Assessment of remobilization variation of bread wheat cultivars under different irrigation and nitrogen fertilizer treatments

In order to investigate the effect of water treatment and nitrogen fertilizer application on remobilization and grain yield of bread wheat cultivars, an experiment was carried out as split-split plot design based on randomized complete blocks with three replications. Three levels of irrigation (full irrigation, withholding irrigation at heading, withholding irrigation at anthesis) were assigned to main plots, different times of nitrogen fertilizer application (application of 120 kg/ha nitrogen in four different times: 20 kg at sowing + 100 kg/ha at tillering, 20 kg at sowing + 100 kg/ha at bolting, 20 kg at sowing + 50 kg at tillering + 50 kg at bolting, 20 kg at sowing + 50 kg at tillering + 50 kg at heading) were randomized in sub-plots and five bread wheat cultivars (Zarrin, Pishgam, Urum, Zare, Mihan) were assigned to sub-sub-plots. Withholding irrigation at different developmental stages of wheat increased remobilization percentage of all cultivars. However, application of nitrogen at the heading stage reduced remobilization. The highest and lowest remobilization were recorded for Urum and Zarrin with 62.13% and 20.33%, respectively. Grain yield was significantly reduced with the reduction of water availability. Mean grain yield of all cultivars was 7.500 ton/ha under full irrigation, which reduced to 6.500 ton/ha when irrigation was withheld. Nitrogen fertilizer applicationimproved the grain yield of wheat cultivars. The highest grain yield was obtained for Mihan by 9.39 ton/ha under full irrigation and nitrogen application at sowing + tillering + heading. The higher grain yield of tolerant cultivars under water deficit treatments was attributed to remobilization of unstructured carbohydrates from shoot to grain. It seems that selection of cultivars with higher translocation of dry matter and contribution of pre-anthesis assimilates in grain filling under water stress, can be a suitable strategy to produce high yielding cultivars under water deficit stress condition.