Document Type : Research Paper



To study the effect of different N-P-K levels and planting dates on wheat yield and N-use efficiency, a field experiment was conducted in Agricultural Faculty of Shahid Chamran University at 2008-2009. Experimental design was split plot on RCB with 3 replications. Main plot was planting date in 3 levels (27 Oct, 16 Nov, 6 Dec) and sub-plot was different N-P-K levels including F1-control (0-0-0), F2- 40% lower than optimum (70-50-40), F3- optimum (110-90-80), and F4- 40% higher than optimum (150-130-120). Crop grain yield and yield components and also different N-use efficiency indices were measured. Results showed that best grain yield was obtained at range of optimum planting date (second and third planting date). Early planting date had the lowest grain yield for fertilizer treatments. Highest and lowest grain yield belonged to level of 150-130-120 and control plot (6.18, 3.27 t/ha) respectively. Seed 1000-weight and No. raceme per m2 had the best effect on the grain yield improvement, respectively. Best NUE (38/08 kg/kg) was obtained in the second planting date and N-P-K level of 40% lower than optimum treatment. In addition, NUE declined with increase in N application. Also, in all planting dates, 70-50-40 fertilizer level had the best NUE. In conclusion, the treatment which produced the highest grain yield had not the best NUE.