Drip irrigation under film mulch used on flat-bed increased vegetable yield by altering soil microbe community structure and soil nitrogen

The leafy vegetable production is challenged by the excessive water and fertilizer input, as well as the continuous cropping obstacle caused by the soil environment change. The different combinations of irrigation methods, bedding types and film mulch would change the irrigation input and the soil environment, but the influence of these different combinations on yield and its relation to the soil microbial communities were not fully researched. Therefore, a 4-year experiment was designed. There were five treatments: flat-bed with flood irrigation (FF), flat-bed with drip irrigation (FD), flat-bed with drip irrigation under film mulch (FDM), raised-bed with drip irrigation (RD) and raised-bed with drip irrigation under film mulch (RDM). As a result, FDM had the highest celery yield and moderate crop quality when comparing the three seasons’ average. It produced relatively lower yield in 2016, and the highest yield in both 2017 and 2019, which were, respectively, 13.64% and 10.69% higher than the FF did. The FDM also led to the highest soil nitrate and second-highest ammonium nitrogen concentration by the end of the whole experiment, which was 25.62% and 49.63% higher than FF did. After 4-year cultivation, the key microbes promoted by FDM related to nitrogen-fixing included norank_f_Rhodospirillaceae, norank_c_Nitrospira and Nitrosomonadaceae. Meanwhile, the quantity of Caldilineaceae, Hydrogenispora and Halocella was reduced in the soil of FDM, potentially helping maintain the soil organic carbon pool. Besides, FDM suppressed several potential pathogenic communities, including bacteria family BIrii41 and fungi genera Aspergillus and Gibellulopsis . The water flow pattern in flat-bed and film plastic residue could cause the change of soil nitrogen cycling pattern and microbial community. In a word, FDM benefitted the crop yield mainly by improving crop available nitrogen, and it potentially reduced the soil carbon loss and crop disease pathogens.