Soil structural control of partial root-zone drying improves irrigation efficiency and yield stability in maize under deficit water conditions

Partial root-zone drying (PRD) is widely recognized as an effective deficit irrigation strategy to enhance water-use efficiency; however, its performance depends strongly on the soil physical environment. This study investigated how contrasting soil management systems regulate the physiological and biochemical responses of maize to PRD under semi-arid field conditions. A field experiment was conducted using contrasting soil disturbance regimes combined with full irrigation, uniform deficit irrigation, and PRD at two levels of soil water availability. Results showed that the effectiveness of PRD was strongly modulated by soil structural continuity. Under moderate PRD, irrigation water was reduced by approximately 25%, while grain yield remained within 5–8% of full irrigation. In contrast, structurally disturbed soil exhibited significantly greater yield reductions under equivalent water deficit. Improved performance under structurally stable soil conditions was associated with higher relative water content, reduced membrane damage, and sustained photosynthetic activity. Lower sub-stomatal CO₂ concentration together with higher net photosynthesis indicated that photosynthetic limitation remained primarily stomatal rather than metabolic. In addition, PRD combined with improved soil structure reduced excessive accumulation of secondary metabolites while maintaining moderate activation of enzymatic antioxidant defenses, suggesting a more efficient regulation of oxidative stress. Although soil hydraulic conductivity and root-derived hormonal signals were not directly quantified, the integrated physiological responses observed across treatments strongly indicate that soil structural continuity enhances the effectiveness of PRD by stabilizing root-zone water availability and facilitating coordinated plant water regulation. These findings demonstrate that the agronomic success of PRD is contingent upon soil physical conditions and highlight the importance of integrating deficit irrigation strategies with soil-conserving management practices to improve water productivity in water-limited environments.