Effect of split application of sulphur and nitrogen on growth and yield attributes of Brassica genotypes differing in time of flowering

According to prevalent agronomic practices for cultivation of Brassica genotypes, N is applied in split doses, while S is applied as a basal dose. This may create imbalance in the supply of these nutrients during the growth and development of the crop because metabolism of N and that of S are closely linked and play a central role in protein synthesis. The requirement of one depends on the supply of the other, and the imbalance in their supply causes a reduction in the yield because of reduced uptake and assimilation of the two nutrients. In the present investigation, therefore, S was applied in split doses, along with N, to study its effect on growth and yield attributes of Brassica juncea (L.) Czern. and Coss. (V 1 ) and Brassica campestris L. (V 2 ). In the experiment, conducted in the field, 40 kg S ha −1 as CaSO 4 (gypsum) was applied either in a single basal application (S 1 ) or in two (S 2 ) or three (S 3 ) split applications; and 100 kg N ha −1 as urea was applied either in two (N 2 ) or three (N 3 ) splits. Biomass accumulation, leaf-area index (LAI), leaf-area duration (LAD), crop growth rate (CGR) and photosynthesis in the leaves were determined at various phenological stages. Split application of S and N (S 2 N 2 or S 3 N 3 ) resulted in significant improvement in growth and yield of both the genotypes compared with the application of S in a single basal application and N in two splits (S 1 N 2 ). Genetic variability was observed between the two genotypes in response to split application of S and N. V 1 responded better when S and N was applied in two split doses (S 2 N 2 ) than when it was applied as S 1 N 2 or S 3 N 3 This S 2 N 2 treatment resulted in 40.0, 39.7, 35.5, 48.2 and 18.1% enhancement in biomass accumulation, LAI, LAD, CGR and photosynthetic rate, respectively in comparison with S 1 N 2 . Seed yield, biological yield and harvest index were improved by 38.3, 26.3 and 9.5%, respectively, by S 2 N 2 over the results obtained with S 1 N 2 . In the case of V 2 , three split applications of S and N (S 3 N 3 ) resulted in maximum growth and yield. Increases in biomass accumulation, LAI, LAD, CGR and photosynthetic rate due to application of S 3 N 3 were 48.4, 81.3, 77.9, 101.1 and 28.6% respectively, over the results of S 1 N 2 . Seed yield, biological yield and harvest index improved by 41.3, 26.9 and 11.6% respectively, with this treatment.On the basis of results obtained in this study, it can be concluded that S must be applied in split doses for optimum growth and yield of Brassica genotypes. The variability in response of these genotypes to split application of S and N was due to differences in flowering time, as V 1 flowered earlier (just after the application of the second dose of S and N) than V 1 (just after the application of the third dose of S and N).