7. Reconstructing the origin of Terra Preta – a mechanistic, stoichiometric nutrient balance approach
Attempts to understand the origin of Terra Preta (and thereby also the creation of Terra Preta Nova) suggest that neither charcoal alone nor mineral nutrients alone can raise the fertility of these soils sustainably. Interactions between the different components of the input are poorly understood. Therefore, our understanding of the possibly differential intentionality with which Terra Preta and Terra Mulata were created remains inadequate. The following research questions will be addressed: (1) how do C:N, C:P and N:P ratios differ between charcoal and non-pyrogenic C? (2) how do Ca and P scale between the different input sources, and what information does it provide on the relative importance of terrestrial and aquatic inputs?; (3) how do Ca and Mg scale, and what information does it provide over the relative importance of terrestrial and aquatic inputs; (4) to what extent do micronutrients contribute to the properties of Terra Preta? (5) how do pyrogenic and non-pyrogenic carbon sources interact, and contribute to humus formation (especially Dissolved Organic Carbon); (6) how do Ca, P, Fe oxides and pyrogenic carbon interact in stabilizing organic matter (litter input)?; (7) how do pyrogenic carbon sources contribute to differential functioning of Terra Preta and Terra Mulata? Together with project #6 it will study the quantities of inputs to reconstruct 3-D models of Terra Preta (spatial extent, depth).