Growth and yield of a semi-dwarf and a standard height wheat cultivar in the Murrumbidgee Irrigation Area

A semi-dwarf cultivar (WW 15) and a standard height Australian wheat variety (Timgalen) were grown at two nitrogen levels and under three irrigation regimes in the Murrumbidgee Irrigation Area. Numerous plant measurements were taken to determine which attributes were associated with the superior yield of semi-dwarf wheat in this environment. WW 15 yielded 42% more grain than Timgalen and nitrogen fertilizer increased the yield of both varieties. The irrigation treatments did not affect yield because rainfall was above average. Total dry matter production and leaf area of WW 15 were similar to those of Timgalen, but WW 15 put a much greater proportion of its dry matter into grain. A greater number of grains per spike was the yield component responsible for the higher yield of WW 15. The increase in grain yield with the addition of nitrogen fertilizer was due to a general improvement in all aspects of crop vigour (e.g. tiller density, leaf area, total dry matter). There was no interaction between cultivars and nitrogen rates in their effect on grain yield.