[Renfield]

Yes. Typically, in tropical rainforest soils there is a thin layer of partially decomposed organic material right at the soil surface, and all of the soil's fertility is contained therein. The mineral portion of the soil below this organic layer is composed largely of minerals highly resistant to weathering; mostly amorphous hydrated oxides and hydroxides of aluminum and iron (Gibbsite, Goerthite, etc). There is virtually no fertility in these minerals. I find the story posted here to be highly suspect. There is, however, a type of soil, naturally occuring, that these people might be referring to. Vertisols are soils composed principally of 2:1 expanding clays such as Montmorillonite. These clays expand as they absorb water when they are wet, and contract and crack when they dry. Organic material is incorporated into the soil by falling into the cracks, and thus these clays appear dark. Montmorillonitic soils have a high cation-exchange capacity (the ability to retain, and slowly release, plant nutrient cations such as Calcium, Potassium, Magnesium, etc), and are generally relatively fertile. These are widespread, though not abundant, in some tropical and temperate regions of the globe, usually in regions that have short rainy seasons followed by long dry seasons. They normally are NOT found in rainforest (humid or perhumid tropical) areas, because the rates of weathering are too high to sustain these minerals for long periods. These people need to have their site examined by competent soil scientists.

[blam]

An Origin Of New World Agriculture In Coastal Ecuador (12,000BP)

[oldbones]

Soil scientists from around the globe and renewable hydrogen researchers are discovering that these soils (which have extensive published work in the past few years) are pointing to a solution for carbon buildup and for sustainable agriculture. It is hard to believe, but not really when you know what thay did. Charcoal is an adsorbent and is used for poisoning victims. Centuries ago the indigeneous population of the Amazon learned that charcoal applied (or invested) to their soil gave them a tremendous increase of crop productivity. There are sites around the web that are exploring what this means.

Terra Preta at Cornell Univ. or do a search on terra prata. Most of the links are hard science stuff but one is a R&D site.

Eprida with a conference link

Conference