Deciphering the mechanisms through which arbuscular mycorrhizal symbiosis reduces nitrogen losses in agroecosystems

Abstract

Nitrogen (N) cycling within terrestrial ecosystem is largely controlled by networks of prokaryotic microbial communities that mediate the conversion, immobilization, and turnover of various forms of N present in soil. Recently, the role of arbuscular mycorrhizal (AM) symbiosis in N cycling within terrestrial ecosystems has gained considerable attention. However, a comprehensive assessment of how AM symbiosis can contribute to reducing N loss within the agricultural ecosystems remains incomplete. In this review, we examine the direct and indirect mechanisms by which arbuscular mycorrhizal fungi (AMF) can help mitigate N loss from agricultural ecosystems. Direct mechanisms include the interception and immobilization of organic and inorganic N within fungal and plant biomass. Indirect mechanisms involve the contributions of AMF to plant nutrition and diversity, soil organic matter mineralization, soil structure formation, plant–soil–water relations, microbial biomass N immobilization. Both the direct and indirect mechanisms ultimately influence the composition and functioning of N-cycling communities. This review reinforces the relevance of ecologically based approaches not only for addressing agricultural N losses but also for advancing sustainable development goals, especially the target to halve N waste from all sources by 2030.