Uncovering the functional roles of soil fauna in nitrogen cycling and agricultural sustainability

Soil fauna play crucial roles, both directly and indirectly in nitrogen (N) cycling thereby strongly influencing soil health, fertility, and agricultural productivity. They interact with soil microorganisms and organic matter to drive processes such as decomposition, mineralization, nitrification, and denitrification. However, the complex and context-dependent nature of soil faunal contributions to nutrient cycling remain underexplored, limiting their integration into sustainable agricultural practices. This review examines the functional roles of key soil faunal groups – microfauna (e.g., nematodes, rotifers), mesofauna (e.g., mites, collembolans), and macrofauna (e.g., earthworms, termites) in regulating N dynamics and shaping agroecosystem function. We highlight the synergetic relationships between soil fauna and microbial communities, emphasizing their roles in N transformations, soil structure formation, and organic matter retention. This review further explores how agricultural practices, plant-soil feedback, and abiotic factors shape soil faunal communities and their roles in N-cycling. Sustainable agricultural practices such as reduced tillage, multi-species cropping, and organic amendments have been shown to promote soil faunal activity, thereby improving N-use efficiency and reducing nutrient losses to the environment. Despite recent advances, critical knowledge gaps remain, particularly regarding the mechanistic pathways linking faunal activity to microbial processes, and their responses to climate change, land-use intensification, and other anthropogenic stressors. Addressing these gaps through integrative, interdisciplinary approaches is critical to harnessing the potential of soil fauna as drivers of nutrient cycling and ecosystem resilience. Incorporating soil fauna into nutrient management frameworks offers a promising pathway toward more sustainable, efficient, and climate-resilient agricultural systems.