Multivariate assessment of green pepper responses and water productivity under delayed irrigation regimes

Shamgani Mashhadi, Bahareh; Shiukhy Soqanloo, Saeid

doi:10.22098/mmws.2026.20610.1876

Multivariate assessment of green pepper responses and water productivity under delayed irrigation regimes

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نوع مقاله : پژوهشی

نویسندگان

¹ Ph.D. candidate of Agricultural Meteorology, Department of Water Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

² Assistant Professor of Agricultural Meteorology, Department of Water Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

10.22098/mmws.2026.20610.1876

چکیده

Climate change, precipitation fluctuations, and increasing evaporative demand necessitate optimal irrigation scheduling, even in humid temperate regions. Although crop responses to volumetric deficit irrigation are well documented, the integrated physiological and biochemical trade-offs governing pepper adaptation to cyclic irrigation timing delays remain largely unexplored. This study was conducted to evaluate the multidimensional responses of green pepper (Capsicum annuum L. cv. 'Hamedani'), identify critical stress tolerance thresholds, and model water productivity under delayed irrigation regimes using a randomized complete block design with three replications in Sari, northern Iran. Experimental treatments comprised timely irrigation at field capacity (on-FC, 70% available soil water) and irrigation delayed by 24 h (24hr-FC), 48 h (48hr-FC), and 72 h (72hr-FC). Extending the irrigation delay progressively reduced total fruit yield from 564.47 ± 368.93 g plant⁻¹ in FC to 262.44 ± 146.81 g plant⁻¹ in 72hr-FC (a 53.5% reduction), while irrigation water productivity (WPᵢ) increased from 1.66 ± 1.17 kg m⁻³ to 3.20 ± 2.05 kg m⁻³ due to a 57.1% reduction in seasonal water application. Principal component analysis (PCA) explained 84.18% of the cumulative variance across three orthogonal dimensions, delineating vegetative yield and dry biomass (PC1) from photosynthetic pigment stability (PC2) and tissue hydration (PC3). Ward's hierarchical cluster analysis and stress index evaluation (YSI = STI = 0.7051) revealed that the 24hr-FC regime co-segregates with the well-watered control, representing the critical agronomic threshold that stimulates secondary antioxidant defense (a 47.8% increase in total phenols) while avoiding severe structural biomass depletion and economic yield collapse.

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