<p>Understanding water use efficiency (WUE) dynamics and its influencing drivers is essential for sustainable agricultural water management. This study examines WUE at leaf (WUE_L) and plant (WUE_P) scales in maize under different soil, irrigation, and mulching regimes. Experiments with a combination of two soils (red sandy loam and black clayey), three irrigation (alternate partial root-zone drying-APRD, fixed partial root-zone drying-FPRD, conventional irrigation-CI), and two management (mulch and non-mulch) treatments were performed. Key physiological parameters including net carbon assimilation (A_n), stomatal conductance (g_s), vapor pressure deficit (VPD_L) at the leaf level, as well as plant biomass, transpiration, and soil moisture at the plant level were monitored over two seasons (monsoon and winter) to observe their role on WUE, and to establish scaling relations between WUE_L and WUE_P. Results revealed that PRD has significantly reduced g_s (43.33 ± 5.06%) with a marginal gain in A_n (15.61 ± 2.56%) over CI. APRD with mulch in red sandy loam soils achieved the highest WUE_L (199.42 ± 20.51µmol CO₂ mol^− 1 H₂O) and WUE_P (11.42 ± 1.86&#xa0;g L⁻¹) without reduction in biomass. Relative to CI, FPRD and APRD increased WUE_L by 18.77% and 38.91% in red sandy loam soils, and by 8.91% and 23.71% in black clayey soils. Mulching has further enhanced WUE_L by 23% and 6%. Statistical analysis showed g_s as the dominant driver of WUE_L during monsoon, and A_n, VPD_L as the dominant drivers of WUE_L during winter. A strong linear association between WUE_L and WUE_P was observed under APRD with mulch (R² = 0.73). Our results conclude that APRD with mulching can substantially improve maize WUE without compromising on yield, demonstrating the potential for sustainable irrigation in semi-arid regions.</p>