Exploring optimal film mulching to enhance potato yield in China: A meta-analysis

China is the world's largest potato (Solanum tuberosum L.) producer. Film mulching is widely used in potato production because it can effectively modify the soil micro-environment. Here, we conducted a meta-analysis to quantitatively evaluate the effects of film mulching on the potato yield in China. Film mulching noticeably increased potato yield by an average 32.5%. The enhancement was significantly higher with plastic film (33.5%) than with biodegradable (19.5%) or liquid (16.9%) film. Yield increases under plastic film mulching (PFM) varied across regions, with the largest increases observed in Northwest and North China. The improvements in potato yield tended to increase along with experimental duration and film thickness. Loam and clay loam soils, mulching ratio (ratio of the area of farmland mulched with film to the total area of farmland) of 50-99%, and potato monoculture or rotations with legumes had favorable effects on potato yields under PFM conditions. Whole season film mulching benefitted more from PFM than partial season film mulching, and ridge-furrow planting benefitted more from PFM than traditional flat planting. White film was more effective in regions having lower average annual precipitation (<400 mm) and temperature (<10 degrees C), while black film was the opposite. In conclusion, this meta-analysis suggests the adoption of PFM should be site specific. Moreover, although PFM may significantly enhance potato yield, the development of biodegradable film with comparable mulching effects and the improvement of technology for recovering residual film are important to achieve a sustainable and healthy agricultural industry.