Effects of biodegradable films on melon quality and substrate environment in solar greenhouse.

With the increase in plastic pollution of farmland substrate, biodegradable mulch film research has become a hotspot. However, the degradation rate of biodegradable plastic film over the entire crop growth period is still unclear, as well as its impact on crop growth and product quality. Here, several properties of two kinds of composite biodegradable mulch films, PBAT/PLA-[S1] and PBAT/lignin-[S2], are studied with polyethylene-[PE] and uncovered substrate (CK) as controls. We tested the differences in morphological characterization, physical properties, and weight loss rate of the plastic films, as well as the effects of the different plastic films on melon yield and quality, substrate temperature and humidity, physical and chemical properties of the substrate, and substrate fungal species composition. Compared to PE, biodegradable plastic films S1 and S2 increased substrate temperature and the net photosynthetic rate of leaves. The results of substrate 18 s rDNA assay of CK, PE, S1, and S2 after 80 days of treatment and pre-treatment showed that a total of 12 fungal phylum, with 317 fungal genera were found, in which Ascomycota as the main phyla and Penicillium as the main genera. Compared with PE, the S2 treatment significantly increased the single fruit weight, central sugar content and soluble sugar of melon by 225.35 g, 1.26%, and 0.68%, respectively (p < 0.05). When buried for 240 d, the weight loss rate of S2 was significantly increased by 86.08% compared with PE (p < 0.05). From these results, we extrapolated that covering the substrate with the most biodegradable film, PBAT/lignin composite (10 μm), improved the yield and fruit quality of the melon in winter greenhouse production.