Mulching coordinated the seasonal soil hydrothermal relationships and promoted maize productivity in a semi-arid rainfed area on the Loess Plateau

Mulching can improve crop productivity in semi-arid regions by improving hydrothermal conditions. However, there is a lack of systematic understanding of hydrothermal coordination mechanisms in long-term field ex-periments, which is also critical for sustainable agricultural development. This experiment had four treatments: (1) plastic mulching (PM); (2) sand mulching (SM); (3) alternate plastic and sand mulching (PSM); and (4) without mulching (CK). The results showed that before sowing, the soil water storage in the 0-300 cm profile of the PM, SM, and PSM treatments increased by 20.4%, 13.9%, and 12.2% compared with CK, respectively. The water consumption was ranked in the order of PM > PSM > SM > CK in the filling stage; and the > 10 degrees C accumulated soil temperature in PM, SM, and PSM increased by 126.9 degrees C, 58.3 degrees C, and 77.3 degrees C in the seed-ling-jointing stage compared with CK, respectively. There was a significant positive correlation between maize growth rate and > 10 degrees C accumulated soil temperature in all treatments in the seedling-tasseling stage, and the response sensitivities of maize growth rate to > 10 degrees C accumulated soil temperature of PM, SM, and PSM were highest in seedling-jointing, jointing-tasseling, and filling stages, respectively. There was a significant positive correlation between maize growth rate and seasonal water consumption, and response sensitivity was ranked in the order of PM > PSM > SM > CK in the seedling-jointing, jointing-tasseling, and tasseling-filling stages and PM < PSM < SM < CK in the filling stage. The seasonal water consumption in the jointing-tasseling stage was most critical to yield formation, and mulching reduced this response sensitivity. After 10 years of cropping, the soil water storage in the 0-300 cm profile decreased by 230.8, 202.9, 243.8, and 228.2 mm in the PM, SM, PSM, and CK treatments, respectively. The mulching practices coordinated soil hydrothermal relationships, with yield and water use efficiency (WUE) ranked in the order of PM > PSM > SM > CK for annual precipitation of 323.1-418.3 mm, and significantly differing (P < 0.05). The yield and WUE of PM and PSM did not significantly differ for annual precipitation of 484.4-533.3 mm and were significantly higher than those for SM and CK. These indicated that PM should be preferentially adopted in areas with rainfall below 420 mm, and the PSM in areas with rainfall above 420 mm, resulting in higher yield and WUE and less plastic film pollution.