Graphical analysis of nitrogen and sulfur supply on yield and related traits of canola in eastern Canada


Ma, B.L., Zheng, Z.M., de Silva, N., Whalen, J.K., Pageau, D., Vanasse, A., Caldwell, C., Earl, H., Smith, D.L. (2020). Graphical analysis of nitrogen and sulfur supply on yield and related traits of canola in eastern Canada. Nutrient Cycling in Agroecosystems, [online] 118(3), 293-309.

Plain language summary

Understanding the interactions among nutrients is essential to optimize fertilizer use efficiency while reducing negative effects on the environment. Canola (Brassica napus L.) is an economically important crop that can be used as edible oil for human consumption and as a protein-rich supplement, based on its meal, for livestock. In terms of cost and profitability, N is the most important fertilizer for canola production to improve its growth and seed yield. However, higher N fertilizer rates can reduce or negatively affect seed yield and quality as well as dramatically increase the environmental footprint. Therefore, improving nitrogen use efficiency (NUE) is a key factor for achieving profitable and sustainable production of canola in eastern Canada. Brassica crops need a larger amount of sulfur (S) than other field crops to synthesize primary and secondary metabolites, such as S-containing proteins and glucosinolates. Crops that grow in an environment with balanced nutrient availability tend to require less N fertilizer, as demonstrated by the lower N fertilizer rates in a balanced N and S fertilizer program for wheat and the greater NUE of canola with balanced N and S fertilizers. Sulfur alone cannot boost crop growth unless S is added together with sufficient levels of the three macronutrients. Deficiency in S can reduce the NUE, and vice versa (i.e., N deficiency reduces S use efficiency) in oilseed rape.

The objective of this multi-site-year study across eastern Canada (Ottawa, Guelph, Montreal, Quebec, Nova Scotia) was to test the hypothesis that environmental factors and N and S rates interactively affected seed yield and yield components. The graphical GGE biplot tool was used to visualize the N x S interaction on yield and NUE, and to identify the traits that were associated with yield formation under specific environments.

In this study, using a novel analysis approach, biplot, we documented the heterogeneity of canola production responses to N and S applications across eastern Canada and highlighted the need to develop a site-specific balanced nutrient management strategy. Unlike soil N, soil S supply is rarely determined prior to crop production, even for high S requiring crops such as canola. Uniquely, the N × S interactions in this study improved seed yields in most cases, and S supply could enhance NUE and/or prevent loss of NUE when high N rates are applied. Therefore, further research is needed to link the soil’s inherent nutrient use efficiency, (especially S), with canola yield and NUE response to fertilization, to effectively use both N and S nutrients while reducing environmental impacts.


Profitable canola production depends upon an adequate supply of nitrogen (N) and sulfur (S) fertilizer. However, agricultural soils in eastern Canada seldom receive S fertilizer and rely on inherent S supply from biogeochemical and anthropogenic sources, which could be a yield-limiting factor for canola. The objective of this study was to document N × S fertilizer interactions to develop site-specific best management practices for canola production in eastern Canada. Factorial field experiments were conducted for four consecutive cropping seasons at five locations across eastern Canada. The N × S and N × S × environment interactions on seed yields and yield-related traits were visualized with the graphical analytical genotype and genotype-by-environment biplot tool. The highest seed yield was achieved with 150 kg N ha−1 together with 20–40 kg S ha−1 in 15 of the 19 test site-years. Seed yield was closely related to harvest index and number of seeds pod−1. Fertilizing canola with 20 kg S ha−1 enhanced the nitrogen use efficiency (NUE) of canola receiving 75 kg N ha−1, but the benefit of S fertilizer on NUE was negligible when N fertilizer rates increased to 150 kg N ha−1. Since canola yield response to fertilizer inputs varied from one site to another, due to the variation in environmental and soil conditions, we conclude that N × S fertilizer recommendations for canola production need to be developed on a site-specific basis in eastern Canada.

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