Optimizing the planting density of Bt. cotton varieties for rainfed vertisols of central India

The field experiment was conducted during the monsoon seasons of 2019–20 and 2020–21 at ICAR-Central Institute for Cotton Research (CICR), Nagpur, Maharashtra. Bt cotton (Gossypium hirsutum L.) hybrids was introduced in India by the private seed industry in 2002. Hybrid seeds were expensive and its cultivation is input intensive, cotton breeders from the public sector R & D institutes released Bt cotton varieties in 2020 suitable for planting under low input situations. This study evaluated the production potential of four Bt varieties released and notified in India, from the ICAR-Central Institute for Cotton Research, Nagpur. The varieties, ICAR-CICR ‘PKV081- Bt’, ICAR-CICR ‘Suraj Bt’, ICAR-CICR ‘Rajat Bt’, and ICAR-CICR ‘GJHV 374 Bt’ were evaluated in a split plot design under rainfed conditions on a Vertisol, with four planting densities, viz. 0.37 lakh (90 cm × 30 cm), 0.55 lakh (90 cm × 20 cm), 0.74 lakh (90 cm × 15 cm) and 1.1 lakh plants/ha (90 cm × 10 cm). The results indicated that there were significant differences among varieties and plant densities with respect to seed cotton yield, lint yield, boll weight, days to first open flower and earliness index. ICAR-CICR ‘PKV081-Bt’ was the most productive variety, yielding 2,639 kg seed cotton/ha at 0.37 lakh plants/ha. The interaction (variety × plant density) was significant for seed cotton yield, lint yield and boll density. Concerning seed cotton yield, for varieties, ‘PKV 081 Bt’ and ‘Rajat Bt’, 0.37 lakh plants/ha was optimum whereas for ‘Suraj Bt’ and ‘GJHV 374 Bt’, 0.74 lakh plant/ha was optimum plant density. At densities of 0.74 and 1.1 lakh plant/ha, the plant height increased and the maturity was delayed. The study highlights the importance of selecting appropriate Bt varieties and optimizing planting density to increase the productivity of rained cotton on Vertisols of Central India.