Molecular Plant Breeding 2024, Vol.15, No.1, 34-41 http://genbreedpublisher.com/index.php/mpb 37 had high ductility and water vapor barrier properties, but also maintained good transparency. Zhang et al. (2018), comparatively studied the mechanical properties and degradation behaviors of PE, starch-polyester and cellulose paper-based membranes in soil. The results showed that under soil weathering, the mechanical properties of starch-polyester and cellulose paper-based membranes were significantly reduced, and even underwent It was found that the mechanical properties of starch-polyester and cellulose paper-based films decreased significantly under soil weathering, and even crushed severely, while PLA/PHA films still had mechanical properties similar to those of PE films. Figure 3 Molecular structure of PLA (Adopted from Qiu et al., 2021) 2.4PBAT PBAT is a new type of biodegradable aromatic copolyester, whose repeating structural unit consists of rigid chain segments of butylene terephthalate (BT) and flexible chain segments of butylene adipate (BA) (Kijchavengkul et al., 2008) (Figure 4), so PBAT has the good biodegradability and flexibility of aliphatic polyester, and the good mechanical properties of aromatic polyester (Wongphan et al., 2022). However, due to the fact that PBAT itself is too flexible, the rigidity and stiffness of the made film products are low, and the price is expensive, which limits its application in the agricultural field. Currently, PBAT-based biodegradable mulch films have appeared on the market, and Touchaleaume et al. (2016) conducted experiments on the growth condition of grapes by utilizing PBAT-based mulch films, and although it helped in the growth of grapes, the yield of grapes was basically the same as that of grapes cultivated with traditional PE mulch films after the degradation of the mulch films. Although the comprehensive performance of PBAT-based biodegradable mulch film is enough to be comparable to the traditional PE mulch film, and it can also realize complete biodegradation, the current market price of PBAT-based biodegradable mulch film is 3-5 times higher than that of PE mulch film, so it has not yet been popularized and applied on a large scale in the field of agricultural production. Figure 4 Molecular structure of PBAT (Adopted from Qiu et al., 2021) 3 Effects of Biodegradable Mulch on Soil Microorganisms 3.1 Soil microbial content Soil microbial biomass is the total amount of living organisms in the soil with a volume of less than 5×103 µm3, which is the most active component of soil organic matter. Among them, microbial biomass carbon is its important component. Microbial biomass carbon (MBC) is an easily accessible nutrient pool in the soil and the driving force of organic matter decomposition and nitrogen mineralization, and is closely related to the nutrient cycling of C, N, P and S in the soil. It can fully reflect the soil nutrient effectiveness status and soil microbial activity.
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