User:Paleorthid/Sandbox/Article Nursery/African dark earths

Africa
African dark earths occur in the Upper Guinean forests of Ghana, Guinea, Liberia and Sierra Leone. For a period of at least 700 years, West African farmers have enriched the rain forest soils around their towns with compost derived from kitchen, animal, agricultural, and fire waste to produce a signature dark earth. African dark earths are economically important, and are used judiciously by local communities. The Loma and Mende peoples currently improve soil in this fashion. They well understand how this connects them to the durable legacy of fertile dark earth that encircles the ruined sites in the region. Locals associate the age of their own towns with the depth of their black soil.

Definition
(AfDE) are human-made carbon-rich high-fertility soils analogous to Amazonian terra preta (1) and related to what British archeology terms dark earth.

Targeted waste deposition transforms highly weathered, nutrient- and carbon- poor tropical soils into enduringly fertile, carbon- rich black soils, hereafter “African Dark Earths” (AfDE ). (4)

for a period of at least 700 years, West African farmers enriched rain forest soils with ash, bone, and kitchen waste to produce what the team calls “African Dark Earths.” They detected 200 to 300 percent more organic carbon in the samples of African Dark Earths collected in Ghana and Liberia than in untreated soil. (4.6?)

A 700-year-old farming technique ... centuries old technique converts nutrient-poor rainforest soil into fertile farmland. (4.5)

For at least 700 years, villagers in West Africa have replenished nutrient-poor rain forest soils with charcoal and kitchen waste, transforming the lifeless dirt into rich, fertile compost. (4.8)

Occurence
AfDE occur in the forest and forest-savanna transition zones of Liberia and Sierra Leone, Guinea and Ghana. (1)

...involving the Guinean forest-savanna mosaic, and Upper Guinean forests (Senegal to Western High Plateau), and the Western Sudanian Savanna (5)

The Upper Guinean forest region of humid West Africa provides an appropriate region for us to assess the significance of anthropogenic dark earths given its climatic ecotones; its soils, its diversity of social worlds and agro-ecological practices, and given our preliminary evidence of the importance of ADE and past research experience there. (5)

Extent
In Solomon’s study area, just one percent of the land was treated with the biochar compost. But it produced nearly 25 percent of the total food the farmers grew. (4.3)

According to some villagers, a quarter of all their crops grow in this black soil, even though it represents only a very small proportion of the total cultivated area.(4.6)

In all regions surveyed, farmers identified areas of anthropogenically enriched dark soils that are highly prized and part of the local nomenclature. Anthropological research conducted in Wenwuta village in northwest Liberia revealed three types of dark earths, based on their occurrence in the landscape: (1) AfDE around field kitchens and palm- oil production sites (average size 0.1–0.5 ha), (2) AfDE encircling current settlements (average size 0.5–2 ha), and (3) AfDE surrounding abandoned settlements (average size 0.5–14 ha). (4)

Village farmers are drawn to old ruins ripe with the detritus of people and animal waste, and charred remains of plants and trees, he says. To further improve the soil, they keep goats and chickens in specific areas, and bring food waste like byproducts from processing palm oil, bones, and palm thatch there to burn. These activities turn poor, heavy soil into a dark, nutritious plant medium, which is used judiciously by the communities. ... village elders talk about soil enrichment as if it’s the obvious thing to do, yet no one had ever asked them about it before. “The black soil was not here when people settled there. They always associate the age of their town with the depth of the black soil,” Solomon says. (4.7)

Cultures practicing AfDE formation and use
AfDE is the product of longstanding and ongoing cultural practices of the Loma and Mende peoples (1). .... Kuranko-speakers (see Kuranko people) (5)

Local farmers have a thorough understanding of the soil management practices that transform AS to AfDE, and of the dark soils’ characteristic fertility. additions of several types of waste: ash and char residues from cooking; by products from processing palm oil and producing homemade soap; animal- based organic inputs such as bones from food preparation; and harvest residues and plant- biomass- based domestic refuse such as palm thatch, palm- fruit heads, and rice straw. These continuous, high- intensity nutrient and carbon depositions lead to an ongoing formation of highly fertile and carbon- rich AfDE in and around settlements(4)

Management system
existing, yet overlooked soil management system that has long been – and continues to be – an important feature of the indigenous West African agricultural repertoire. It transforms highly weathered, infertile, yellowish- to- red tropical soils (Oxisols and Ultisols) into black, highly fertile, carbon rich soils (4)

Targeted waste deposition transforms highly weathered, nutrient- and carbon- poor tropical soils into enduringly fertile, carbon- rich black soils, hereafter “African Dark Earths” (AfDE ). (4)

indigenous soil enrichment practice capable of improving the fertility and carbon- storage capacity of highly degraded soils (4)

Research in Guinea revealed the anthropogenic nature of the many forest patches in its forest-savanna ecotone that encircle existing and abandoned villages, hamlets and farm-camps. (5)

These soils are darker than those surrounding them, and often contain pottery. Nearby, villagers speaking Kissi language (see also Kissi people), also appreciate the fertility legacy of former habitation sites (5)

Local people frequently describe these AfDE forming practices as anthropogenic; one local, for example, said, “God made the soil, but we put the dirt there and made it fertile.” (4)

Gayflor Zee Pewee, an 81- year- old chief at Wenwuta, described a connection between AfDE depth and settlement age: “The black soil was not here [when people arrived to settle] but when they put the town down, the dirt they threw started forming black soil…If you dig a hole you can see how far down the black soil goes, and this shows how old the town is.” (4)

the ancient West African method of adding charcoal and kitchen waste to highly weathered, nutrient poor tropical soils can transform the land into enduringly fertile, carbon-rich black soils which the researchers dub ‘African Dark Earths’. (4.4)

indigenous communities who disposed of ash, bones and other organic waste to create the African Dark Earths. (4.4)

...in Feb 2009, Rademakers described in the Terra Preta Network biochar practices in Cameroon grassfields in which buried grass is burnt during soil preparation (5)

unusually high concentrations of available calcium and phosphorus in surface and subsurface layers of AfDE are likely to be due to anthropogenic addition of animal bones, which are typically rich in calcium phosphates. The combination of char and bones – along with additions of ash with very high acid neutralizing capacity – raises the pH of the otherwise highly weathered acidic AS. This improves phosphorus availability. (4)

The availability of higher concentrations of plant nutrients in AfDE, coupled with the moderate to neutral pH in surface and subsurface layers, is important for supporting the highly diversified multistory homestead cultivation practiced on most AfDE in West Africa. (4)

The TOC stocks stored in AfDE to a depth of ~2.0 m are generally 2–3 times as large as those in AS, with 2–26 times greater levels of PyC in the surface layer alone. Soils rich in PyC act as long- term carbon sinks, supporting climate- change mitigation efforts. PyC is also largely responsible for the significantly higher nutrient retention and cation exchange capacity observed in AfDE as compared with the surrounding soils(4)