Plastic film mulching stimulates soil wet-dry alternation and stomatal behavior to improve maize yield and resource use efficiency in a semi-arid region

The mechanism of plastic film mulching combined with ridge-furrow construction to stimulate the soil water variation and then to promote the photosynthesis and resource utilization of maize are unclear. Unfortunately, this mechanism forms the scientific basis for optimizing the mulching design. A field experiment was conducted in a semi-arid region of China in 2015 and 2016 to evaluate the effects of plastic film mulching and ridge-furrow construction on soil hydrothermal conditions, photosynthetic characteristics, maize yield and resource use efficiency. Four treatments were established: ridge-furrow construction with full plastic film mulching (RF), ridge-furrow construction with half plastic film mulching (RH), flat planting with half plastic film mulching (FH), and traditional flat planting with no plastic film mulching (CK). Our results showed that plastic film mulching significantly improved soil water content and temperature, thereby enhancing the photosynthetic rate (P-n) of maize mainly by facilitating stomatal opening. The thermal effect of mulching accelerated maize growth and indirectly promoted water utilization, resulting in marked soil wet-dry alternation. This alteration was more obvious in 20-120 cm soil profile, which was characterized by relatively wet within 50 days after sowing (DAS), relatively dry from 50 to 130 DAS, and relatively wet again after 130 DAS, in comparison with that without mulching (CK). This intense soil moisture transform between wetting and drying was indicative of an efficient water use strategy because it drives water from soil evaporation to crop transpiration, thereby improving photosynthesis and plant resource capture. Results suggested the RF treatment, driving intense wet and moderate dry in soil relative to RH (moderate wet and slight dry) and FH (slight wet and intense dry), is an efficient farming strategy, which improved maize grain yield by 21.1-92.3%, radiation use efficiency (RUE) by 15.5-66.2%, water use efficiency (WUE) by 27.4-87.4%, and nitrogen use efficiency (NUE) by 15.4-37.8% based on grain yield than the other treatments. Therefore, the soil wet-dry alternation behavior (especially in 20-120 cm soil profile) during growth period can be used as a reference evaluation indicator for mulched maize utilization of resource in semi-arid regions.