumn, rate of tillering was maximal within the first week after cutting and declined rapidly thereafter, regardless of the level of applied N. Rate of tillering was greater in spring than in autumn. Tiller survival decreased as tiller emergence was delayed, and with increasing levels of applied N. At seed harvest, early-emerged tillers were consistently taller, heavier, thicker, and more fertile than late-emerged tillers, and they contributed most of the inflorescences. Fertility of all tillers was increased by application of N, particularly in spring. Seed yield, percentage seed set, and 1000-seed weight were larger in early-emerged tillers, which also bore the biggest inflorescences with the most spikelets per inflorescence, although spikelet number per unit raceme length was lower than on inflorescences borne on late-formed tillers. In general, the effect of N on seed yield components (inflorescence size, 1000-seed weight and seed set) was not significant. Early-emerged tillers contributed more than 70% of the total seed yield in both seasons.