Effects of film mulching on cotton yield and water use efficiency in China: a meta-analysis

Film mulching (FM) has the positive effectiveness of increasing production and retaining soil water, which indicated that film mulching is a widespread technique. However, the agreement about the effects on cotton yield and water use efficiency (WUE) has not yet been established. We collected 222 yield and 55 WUE observations from 68 articles and used meta-analysis to investigate whether FM is effective on cotton yield and WUE. FM markedly enhanced cotton yield and WUE by 30.11% and 40.03%, respectively, in comparison to no mulching. Importantly, FM performed better at mean annual precipitation (MAP) < 200 mm and mean annual temperature (MAT) < 12 ℃. Higher cotton yield and WUE under FM was observed in medium and fine-textured soils with soil bulk density (BD) < 1.4 g cm^-3, soil organic matter (SOM) < 20 g kg^-1 and total nitrogen (TN) < 0.8 g kg^-1. Additionally, FM achieved higher cotton yield and WUE at nitrogen fertilizer application rate (NFAR) < 250 kg ha^-1, phosphorus fertilizer application rate (PFAR) < 125 kg ha^-1 and potassium fertilizer application rate (KFAR) ≤ 380 kg ha^-1, respectively. The equally space planting (ESP) with flat planting with film mulching (FPFM) was more beneficial for cotton yield and WUE. In conclusion, our findings suggest FM can enhance higher cotton yield and WUE simultaneously, and the above results can provide practical guidance and reduce the adverse environmental effects under FM.