Secret of Terra Preta Soil Discovered?

We’ve discussed the basics of terra preta soil – the most fertile soil in the world – in two previous blog posts. As I explained in the earlier blog posts, scientists are racing to unlock the secrets of terra preta soil and the role that biochar plays. New biochar research is coming out that may hold the keys to restoring land degraded from years of industrial chemical farming. If the claims made in the following videos turn out to be true then that means we now know how to develop permanent soil fertility. In addition, you can heat your home and greenhouse from waste heat given off during the biochar making process. This BBC documentary — The Secret Of Eldorado – TERRA PRETA — explains why terra preta is more valuable than gold. Test trials have shown terra preta can produce 880% increase in plant yields.

In this video at 12:37, soil scientist John Nilsson says to mix biochar with compost up to 50/50 (1:1) for fertility that can last indefinitely. He said the compost alone might last 10 years if you’re lucky. Combined with biochar it can last thousands of years, because the microbiology and nutrients get stored in the biochar cavities (living spaces). John references the terra preta soils in the Amazon and grasslands in the United States that were burned by Native Americans. John recommends adding biochar to a compost pile after an initial settling period. He believes the biochar will absorb many of the nutrients that would otherwise be lost during the composting process. Here’s a good video that goes into more depth about terra preta soil. And just for fun, here’s a microscopic photograph of biochar that shows the porous structure.

Tips on how you can make a version of terra preta soil (link to video above on YouTube): Gardening expert John Kohler advises gardeners to activate or colonize biochar with beneficial microbiology before adding to the garden, otherwise it can actually take nutrients away from plants. This video explains five good ways to activate biochar: 1. Mix biochar with grass clippings, moisten, cover with straw etc. to block light and then let decompose for a few months. 2. Mix biochar with an equal amount of worm castings and about 5% flour or similar food source, moisten and cover for about two weeks. 3. Add biochar to a chicken coop. It will mix with the manure and litter, and absorb the ammonia (nitrogen) to reduce odor. (This captures the nitrogen before it can escape so it can be put back in the soil.) 4. Mix biochar with urine. 5. Mix biochar with micronized rock dust 4:1. Then add one part worm castings and slightly less than one-half part flour or rice bran as a microbial food source. Allow to mature for at least two weeks. The end result is a mycorrizal inoculated biochar.

Alternately (possibly the ultimate version), mix biochar with compost made with rock dust such as Azomite, worm castings, manure, organic plant residues, a food source such as rice bran, and indigenous microorganisms (IMOs). This method would combine the benefits from all of these materials in one process. For a ‘gourmet biochar blend’ for orchards and forest gardens, consider mixing this biochar compost 50/50 with ramial wood chips and let it age undisturbed (unturned) for 6-12 months to develop into fungal dominant compost that has a C:N ratio of around 40:1, which is what trees prefer.

A video on Cover Crop Innovations by Dr. Ron Morse, Professor Emeritus at Virginia Tech, explains how to obtain 50% average increase in early crop yields using biochar inoculated with fish emulsion. This was the average increase over 3-6 years. Instead of spreading biochar over the whole acreage, which is costly, they put biochar right in the row, and in the potting mix at 3.5%. The biochar acts as a condominium for microorganisms to live. This effect is part of a larger, longer process of using compost, cover crops, organic farming, no compaction and no till.

Here’s another video by Bob Wells who shares his biochar experiences. His first trial involved putting biochar in rows of turnips. The turnips with biochar doubled in size in comparison to rows of turnips without biochar. At 31 minutes, John Nilsson talks about the best soils in the US that have a CEC value of around 10-15. John was shocked to learn that terra preta Amazon soils are as high as 222. At 51:40 Bob says you can make more money by growing bigger, better, healthier, more drought resistant, more nutrient dense plants. Biochar holds water in addition to holding nutrients and biology. It acts like a sponge in sandy soils. Less fertilizer is required every year, because it’s being stored up not washed away.

More good news: Part 4 of the Biochar Workshop video shows how to set up a biochar operation to heat your home and greenhouse in addition to making biochar. Many thanks to Living Web Farms for all these great videos.

4 thoughts on “Secret of Terra Preta Soil Discovered?”

  1. Random bits and pieces of biochar info from various sources (things to think about/look into more):

    – Note the large amount of broken pottery in terra preta soil. There’s way more than just a few pieces of broken pottery. Large amounts were obviously added for a reason. One possibility is pottery is adsorbent — it takes contaminants out of the soil.
    – Consider adding rock dusts for additional minerals.
    – Add nitrogen-fixing bacterial inocculants and mychorrizal inocculants — possibly gleaned from good soil under old growth trees (IMOs).

  2. By the way, there’s plenty of other positive information supporting biochar. For instance, there’s a world class research center 15 minutes down the road that uses it in all of their potting mix and probably all of their plants. They could use anything they want and so this speaks volumes. They make a slow compost where all of the materials are aged a year or so. I used to have their recipe. It’s something close to this:
    – aged rice hulls
    – rice hull ash (biochar)
    – local sandy/clayey soil
    – aged cow manure
    – last time they were sprinkling in some lime on the final step

    We visited a nursery east of here that uses the same basic recipe. They age the mixture an additional year to allow time for the microorganisms to populate the mix.

  3. I question a lot of biochar claims. I read one peer review study showing that biochar buried in a forest broke down over a 10 to 30 year period depending on the type of pyrolysis, not thousands.

    I’d rather see people make quality compost with high water holding capability with the organic material instead of burning off the volatile compounds and exposing the less volatile ones that some soils may be deficient in.

    The only scientific research I’ve seen where biochar alone improved growth rather than reduced it (most peer review studies) was for Avocado trees and other plants planted in saline soils. Whereby as saline ground water rises, the biochar then acted like a carbon filter.

    For me, innoculating biochar is akin to liquid fertilizing using an absorbant medium as biochar holds water ~50% by volume. To me it has some parallels to the Mittleider method, which may explain some exceptional results. Plants love liquid fertilizer, they love anything that saves their roots and the symbiotic microbes in the soil from having to do all the work mining those minerals. And since soil moisture of about 40% is ideal for most plants biochar may actually help some with hydrophobic soils, but then so would compost.

    I’m also skeptical that microbes populate biochar cells. I read a biochar thesis that showed electron microscope images where microbes hadn’t populate the pores of biochar, and rather stuck to the surface, and that clay particles in soil tended to block the pores. Many clays actually have antimicrobial properties too, and even kill drug resistance superbugs.

    From my research, if you really want to sequester carbon for long periods it needs to be prevented from oxidizing. Some plant and microbial exudates do this by surrounding the carbon with a membrane, and some fungi also sequester and store carbon inside microaggregates where other microbes can’t get to it. However the best way I’ve seen to build long lasting soil organic carbon is to send it deep into the soil horizon and to do that you need perennials with long thin hair-like roots capable of penetrating small crevices. Over the seasons these roots grow and die and sequester organic carbon.

    • Yes, it’s good to be skeptical. That’s why I wrote the title as a question. When I heard the people in these videos all talking about permanent fertility like terra preta soil, it really piqued my attention. Let’s hope it’s true. One thing is for sure — terra preta soils were man-made and they’re still super fertile. Someday soon we may understand how it works so it can be replicated.

      What are you favorite deep rooted soil building plants? Comfrey?


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