EFFECT OF NITROGEN ON THE GROWTH, YIELD AND GRAIN PROTEIN-CONTENT OF BARLEY (HORDEUM-VULGARE)

Barley (Hordeurn vulgare) cvv. Grimmett, Galleon and Corvette were grown under irrigated conditions at The University of Queensland, Gatton College. to determine the effects of nitrogen (N) rates (0-200 kg N/ha) on plant growth, yield and grain protein content. Nitrogen delayed maturity in all cultivars, especially in Galleon. Total tiller number and fertile tiller number were increased by N and there was a significant cultivar x N rate interaction. Similar trends were evident in total dry matter at maturity and grain yield, with Galleon producing the highest yields. Fertile tiller percentage was reduced by increasing N rate. Grain protein content increased with the increasing N rate, with differences in the nature of the response between cultivars (i.e. linear in Corvette, quadratic in the other 2 cultivars). Total and fertile tiller numbers were explained by quadratic regressions, with maximum values at 150 kg N/ha (except fertile tillers in Grimmett, maximum value at 100 kg N/ha). The declines in fertile tiller percentage were explained by quadratic equations except in Grimmett, which showed a negatively linear response to increasing N rate. Dry matter yield and grain yield showed quadratic responses to N in Grimmett and Galleon (predicted maximum values near 200 kg N/ha) and linear responses in Corvette, over the experimental range of N rates. The response in grain protein content was explained by quadratic equations for Grimmett and Galleon, with minimum grain protein content occurring at close to 0 and 55 kg N/ha respectively. Corvette showed a linear increase in protein content in response to increasing N rate. It is concluded that plant breeding programs should consider variation in grain yield and protein content in response to N supply and select for efficiency of utilisation of N. Recommended N rates for irrigated barley could be 150-200 kg N/ha. Lower rates will promote strong yield responses, but protein content would remain low. © 1990 ASEG.