Response of Bt. cotton hybrid (Gossypium hirsutum) to integrated nitrogen management and potassium

A field experiment was conducted to evaluate the influence of integrated nutrient supply on the Bt. cotton (Gossypium hirsutum L.) hybrid Mallika during kharif season of 2009 and 2010 at the Agricultural Research Sta- tion Adilabad in Andhra Pradesh. The results showed that the leaf area, dry matter, bolls/plant and seeds/boll in- creased significantly through the substitution of 25% N with vermicompost both in 2009 and 2010. This treatment also found to remove significantly more N, P and K. Recommended dose of 120 kg N and 60 kg P O /ha P yielded 2 5 2.09 t/ha seed cotton in 2009. This was on par with the yield of 2.0 t/ha due to substitution of 25% N with vermicompost. In 2010 seed cotton yield of 3.36 t/ha was recorded with substitution of 25% N with vermicompost, which was significantly higher than seed cotton yield of 3.13 t/ha recorded with recommended dose of N and P through inorganic. Maximum net profit of 39,564/ha and 96,421/ha were obtained with the application of rec- ommended dose of 120 kg N and 60 kg P/ha with 60 kg K/ha in 2009 and 2010 respectively. Maximum benefit:cost ratio of 0.95 and 2.32/ were also realized from this treatment in the corresponding years. The inte- grated nutrient management reduced the profits per rupee investment. Seed cotton yield recorded significant re- sponse to K application up to 60 kg/ha in 2009 and 90 kg k/ha in 2010. Variation in response across the two sea- son attributed to rainfall variation and its distribution