water use efficiency of four dryland wheat cultivars under different levels of nitrogen fertilization

it is suggested that cultivars of wheat (triticum aestivum l.) with regulated growth and development would be able to produce higher yields under water-limited conditions, which is crucial in future food production. water use efficiency (wue) is worthy of exploration in this regard. in this study, the effects of nitrogen fertilizer levels (0, 40 and 80 kg nha-1) and a plant growth retardant (chlormequat chloride = ccc) on wue of four dryland wheat cultivars (agosta, nicknejad, azar-2 and fin-15) were examined in a field experiment during 2006-07 and 2007-08 growing seasons at college of agriculture, shiraz university, iran. the results showed that there existed significant differences between cultivars for grain yield, biomass and wue. in the first season, the highest grain yield and biomass production (192.4 and 431.2 gm-2, respectively) were obtained from nicknejad cultivar, ccc application and using 80 kg nha-1, and in the second season, from azar-2 cultivar (121.5 and 333.5 gm-2, respectively). ccc and nitrogen had significant effects on photosynthesis rate and wue in both seasons. interaction of ccc and 80 kg nha-1 on wue were significant in both seasons (1.24 and 2.72 gm-2mm-1, respectively). it is suggested that interactive application of ccc and nitrogen fertilizer could have beneficial effects on wheat grain yield under similar agro-climatic conditions.