Nitrogen scheduling for Bt-cotton hybrids and its evaluation using cropgro-cotton model under light textured soils of South-Western Punjab

Nitrogen (N) availability is a critical factor influencing cotton yield and productivity. To evaluate the response of American cotton hybrids to split applications of nitrogen for enhanced productivity, field experiments were conducted during the kharif seasons of 2017 and 2018 at the Punjab Agricultural University (PAU)-Regional Research Station, Bathinda. The study aimed to assess the effects of various nitrogen application schedules on cotton yield. The experiment followed a split-plot design and was replicated three times. Three BG-II cotton hybrids viz., RCH 650 (V1), RCH 773 (V2), and NCS 855 (V3) were assigned to the main plots, while three nitrogen application schedules were tested in the sub-main plots: (1) ½ N at the 1^st irrigation + ½ N at 50% flowering (N₁), (2) ¼ N at the 1^st irrigation + ¼ N at the 2^nd irrigation + ½ N at 50% flowering (N₂), and (3) ½ N at the 1^st irrigation + ¼ N at the start of flowering + ¼ N at 50% flowering (N₃). The results indicated a significant increase in seed cotton yield under the N₃ schedule, followed by N₂, with the lowest yield observed under the N₁ schedule across both years. The highest seed cotton yield was recorded in the Bt hybrid RCH 773, followed by NCS 855. The yield reductions were 12.9% for RCH 650 and 5.9% for NCS 855 when compared to RCH 773. Regarding total crop water use, NCS 855 exhibited the highest water consumption, closely followed by RCH 773. In terms of nitrogen application schedules, N₃ resulted in the highest total crop water use, followed by N₁ and N₂. Water use efficiency was highest in RCH 650, followed by RCH 773 and NCS 855, with N₃ demonstrating the greatest water use efficiency overall. These findings highlight the importance of nitrogen application schedules in optimizing both cotton yield and water use efficiency, with the N₃ schedule showing the most promising results for enhancing productivity.