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.

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The need for sustainable alternatives to industrial farming has led to a revival of interest in traditional agro-ecosystems. Whilst it is well recognised that traditional agro-ecosystems are both social and physical-technical-few case studies have examined interactions between both these dimensions in a single system. For a system to be considered sustainable it needs to be shown to have retained key characteristics over several generations. Case studies therefore demand a location where intergenerational transmission of agro-ecological knowledge and practice is ongoing. This paper examines the intergenerational transmission of social and physical-technical dimensions of a traditional agroecosystem of the Loma people in NW Liberia. We engage an innovative interdisciplinary combination of methodologies in analyzing interactions between: (i) energy efficiencies (yield to labour) in 3 different Loma food production systems, using longitudinal quantitative surveys, and, (ii) the social institutions that mediate food production practice, using qualitative methods. Our energy efficiency calculations show that AfDE cultivation is more than twice as efficient at producing calories as either shifting cultivation or forest and river extractivism, yet GPS mapping demonstrates that AfDE cultivation is highly spatially restricted despite clear opportunities for expansion and optimisation. This raises an important question: why have the Loma not expanded AfDE cultivation? We propose that despite being fully aware of the opportunities AfDEs present, a Loma 'ancestral habitus' and substantive economic rationality restrict areal expansion and optimisation of AfDE cultivation, curtailing growth and structuring a social-ecological system in dynamic equilibrium. Our findings underline that sustainability is not simply a physio-technical issue; social and belief issues appear to be far more important in framing behaviour in traditional agro-ecosystems.