Impact of varying nitrogen levels on seed cotton yield using CROPGRO-cotton model for South-Western region of Punjab

The performance of the CSM-CROPGRO-cotton model was evaluated for seed cotton yield under different nitrogen application levels for Bathinda, Punjab. In this context, experiments were laidout as normal (May 01) and late sowing (May 25) under three different nitrogen (N) levels i.e. <25% of recommended (N-1), recommended (N-2) and >25% of recommended (N-3). The study results revealed that, observed seed cotton yield ranged from 1540-3384 and 872-2210 kg ha(-1), while, simulated seed cotton yield varied from 2271-3249 and 1984-2422 kg ha(-1) for normal and late sown crop, respectively. Observed and simulated seed cotton yield was found to be decreased when amount of N-application reduced and vice-versa. Moreover, greater variations in seed cotton yield were recorded with reduced N-application than increased level of nitrogen over recommended. CROPGRO-cotton model was found underestimated during 2014, while overestimated in 2015. The year 2015 also had larger variations between observed and simulated yield during Kharif 2015 as it is observed that the seed cotton yield was affected by whitefly infestation. Statistics also showed slightly higher R-2 (0.75) and d-Stat. (0.68) for recommended N-application than rest. Similarly, normal sown crop showed close proximity between observed and simulated value having higher r-square (0.67) and d-Stat. (0.73) value than late sown crop.