Yesterday I posted a video on our new terra preta burn pit:

As an addendum to that video, this article shared by David Kindltot provides some new information supporting the anthropogenic origin of terra preta, via the study of the farming and waste disposal practices of a surviving indigenous population.

“To determine what practices formed dark earth and whether it was intentionally created, we augmented our archaeological and soil analyses with ethnographic research in the present-day Kuikuro II village (Figs. 1B and 3E), which has documented enriched soils from contemporary Indigenous land management practices (Materials and Methods) (48). Fishing and manioc agriculture create large quantities of nutrient-rich organic waste (Fig. 3A), much of which is deposited in trash middens mounded up to ~50 to 60 cm above the original ground surface (Fig. 3B), creating the most fertile and intensely modified soil in areas surrounding residences (Fig. 2A and figs. S3, S7 to S15, and S19 to S21) (47). Once dark earth begins to form in these midden areas, typically within a few years, residents often exploit it for planting nutrient-demanding crops (Fig. 3C) that do not grow well on unmodified soils according to Kuikuro farmers (tables S5 and S6). We also observed farmers spreading this organic refuse, particularly ash and charcoal (Fig. 3D) and manioc waste (Fig. 3F), as well as mulching (Fig. 3G) and in-field burning (Fig. 3H), in fields on the periphery of the village (Fig. 3I).”

One question that this article raised in my mind was: what about human waste?

Is it incorporated into these middens? Or are the residents of Kuikuro II going further into the woods to relieve themselves?

Current List of Possible Terra Preta Ingredients

In our new biochar burns we are now incorporating animal bones and meat, as you can see in the video. We’ll also add non-burned bones and slaughter waste. Yesterday, we also dug up some clay and are making rough pottery which we can then burn and turn into shards.

From what we’ve found so far, terra preta was created in poor clay soils and contains:

Ashes
Charcoal
Bones
Pottery shards
Cassava waste

It also likely contains fish waste, other crop waste, human and/or animal manure and slaughter waste, and possibly aquatic material and muck from flooding events.

If I seem to be missing anything, let me know in the comments.

We have sandy soil here, and therefore do not have the proper substrate for our midden creation, but we’ll work on getting some more clay we can use. It may be possible to have a load dropped which we can work with.

The addition of the “slaughter waste” from a local restaurant is a good step forward.

The Current Terra Preta Plan:

If we make a pile of clay, then layer our pit-burned materials on it with more clay along with other organic wastes, we may get there. We’ll leave it to sit and see if there is any change over time. We may also dig some freshly mixed material into a garden bed, and have a second non-amended bed next to it as a control.

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Today’s accompaniment: