Assessing the Health of Tropical Soils in Sub-Saharan Africa: Indicators, Challenges and Future Directions

Abstract

Soils are facing critical and overlapping challenges that threaten food security. Assessing soil health is critical for providing scientific evidence-based, appropriate, site-specific and sustainable solutions to support the resilience of our agrifood systems. This systematic review analyzes 48 publications published between 2015 and 2025 on soil health assessment of tropical soils in Sub-Saharan Africa. The objective was to identify the indicators used, the analytical methods, the technologies used and the associated management strategies, in order to characterize the dominant scientific orientations and the persistent gaps, and future directions. 48 relevant papers out of 220 downloaded were examined. The results highlight that soil health assessment studies were concentrated in East and West Africa, primarily Ethiopia, Ghana, and Kenya while it remains very rare in Central and Southern Africa. Key findings include a dominance of physicochemical indicators, with organic carbon as a focus in 75% of studies, pH at 31%, total nitrogen at 24% and CEC at 22%; whereas biological indicators remain less frequent. Analytical methods included regression and ANOVA, with emerging techniques like digital soil mapping. Conventional laboratory analyses are used in more than 80% of studies. However, soil health assessment using observational and indigenous knowledge indicators remains very rare in Sub-Saharan Africa. Recommendations emphasize methodological harmonization and incorporating observational and local knowledge for a comprehensive soil health assessment.