Effects of Nitrogen Application and Irrigation Water on Grain Yield and Water use Efficiency of Safflower in Isfahan

An experiment was conducted to evaluate the effects of different levels of nitrogen and irrigation on yield and yield components of safflower. Three nitrogen rates (0, 50 and 100 kg ha-1) under three irrigation levels (100% as control; 80% as mild limited irrigation, and 60% of crop water requirement as severe limited irrigation) were investigated using a factorial laid out in a randomized complete block design with four replications. Nitrogen application led to a significant increase in leaf chlorophyll content, photochemical efficiency, leaf relative water content, leaf proline content, leaf area index, shoot dry weight,, number of buttons per plant, number of grains per button, grain weight, grain yield, harvest index and water use efficiency. Photochemical efficiency, leaf relative water content, leaf area index, shoot dry weight, number of buttons per plant, number of grains per button, grain weight, grain yield, harvest index were decreased and leaf chlorophyll content, leaf proline content and water use efficiency were increased as the level of soil moisture was decreased. The highest amount of grain yield was obtained with application of 100 kg/ha nitrogen under irrigation regimes of 100 and 80% crop water requirement. While, the highest value of water use efficiency was obtained with application of 100 kg/ha nitrogen under irrigation regimes of 80 and 60% crop water requirement. According to the results obtained in this experiment, the application of 100 kg/ha nitrogen under irrigation regime of 80% crop water requirement seems to be appropriate to achive highest values for both safflower grain yield and water use efficiency.