Optimization of plant density and nitrogen levels in Bt and non-bt cotton using the cropgro-cotton model on alfisols of the southern Telangana zone

A field experiment was conducted at the Agricultural Research Institute, Rajendranagar, during the kharif seasons of 2015 and 2016 to calibrate and validate the CROPGRO-Cotton model. The study evaluated two cotton cultivars (MRC 7201 BG II and WGCV-48), three plant densities (18,518, 55,555, and 1,48,148 plants ha^-1), and three nitrogen levels (120, 150, and 180 kg ha^-1). After calibration and validation, the model was used to determine optimal plant densities and nitrogen levels for cotton production under semi-arid conditions using DSSAT v4.6’s seasonal analysis tool. The model simulated seed cotton yield across nine plant densities (18,518 to 1,48,148 plants ha^-1) and eight nitrogen levels (110 to 180 kg N ha^-1) based on 30 years of historical weather data (1986-2015). Results indicated that the optimal plant density for MRC 7201 in Telangana’s semi-arid conditions was 55,555 plants ha^-1, with a nitrogen application rate of 120 kg N ha^-1, resulting in the best economic performance. Further validation with long-term datasets is suggested to improve the model’s accuracy and applicability.