Evaluation Nitrogen and Radiation Use Efficiency of Wheat (Triticum aestivum) under Irrigation Levels

Water and nitrogen are among the most important limiting factors controlling yield in crops. With due attention to importance this subject, in wheat a split plot experiment was carried out in the field, using randomized complete block design with three replications under different irrigation and nitrogen levels during the cropping season of 2009-10 in Shirvan region. The experimental treatments consisted of four levels of irrigation, I1= optimum irrigation (field capacity, FC), I2= Irrigation at 80% FC, I3= Irrigation at 60% FC and I4= without irrigation which were assign to main-plots, and four levels of nitrogen fertilizers, namely, N1= 0, N2= 100, N3= 175 and N4= 250 kg N/ha to sub-plots. The results of experiment showed that the highest amount of seed yield, biological yield, leaf area index during different growth stages, radiation use efficiency and nitrogen content in whole wheat and seed obtained from treatment of optimum irrigation (I1) and applications of highest nitrogen fertilizer level (N4), but there wasn’t significant different between this treatment with treatment of optimum irrigation and consumption of 175 kg N/ha (I1N3). The lowest values were obtained from treatment of no irrigation and nitrogen (I4N1). For nitrogen use efficiency there was two different conditions. In the first condition, nitrogen use efficiency increased under optimum irrigation (I1) and irrigation at 80% FC (I2) with increasing nitrogen level from N1 to N4. In the second condition, nitrogen use efficiency decreased under irrigation of 60% FC (I3) and without irrigation (I4) with increasing nitrogen level from N1 to N4. Generally, it can be concluded that to obtain the highest yield in region, optimum irrigation is necessary. To obtain highest nitrogen fertilizer consumption and seed yield 250 kg N/ha would be required however there wasn’t significant difference between 250 an 175 kg N/ha applications.