Maize yield reduction is more strongly related to soil moisture fluctuation than soil temperature change under biodegradable film vs plastic film mulching in a semi-arid region of northern China

The replacement of plastic film with biodegradable film is important for reducing plastic film residual pollution in semi-arid regions of northern China. However, information on biodegradable film improvements based on the hydrothermal requirements of major food crops in the typical plastic film mulching area is limited. This study used a combination of field data measurements and curve fitting to assess the spatiotemporal distribution of soil hydrothermal variation and the corresponding maize yield in the field under biodegradable film mulching (BM), polyethylene film mulching (PM), and without mulching (CT). The warming effect of BM was between those of PM and CT and all treatments differed significantly from each other. The duration of the warming effect of BM was shorter than that of PM, and the warming effect of both disappeared at the early jointing stage of maize. The BM soil moisture was significantly lower compared with PM and CT throughout the soil profile (0–180 cm). Moreover, moisture fluctuations were observed in the 0–40 and 40–120 cm soil layers of BM after degradation, and the timing of fluctuations coincided with the filling period of maize. Consequently, the water use efficiency and yield of BM were lower than those of PM. Hence, we suggest that the conservation effect of biodegradable film mulching on soil moisture should persist until the end of the maize filling period, and that the start-up stage of degradation cannot be based solely on the disappearance of the warming effect.