Effects of plastic film mulching on yield, water use efficiency, and nitrogen use efficiency of different crops in China: A meta-analysis

Context: Rainfed agriculture is crucial for global food security, with plastic film mulching a widely adopted practice in this domain. However, the impact of plastic film mulching varies significantly across different crop species. Objective and methods: This study conducted a comprehensive meta-analysis to evaluate the overall effects of plastic film mulching on the yield, water use efficiency (WUE), and nitrogen partial factor productivity (NPFP) of 13 different crop species. Results: Plastic film mulching significantly enhanced crop yield (26%), WUE (33%), and NPFP (26%) compared to non-mulched conditions. However, the promotional effects varied significantly among different crop species, with noteworthy improvements observed in soybean (44%, 41%, and 45%, respectively) and millet (42%, 57%, and 39%, respectively). For China's major staple crops, plastic film mulching improved the yield, WUE, and NPFP of wheat (29%, 23%, and 27%, respectively), rice (12%, 36%, and 12%, respectively), maize (25%, 29%, and 26%, respectively), and potato (27%, 29%, and 27%, respectively). Regional suitability for plastic film mulching varied among different crops, with rice, maize, soybean, sunflower, linseed, and millet showing increased benefits in cold, semi-arid and arid areas (mean annual temperature (MAT) ≤ 10°C, mean annual precipitation (MAP) < 450 mm, and aridity index (AI) < 0.5). Conversely, peanut and wheat performed better in warm, moist and semi-humid regions (MAT > 10°C, MAP > 450 mm, and AI > 0.5). Moreover, nitrogen fertilizer application influenced the efficacy of plastic film mulching. For soybean, linseed, and millet, the optimal outcome of plastic mulching was observed under low nitrogen application (<110 kg ha^–1). For sorghum, sunflower, sweet potato, rice, peanut, potato, and wheat, the optimal outcome of plastic mulching was found under moderate nitrogen application (110–220 kg ha^–1). As for maize, cotton, and oilseed rape, the optimal outcome of plastic mulching was observed under high nitrogen application (>220 kg ha^–1), but there was no significant difference between moderate and high nitrogen application. Conclusions: A tailored approach considering specific crop requirements and nitrogen application rates is essential for maximizing the benefits of plastic film mulching across diverse local conditions. Implications: This study offers valuable insights into optimizing crop productivity under plastic film mulching management systems.