The Toronto Star has a news article on my current favorite soil subject: terra preta do Indio. It highlights some important nuances. Terra mulata, the lighter type of terra preta, covers much more area than the celebrated black type central to the concept of terra preta. Terra mulata was probably used for farming. Terra preta proper formed from kitchen middens and may, or may not, have been used for home gardens.
Both types have bio-char, and the term terra preta do Indio applies to both. Am I correct in thinking that terra preta proper can be expected to have been infuenced by bones and excrement, but not so with the terra mulata? I am on alert as to the need to distinguish potential soil perfomance differences between the two types.