Biochar: Ancient Method for Long-Term Soil-Building

Reader Contribution by Tom Stephan and Barn Owl Boxes
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Photo byNatural Resources Conservation Service Oregon

I was interested in falconry in my grade-school years, and became quite proficient at tree climbing, although I never had any safety equipment. Something unheard of today. We were never to let our mothers know just exactly what we did setting loose upon the countryside every Saturday morning. We just came home dirty, tired and hungry, sometimes arriving with a meat-hungry chicken hawk in a wicker basket. In time, I became a certified arborist and the owner-operator of a small tree service.

Whenever I had sick trees, an arborist friend would come and do his magic to save the trees. He, unlike some others, was invariably successful, bringing back to life seemingly hopeless cases. His methods of patient recovery involved surveying and often reintroducing life back into the soil. This at a time when everyone else was using macronutrient NPK chemical fertilizers, which did more long-term harm than good. This skilled arborist taught me his recipe of organics, which he applied to the root zones of trees. He took me on an education of soil fertility, one that has become my most recent passion.

Biochar’s Ancient Roots

The ancient Mesoamericans knew about these methods of soil fertility, too. They used beneficial life in the soil to grow their food to a great degree. So much so, that these soils can still be found today, centuries after the great cultures have vanished. The first U.S. spy satellites in the late 1960s were showing blocks of South American jungle that were taller, greener, and thicker than the surrounding jungle. The intelligence community knew the blocks were man-made because of their geometry. But since there were no humans there, they sent out the archaeologists to study them. The denominator common to all the sites was that the dirt was very dark, almost black. That color in the soil was carbon in the form of charcoal.

The First Nation folks hundreds of years ago (and actually even before with the ancient Pleistocene-epoch Paleolithic hunters of unknown origin, whom the Indians called “the ancient ones”), would slash down the forest and dig pits. The slash was piled in the pits and partially burned to produce a type of charcoal now called terra preta, or “biochar.” Piled on the raw charcoal was added all manner of fish and animal offal, pottery shards for minerals, bones, and human waste. These reeking piles were left to rot in contact with the charcoal for a few months or years.

Biochar Encourages Microorganism Growth

Photo byMarcia O’Connor

In the ancient ones’ compost-with-biochar amendment, micro flora and fauna, as we modern hominids call them, proliferate in the char, where they persist for many generations. All wildlife, and people too, need just three things to survive: food, water, and shelter. The micro-organisms are no different and take up residency in the burnt, open-ended cells of the charcoal. This is their food as well as their cover. Later, the micro-critters in the biochar venture out into the surrounding organic deposits — leaves, stems and other carboniferous material, which rain down daily from the surrounding forest, turning it into compost. They break down the biochar much more slowly. The resulting compost is earthworm food as well as food for many other bug and bug larvae.

Worms are an integral part of the process of forest regeneration. They eat the compost and micro-critters, while they tunnel up and down in slow-moving, greyhound-like undulations from the top “A” horizon soil layer, where the plant’s feeder roots are located, into the “O” for organic horizon. This mixing of the two improves the soil texture, also known as “tilth”, from a hard, negatively charged crust to a moist, soft and fluffy horizon full of life and carbon. As they feed in this fashion, they take with them the beneficial fungi in their gut and on their bodies in, under, around and through the feeder roots, inoculating them with the coveted fungal spores.

There are two branches of mycorrhizal fungi: “ecto” and “endo” One attaches the spores to the roots and the other actually implants the spores into the roots for enhanced plant surivival. No plant and the fungi die. No doubt this method is a drought survivability adaptation on the fungi’s part. As they tunnel and feed, the worms leave worm casting-laden tunnels that act as rainwater drains to rapidly percolate down mineral laden rain water to the feeder roots. The difference in the field charge between the positively charged A horizon and the less charged B horizon helps to retain the moisture from rain in the roots of the plants in the A horizon.

Emulating These Processes Is the Key to Great Gardening and Agriculture

Most of the minerals that a plant needs to build its structure is in the char, The rest in the soil and compost. The fungi prepare, or “chew up”, the minerals to the molecular level so to speak. They essentially are the plant’s “teeth,” combining minerals and other nutrients it into a rainwater soup. This feeding renders the nutrients availability from the charred wood, soil, and compost to the next generation of plants, and the next, and the next.

Forests grow and mature in time. They then begin to decline from maturity, rot, or burn. The now-open forest canopies with carbon in the soil supply the next generation of plants with the sunlight and mineral building blocks needed to thrive and compete with their neighbors. Plant life as we know it would not be possible without the unfathomable numbers of single-celled organisms, living on the hair-like absorbing roots of 97% of all vegetation on earth.

If soil conditions become adverse to the plants through tilling, pollution, soil compaction, or erosion (and even strong sunlight and rain), the fungi and bacteria living on those plant rhizomes’ can begin to die. The plants in turn, especially trees, cannot draw up much in the way of minerals and water without the fungi. They then begin to decline and die if something is not done to remedy the situation.

Biochar Builds Long-Term Soil Health

There are USDA studies showing huge tracts of the Rocky Mountain West that stretch from state to state. The roots are interlocking from tree to tree, using the mycorrhizae as a common but simple brain. The soil life forms tell the trees over entire regions to prepare for droughts, fires and insect infestations. Think of all we have yet to learn about nature!

The Native Americans would, after a period of a few years, spread out all the char and compost mixture on their now-ready farm plots and plant crops such as squash, yams, and corn. The corn grew ten feet high and fed thousands of hungry mouths, all grown in the most nutrient-poor soils on the planet. This was only possible through the making and use of biochar. These areas are still fertile today, hundreds, sometimes thousands of years later from a single application! One plot was 1,800 hundred years old and was dug up and sold as farming soil!

After my friend passed to the great cloud forest in the sky, I began to use his recipe to help my clients’ trees, but added my own homemade biochar. It was then that I began a new hobby about a decade ago: I planted a vegetable garden.

In the followup post for this series, the author outlines his innovative, small-scale, regenerative agriculture method using soil biochar and crop rotation paired with a particular paddock system for moving his chickens. Follow allTom’s posts here.

Tom Stephan works in the green industry treating sick trees to improve their vigor and vitality through anti compaction and soil fertility. He is a former certified arborist, a master falconer, and has incurable minimalist tendencies. Connect with him at BarnOwlBoxes.


The key to growing bigger, more productive, more nutrient-dense plants starts at ground level. Biochar, which is slow-roasted organic matter inoculated with compost, creates the perfect habitat for soil-enriching microorganisms. In Gardening with Biochar, longtime garden writer Jeff Cox explains what biochar is and provides detailed instructions for how it can be made from wood or other kinds of plant material, along with specific guidelines for using it to enrich soil, prevent erosion, and enhance plant growth. If you want to create long-term benefits for your garden through better soil, this is the book you want to pick up.

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