Conservation tillage or plastic film mulching? A comprehensive global meta-analysis based on maize yield and nitrogen use efficiency

Rain-fed agriculture is an important part of the global agriculture system and plays a vital role in ensuring food security. Conservation tillage (CT) is widely used in USA maize cultivation in the Mid-west Corn Belt. Meanwhile, Chinese farmers' adoption of CT is limited and plastic film mulching (PM) is widely developed to increase maize yield in northern China. This paper compared the yield and nitrogen use efficiency (NUE) between CT and PM, and analyzed the reasons for the differences in the choice of maize cultivation practice. We collected 767 observations for CT and 217 observations for PM and analyzed how these two tillage practices affected yield. For NUE, there were 66 and 56 observations, respectively. The meta-analysis showed that PM significantly increased maize yield by 36% and NUE by 34% compared with the control, and CT significantly decreased maize yield by 5% and NUE by 15%. The effects of PM on maize yield were mainly determined by growing season precipitation (GSP) and temperature (GST). The yield response ratio was also influenced by the type of plastic film, mulching cycle, pH, soil saturated hydraulic conductivity, and soil bulk density. The negative effects of CT on yield could be alleviated under good hydrothermal conditions and with straw mulching. The yield response ratio was also affected by soil texture and N application rate. In conclusion, PM should be applied under limited hydrothermal conditions (GSP < 650 mm or GST < 23 °C), and CT was conducive to higher maize yield under good hydrothermal conditions (GSP > 650 mm or GST > 23 °C) . Besides, the average farm size was positively correlated with the CT total areas.