Uptake and nutrient balance of nitrogen, sulfur, and boron for optimal canola production in eastern Canada

Citation

Ma, B.L., Zheng, Z., Whalen, J.K., Caldwell, C., Vanasse, A., Pageau, D., Scott, P., Earl, H., Smith, D.L. (2019). Uptake and nutrient balance of nitrogen, sulfur, and boron for optimal canola production in eastern Canada. Journal of Plant Nutrition and Soil Science, [online] 182(2), 252-264. http://dx.doi.org/10.1002/jpln.201700615

Plain language summary

The best way to improve nitrogen (N) fertilizer use efficiency (NUE) in canola is to adopt a nutrient balance approach, which considers the synergistic and antagonistic interactions between macro- and micro-nutrients that occur in soils and plants. If crop growth is limited by an excess or deficiency of another essential nutrient, focusing on the crop response to N fertilizer inputs alone is unlikely to improve N fertilizer use efficiency. Canola is expected to be sensitive to sulfur (S) concentrations in plant tissue, as S is an essential component of the amino acids cysteine and methionine, and oilseed crops in the Brassiceae family require larger amounts of S than small grain cereal crops. Brassica crops also have relatively high boron (B) requirements and are among the most susceptible to B deficiency. A steady supply of B during the peak vegetative, flowering, pod production and seed development stages is essential for optimum canola yields, due to the critical role of B in seed production.

A field study was therefore conducted at 9 site-years across eastern Canada to investigate the effects of N, S and B fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. In this study, we hypothesized that there are underlying interactions of N, S and B related to the seed yield and nutrient uptake of canola, and such interactions vary among site-years in the rainfed humid regions.

we found that fertilizer S application at a rate of 20 kg ha-1 greatly enhanced seed yields of canola and improved NUE at six of nine site-years, especially at the 150 kg N ha-1 + 20 kg S ha-1 combination. Our results suggest the importance of S supplement when high N rates are applied for canola production. In contrast, B fertilization had scant effect on seed yields in this study, irrespective of the amount and the application method. This plainly raises question on the necessity of B fertilization for canola production in eastern Canada.

The S concentrations at the 20% flowering stage were well within the sufficiency range (2.0 < S < 10.0 mg g-1). However, the N:S ratio at this stage was close to or over the critical value of 12 at five of seven site-years, when high N of 150 kg ha-1 was applied without S supplement. Though the effects of S fertilization on tissue S concentration were site-year specific, fertilizer N and S incorporation generally elevated seed S removal and plant total S uptake in most site-years. Boron fertilization mainly contributed to the increased straw B concentration and content. In addition, our pooled data analysis revealed that canola attained maximum seed yield of 3580 kg ha-1 with plant N uptake of 197 kg ha-1, plant S uptake of 33 kg ha-1, and seed and plant total B uptake of 60 and 200 g ha-1, respectively. Those critical N, S and B values and their potential for a posteriori nutrient diagnosis in canola warrant further field validation in the humid regions in eastern Canada.

Abstract

Balanced plant nutrition is essential to achieve high yields of canola (Brassica napus L.) and get the best economic return from applied fertilizers. A field study was conducted at nine site-years across eastern Canada to investigate the effects of nitrogen (N), sulfur (S) and boron (B) fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. The factorial experiment consisted of four N rates of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg ha−1, two S rates of 0 (S0) and 20 (S20) kg ha−1, and three B treatments of 0 (B0), 2 kg ha−1 at preplant (B2.0P), and 0.5 kg B ha−1 foliar-applied at early flowering stage (B0.5F). Each site-year used the same experimental design and assigned treatments in a randomized complete block design with four replications. Fertilizer S application greatly improved seed yields at six out of nine site-years, and the highest N use efficiency was in the N150+S20 treatment. Sulfur application generally increased seed S concentration, seed S removal, and plant total S uptake, while B fertilization mainly elevated straw B concentration and content, with minimal effect on seed yields. At the early flowering stage, plant tissue S ranged from 2.2 to 6.6 mg S g−1, but the N : S ratio was over or close to the critical value of 12 in the N150+S0 combination at five site-years. On average across nine site-years, canola reached a plateau yield of 3580 kg ha−1 when plants contained 197 kg N ha−1, 33 kg S ha−1 and 200 g B ha−1, with a seed B content of 60 g B ha−1. The critical N, S, and B values identified in this work and their potential for a posteriori nutrient diagnosis of canola should be useful to validate fertilizer requirements for canola production in eastern Canada.

Publication date

2019-04-01

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