Microbial Biomarkers for Soil Health Assessment: A Review of Current Approaches and Future Directions

Soil health is fundamental to agricultural productivity, ecosystem stability, and climate resilience, yet traditional assessments based on physical and chemical properties fail to capture key biological processes. Microbial biomarkers encompassing taxonomic, functional, and metabolic indicators offer a transformative approach by linking microbial communities to soil functionality. This review synthesizes current knowledge on microbial biomarkers, evaluating their utility in assessing nutrient cycling, carbon dynamics, and stress responses. We systematically analyzed peer-reviewed studies (2010–2024) from major databases (Scopus, Web of Science), focusing on standardized methodologies, biomarker correlations with soil functions, and field applications. Key findings demonstrate that enzymatic biomarkers (e.g., β-glucosidase) strongly predict carbon turnover (explaining 62–85% of variability), while functional genes (nifH, phoD) outperform taxonomic data in forecasting crop yields and nutrient availability. However, challenges persist, including high spatial-temporal variability in microbial communities, methodological inconsistencies, and limited adoption in developing regions due to cost and expertise barriers. Emerging solutions include portable nano-sensors for real-time enzyme monitoring, AI-driven integration of multi-omics data, and CRISPR-based field tests. Future research must prioritize: (1) global standardization of protocols, (2) affordable tools for resource-limited settings, and (3) policy frameworks integrating microbial metrics into soil health indices (e.g., USDA Soil Health Index). The review conclude that microbial biomarkers are indispensable for advancing precision soil management, but their potential hinges on interdisciplinary collaboration and equitable technology access. By bridging lab-to-field gaps and fostering data-sharing initiatives, these tools can revolutionize sustainable land-use practices worldwide.