Evaluation of irrigation strategies and crop water stress index in maize under Mediterranean conditions

As water resources become increasingly constrained, irrigation strategies that reduce water use are essential for sustaining crop production in water-limited regions. A two-year field experiment (2020-2021) under Mediterranean climatic conditions evaluated ‘Pioneer P1574’ hybrid maize (Zea mays L.) yield responses to deficit irrigation and examined the crop water stress index (CWSI) as an irrigation-scheduling indicator. The trial followed a randomized complete block design with three replicates. Five irrigation strategies were compared: Full irrigation (FI), where the measured soil water deficit in the 0-60 cm profile was refilled to field capacity at 7 d intervals; DI75, DI50 and DI25, receiving 75%, 50% and 25% of the irrigation water applied in FI; and rainfed (RF) without irrigation. Canopy temperature was monitored throughout the growing season using an infrared thermometer, and CWSI was calculated using the air vapor pressure deficit (VPD) to represent atmospheric demand. Grain yield was highest under FI (17 370 kg ha−1) and lowest under RF (7460 kg ha−1). Although yield decreased with increasing water restriction, water productivity (WP) and irrigation water productivity (IWP) improved as irrigation inputs declined, with maximum WP and IWP obtained in DI25. Seasonal mean CWSI values decreased as applied water increased, ranging overall from 0.21 to 0.66. Across both years, yield, thousand-grain weight, plant height, WP and IWP showed significant second-order polynomial relationships with CWSI. Based on these relationships, the approximately 0.23 threshold value for mean CWSI was identified as a practical threshold for achieving high maize yields while promoting efficient water use under Mediterranean conditions. This approach supports climate-smart management.