Indigenous African soil enrichment as a climate-smart sustainable agriculture alternative

• Published in: Frontiers in ecology and the environment 2016-03, Vol.14 (2), p.71-76
• Main Authors: Solomon, Dawit, Lehmann, Johannes, Fraser, James A, Leach, Melissa, Amanor, Kojo, Frausin, Victoria, Kristiansen, Soren M, Millimouno, Dominique, Fairhead, James
• Format: Article
• Language: English
• Subjects: RESEARCH COMMUNICATIONS
• ISSN: 1540-9295; 1540-9309
• DOI: 10.1002/fee.1226

We describe for the first time a current indigenous soil management system in West Africa, in which targeted waste deposition transforms highly weathered, nutrient-and carbon-poor tropical soils into enduringly fertile, carbon-rich black soils, hereafter "African Dark Earths" (AfDE). In comparisons between AfDE and adjacent soils (AS), AfDE store 200-300% more organic carbon and contain 2-26 times greater pyrogenic carbon (PyC). PyC persists much longer in soil as compared with other types of organic carbon, making it important for long-term carbon storage and soil fertility. In contrast with the nutrient-poor and strongly acidic (pH 4.3-5.3) AS, AfDE exhibit slightly acidic (pH 5.6-6.4) conditions ideal for plant growth, 1.4-3.6 times greater cation exchange capacity, and 1.3-2.2 and 5-270 times more plant-available nitrogen and phosphorus, respectively. Anthropological investigations reveal that AfDE make a disproportionately large contribution (24%) to total farm household income despite its limited spatial extent. Radiocarbon (¹⁴C) aging of PyC indicates the recent development of these soils (115-692 years before present). AfDE provide a model for improving the fertility of highly degraded soils in an environmentally and socially appropriate way, in resource-poor and food-insecure regions of the world. The method is also "climate-smart", as these soils sequester carbon and enhance the climate-change mitigation potential of carbon-poor tropical soils.