Synergistic effects of mulch type and deficit irrigation on physiological determinants and yield of spring maize (Zea mays L.)

Water scarcity necessitates a paradigm shift in maize production from maximizing yields to optimizing water productivity. Deficit irrigation (DI) offers significant water savings, but its effectiveness is often compromised by non-productive soil evaporation. This two-year field study quantified the synergistic effects of mulch type and DI on the physiology and yield of spring maize (Zea mays L.) in a semi-arid environment. A factorial experiment tested three mulch types (black plastic mulch-BPM, paddy straw mulch-PSM, no mulch-NM) and three drip irrigation levels (80%, 100%, 120% of crop evapotranspiration-ETc) and a conventional flood irrigation control. The combination of PSM with 100% ETc sustained superior photosynthetic physiology maintaining high photosynthetic rates, stomatal conductance, and photosystem II efficiency and achieved a grain yield of 84.04 q ha⁻1, statistically equivalent to the surplus-water treatment (120% ETc) and significantly greater than conventional flood irrigation (75.44 q ha-1). Crucially, PSM with 80% ETc achieved a grain yield (71.10 q ha-1) comparable to both NM with 100% ETc and the conventional control, thereby saving 20% of irrigation water with no significant yield penalty. In contrast, BPM resulted in the lowest physiological performance and yields under the high-temperature spring conditions, likely due to root zone overheating and restricted gas exchange. This study demonstrates that PSM with 100% ETc is optimal for yield maximization, while PSM with 80% ETc establishes a resilient, water-smart ‘more crop per drop’ strategy for sustainable maize intensification.