Optimizing sowing strategies for winter maize: phenological and light use dynamics in the middle Indo-Gangetic plains

A comprehensive understanding of crop phenology and light dynamics, particularly the spatial variability of these interactions within the canopy, is critical for developing new strategies to enhance field-scale productivity. In pursuit of this, an innovative field experiment on winter maize was conducted during 2021-2023, aiming to elucidate the complex relationships among phenological development, canopy light balance components, and light use efficiency across diverse microenvironments. This study offers new insights into optimizing yield potential under real-world field conditions. Winter maize was sown on five dates at 10-day intervals, viz., 1st November, 10th November, 20th November, 30th November, and 10th December in two consecutive winter seasons (2021-22 and 2022-23) at Pusa (25.7°N, 87.5°E, 52 m), Bihar, situated in the middle Gangetic plains of India. The results revealed notable variations in the crop's phenological responses across sowing dates. Delayed sowing extended the emergence phase but shortened the vegetative period, leading to an accelerated progression to reproductive stages. Moreover, key phenophases such as tasseling, silking, and milking occurred more rapidly in later sowings, likely due to variations in temperature and day length. Incident photosynthetically active radiation (PAR_in) over the canopy was significantly affected by sowing date. This caused differences in intercepted, transmitted, and absorbed PAR depending on the crop stage and canopy density. Among all sowing dates, the 20th November sowing recorded the highest levels of intercepted and absorbed PAR, attributed to the maximum leaf area index. The fraction of absorbed PAR (fAPAR) consistently remained lower than the fraction of intercepted PAR (fIPAR) throughout the phenological stages. Additionally, fIPAR and the light extinction coefficient (k) exhibited logarithmic and linear relationships with leaf area index, respectively. The highest light use efficiency (5.72 g MJ^- 1) was achieved with the 20th November sowing, indicating effective utilization of the prevailing resource environment to maximize maize yield.