Delphine Moreau, Richard D. Bardgett, Roger D. Finlay, Davey L. Jones and Laurent Philippot
Interest in how plants influence soil microbial communities is growing because of their important role in supporting plant growth. Nitrogen (N) is a major nutrient limiting plant growth, but the transformation of inert N to forms that can be taken up by plants is mediated by soil microorganisms. The last decade has witnessed major advances in our understanding of how plants and microorganisms interact with each other, and there is now much evidence that plants have evolved multiple ways to cope with N limitation by shaping and recruiting N-cycling microbial communities. The amount of atmospheric N2 industrially converted into ammonia to produce fertilisers now exceeds that produced from all Earth’s terrestrial processes. Therefore, there is a critical need to increase the efficiency of plant N capture from soil and reduce our reliance on N fertilisers in agricultural systems.
Our review synthesizes recent advances in our understanding of the various ways by which plants influence the availability of N in soil via an array of interactions with different groups of N-cycling microorganisms. We outline that plants are not passive conduits, taking up whatever N diffuses to their roots. Rather they can influence both the availability and uptake of different forms of N through their interactions with different groups of N cycling microbes in soil.
We also propose a plant-trait based framework which links plant N use strategies to the activities of N-cycling microorganisms. In doing so, we provide a more comprehensive picture of the ecological relationships between plants and N-cycling microorganisms in terrestrial ecosystems. Ultimately, an improved understanding of how plants harness soil microorganisms to enhance N capture and reduce N losses is of critical importance for sustainable agriculture and we advocate for a more integrated and comprehensive approach in which the N-cycle is considered as a whole.