NITROGEN-FERTILIZER EFFECTS ON THE DURATION OF THE PREANTHESIS PERIODAND SPIKELET NUMBER PER SPIKE IN BARLEY

The effects of increased yield and grain number per unit area in barle y in response to nitrogen application are well known. However, the inf luence of applied nitrogen on the rates and durations of developmental phases in barley are less well understood. Our objective was to inves tigate the effects of applied nitrogen on the duration of pre-anthesis development in barley and the number of spikelets per spike in two ba rley cultivars, Franklin and Schooner, in two studies. We found no eff ect of nitrogen on the duration of the pre-anthesis period in Schooner , when applied to pots at a rate of 0 or 55 kg N ha(-1), or when appli ed in the field at 0, 40 or 160 kg N ha(-1). However, this duration wa s extended in Franklin in the first study by an application of 55 kg N ha(-1). Both plant biomass and grain yield at maturity were increased between 0 and 55 kg N ha(-1), and 0 and 160 kg N ha(-1). Yield increa se largely associated with an increase in the number of tillers per pl ant.