Evaluating water stress through stress degree days and phenology of summer maize under silicon and irrigation management strategies

A two-year field experiment was conducted during the summer seasons of 2023 and 2024 at Visva-Bharati, Sriniketan, West Bengal, to assess the effects of irrigation scheduling, irrigation methods, and silicon application on stress degree days (SDD) and phenological traits in summer maize (Zea mays L.). The study followed a split-plot design with three irrigation regimes based on cumulative pan evaporation (CPE: 40 mm, 50 mm, and 60 mm), three irrigation methods (border strip, every furrow, and alternate furrow) in main plot, and two silicon levels (control and foliar application @ 2 mM L-1) in sub plot. Results showed that frequent irrigation at 40 mm CPE and every furrow irrigation significantly reduced canopy stress (SDD:-0.311) and delayed tasseling (59.44 days) and silking (62.61 days), while wider irrigation intervals (60 mm CPE) advanced reproductive stages due to stress (SDD: 0.200). Every furrow irrigation proved most effective in minimizing stress and promoting phenological stability. Silicon application marginally lowered SDD (-0.015) but had no significant effect on tasseling and silking timing. Regression analysis indicated strong negative correlations between SDD and phenology (R2 = 0.46 for tasseling; R2 = 0.49 for silking), suggesting that increased stress accelerates flowering. The findings emphasize the importance of frequent irrigation, efficient water application methods, and supportive silicon use in managing water stress in summer maize.