Effect of nitrogen on the growth, yield and grain protein content of barley (Hordeum vulgare)

Abstract

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.