Boosting Photosynthesis and Antioxidative Enzyme Activity in Wheat-Cotton Cultivation with Drip Irrigation

Abstract

A two-year study (2020–2022) in Punjab, India, examined subsurface drip irrigation (SDI) configurations: lateral depths (20, 25 and 30 cm) and emitter spacing (20, 30 and 40 cm) under deficit irrigation [100%, 80% and 60% crop evapotranspiration (ETc)] in a cotton (Gossypium hirsutum L.; Malvaceae)-wheat (Triticum aestivum L.; Poaceae) system, compared to flood and surface drip controls. Using a split-plot design with three replications, the study assessed yield, irrigation water productivity (WPI), and physiological responses amid water scarcity. Deficit irrigation at 60% ETc reduced seed cotton yield by 16% (2825 –2367 kg ha^− 1) and wheat grain yield by 11–13% (50.4–51.9 to 44.7–45.0 q ha^− 1), with cotton more sensitive to water levels and wheat to drip configurations. Both crops showed stress during reproductive stages, with lower stomatal conductance; cotton maintained stable quantum yield (ФPSII) early in boll development, while wheat down-regulated ФPSII throughout reproductive phases. SDI mitigated moisture stress, enhancing chlorophyll content and stomatal conductance during critical growth stages compared to flood irrigation. Antioxidant enzyme activities increased significantly under water deficit, with cotton showing 24% higher ascorbate peroxidase activity and wheat exhibiting 21.6% and 24.8% increases in superoxide dismutase and catalase respectively. Malondialdehyde content increased by 24.9% in cotton and 13.3% in wheat under 60% ETc, while proline accumulation was more pronounced in cotton (22.9%) than in wheat (10.9%). Drip fertigation increased seed cotton yield by 10.5% (2258–2320 to 2685 –2373 kg ha^− 1) and wheat by 8.9% (45.0-49.5 to 48.8–54.1 q ha^− 1), with WPI improvements of 85–134% in cotton and 84 − 66% in wheat over flood irrigation. The optimal SDI configuration: 20 cm lateral depth, 20 cm emitter spacing, and 80% ETc: maximized WPI (cotton: 1.19–2.43 kg m^− 3; wheat: 2.83–3.43 kg m^− 3), outperforming surface drip and flood irrigation. Correlation analysis revealed significant relationships between physiological parameters and economic yield, with protein content positively correlating with antioxidant activities. These findings support SDI at 80% ETc with shallow laterals and close emitter spacing as a sustainable approach to enhance crop productivity and water efficiency in water-scarce cotton-wheat systems.