Effects of different nitrogen application rates and supplemental irrigation on agronomic characteristics and grain yield of bread wheat (Triticum aestivum L.) cultivars under rainfed conditions

This study was conducted to investigate for the effects of optimum nitrogen application rates and supplemental irrigation on agronomic characteristics and grain yield of bread wheat cultivars in Koohdash under rainfed conditions. The experiments were carried out split- split- plot in randomized complete block design arrangements from 2013- 2015 cropping years. The irrigation treatment (rainfed, planting, planting + flowering with rates of 50 mm), two cultivars (Karim and Koohdasht) and different nitrogen rates (0, 60 and 120 kg/ha) were arrangement in main plots, sub- plots and sub- sub- plots, respectively. The results showed that grain yield, biological yield and number of spike per m2 were significantly increased, but significant difference was not observed between two levels of nitrogen application. Therefore, the most appropriate management of nitrogen application is 60 kg/ha, considering economic issues. Also, the supplemental irrigation significantly increased grain yield, but significant difference was not observed between irrigation treatments. Considering economic issues, it can be concluded that irrigation at planting was superior to non- irrigation and irrigation at planting + flowering. Although, the main effect of cultivar was not significant for evaluated traits, but Karim cultivar produced the highest grain yield under supplemental irrigation at planting and nitrogen application 60 kg/ha. Finally, it can be concluded that wheat grain yield can be improved using supplemental irrigation management and nitrogen under rainfed conditions.