Tillage system affects soil water and photosynthesis of plastic-mulched maize on the semiarid Loess Plateau of China

Water deficit is a threat to agricultural sustainability in the semiarid Loess Plateau of China due to low and variable precipitation. Technologies to improve soil water content (SWC) are necessary for sustainable intensification of maize production. The potential of plastic film mulch and reduced tillage to improve SWC has been reported for the Loess Plateau. However, there has been little research on how tillage management can be integrated with plastic mulching as an approach to improve SWC and maize photosynthesis. A 3-yr field study was conducted to investigate how tillage system influences SWC, photosynthetic performance, grain yield, and grain water use efficiency (WUE_g) of plastic-mulched maize in a semiarid environment. Treatments were conventional tillage (CT), rotary tillage (RT), subsoiling (SS), and no-till (NT). Soil water content in the 0–30 cm depth with SS was 24, 31, and 13% greater at the flowering, kernel milk, and physiological maturity stages of maize phenological development, respectively, compared to CT. These improvements in SWC were associated with increased leaf water potential (17%), net assimilation rate (41%), transpiration rate (54%), and stomatal conductance (42%), and decreased intercellular CO₂ concentration (15%) and stomatal limitation (20%) with SS compared to CT. Subsoiling used more water (9%) and increased grain yield by 21% compared to CT, thus enhancing WUE_g by 11%. On average, reduced tillage systems had improved performance (SS > NT > RT > CT) for almost all parameters measured. These results show that SS is a viable option for increasing grain production of plastic-mulched maize in semiarid areas.