Effects of biochar versus film mulching on soil hydrothermal properties and wheat crop performance in semi-arid loess

Film mulching and biochar have been applied as effective measures for increasing crop yields in arid and semi-arid areas for many years. However, the effects of the temporal and spatial distributions of soil hydrothermal properties on crop yields are still unclear under film mulching and biochar addition. Thus, we conducted a field experiment with winter wheat on the Loess Plateau of China for two years (2020–2022) with three treatments: control, film mulching, and biochar. The results demonstrated that film mulching and biochar addition increased the average soil temperature in the 0–50 cm soil depth throughout the whole growth period and the influence depth exceeded 50 cm. Biochar addition only significantly increased soil temperature in the overwintering stage (p < 0.05). Film mulching increased the maximum and minimum temperatures in the 0–50 cm soil depth at seedling stage. Film mulching and biochar increased average ≥10°C accumulated soil temperature by increasing the ≥10°C accumulated soil temperature in the daytime and nighttime, and the number of days with a daily soil temperature ≥10°C during the whole growth period. Film mulching improved soil water storage in the 0–300 cm soil depth in each growth stage during both years, and also increased the wheat grain yield, aboveground biomass, and water use efficiency. Biochar addition increased the wheat grain yield and aboveground biomass of two years compared with control, but the increases were not significant (p > 0.05). In addition, correlation analysis showed that adequate temperatures in the 0–50 cm soil depth during the seedling and overwintering stages, and suitable soil moisture conditions in the 0–300 cm soil depth before sowing, jointing, and filling stages were important factors for increasing wheat grain yields under film mulching. In summary, film mulching mainly regulated the soil temperature in the 0–50 cm soil depth and moisture conditions in the 0–300 cm soil depth during different growth stages to increase grain yields. Film mulching has more obvious effects on moisture regulation, temperature regulation, and yield increases than biochar addition. Some environmentally friendly measures (such as conservation agriculture) with the same yield improving effect as mulching are also recommended to explore and promote in theLoess Plateau region.