Enrichment of nosZ ‐type denitrifiers by arbuscular mycorrhizal fungi mitigates N 2 O emissions from soybean stubbles

Abstract

Summary Hotspots of N 2 O emissions are generated from legume residues during decomposition. Arbuscular mycorrhizal fungi (AMF) from co‐cultivated intercropped plants may proliferate into the microsites and interact with soil microbes to reduce N 2 O emissions. Yet, the mechanisms by which or how mycorrhizal hyphae affect nitrifiers and denitrifiers in the legume residues remain ambiguous. Here, a split‐microcosm experiment was conducted to assess hyphae of Rhizophagus aggregatus from neighbouring maize on overall N 2 O emissions from stubbles of nodulated or non‐nodulated soybean. Soil microbes from fields intercropped with maize/soybean amended with fertilizer nitrogen (SS‐N1) or unamended (SS‐N0) were added to the soybean chamber only. AMF hyphae consistently reduced N 2 O emissions by 20.8%–61.5%. Generally, AMF hyphae promoted the abundance of N 2 O‐consuming ( nosZ ‐type) denitrifiers and altered their community composition. The effects were partly associated with increasing MBC and DOC. By contrast, AMF reduced the abundance of nirK ‐type denitrifiers in the nodulated SS‐N0 treatment only and that of AOB in the non‐nodulated SS‐N1 treatment. Taken together, our results show that AMF reduced N 2 O emissions from soybean stubbles, mainly through the promotion of N 2 O‐consuming denitrifiers. This holds promise for mitigating N 2 O emissions by manipulating the efficacious AMF and their associated microbes in cereal/legume intercropping systems.

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