Anthropogenic dark earth: Evolution, distribution, physical, and chemical properties

Abstract

Anthropogenic dark earth (ADE) is a category of Anthrosols (anthropogenic soils) characterised by dark colour from homogeneous charcoal inclusion and extraordinary fertility compared with non-anthropogenic soils. The study aims to provide a detailed overview of the origin and distributions of ADEs, together with their physical and chemical characteristics, to reveal their fertility status for arable land use. According to this study, most studied ADEs are well distributed in tropical (Amazonian and African dark earth) and temperate (European dark earth) climatic regions. Middens are localised, with large-sized ones well preserved in the Arctic region due to the wet and cold weather conditions. The formation of ADE is mainly associated with deliberate and unintentional ancient human activities: deposition of domestic and occupational wastes, charred residues, biomass ashes, burning, and fertilisation of fields.

The Terra Preta Model soil for sustainable sedentary yam production in West Africa

“…While some viewed the ADEs to be of natural origin, others believe that they are human artifacts [ 33 ]. Nonetheless, the ADEs are now considered to be anthropic (unintentionally formed) or anthropogenic (intentionally formed) [ 30 , 43 ]. Previous studies suggest that the ADEs formed from biogeochemical transformations of a mixture of domestic wastes such as kitchen wastes (including ash mixed with charcoal fragments), faecal matter, animal manure and charcoal dumped over time [ 24 , 44 ].…”

“…Previous studies suggest that the ADEs formed from biogeochemical transformations of a mixture of domestic wastes such as kitchen wastes (including ash mixed with charcoal fragments), faecal matter, animal manure and charcoal dumped over time [ 24 , 44 ]. The whole process was influenced by (a) a high population density at the time, (b) persistent deposition of materials [ 30 , 31 , 43 ], and (perhaps intermittently or alternating cycles) as part of their livelihood strategies. Consequently, ADEs are Oxisols, Ultisols and Inceptisols enriched with a thick dark carbon-rich anthropic A horizon [ 34 , 36 , 45 ].…”

“…Besides, its alkali content enhanced the pH, CEC and base saturation of the native soils [ 45 ]. The original black carbon in the ADEs was mostly described as charcoal [ 30 , 43 , 45 , 55 ], which persists in soils compared to normal SOM and has a residence time of less than four years [ 56 ]. Considering the nature of the peoples livelihoods, it is clear the black carbon was charred biomass produced under natural or traditional charcoal burning conditions compared to the current biochar produced from different feedstock of both plant and animal origin and under controlled conditions.…”

“…Previously, Glaser [ 24 ] advocated the generation of the Amazonian dark earth (ADE) to establish “highly productive and sustainable land use systems” and long-term sequestration of C by adopting well-thought-out material management [ 25 ]. Further, Alho et al [ 29 ] emphasized that studies on the ADEs affords the insights required for future sustainable agricultural practices in the tropics, while Asare [ 30 ] suggested that the adoption of ADEs development process in arable lands has sustainable prospects for the future of agriculture. Although the ADEs have been widely examined and studied under different disciplines to decipher the origin, history and properties [ [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] ], the specific processes that led to their formation is still under contention.…”

“…Further, Alho et al [ 29 ] emphasized that studies on the ADEs affords the insights required for future sustainable agricultural practices in the tropics, while Asare [ 30 ] suggested that the adoption of ADEs development process in arable lands has sustainable prospects for the future of agriculture. Although the ADEs have been widely examined and studied under different disciplines to decipher the origin, history and properties [ [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] ], the specific processes that led to their formation is still under contention. This has created a bottleneck in the effective replication of ADEs in other places to generate a new research discourse.…”