Influence of sowing date and nitrogen schedule on growth and productivity of canola oilseed rape (Brassica napus)

A field study was carried out at Ludhiana, Punjab during the winter (rabi) season of 2016–17, to ascertain the effect of dose and time of application of nitrogen on productivity of canola oilseed rape (Brassica napus L.) sown on different dates. The experiment was conducted on loamy sand soil low in organic carbon and available nitrogen, in a split-plot design in 3 replications with 3 sowing dates (15 October, 30 October and 15 November) in the main plots and 7 treatments of dose (100 and 125 kg/ha) and time of application of nitrogen (2 or 3 splits) in subplots. Variety ‘GSC 7’ was sown at row spacing of 45 cm, with plant spacing within row of 10–12 cm. Crop sown on 15 October required conspicuously lesser number of days for emergence, experienced longer crop duration, attained significantly better growth, showed increased number of yield attributes, seed and stover yields than that sown on 30 October which in turn significantly outperformed the crop sown on 15 November for various growth and yield traits and yields. The 15 October-sown crop gave (2.48 t/ha) 4.1% and 41.6% higher seed yield than 30 October-and 15 November-sown crop respectively. Application of 125 kg N/ha resulted in 11.9% higher seed yield (2.13 t/ha) than 100 kg N/ha through significant improvement in number of siliquae/plant and 1, 000-seed weight. Effect of N application time on different growth and yield attributes was variable. Mean maximum seed (2.40 t/ha) and stover (7.92 t/ha) yields obtained with 125 kg/ha of N applied in 3 splits as 50 kg at sowing + 50 kg at initiation of stem elongation + 25 kg at initiation of flowering were at par with application of 125 kg/ha of N in 2 equal splits at sowing and initiation of stem elongation (2.36, 7.84 t/ha). Seed yield produced by the crop sown on 15 October (2.68 t/ha), 30 October (2.51 t/ha) and 15 November (2.02 t/ha) with 125 kg/ha of N applied in 3 splits (50 kg at sowing + 50 kg at initiation of stem elongation + 25 kg at initiation of flowering) was at par with its yield in respective sowing dates with application of 125 kg/ha of N (2.60, 2.46, 2.02 t/ha respectively) and 100 kg/ha of N (2.57, 2.46, 1.94 t/ha respectively) in 2 equal splits at sowing and at initiation of stem elongation.