Regulating Plastic Film Mulching on Soil Temperature, Moisture and Functional Bacteria Enhances Winter Wheat Yield in the Loess Plateau of China

Ridge furrows with plastic film mulching (RP) and flat soil surfaces with plastic film mulching (FP) are two main film mulching methods in the Loess Plateau of China. Our previous study indicated that FP could improve wheat yield more effectively than RP, although the reason remains unclear. The effect of film mulching on functional bacteria also needs to be further studied. The results showed that FP had a warming effect when the soil temperature was low and a cooling effect when the temperature was too high. However, the ability to regulate soil temperature in RP was unstable and varied with year. The lowest negative accumulated soil temperature was found in FP, which was 20-89% and 43-99% lower than that in the RP and non-film mulching control (NP), respectively. Film mulching could better transfer deep soil moisture to topsoil for wheat growth, which made the topsoil moisture in film mulching treatments (especially for FP) more sufficient than that in NP during the early growing stage of wheat. However, due to the limited water resources in the study area, there was almost no difference in topsoil water storage of all treatments during the later stage. Finally, the wheat yield in FP significantly improved by 12-16% and 23-56% compared with that in RP and NP, respectively. In addition, significant positive correlations were observed among the negative accumulated soil temperature, spike number and wheat yield. Although the interspecific relationship was weakened by film mulching, bacterial activity was improved. Meanwhile, phosphorus solubilizing, ammonification and nitrification bacteria were activated by plastic film mulching and microbes with nitrate reduction and plant pathogens were also inhibited, which provided more available nutrients and preferable habitats for wheat