Nitrification inhibitor shifts the composition of soil microbial communities and increases N utilization potentials in wheat soil under elevated CO₂ concentration

Elevated atmospheric [CO₂] generally increases wheat growth and biomass by improving photosynthesis. These increase cause greater N uptake by plants from soil, which may affect soil properties and microbial communities. Nitrification inhibitor is useful tool to inhibit the nitrification process and effectively slow down nitrogen (N) losses. However, it remains unclear how the addition of nitrification inhibitor under elevated [CO₂] will affect the soil microbial community and function.

We investigated the changes in soil properties, microbial community and function by using a metagenomic technique in soil fertilized with urea (C) with or without nitrification inhibitor (NI) under ambient [CO₂] or elevated [CO₂] (+ 200 μmol mol^–1 above ambient [CO₂])

A large number of microbial genes related to carbon (C) fixation and phosphorus (P) release were increased by elevated [CO₂], but those related to C degradation were decreased. Elevated [CO₂] decreased soil ammonium (NH₄⁺) (-46.23%) and nitrate (NO₃⁻) (− 5.35%), and shifted the microbial community towards oligotrophic microorganisms due to soil N limitations. The addition of nitrification inhibitor under elevated [CO₂] decreased the ammonium-oxidizing amoA gene abundance to keep soil N stable for longer, and promoted soil C and P cycle compared with elevated [CO₂] alone.

The overall changes in microbial communities and soil N pools induced by nitrification inhibitor under elevated [CO₂] kept soil N stable, and promoted soil biogeochemical cycle, thereby increasing the potential growth rate of the microbial community.