Effect of nitrogen doses and its time of application on growth and yield of Bt cotton (Gossypium hirsutum)

A field experiment was conducted during the rainy (kharif JuneNovember) season of 2014 at New Delhi, to study the effect of different levels and time of nitrogen (N) application on growth and yield of Bt cotton (Gossypium hirsutum L.). The results revealed that application of increasing levels of N from 100 to 175 kg/ha showed an in- crease in plant height (134.1 cm to 164.4 cm), leaf-area index (LAI) (2.50 to 8.91), dry-matter production (301.7 to 362.8 g/pl), crop growth rate (CGR) in Bt cotton, although the highest values of these parameters were recorded with application of 175 kg N/ha. Application of N when applied basal also recorded significant influence on various growth parameters over without basal dose of N. The yield of Bt cotton was also increased significantly by differ- ent N levels. The highest seed cotton yield (2.65 t/ha) was recorded with the application of 175 kg N/ha, being 25.6, 14.7 and 3.5% higher than 100, 125 and 150 kg N/ha, respectively. Basal application of N @ 30 kg/ha has an edge over the treatments where basal application of N was not done with respect to yield-contributing charac- ters (sympodial branches/plant, opened bolls, total number of bolls and boll weight) and yield of Bt cotton.