Influence of sowing windows and irrigation scheduling on agro-meteorological indices and wheat yield

At the experimental research farm of the Department of Agronomy, Experimental Research Farm in Palampur, Himachal Pradesh, during the rabi seasons of 2021–2022 and 2022–2023, a field experiment titled “Agro meteorological indices influenced by different sowing windows and irrigation scheduling using weather model and spatial data of wheat in Western Himalayas” was carried out. The experiment comprised a split plot design with 3 replications and included 5 irrigation treatments: rainfed conditions (I1), 2 irrigations (I2), 3 irrigations (I3), irrigation scheduling based on Penman Monteith modified (I4) and irrigation scheduling based on spatial reference ET of grid (I5). The crop sown on 25th October had the highest values of growing degree days (GDD), helio-thermal units (HTU), heat use efficiency (HUE), photo-thermal units (PTU) and photo-thermal index (PTI) compared to the crop sown on 10th December in 2021–2022 and 2022–2023. This helped to increase the grain yield by 47.4 and 35.8 %, respectively, over the crop sown on 10th December. Due to the highest values of GDD, HTU, HUE, PTU and PTI observed under the highest irrigation treatments, the largest increase in grain yield was recorded with 3 irrigations (33.1 and 19.4 %) and Penman Monteith modified (33.7 and 13.5 %) over rainfed conditions. The findings recommend timely sowing around late October and the use of weather-based irrigation scheduling-especially the Penman-Monteith method as sustainable strategies to improve wheat productivity and climate resilience in the Western Himalayan region. These practices optimise thermal indices and water use efficiency, supporting adaptive agriculture under variable climatic conditions.