Abstract:Plastic film mulching is an efficient agronomic method to increase yield and improve water use efficiency in arid and semi-arid regions. However, with the overuse of traditional refractory plastic film, the residual of plastic film was constantly increasing in the soil during the last recent decades, which had led to some negative impacts, such as environmental pollution and land degeneration. In order to maintain the function and reduce the negative impacts of traditional refractory plastic film, some degradable films were obligatory to take place of it. Several studies had demonstrated that biodegradable film could apply to maize and cotton cultivation instead of traditional plastic film, but few of them were dedicated to studying whether biodegradable film was suitable for winter oilseed rape ( Brassica napus L.), which is the most important oil crop in China. Three treatments, including plastic film (PM), biodegradable film (JM) and no film (CK), were conducted to systematically analyze and compare the effects of different types of film on soil temperature at 5 cm and 25 cm depths, soil water capacity in 0~100 cm depth, crop growth, root morphology characteristics, yield, quality and water use efficiency of winter oilseed rape in two growing seasons (2012—2013 and 2013—2014). The results showed that the effects of improving soil temperature and conserving soil moisture of JM were similar to PM and significantly better than those of CK （ P ＜0.05) before 150 DAS (days after sowing), but the effects were significantly lower than those of PM after 150 DAS because of the degradation of degradable film. No significant differences were found between PM and JM in plant height, leaf area index, shoot dry matter weight at different growth stages and taproot diameter of different soil depths at maturity stage （ P ＞0.05), but they were all significantly better than those of CK （ P ＜0.05). And the same characteristic was found in branch numbers, pod numbers and seed numbers of main raceme and branch raceme. Compared with PM, JM could better promote taproot to extend to deep soil layer, and effectively increase lateral root mass density in soil layer of 20~30 cm. No significant difference was found between PM and JM in saving water and increasing yield （ P ＞0.05), and yield and water use efficiency of two types of film were significantly higher than those of CK in two years （ P ＜0.05). When treated with PM and JM, the yields of winter oilseed rape were increased by 45.91% and 37.02%, respectively, and the water use efficiencies were increased by 81.68% and 53.86%, respectively. JM could also reduce erucic acid and glucosinolate content, which were harmful to human health, compared with PM. Then, from the perspective of application effects, biodegradable film could be applied to winter oilseed rape cultivation instead of traditional refractory plastic film.
