Effect of sowing time on growth, yield and water-use of rain-fed wheat in the Wimmera, Vic

Abstract

Crops of wheat (Triticum aestivum cv. Olympic) were sown after a 10-month fallow at three times in both 1979 and 1980 in the Wimmera district of Victoria. Total above-ground plant material (biomass) and soil water content were measured for each crop at monthly intervals from sowing to anthesis and thereafter every 2 weeks. The duration of the phenophase, sowing to anthesis, varied from 88 to 163 days, but the maximum difference between anthesis date for the early (May) and late (August) sown crops was only 21 days. The duration of this phenophase was best described by a photothermal unit of 6846 day-degree-hours (>2¦C, >6 h). The pattern of biomass accumulation varied markedly between crops, with biomass ranging from 9 to 13 t ha-1 and yield between 3 and 4 t ha-1. Total wateruse efficiency in the production of biomass to anthesis ranged from 30.5 to 19.8 kg ha-1 mm-1 and in the seasonal production of grain from 8.6 to 6.6 kg ha-' mm-'. Whilst the data include only one early sown crop, it was possible to identify an optimum balance between pre- and post-anthesis growth in crops sown in June to produce 9 t ha-1 of biomass at anthesis in early November, a yield sink of 12500 grains m-2 and in the 2 years of the experiment a grain yield of 4 t ha-1.