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 ove r four years in the winter rainfall wheatbelt of Western Australia. Ro tation 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 con tinuous wheat rotations, but only by 1-2% by factors such as delayed s owing time, applied nitrogen, cultivar or grass weed control. In legum e based rotations, wheat crops sown at their highest yielding times pr oduced proteins in the appropriate ranges for premium paying grades. A pplying N fertilisers up to the optimum rates for yield did not result in proteins below the levels required for premium paying grades, exce pt for hard wheats at >11.5% grain protein. Legume rotations and appro priate soil types were required for hard wheats to exceed 11.5% at eco nomic N rates. The yield penalty often associated with high quality cu ltivars has been reduced or eliminated in the modern cultivars used in the experiments. Some longer season cultivars only produced grain pro teins >10% if sown after their optimum time for yield, but sowing at o ptimum time reduced the probability of producing small grain sievings. Some cultivars were more susceptible than others to producing excessi ve sievings, especially those with inherently smaller than average see d size. Seed rates up to the optimum for grain yield did not result in excessive small grain sievings except where the site was highly ferti le, where the crop was sown too late for optimum yield or where too mu ch N fertiliser was used.