Grain yield and quality: does there have to be a trade-off? (Reprinted from Wheat: Prospects for global improvement, 1998)

The effect of agronomic practices and cultivars on grain yield, grain protein and small grain sievings was examined in field experiments over four years in the winter rainfall wheatbelt of Western Australia. Rotation with legume crops and pastures was the main factor responsible for increasing grain protein percent. Grain proteins were increased by 4-5% for crops grown in good legume pasture rotations compared to continuous wheat rotations, but only by 1-2% by factors such as delayed sowing time, applied nitrogen, cultivar or grass weed control. In legume based rotations, wheat crops sown at their highest yielding times produced proteins in the appropriate ranges for premium paying grades. Applying N fertilisers up to the optimum rates for yield did not result in proteins below the levels required for premium paying grades, except for hard wheats at >11.5% grain protein. Legume rotations and appropriate soil types were required for hard wheats to exceed 11.5% at economic N rates. The yield penalty often associated with high quality cultivars has been reduced or eliminated in the modern cultivars used in the experiments. Some longer season cultivars only produced grain proteins >10% if sown after their optimum time for yield, but sowing at optimum time reduced the probability of producing small grain sievings. Some cultivars were more susceptible than others to producing excessive sievings, especially those with inherently smaller than average seed size. Seed rates up to the optimum for grain yield did not result in excessive small grain sievings except where the site was highly fertile, where the crop was sown too late for optimum yield or where too much N fertiliser was used.