VARIATION IN TEMPERATE CEREALS IN RAIN-FED ENVIRONMENTS .2. PHASIC DEVELOPMENT AND GROWTH

Barley yields more grain and total biomass than does triticale which in tum yields more biomass than do bread wheat, durum wheat and oats when sown at the same time in rainfed environments in southern Australia. To determine reasons for these differences, cultivars of each species were grown at five field sites and variation in their phenology and both pre- and post-anthesis growth was measured. Barley achieved a higher yield of grain and biomass in a shorter duration than the other species. It reached physiological maturity about 10 days (180 thermal units) before the other species, and reached double ridge and anthesis earlier. Triticale was also earlier to reach double ridge and terminal spikelet than the mean for the other species, although it had a similar physiological maturity to the wheats. Barley and triticale developed a greater leaf area and dry mass faster than the wheats and oats. The difference in leaf area was established from the time the first leaf had fully expanded. Barley also developed mainstem leaves and tillers faster than the other species whereas triticale was slower in this respect. Crop growth rate was greatest in barley and triticale up to anthesis, but no differences between species were found in their relative growth rates. The growth rate of individual grains and of total grain per unit ground area were substantially greater in barley than the other species. Oats and durum wheat had the slowest individual grain and total grain growth rates. Grain growth rate per unit ground area was significantly associated with grain yield at one site where this was examined. The change in stem mass between anthesis and physiological maturity, which was determined to assess the possible contribution of stem reserves to grain, was also positively associated with grain yield at the two sites where it was determined, and more so at the drier site. The change in stem mass averaged 76 g m-2 at the two sites and this represented 25% of the total grain yield. However, the range varied from 13 to 39% of grain yield (corrected for husk mass in barley and oats). The loss in leaf sheath mass averaged 68 g m-2 at both sites; this was not associated with grain yield.