Interactive effects of ETc-based drip irrigation scheduling and phytohormones on root architecture, physiological...

Wheat productivity is increasingly threatened by inefficient irrigation practices and declining groundwater resources. Therefore, the identification of efficient irrigation strategies is essential to enhance water productivity without compromising crop yield. A two-year field experiment was conducted using a split-plot design with three replications. The main plot treatments consisted of three crop evapotranspiration (ETc)-based drip irrigation scheduling levels, namely 0.6, 0.8, and 1.0 ETc. The sub-plot treatments included foliar application of salicylic acid (SA), gibberellic acid (GA), and abscisic acid (ABA), along with water spray as the control treatment. The results revealed that deficit irrigation at 0.6 ETc significantly increased root length and specific root length compared with 1.0 ETc, indicating adaptive root responses under water-deficit conditions. In contrast, full irrigation at 1.0 ETc maintained superior plant water status, as evidenced by higher relative water content, membrane stability index, chlorophyll index, and lower canopy temperature and electrolyte leakage compared with deficit irrigation treatments. Among the phytohormone treatments, foliar application of SA significantly enhanced root dry weight (18.5-26.2%), antioxidant enzyme activities (catalase and peroxidase), and physiological attributes compared with the water spray control and other phytohormones. The improved antioxidant activity under SA application suggested its role in alleviating drought-induced oxidative stress. The highest grain yield was recorded under 1.0 ETc, showing a 7.9-8.8% increase over 0.6 ETc irrigation. However, irrigation at 0.8 ETc in combination with SA produced grain yield statistically comparable to 1.0 ETc while using comparatively less irrigation water. Foliar application of SA under deficit irrigation conditions improved physiological stability through enhanced photosynthetic pigments and antioxidant defense mechanisms, thereby contributing to improved water-use efficiency. Overall, the findings suggest that ETc-based drip irrigation integrated with salicylic acid application can enhance drought tolerance, sustain wheat productivity, and improve water-use efficiency under limited water availability. The study provides valuable insights for developing climate-resilient and water-efficient wheat production strategies.