H 2 O 2 Oxygenation Improves Root‐Zone Conditions, Cotton Productivity and Water Use Efficiency Under Subsurface Drip Irrigation

ABSTRACT Optimizing rhizosphere oxygen availability may improve crop performance under subsurface drip irrigation (SDI), but how root‐zone resource responses are coordinated with crop productivity and environmental performance remains unclear. A pot experiment evaluated four H 2 O 2 levels (0, 600, 800 and 1000 mg L −1 , denoted as H0, H1, H2 and H3, respectively) under three nitrogen rates (150, 300 and 450 kg N ha −1 ). Moderate H 2 O 2 oxygenation (600–800 mg L −1 ) improved soil water availability and shifted mineral nitrogen from NH 4 + ‐N towards greater NO 3 − ‐N availability. Compared with H0, H2 increased the mean soil water content by 17% and 24% at the bud and boll stages, respectively. At these stages, H2 increased NO 3 − ‐N by 16% and 29%. H2 also promoted root development and canopy performance, increased seed cotton yield by 20%–53% and water use efficiency by 21%–54%, and reduced greenhouse gas intensity by 29%–44%. However, moderate oxygenation increased CO 2 and N 2 O emissions while suppressing CH₄ emissions. Excessive H 2 O 2 application (1000 mg L −1 ) weakened root and canopy responses and reduced yield and WUE despite high nitrate availability. Overall, moderate H 2 O 2 oxygenation improved SDI performance by coordinating root‐zone water–nitrogen conditions with crop resource acquisition, highlighting the importance of matching oxygenation intensity with nitrogen supply.