Trends in Global Soil Research and a Microbiome-Based Framework for Soil Health Assessment

Soil health is fundamental for food security, climate regulation, and ecosystem resilience, yet global research and development efforts remain uneven and fragmented. To provide a more integrated perspective, this study examines global soil health research and development trends between 1990 and 2025 while proposing a microbiome-based framework for soil health assessment. Using a PRISMA-based methodology, we combined data from international development projects, scientific publications, patent data, and microbiome-related initiatives to evaluate temporal, thematic, and regional patterns in soil research. The results reveal a sustained increase in global soil-related research, with nutrient management and soil degradation remaining dominant topics, while soil microbiome research and carbon sequestration have emerged as the fastest-growing areas, particularly since 2015. However, significant regional disparities persist, with research concentrated in Asia, Europe, and North America. To address the lack of a coherent microbiome-based soil health assessment system, we propose a structured microbial indicator framework based on twelve functional microbial groups, evaluated through culturable abundance, functional gene abundance, and relative abundance. Additionally, we introduce a unified, database-driven microbiome reference framework that interprets soils relative to known types and conditions. Overall, this study highlights the global transition toward biologically driven and system-oriented soil research and provides a conceptual foundation for more standardized, scalable, and ecologically meaningful soil health assessment.