Effect of timing of sulfur fertilizer application on growth and yield of rapeseed

There is usually a positive yield response when sulfur ( S) is applied to rapeseed ( Brassica rapa L.) plants grown on S-deficient soils. Recommendations include application of some of or the entire amount of S at planting, but the plant requirement as well as availability of S to rapeseed during its various phenological stages is not well documented. In a field trial, 40 kg S ha(-1) was applied as gypsum (CaSO4 center dot 2H(2)O) at planting (T-1), during vegetative (T-2, 30 days after sowing), flowering (T-3, 50 days after sowing), and pod-filling (T-4, 65 days after sowing) stages, and in split doses (T-5). Biomass accumulation, leaf-area index, and leaf photosynthetic rate were studied at various growth stages. Seed S ( sulfate and organic S) and yield parameters were studied at harvest. Sulfur (40 kg S ha(-1)) applied in three split doses during different growth stages caused maximum increase in these parameters, followed by T-2 and T-1. However, no significant discernable difference was observed for the application at planting (T-1) and during vegetative stage (T-2). No significant response was seen following the application of T-3 and T-4 when compared with the control (T-0). On the basis of these results, we concluded that application of S fertilizer in split doses during growth stages is better than application of the entire amount of S at any stage for obtaining optimum yield of rapeseed.