Effects of post-anthesis water stress on the yield and grain protein concentration of barley grown at two levels of nitrogen

The interaction between nitrogen (N) rate and post-anthesis moisture stress in 6 cultivars of barley (Clipper, Stirling, Weeah, Schooner, Chebec, and Skiff) was examined. Plants were grown in a glasshouse at 2 rates of N under well-watered conditions until 3 days after ear emergence, when the stress treatment was started. Yield and grain protein concentration (GPC) responses and changes in the dry matter and N content of the straw and grain in the main stem and tillers were examined separately. Nitrogen increased grain yield in all cultivars except Weeah, with Skiff and Stirling being the most responsive. Post-anthesis stress did not reduce yields at the low N rate but large reductions occurred at the high N rate in all cultivars; the yields of Stirling, Chebec, and Skiff were most affected. At the low N rate, stress did not significantly affect kernel weight and GPC, but kernel weight declined and GPC increased at the high N rate. Compared with the main stem, tillers produced smaller grain with a lower GPC. The responses to Nand water stress, and the different sensitivities of cultivars to stress, were largely due to the effects of the treatments on the growth of the tillers. In Stirling, Chebec, and Skiff, grain yield and kernel weight from the tillers were greatly reduced by stress, whereas Clipper showed relatively little effect of N and stress on yield and kernel weight. Net remobilisation of dry matter was increased by stress but not by N treatment, and the amount remobilised varied between genotypes. At the high N rate, post-anthesis stress increased the N content per kernel and net remobilisation of N. Although genotypes differed in the net amount of N remobilised and in the N harvest index, there was little variation in GPC between cultivars. The work demonstrated that reductions in yield and kernel weight and increases in GPC from post-anthesis stress can be greater when plants are grown at a high rate of N than when the supply of N is limited. The different responses to stress and N among the 6 cultivars were associated, in part, with the pattern of tiller development. However, there appeared to be differences in the sensitivity of grain filling to stress independent of the responses in tiilering. While the net remobilisation of dry matter and N differed between cultivars, the amounts did not appear to be related to differences in kernel weight or GPC.