EFFECT OF TIME OF TILLER EMERGENCE AND NITROGEN-FERTILIZER ON SEED YIELD COMPONENTS OF DIGITARIA-ERIANTHA CV PREMIER

The effect of fertiliser nitrogen (N) and season (spring or autumn see d harvests) on tiller appearance, development and survival, and seed p roduction in D. eriantha was investigated in a trial in south-east Que ensland. In both spring and autumn, rate of tillering was maximal with in the first week after cutting and declined rapidly thereafter, regar dless of the level of applied N. Rate of tillering was greater in spri ng than in autumn. Tiller survival decreased as tiller emergence was d elayed, and with increasing levels of applied N. At seed harvest, earl y-emerged tillers were consistently taller, heavier, thicker, and more fertile than late-emerged tillers, and they contributed most of the i nflorescences. Fertility of all tillers was increased by application o f 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, alt hough spikelet number per unit raceme length was lower than on inflore scences borne on late-formed tillers. In general, the effect of N on s eed yield components (inflorescence size, 1000-seed weight and seed se t) was not significant. Early-emerged tillers contributed more than 70 % of the total seed yield in both seasons.