Jeetan Raj, A.K. Singh, S.R. Mishra, A.N. Mishra, Kirti Vardhan Pandey, Shubham Pandey, Brajesh Kumar and *Gaurav Kumar Chaturvedi
Abstract
A field experiment was conducted during the Rabi seasons of 2024â25 and 2025â26 at the Agro-meteorology Research Farm of Acharya Narendra Deva University of Agriculture and Technology, Kumarganj, Ayodhya (Uttar Pradesh), to evaluate the phenological and thermal index responses of wheat (Triticum aestivum L.) varieties under different growing environments. The experiment comprised three dates of sowing, viz., 30 November (D1), 10 December (D2), and 20 December (D3), and three wheat varieties (HD-2967, PBW-343, and PBW-502) arranged in a split-plot design with four replications. Agro-meteorological indices including growing degree days (GDD), photo-thermal units (PTU), and helio-thermal units (HTU) were computed at different phenophases using a base temperature of 5 °C. The results revealed that timely sown crop (D1) recorded significantly higher accumulation of thermal indices and longer crop duration compared to delayed sowing (D2 and D3). Accumulated GDD, PTU, and HTU at maturity were highest under D1 and lowest under D3, indicating better utilization of thermal and radiational resources under timely sowing. Among varieties, HD-2967 exhibited longer duration and higher accumulation of GDD (1613.7 and 1655.0 °C days), PTU (19363.8 and 19860.0 °C day-hours), and HTU (11413.3 and 10423.7 °C day-hours), whereas PBW-502 showed early maturity with lower thermal requirements. Correlation analysis indicated a positive and significant relationship between grain yield and agro-meteorological indices, with PTU showing the highest association (R² = 0.63), followed by GDD (R² = 0.58) and HTU (R² = 0.51). The study concludes that timely sowing enhances thermal resource utilization and prolongs crop duration, thereby improving yield potential, while varietal differences in thermal requirements influence phenological development and adaptation under varying thermal regimes.