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

Abstract

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.

The contributions of Indigenous Peoples and local communities to ecological restoration

“…Researchers have documented instances when, through traditional practices, IPLC manage, adapt, and restore the land on which their livelihood depends, sometimes creating new types of highly biodiverse ecosystems (Posey ; Babai & Molnár ; Comberti et al ). Examples of traditional practices contributing to maintaining and restoring ecosystems include (1) anthropogenic burning purposively altering spatial and temporal aspects of habitat heterogeneity to create diversity (Shaffer ; Welch et al ; Trauernicht et al ); (2) waste deposition practices resulting in soil carbon enrichment (Solomon et al ); (3) rotational swidden cultivation systems able to maintain forest cover and plant diversity (Wangpakapattanawong et al ; Singh et al ); (4) interplanting useful plants in native forests thereby increasing forest diversity (Garibaldi & Turner ; Ford & Nigh ); and (5) scattering species‐rich hayseed, and weeding and cleaning meadows to maintain grassland productivity and resilience (Babai & Molnár ).…”

Raising Crop Productivity in Africa through Intensification

“…African Dark Earths: African Dark Earth, which is made traditionally in West Africa from waste deposals, is not only source of soil fertility, but also improves soil properties including carbon sequestration. Using these earths, organic carbon has increased up to three-fold and cation exchange capacity up to four-fold over the soil without dark earths [144].…”

Cultural valuation and biodiversity conservation in the Upper Guinea forest, West Africa

“…Samples were taken to Cornell Nutrient Analysis Laboratory, and were analyzed for chemical properties (aluminium, phosphorous, copper, zinc, manganese, calcium, lead, potassium, sulphur, iron), organic matter content and pH (Appendix 3). A separate study showed that the upland soils in the region were uniformly Oxisols (Solomon et al 2016). Although we did not collect soil samples under OF, we examined in situ a sample taken in each transect to confirm that the OF were located on yellowish/red Oxisols.…”

“…Wenwuta is a settlement of ~250 people and around 2.5 ha in size. C 14 dating shows the town was founded between 1670 and 1682 (Solomon et al 2016). To estimate the extent of SA around the settlement, in collaboration with locals we GPS-mapped all SA within a 3-km radius of Wenwuta ( Fig.…”

“…The activities of ancestors transformed the soil through deposition of charred and fresh organic materials at loci of domestic and food processing. These actions created, over time, anthropogenic soils called "African dark earth" (AfDE) that have double to triple the amount of organic carbon, significantly higher pH, cation exchange capacity, and more plant-available nutrients when compared with background Oxisols (Solomon et al 2016). SA feature a canopy of culturally significant mature rainforest tree species, and a midstory of cocoa (Theobroma cacao), kola (Cola nitida), and various native and exotic fruit trees.…”