Heat use efficiency and yield optimization in wheat as influenced by irrigation scheduling

Efficient irrigation scheduling is critical for sustaining wheat (Triticum aestivum L.) productivity under water-limited and thermally stressed environments. A two-year field study (Rabi 2022–23 and 2023–24) was conducted at Lovely Professional University, Punjab, to evaluate the impact irrigation scheduling on agrometeorological indices, heat use efficiency (HUE), dry matter accumulation, and yield performance of wheat. The experiment was laid out in a randomized block design with ten irrigation treatments, including soil moisture depletion- and plant stress index (PSI) based schedules, alongside rainfed and recommended irrigation regimes. Results revealed that irrigation at 50% depletion of field capacity significantly enhanced phenological duration, leaf area index, crop growth rate, and relative water content compared with sub-optimal and rainfed treatments. The highest grain (5.99 t ha⁻¹) and straw yields (7.58 t ha⁻¹) were recorded under 50% FC depletion, followed closely by 0.50 PSI and 30% FC depletion. Heat and heliothermal use efficiencies were also superior in these treatments, underscoring the importance of maintaining adequate soil moisture during critical growth stages. The findings demonstrate that thermal indices can serve as reliable predictors of wheat growth and yield, while precise irrigation scheduling is essential for enhancing resource use efficiency and mitigating climate-induced yield losses.