Abstract:
Abstract: Plastic film mulching has become an important cultivation practice in agricultural production in China. However, the residuals of plastic film in soil continuously increase with its considerable application. These residuals cause a series of negative effects on environment and land. Degradable film is recognized as a feasible choice to replace plastic film. This study aimed to reveal the influence mechanism and comprehensive effects of degradable film mulching on maize yield. A total of 28 papers were selected from published articles before November in 2016, and meta-analysis was applied. Critical information was obtained from each study, including experimental site, planting pattern, site altitude, average annual precipitation, average annual temperature, experimental duration, degradable film thickness, degradable film types, and maize yield. The collected data were divided into 2 groups. In the first group, no mulching was taken as the control for degradable film mulching, including 24 available comparison pairs. In the second group, plastic film mulching was taken as the control for degradable film mulching, including 24 available comparisons. The main steps included heterogeneity test, comprehensive effect size calculation, publication bias test and correction, sensitivity analysis, cumulative meta-analysis, meta regression analysis and influence factor analysis. The results showed that in the first group, degradable film mulching averagely increased maize yield by 17.8% compared with no mulching. There were no publication bias and extreme value. The cumulative yield increasing effect of degradable film mulching trended to be stable over time. Biodegradable film had a stable maize yield than photo degradable film and photo-biodegradable film. The degradable film with 0.008 mm thickness had a significantly higher maize yield than that with 0.006 mm. The yield increasing effect of degradable film mulching trended to be smooth during years of 2002-2015 with a range of 13.4%-17.3%, and was the highest (29.0%) in Gansu Province. There was a publication bias but no extreme value in the second group. Before publication bias was corrected, the maize yield was significantly lower under degradable film mulching than that under plastic film mulching. However, this difference was not significant after publication bias correction. The maize yield was not significant between degradable film mulching and plastic film mulching in regions, where altitude was higher than 1 000 m, average annual temperature was lower than 10 ℃, and flat planting and 0.008 mm film was used. The difference and variation of maize yield under degradable film mulching and plastic film mulching decreased in the last 5 years. In summary, degradable film mulching could achieve a high maize yield in regions with high altitude and low temperature, and flat planting using 0.008 mm film. This research can provide valuable information for the development and large-scale application of degradable film.