Green manure substitution for potassium fertilizer promotes agro-ecosystem multifunctionality via triggering interactions among soil, plant and rhizosphere microbiome

AimsGreen manuring exhibits strong positive effects on soil fertility and crop yield, while its effects on agro-ecosystem multifunctionality (agro-EMF) and the underlying mechanisms are poorly understood.MethodsBased on a 7-year potato cropping field experiment, we conducted a holistic survey of soil and rhizosphere microbiomes, plant performance (i.e. yield and disease resistance) and soil functions, and assessed agro-EMF under conventional chemical potassium (K) fertilization and green manure (GM) amendment practices.ResultsWe demonstrated that GM application significantly promoted agro-EMF compared to chemical K fertilizer, as indicated by improved crop yield (5.8%-20.6%), reduction in potato late blight incidence (2.8%-46.2%), and increased soil nutrient contents. GM amendment drastically altered microbial community composition, especially in the rhizosphere. Intriguingly, agro-EMF was primarily predicted by microbial community composition, rather than microbial diversity, with a higher agro-EMF variation explained by the rhizosphere microbiome. In comparison to chemical K fertilizer, GM treatments greatly improved the complexity (58.5%-125.8%) and stability (8.2%-21.5%) of the microbial inter-kingdom network. Correspondingly, GM amendment significantly enriched keystone taxa, including the bacterial taxa Xanthomonadaceae, Rhizobiaceae and Sphingobacteriaceae, the fungal taxon Chaetomiaceae and the protistan taxon Cercozoa in the rhizosphere, of which are closely associated with soil nutrient cycling, plant growth promotion, and disease resistance.ConclusionTaken together, our study revealed that green manuring greatly promoted agro-EMF via coordinating soil nutrient cycling, rhizosphere microbiome and microbial network interactions for greater crop yield, disease resistance and soil functions. This study provides critical information on the mechanisms of ecosystem functions maintenance in agro-ecosystems and presents a basis towards developing conservation farming practices for agricultural sustainability.