Growth dynamics and cotton yield under variable thermal regimes in south-western Punjab

A study was carried out during 2020 and 2021 to examine the growth dynamics and cotton yield under various thermal regimes in south western Punjab. The experiment was planned in a factorial randomized complete block design with four sowing dates and two cultivars and replicated thrice. There was a significant decline in growth and yield attributes of tested cultivars with each successive delay in sowing from April 01. Early sown crop recorded higher seed cotton yield (2223-2956 kg ha^-1), which was 4-5% higher than April 20, 17-18% higher than May 10 and 36-46% higher than May 30 sown crop. This increase in seed cotton yield was due to congenial weather conditions which resulted in extended phenophases, better growth attributes like plant height and leaf area index, improved yield attributes like monopods plant^-1, sympods plant^-1, bolls plant^-1 and boll weight that lead to higher seed cotton yield. Results also confirmed the outperformance of Bt hybrids in comparison to non-Bt genotype. The Bt cotton sown in the month of April was found to give higher seed cotton yield as compared to its non-Bt version.