Browsing by Author "Fairhead, J."
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Item Anthropogenic dark earths and africa: A political agronomy of research disjunctures(Contested Agronomy: Agricultural Research in a Changing World, 2012) Fairhead, J.; Leach, M.; Amanor, K.Anthropogenic dark earths (ADE) and biochar are current foci of extraordinary levels of technological optimism, agricultural research and political debate. ADE comprise both black soils associated with long enduring settlement sites and their depositions, and slightly lighter coloured soils that have also been rendered more enduringly fertile than the soils on which they are formed through deposition and cultivation practices. These anthropogenically enriched soils can sustain permanent farming; their fertility is thought to be due in part to their high biochar content. Biochar refers to the carbon-rich products that result when biomass is burned under oxygen-deprived conditions and then buried in the ground (Lehmann and Joseph 2009).Item Indigenous African soil enrichment as a climate- smart sustainable agriculture alternative(2016) Solomon, D.; Lehmann, J.; Fraser, A.; Leach, M.; Amanor, K.; Frausin, V.; Kristiansen, S.; Millemouno, D.; Fairhead, J.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.