Sulphur uptake and distribution in double and single low varieties of oilseed rape (Brassica napus L.)

Sulphur (S) uptake and distribution in double low (Cobra) and single low (Bienvenu) winter oilseed rape were studied in field experiments at Cockle Park, Northumberland, at a site where the S supply was adequate. Total S uptake at maturity of between 80-100 kg ha⁻¹ was similar in both varieties. Applications of S at a rate of 100 kg ha⁻¹ increased S uptake by 10-15 kg ha⁻¹, while applications of nitrogen (N) at a rate of 300 kg ha⁻¹ increased S uptake by 29-34 kg ha⁻¹. Sulphur distribution in the vegetative tissues varied little between the two varieties but the distribution within the pods differed significantly between the two varieties. In Bienvenu 65.8% of pod S was located in the seeds, while in Cobra 57.4 and 68.8% in the 1988-89 and 1989-90 seasons, respectively, was retained in the pod walls. The high S content of the seeds of Bienvenu was due to their high glucosinolate content, whereas the high content of S in the pod walls of Cobra was associated with the presence of free$SO_4^{2 - }$;, which accounted for 70.6 to 89.4% of total S in the pod walls. The percentages of total plant S present in the pods were significantly increased by N applications and slightly decreased by S applications.