Sulfur Nutrition of Rapeseed: I. Influence of Fertilizer Nitrogen and Sulfur Rates

Abstract

Both sulfur and nitrogen deficiencies have been observed in large acreages of western Canadian soils. These deficiencies prompted an investigation of the interactive effects of N and S on rapeseed (Brassica napus L.), a S‐sensitive crop that is extensively grown on these soils. Four rates of N (0, 50, 100, 300 mg N kg−1 soil) and four rates of S (0, 5, 15, 40 mg S kg−1 soil) were applied in all combinations to rapeseed grown in a pot culture experiment. Maximum seed yield responses to N and S were observed only when the availability of N and S was in approximate balance. Excessive N applications relative to S availability severely suppressed seed production. This effect was attributed to the accumulation of toxic levels of N metabolites. Excessive S applications relative to N availability produced excessive accumulation of S in the plant tissue. The leaves, and, to some extent, the stems, were the predominant sites of excess nutrient accumulation. Seed nutrient concentrations remained relatively stable over all fertilizer treatments. In most plant parts, the applications of one element reduced the concentrations of the other element by a “dilution” effect. The optimum ratio of available N to available S in the soil was estimated to be 7 to 1. Ratios below 7 resulted in inefficient utilization of the assimilated S, while ratios exceeding 7 resulted in reduced seed yields.

Influence of four successive annual applications of elemental S and sulphate-S fertilizers on yield, S uptake and seed quality of canola

“…The 20 kg S ha -1 rate produced or tended to produce more seed yield than 10 kg S ha -1 . These results were similar to those observed by Janzen and Bettany (1984a), who obtained a positive response of canola seed and straw yield to increasing S rate when adequate N was also applied.…”

“…Because S is immobile in the plant, deficiency of S in soil in the growing season can cause a drastic reduction in seed yield without serious reduction in straw yield (Malhi and Gill 2002). Extremely low seed yields in the zero-S treatment were due to nutrient imbalance of N:S, because only N was applied to a S-deficient soil (Janzen and Bettany 1984a). But, relatively lower seed yields in the sulphate-S fertilizer treatments, particularly at 20 kg S ha -1 rate, could not be due to N:S imbalance.…”

Resposta de culturas à aplicação de enxofre e a teores de sulfato num solo de textura arenosa sob plantio direto

“…Esta cultura se mostra muito importante para a reciclagem de sulfato, pois apresenta sistema radicular profundo e com alta capacidade de absorção de enxofre (JANZEN & BETTANY, 1984).…”

Nitrogen and sulphur fertilizer management for growing canola on sulphur sufficient soils

“…Subsequently, more work substantiated and quantified this interaction (Janzen and Bettany 1984;Bailey 1986;Grant and Bailey 1993;Jackson 2000;Malhi and Leach 2002). Janzen and Bettany (1984) and Nyborg et al (1974) observed decreases in canola (rapeseed) yield as a result of N application, when N was applied alone to S deficient soils. Janzen and Bettany (1984) estimated an optimum ratio of available N to available S in the soil to be 7 to 1.…”

“…Janzen and Bettany (1984) and Nyborg et al (1974) observed decreases in canola (rapeseed) yield as a result of N application, when N was applied alone to S deficient soils. Janzen and Bettany (1984) estimated an optimum ratio of available N to available S in the soil to be 7 to 1. Work by Malhi and Leach (2002) showed that although a N and S balance was necessary to obtain optimum canola yields, the N:S ratio could not be exploited further once the S deficiency had been corrected.…”