Effects of degradable film mulching on crop yield and water use efficiency in China: A meta-analysis

Degradable film (DF) has recently been demonstrated to be a good alternative to plastic film (PF) for mulching crops such as maize, wheat, potato and cotton. Whether or not the yield-increasing and water-saving effects of DF mulching vary with DF properties (type, color and thickness), field management (planting pattern) and environmental conditions (altitude, air temperature, rainfall and evaporation), however, are largely unknown. We therefore conducted a meta-analysis to: (1) determine the optimal type, color, thickness and mulching pattern of DF for maize, wheat, potato and cotton; and (2) identify the best environmental conditions of the yield-increasing and water-saving effects of DF mulching for maize, wheat, potato and cotton. The yield and water-use efficiency (WUE) for maize, wheat, potato and cotton were significantly higher for DF than non-film (NF) mulching, except for potato WUE. Yield and WUE for maize, wheat and cotton were lower with DF than PF. The properties of DF, planting pattern and environmental conditions greatly influenced the yield-increasing and water-saving effects of DF mulching. For maize, these effects were best at altitudes of 1000–1500 m, air temperatures of 10–15 °C, rainfalls of <500 mm, evaporation>2000 mm and effective accumulated temperatures of 2000–4000 °C, and the optimal type, color and thickness were biodegradable film (BDF) or photodegradable film, black and 0.008 mm, respectively. For wheat, yield and WUE were highest with BDF, especially at altitudes of 500–1000 m, air temperatures of 5–15 °C, rainfalls of <1000 mm and effective accumulated temperatures of 2000–3000 °C. For potato, yield was markedly higher under white BDF with a thickness of 0.008 mm, especially at altitudes >1500 m, air temperatures of 5–10 °C, rainfalls of 500–1000 mm, evaporation of 1000–2000 mm and effective accumulated temperatures of 2000–3000 °C. For cotton, PF could be replaced by BDF with 0.010 mm thick for altitudes of 1000–1500 m, air temperatures of 10–15 °C, rainfalls of <500 mm, evaporation>2000 mm and effective accumulated temperatures of 3000–4000 °C. For each crop, yield and WUE using DF were higher with a ridge-furrow planting pattern than a flat planting pattern, but not significantly This study provides a basis for the reasonable application of DF. Reducing production costs, however, is also very important in order to popularize DF mulching to a larger area.