降解周期可调控的甘蔗渣生物降解地膜增温保墒性能分析

针对云贵高原地区春季播种时存在季节性干旱的问题,使用塑料地膜容易导致农田土壤污染的现状,该研究采用Box-Behnken设计试验,将施胶剂成分的硅酸钠、可溶性淀粉、硅油含量作为因变量,将降解率、抗张强度、土壤温度、土壤水分作为响应值,制备了一种降解周期可调控增温保墒甘蔗渣生物降解地膜。以不覆膜作为对照组（CK）,探讨生物降解地膜的降解性能、抗张强度及对土壤水分和温度的影响,并观察降解过程中地膜纤维结构的变化。结果表明,地下覆膜的降解速度和降解强度均高于地表覆膜,覆膜72 d时,二者的降解率最高分别达86.41%、70.44%。在覆膜72 d时,地表试验组抗张强度下降到9.77～21.97 N/m,地下试验组在49 d后抗张强度接近为0;扫描电镜观察到地膜出现断裂的短纤维,与降解过程中地膜宏观表现出的膜片出现孔洞、质量逐渐下降规律一致。与CK相比,覆膜对提高土壤早间、午间、晚间温度均具有显著作用（P<0.05）,且所有试验组对提高土壤含水率均有显著影响（P<0.05）。综上,甘蔗渣生物降解地膜的增温、保墒性好,为农业生产上推荐适宜的地膜组成及含量以指导生产实践具有较好的应用价值。

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.