Plastic film mulching significantly boosts crop production and water use efficiency but not evapotranspiration in China

It is a huge challenge for China to produce enough food on its own croplands to feed a population of over 1.4 billion. Plastic film mulching technology has been applied widely in the past decades and China represents a major player in terms of plastic film use in the world. So far, a series of field experiments have been conducted across the croplands to investigate the effects of plastic film mulching on crop productivity. This offers an op-portunity to comprehensively identify the crop yield and water use improvement potential and their key drivers based on local environmental conditions. Here, a synthetic analysis was conducted to illustrate the overall effects of plastic film mulching on relative changes in crop yield, water use efficiency (WUE), and evapotranspiration (ET), as well as the key impacting factors behind the changes. The results showed that plastic film mulching significantly increased crop yield by 39.5% and WUE by 37.9%, whereas the increase of ET under plastic film mulching (1.9%) was insignificant. The crop yield improvement under traditional film was significantly higher than that under degradable film, whereas the difference of crop yield improvement between film colours was not significant. Furthermore, crop yield and WUE improvements varied among different cropping regions and crop species, and were influenced by mean annual precipitation (MAP), mean annual temperature (MAT), elevation, and soil organic carbon (SOC) concentration. Generally, the performance of plastic film mulching in sustaining crop production was better in regions with poor environmental conditions, including low temperature and precipitation, high elevation, and poor SOC content. Unlike the significant increases of yield and WUE in most cases, the changes in ET varied among groups, ranging from significant decline to insignificant change to sig-nificant increase. The results of this study illustrate that plastic film mulching plays a critical role in terms of promoting crop production, improving water use, increasing farmers' income and securing food security. The successful application of plastic film mulching in China may have important implications for other developing regions in the world to overcome the severe problems of food shortage. However, the adverse effects on envi-ronment must be properly addressed by upgrading mulching film materials in the future.