[Terrapreta] Inorganic & organic

[Christoph Steiner]

Dear All,

Most soils in the Amazon Basin have very low contents of inorganic
nutrients. These are deeply weathered soils and the predominant minerals
are iron and aluminum. Therefore most nutrients in Terra Preta have
organic origin. Terra Preta fertility is linked to an anthropogenic
accumulation of phosphorus and calcium associated with bone apatite, thus
increasing the pH. Increased pH alters the availability of nutrients.
Phosphorus, which is considered to be the primary limiting nutrient to
plant production on the highly weathered soils of the humid tropics, could
become available through fine root endomycorrhizal associations and
through heterotrophic phosphate solubilising microorganisms, which are
supposed to be stimulated by soil charcoal additions.

Best,

Christoph