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Large amounts of plastic film residues in soil have posed a negative impact on the crops and environment. Alternatively, the sugarcane bagasse has widely been used as inexpensive, abundant, easily available, and sustainable raw material. In this study, a biodegradable film was developed to treat the sugarcane bagasse, in order to reduce the pollution of plastic film and the seasonal drought in the spring in Yunnan-Guizhou Plateau of South China. A Box-Behnken experiment was designed, where the sizing agent components of sodium silicate, soluble starch, and silicone oil content were chosen as the independent variables, whereas, the response values were the degradation rate, tensile strength, soil temperature, and soil moisture. Field experiments were conducted in the School of Modern Agricultural Engineering, Kunming University of Science and Technology, China from September to November 2017, where ten mulching times (10, 19, 27, 34, 40, 45, 49, 52, 62, and 72 d) were designed. Taking the no film mulching as a control (CK), the influence of the film was determined on the degradation rate, tensile strength of two mulching modes, as well as soil temperature and moisture. Scanning Electron Microscopy (SEM) was used to characterize the fiber structure of biodegradation film under two mulching modes during the test period. A bagasse biodegradable film was verified to regulate the degradation cycle for the high soil temperature and moisture, particularly for the better soil environment of sowing in spring. The results showed that the degradation rate and the intensity of the underground film were higher than that of the surface film after 72 days of mulching, where the mass-loss rates of the two mulching modes were 86.41% and 70.44%, respectively. Under the surface biodegradable film mulching, the average degradation rate in test group 1 was the lowest during the entire degradation period, which was 20.1%. The tensile strength in the surface test groups decreased to 9.77-21.97 N/m after 72 days of degradation, whereas, the mechanical properties in the underground tests group were close to 0 N/m after 49 days. The fiber of the mulch film was outstandingly dispersed, where the short fibers were appeared in the SEM images, indicating an excellent consistence with the biodegradable film holes and the gradual decline in the quality during degradation. There was no significant difference in the daily accumulated temperature of the soil in the two mulching modes (P>0.05), compared with the CK, but the significant differences in the accumulated temperature of the soil in the morning, noon, and evening. In the case of ground surface mulching, the thermal preservation performance in test group 1 was the best, where the accumulated temperature in the morning and evening was higher by 6.1% and 5.4%, respectively, and that lower by 7.9% at noon, compared with the CK. The soil moisture content in each test group was significantly higher than that of the CK (P<0.05) during the entire experimental period. In addition, the water retention capacity in test group 1 was the highest. It infers that the capacity of water retention decreased with the degradation of biodegradable film. However, the soil water content in test group 1 was 11.36%, which was significantly higher by 158.77% than CK. To sum up, considering soil moisture, soil temperature, degradation rate of biodegradable film and tensile strength comprehensively, the sizing agent of test group 1 had the best performance among all test groups, and the contents of which were: sodium silicate 10%, soluble starch 20%, and silicone oil 15%. Therefore, the sugarcane bagasse biodegradable mulching film was feasible to increase the soil temperature and moisture, providing for promising application prospects in agricultural production. [ABSTRACT FROM AUTHOR]

Plastic pollution has posed a serious threat to the environment in the world. Biodegradable plastics can be widely expected to effectively mitigate plastic pollution. The subsequent industrial composting can also be treated to reduce the growing demand for landfills. In this research, the microorganisms responded to the biodegradation mechanism was proposed for the PBAT-PLA biodegradable packaging under the controlled industrial aerobic composting, according to the national standard (GB/T 19277.1-2011). Microcrystalline cellulose was used as reference material. The compost samples were taken on day 140 when the degradation was in the active period. The initial compost (before degradation), compost without any biodegradable material, compost with microcrystalline cellulose, and compost with PBAT-PLA packaging materials were then labeled as compost A, B, C, and D, respectively. The bacterial/fungal community was analyzed during degradation, including the species diversity, speciation, and species difference. A sample comparison was made through 16S/18S high-throughput sequencing of microorganisms in compost. The microscopic morphologies of PBAT-PLA packaging materials and microcrystalline cellulose were characterized by a Scanning Electron Microscope (SEM), in order to explore the intrinsic microbial response to the degradation mechanism. The results showed that the bacterial diversity of compost B under the industrial composting at 58 ± 2 ℃ was significantly lower than that of initial compost A since only some thermophilic bacteria survived. The bacterial diversities in compost C and D were significantly higher than that of compost B, due to the addition of cellulose or biodegradable packaging materials which provided carbon sources. There was no significant change in the fungal diversity, due to unsuitable for most fungi to survive at high temperatures. The fungal abundance changed, due to the temperature and carbon source in the compost, where the compost B (blank sample) showed the lowest fungal abundance. The dominant bacteria in the compost C and D were Sphaerobacter, Longispora, norank_f_norank_o_Actinomarinales, and Rubrobacter, which belonged to Actinomycete. The student’s T-test was used to compare the composition of bacteria and fungi in the compost C and D with those in the compost B. The significant growing bacteria in the compost C and D, including norank_f_Euzebyaceae, unclassified_c_Actinobacteria, and Actinobacteria, belonged to Actinomycetes. Therefore, there were similar degrading microorganisms of PBAT-PLA membrane bag and microcrystalline cellulose at (58±2) ℃. The SEM images showed that the surface of PBAT-PLA packaging after degradation was covered with a layer of biofilm. The biofilm was mainly composed of the clusters of ellipsoid bacteria, which were inferred to be Sphaerobacter. Actinomycetes presented a positive effect on the depolymerization of polyester and the degradation of cellulose under industrial composting conditions. The complete biodegradation of polyester and cellulose depended on the microbial synergy, rather than a single strain. Therefore, the dominant bacteria and significant growth bacteria of biodegradable materials under industrial composting conditions can be expected to serve as a theoretical basis for screening key biodegradation bacteria in the future. It can also greatly contribute to breaking through the technical barriers of the long detection cycle with the current biodegradation for higher efficiency and speed. The identification of microbial communities can be an important indicator to evaluate the impact of the compost produced by biodegradable plastics on crops growth, and agricultural ecological environment. Consequently, a theoretical foundation can be made to optimize the industrial composting and biodegradable plastic testing standards. The finding can also provide a scientific basis for the large-scale promotion of biodegradable plastic films and the application of the compost produced from biodegradable plastics in advanced (or modern) agriculture. [ABSTRACT FROM AUTHOR]