Effect of Supplemental Irrigation and Nitrogen Rate on Grain Yield,
Yield Components and Protein of Wheat Variety Koohdasht

This experiment was carried out at Agric. Exp. Stn. of Gonbad. The experiment design was a Randomized Complete Block arranged in a strip-plot. Vertical factor consisted of four irrigation levels (I0= without irrigation, I1= Irrigation at flowering, I2= Irrigation at grain filling and I3= Irrigation at flowering and at grain filling). Four rates of N fertilizer (0, 30, 60 and 90 kg N (as urea)/ha) were horizontal factor. The results revealed that increasing N fertilizer significantly increased grain yield and protein content and yield, biologic yield, harvest index, while N.U.E. significantly reduced. The highest yield was obtained at 90 N kg/ha, however it had not any significant difference with 60 kg N/ha. Irrigation at both flowering and filling period (I3) significantly increased grain yield, grain per spike, grain yield and protein content and yield, N.U.E. while other traits reduced. Interaction of N fertilizer and irrigation was non-significant for all traits with the exception of protein content and N. U. E.