Dr.D. P. BIRADARMANJUNATHA S. B.2018-02-162018-02-162014-12http://krishikosh.egranth.ac.in/handle/1/5810041006Two field experiments entitled “Effect of nitrogen levels and K:N ratio on the productivity of Bt cotton” and “ Response of Bt cotton hybrids to nutrient levels applied based on target yields” were conducted during 2012-13 and 2013-14 at Main Agricultural Research Station, Dharwad. The first experiment consisted nitrogen levels of 120, 150 and 180 kg ha-1 as factor I and K:N ratios of 0.25, 0.50, 0.75 and 1.00 as factor II which were laid out in Randomized Block Design with factorial concept having three replications. The second experiment consisted of Bt BG-II cotton Hybrids namely MRC-7351, Mallika, Brahma and Chiranjeevi as main plots and nutrients applied for target seed cotton yields of 2.5 t/ha (120: 55:125 NPK kg ha-1), 3.0 t/ha (145:70:150 NPK kg ha-1), 3.5 t/ha (170:85:175 NPK kg ha-1), 4.0 t/ha (195:100:200 NPK kg ha-1) and RDF (120:60:60 NPK kg ha-1) as sub plots. The treatments were laid out in split plot design with three replications. Mean of two years data indicated that, application of 180 kg N ha-1 with K:N ratio of 0.75 (180 kg N : 135 kg K ha-1) recorded significantly higher seed cotton yield (3347 kg ha-1), total dry matter production (298.7 g plant-1), higher gross returns (` 1,50,632 ha-1), net returns (` 1,01,258 ha-1) and B:C ratio (3.05) as compared to other treatment combinations. However, it was on par with the application of 150 kg N ha-1 with K:N ratio of 1.0 (150 kg N : 150 kg K ha-1). Among the different Bt cotton hybrids, Mallika Bt recorded significantly higher seed cotton yield (3392 kg ha-1), total dry matter production (299.9 g plant-1), higher gross returns (` 1,52,640 ha-1), net returns (` 1,01,612 ha-1) and B: C ratio (2.93) as compared to other hybrids. However, it was on par with Brahma Bt. Application of nutrients as per the target yield of 4.0 t ha-1 (195:100:200 NPK kg ha-1) recorded significantly higher seed cotton yield (3.94 t ha-1), gross returns (` 1,77,305 ha-1), net returns (` 1,21,022 ha-1) and B: C ratio (3.15) over other nutrient levels as per target yields. Mallika and Brahma Bt cotton hybrids with application of nutrients for the target yield of 4.0 t ha-1 (195:100:200 NPK kg ha-1) recorded significantly higher and comparable seed cotton yield (4220 and 4085 kg ha-1), net returns (` 1,32,598 and ` 1,27,035 ha-1) and B:C ratio (3.31 and 3.23) as compared to other treatment combinations.ennullThesis