Sulfur Nutrition of Rapeseed II. Effect of Time of Sulfur Application

A growth chamber pot experiment was conducted to compare the efficiency of 35 S labeled sulfate applied at various stages of growth (at seeding, rosette, bud, and flowering stages) in rapeseed grown on S‐deficient soils. Plant uptake of fertilizer S was generally higher when S was applied at later growth stages. Much of the S applied during these stages, however, accumulated in excessive amounts within the leaves and was not retranslocated despite severe S shortages during seed formation. Seed yields were not affected by time of S application except under conditions of severe S stress where S applied after the rosette stage did not allow recovery of maximum seed yields. Plant maturity was delayed when S was applied after the rosette stage. The results suggest that S deficiency diagnosis using plant tissue analysis will allow successful amendment of S deficiency in rapeseed providing sulfate is applied during or shortly after the rosette stage.