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:
4 comments
Do you think burning in the pit may be a problem? If they were using them as waste pits they were probably not burning in the pits but adding burned materials in with the waste.
They probably knew the benefits of charcoal to filter smells. And would have dumped their ashes and charcoal when cleaning out their home fire pits.
Im just thinking that the burning/repeated burns in the pit is reducing a lot of the beneficial bacteria and microorganisms. It may also reduce the ability for things to move between the pit and the soil by charring the floor and walls of the pit. I assume it also probably changes the properties of the added clay.
I love these terra preta experiments, can’t wait to see more!
Good point from Justin above. Maybe an experiment with direct vs indirect burns will be good.
On terra preta itself, I think these indigenous communities had to do this because in the tropics the excessive rainfall washes out most of the soil nutrients. Most of the carbon and nutrients are actually tied to the vegetation. That is why “slash and burn” practices work for a short period of time until rain washes out the nutrients from the soil. Not to different from the dynamics of sandy soils we have here in the Southeast.
My experience in GA with the sandy soil, clay and char is that the clay helps with holding on the char and other organic matter and the sand behaves a little like perlite allowing drainage and air (the char helps with this too).
The only problem I have encountered is when I become too tired (or too lazy) to mix everything correctly. When this happens, I found that the clay mixes or attach itself just with sand creating a hard layer at 1-2 feet below and the char “floats” to the surface.
On the ingredients, I think you just add anything you have available in terms of organic material, pottery, minerals etc. The only thing I can think of is to go out and “rob from nature” some humus from a natural area to help recreate or restore the local soil ecology.
Hey David
I’m reading your posts and watching your videos for quite some time now and just wanted to say thank you for sharing all this useful information.
Yesterday i introduced some friends to terra preta and we tried to recreate it in a very poor, sandy soil in Catalunya/Spain to plant some trees. It was a very beautiful afternoon activity, having fun to collect trash to burn and throw it in a pit. We’ll definitely do this frequently now.
All the best
C.
Thank you – it really is a nice way to spend an afternoon. And better with friends.