Soil Quality Concepts and Indicators: Definitions, Assessment Frameworks, and Degradation Pathways

Abstract Soil quality is a foundational concept for sustainable land management, ecosystem resilience, and long-term agricultural and forest productivity. Over the past three decades, soil quality has evolved from a narrowly agronomic concept focused on nutrient supply to a broader ecological framework encompassing physical structure, chemical fertility, and biological functioning. This narrative review synthesizes key definitions of soil quality, examines major chemical, physical, and biological indicators used in soil quality assessment, and clarifies the conceptual distinction between soil health and soil fertility. The review further explores dominant soil degradation pathways, including physical, chemical, and biological degradation, and their implications for ecosystem services, food security, and climate regulation. Drawing on peer-reviewed literature from Google Scholar, this article highlights current assessment frameworks, identifies methodological challenges—particularly in integrating biological indicators—and discusses emerging research directions. The review emphasizes the need for holistic, context-specific soil quality assessments that link soil processes to ecosystem functioning and sustainable development goals, especially in tropical and rapidly changing landscapes. Keywords: Soil quality, soil indicators, soil health, soil fertility, soil degradation, sustainable land management