不同覆膜方式下PPC地膜降解特征分析

采用大田试验，设置无覆膜（CK）、PPC地膜双层覆盖（DF）及单层覆盖（SF）3种处理，分析玉米生长期间土壤的保温保水性能效果及PPC地膜在降解过程中结构变化。结果表明：2 a试验结果呈相同趋势，从地膜破解时间看，60 d时SF处理地膜表面产生细小裂纹后随时间推移逐渐增大至地膜破碎，而DF处理与SF处理相比较，延迟30～60 d，地膜表面出现裂纹。同时DF处理有效提高土壤温度和含水量，2018年试验中的120~150 d时，DF处理的土壤温度较SF、CK处理分别高7.30%~10.29%;DF处理的土壤含水量分别比SF和CK高5.89%~10.99%。2019年试验中的60 d、120 d和150 d时，DF处理的土壤温度与SF和CK相比，显著高5.44%~24.85%;90~150 d内DF处理的土壤含水量比SF、CK处理高8.60%~22.28%。对不同处理的地膜红外光谱吸收峰相对强度分析可知，与SF处理相比较，DF处理的C-OH、C=O、C-O-C键伸缩振动吸收峰强度下降趋势缓慢；与DF处理相比较，SF处理的数均分子量、重均分子量及力学性能的断裂伸长率、伸拉力强度明显降低。综合分析说明，双层PPC地膜覆盖方式可减缓地膜降解反应而导致的地膜破裂，进而提高土壤保温保水性能，可在实践中应用。

Degradation Characteristics of PPC Film under Different Mulching Methods

For the film-mulching in semi-arid areas, biodegradable plastic film is easily damaged during the crops growth,which it also causes the soil degradation, reduces soil water retention and a decline in crop performance. In this study, a field experiment was conducted under three treatments to determine the effects of the treatments on soil insulation and water retention during the growth stage of maize, and to analyze the structure changes of PPC film during the degradation process, the three treatments were no covering (CK), PPC mulch double-layer covering (DF) and PPC mulch single- layer covering (SF). The results showed that after 2 years of repetition, the time of film cracking under treatment of SF increased gradually and the film broke with time going on. Compared with SF treated film, the cracks on the surface under treatment of DF were postponed 30-60 days. At the same time,DF treatment effectively increases the temperature and water content of the soil.In 2018,the soil temperature with DF was 7.30%-10.29% higher than that SF and CK at 120-150 d;The soil water content of DF treatment was 5.89%-10.99% higher than that of SF and CK,respectively.At 60 d,120 d and 150 din 2019,the soil temperature of DF treatment was significantly higher than that of SF and CK by 5.44%-24.85%;The soil water content of DF treatment with in 90-150 d was 8.60%-22.28% higher than that of SF and CK.After analyzing the relative intensity of infrared absorption peaks of plastic film under the different treatments, the results showed that the absorption peak intensity of C-OH, C=O and C-O-C bonds in treatment DF declined slowly compared with treatment SF. Moreover, the molecular weight Mw,Mn and mechanical properties such as elongation at break and tensile strength significantly reduced in treatment SF compared with DF. The comprehensive analysis showed that the double-layer PPC mulching could slow down the degradation of the mulch, and then improve soil heat preservation and water conservation. In conclusion, the double-layer degradable mulch film can be applied in order to solve the problem related to easy damage of mulch film during the growth of crops,however, due to the influence of climate in different regions and the different degradation properties of different kinds of mulch film, it is necessary to further study the types and regional problems of mulch film and determine whether the residual film has any impacts on the soil after application of the double-layer mulch.