Degradation property of oxo-biodegradable plastic film and its mulching effect on soil moisture, soil temperature and maize growth in rainfed Northeast China

The growing use of plastic film in agriculture has significantly increased crop production as it positively enhances the soil environment. However, the massive disposal of this material has as well increased environmental risk. One way to solve this problem is by developing a substitutable mulching film such as biodegradable films that are ultimately convertible into water, carbon dioxide and soil organic matter by micro-organisms. Oxo-biodegradable plastic film is a newly developed biodegradable film that can increase soil water, soil temperature and crop yield and it also has satisfactory degradation properties. In this study, series of experiments were conducted to determine the degradation properties (degradation rate, tensile strength and elongation) of oxo-biodegradable plastic films and the effects of different mulching treatments on soil moisture, soil temperature, maize growth and maize yield. The mulching experiment was conducted using three kinds of oxo-biodegradable plastic films with different ingredients and different degradation rates (Degradation a, Degradation b and Degradation c) and common plastic film, and using un-mulched field as the control. Maize was ridge-cultivated and films covered all soil surface. The results showed that:1) biodegradation rate of different oxo-biodegradable films met soil and crop requirements for high yield production. Degradation rates of Degradation a, Degradation b and Degradation c after maize harvesting were respectively 14.2%, 10.0% and 6.5%. While the tensile strength on the ridge tops of Degradation a, Degradation b and Degradation c were decreased respectively by 30.4%, 20.3% and 19.1%, elongation decreased by 10.4%, 13.5% and 5.0% under mulching in the field for 120 days. Meanwhile, tensile strength of side ridges decreased respectively by 59.0%, 50.7% and 45.6% for Degradation a, Degradation b and Degradation c and elongation by 71.7%, 55.6% and 51.0%. Decrease in degradation was significantly different for different films. Furthermore, decrease in degradation properties of the film on ridge side was significantly more than that on the top of ridge. 2) Compared with the control, oxo-biodegradable plastic film mulching significantly increased soil temperature in the 5-25 cm soil layer and soil moisture in the 0-40 cm soil layer on early maize growth period. Degradation a, Degradation b and Degradation c treatments increased average soil temperature in the 5-25 cm soil layers respectively by 4.5℃, 4.4℃ and 4.4℃. Soil moistures under Degradation a, Degradation b and Degradation c treatments were increased respectively by 3.2%, 2.9% and 2.2% in the 0-40 cm soil layer. 3) Oxo-biodegradable plastic film mulching promoted maize growth, enhanced early maize emergence and shortened overall growth period by 5-7 days. Also the height and LAI of maize under oxo-biodegradable plastic film mulching were significantly higher than those under un-mulched treatment and slightly better than that under common plastic film mulching. 4) Compared with the control treatment, three oxo-biodegradable plastic films and common plastic film treatments increased ear length, ear diameter and 100-kernel weight of maize. At the same time, Degradation a, Degradation b and Degradation c and common film treatments significantly increased maize yield by 14.3%, 14.3%, 10.4% and 13.2%, respectively. Based on the study, oxo-biodegradable plastic film mulching significantly increased soil temperature and moisture and enhanced maize yield more than common film mulching, with degradation rate adjustable by changing ingredients. The results provided scientific basis for the replacement of common plastic films by oxo-biodegradable plastic films and for the development, popularization and application of oxo-biodegradable plastic films in Northeast China.