Aladakatti, Y.R.Yogikoppa, Shruti M.2020-02-282020-02-282016-06http://krishikosh.egranth.ac.in/handle/1/5810143942A field experiment was conducted in medium deep black soils to assess the optimum drip irrigation regimes and fertigation to intra hirsutum Bt cotton and their effect on endotoxin expression. It was laid out in factorial randomised complete block design with three replications during 2015-16 at Agricultural Research Station, Dharwad. Paired sowing system with drip irrigation at 1.0 Etc recorded significantly higher seed cotton yield per ha (3,606 kg ha-1) over 0.6 Etc and furrow irrigation, but it was on par with 0.8 Etc. Fertigation with 100 per cent recommended dose (RD) N and K (150:75 kg ha-1) in six equal splits was recorded significantly higher seed cotton yield, and it was on par with fertigation 75 per cent RD N and K. The interaction effect of drip irrigating at 1.0 Etc with fertigation of 100 per cent RD N and K recorded significantly higher seed cotton yield (4,024 kg ha-1). However, it was on par with drip irrigation at 0.8 Etc with fertigation of 75 per cent RD N and K (3,943 kg ha-1). The Cry 1Ac and Cry 2Ab protein content in leaves was non-significant at all the growth stages due to irrigation levels except at 45 DAS, but different levels of nutrients had significant effect on endotoxin expression. Water use efficiency (WUE) was significantly higher with drip irrigation at 0.8 Etc level (6.76 kg ha-1-mm). Maximum WUE was recorded at 100 per cent fertigation of RD N and K and it was on par with 75 per cent fertigation of RD N and K. Significantly higher net returns (Rs 1,34,262 ha-1) and B:C (3.25) were realised with irrigating at 1.0 Etc along with fertigation of 100 per cent RD N and K in six equal splits, however it was on par with irrigation at 0.8 Etc with fertigation of 75 per cent RD N and K.ennullThesis