Seed, Oil, and Protein Yields of Canola under Combinations of Irrigation and Nitrogen Application

Canola ( Brassica napus L.), an important oilseed crop in Iran, is intensively managed with high inputs of N and irrigation water. Understanding N and water use characteristics of canola will help improve N and water use efficiency (WUE) and reduce production costs. Here, the effects of irrigation levels (IL 1 , 750; IL 2 , 450; and IL 3 , 300 mm water ha −1 ) and N rates (NR 1 , 0; NR 2 , 40; NR 3 , 80; NR 4 , 120; and NR 5 , 160 kg N ha −1 ) on canola production are evaluated during 2006 and 2007 growing seasons. Data showed that irrigation levels and N rates and their interaction had significant effects on WUE for seed, oil, and protein as well as seed, oil, and protein yields/ha. The maximum values of seed, oil, and protein yields ha −1 , WUE for these traits and seed weight plant −1 were achieved at IL 2 × NR 4 treatment. The highest values of seed N concentration and seed N uptake were produced at IL 2 treatment. Among N rates, maximum averages of seed and straw N concentration were observed at 160 kg N/ha. The highest significant value of straw N uptake was observed at IL 1 treatment. Also, maximum N uptake for both seed and straw was the same at 120 and 160 kg N ha −1 . Total N uptake achieved significantly in IL 2 × NR 4 treatment. With decreasing irrigation water and increasing N rates, N use efficiency decreased significantly. In general, consumption of 450 mm water ha −1 season −1 and supplying 120 kg N ha −1 can produce the highest seed, oil, and protein yields ha −1 , while increasing WUE and decreasing N leaching.