Performance analysis of temperature increasing and moisture retaining of sugarcane bagasse biodegradable film with adjustable degradation cycle

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.