Effects of nitrogen and sulfur on canola yield and nutrient uptake

Spring canola (Brassica napus L. var. napus) is becoming a significant oilseed crop adapted to the western USA. Often N and S limit crop growth, Field experiments were established to study the effects of N and S fertilization on seed yield, oil content, and N, P, K, and S uptake of spring canola, Four N rates in combination with three S rates were evaluated on two irrigated and three rainfed locations in the western triangle area of Montana near Conrad, Seed yields ranged from 0.1 to 3.8 Mg ha(-1). Seed yield and oil content N responses were closely related to available N (fertilizer N plus soil NO3-N in 90 cm of soil). Seed oil content varied from 370 to 510 g kg(-1) and was depressed by increasing N, Optimum seed and oil yield occurred at about 200 kg N ha(-1). Two of the experimental sites responded to S, About 20 kg S ha(-1) was adequate for optimum seed and oil yields. At the optimal N and S levels, total plant N, P, K, and S uptake averaged 140, 25, 170, and 60 kg ha(-1), respectively. Of the total N, P, K, and S accumulation, about 40% of the N, 30% of the P, and 85% of the K and S remained in the postharvest residue.