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

Abstract

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 (IL1, 750; IL2, 450; and IL3, 300 mm water ha−1) and N rates (NR1, 0; NR2, 40; NR3, 80; NR4, 120; and NR5, 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 IL2 × NR4 treatment. The highest values of seed N concentration and seed N uptake were produced at IL2 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 IL1 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 IL2 × NR4 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.