Effects of PBAT biodegradable mulch on lettuce (Lactuca sativa L.) physiology and soil microbial community: Based on a long-term degradation trial

Poly (butylene-adipate-co-terephthalate) (PBAT) biodegradable mulch film has been considered a promising, environmentally friendly, and sustainable alternative to polyethylene. However, its long-term effects on crops and soil remain insufficiently understood. This study aimed to investigate the effects of PBAT mulch film with three application rates (0.05 g/kg, 0.5 g/kg, and 5 g/kg), as well as polyethylene (PE) mulch film (0.05 g/kg), on lettuce (Lactuca sativa L.) growth and soil microbial communities after 4-year pot experiment. The results indicated that the degradation of PBAT biodegradable mulch film in soil was significantly higher than that of PE. The concentrations of chlorophyll a, total chlorophyll, vitamin C, soluble protein, and nitrate in lettuce significantly increased in high application rates of PBAT mulch film. Soil urease (UR) activity increased with the increase of the PBAT application rates, whereas catalase (CAT) activity decreased. Moreover, the application of PBAT biodegradable mulch film significantly altered the composition of soil bacterial and fungal communities. The relative abundances of the bacterial genus Chujaibacter and Pseudolabrys increased with high PBAT application rates. Beneficial fungi such as Amphinema and Trichoderma showed an increasing trend, while pathogenic fungi exhibited the opposite pattern. These trends were also validated with the functional classification of bacteria and fungi. Overall, our findings suggest that PBAT mulch film application exerts significant effects on the soil micro-ecological environment and crop growth.