Canola has high nitrogen (N) and sulfur (S) requirements, yet research on canola nutrient management in eastern Canada is limited. This study aimed to (1) develop site-specific and most economically optimal rate of N (MERN) and S (MERS) to increase nutrient use efficiency and profitability and (2) quantify nutrient uptake per Mg yield across varying production levels. A three-year field study was conducted at two sites on coarse-textured (sandy loam) and fine-textured (clay loam) soils. Four N levels and four S levels were arranged in a factorial randomized complete block design. Soil nutrients, crop N and S uptake, nutrient use efficiencies, yield, MERN, and MERS were determined. Across 12 site-year-soil combinations, yield responded significantly to N fertilization in 11 cases, but significant S or NxS interaction effects occurred only in three cases. Yields were similar between sites but were higher in sandy loam soils than in clay loam soils. Severe drought in 2020 sharply reduced yields and obscured fertilizer effects. Excluding drought-affected cases, canola required on average 47 kg N ha -1 per Mg yield and 9 kg S ha -1 per Mg yield, with 33 kg N ha -1 per Mg yield and 3.1 kg S ha -1 per Mg yield removed from harvested seed. Under non-limiting S and normal weather, MERN and MERS were approximately 157 kg N ha -1 and 23 kg S ha -1 , respectively, to achieve 3.1 Mg ha -1 yields. As yield potential increased, nutrient uptake per unit yield declined. These findings highlight the importance of balanced, site-specific N and S management for canola production.
Ma et al. (Fri,) studied this question.