The effect of rates and times of nitrogen fertilizer on N accumulation and remobilization efficiency at flag leaf in two winter wheat (Triticum aestivum and Triticum durum) cultivars

Understanding the physiological basis of absorption and transportation of nitrogen by plants has specific importance. in this experiment, a bread cultivar and durum wheat cultivar, were treated with different rates and times of nitrogen application, by using split factorial with on the basis of randomized complete block design with three replications at Shiraz region during 20042005. Main plots were consisted of two levels of cultivars (Falat and Yavaros) and sub plots included nitrogen rates (40, 80 and 160 kg ha(-1)) and times of nitrogen application (T1 = all N fertilizer at planting T2 = 1/2 at planting + 1/2 during booting stage and T3 = 1/3 at planting + 1/3 during booting stage + 1/3 at heading stage). The results showed that there were significant differences between cultivars in flag leaf nitrogen content in maturity stage, N remobilization and its efficiency from flag leaf to grains and also grain protein percentage. Durum wheat was more efficient in nitrogen remobilization and therefore, had a higher grain protein percentage. Increasing in rates and times of nitrogen application had significant effect on most of the measured traits. There were significant interactions between cultivars, rates and times of N application, indicating that durum, wheat was more efficient in N remobilization from flag leaf to the grain. It appeared that, N remobilization efficiency was the main factor affecting the grain protein percentage, under the conditions of low N absorption and drought after flowering, in this experiment.