How BioChar Improves Soil

Although making charcoal may sound like a strange way to boost crop production, the concept was proven more than 2,000 years ago, where pre-Columbian farmers in South America added charcoal to the poor soils of the Amazon rainforest to create a rich, fertile soil.

These soils improved with biochar from so long ago are still fertile today, and contain as much as 35 percent of their organic carbon in the form of charcoal. Research studies over the past decade have found that these biochar enriched, charcoal-amended soils hold more water and nutrients while simultaneously making the water and nutrients readily available to plants.

The biochar itself used to improve the soil quality can be made from either wood or agricultural byproducts. The key is to heat the material to a high temperature in an oxygen-starved environment.

Indigenous farmers in pre-Columbian South America did that by burying the material in pits, where it burned for days. Today though, there are dozens of do-it-yourself videos on YouTube that teach how to make biochar in just a few hours using things like steel drums.

The soil fertility enhancing benefits of biochar are just one reason there’s a groundswell of interest in biochar production. Some enthusiasts are drawn by a desire to reduce atmospheric carbon dioxide. That’s because about half of the carbon from wood chips, corn stalks and other biomass — carbon that otherwise typically goes into the atmosphere — can be locked away inside biochar for thousands of years.

Most of biochar’s benefits are related to the extremely porous nature of the charcoal-like material. Biochar is highly effective at retaining both water, and water soluble nutrients while also creating a healthy habitat for beneficial soil microorganisms.

Biochar can improve water quality, help the soil capture carbon for long periods of time, reduce nutrient and fertilizer leaching, reduce soil acidity, and even reduce the amount of water and fertilizer that required in the first place.

Multiple agricultural studies have shown positive effects using biochar to improve crop production in degraded and nutrient poor soils.

Biochar owes its characteristic rich, black color to the charcoal content. Historical studies show that it was originally made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil. The same method was independently discovered and used throughout West Africa  as long as 700 years ago with similar results.

The charcoal portion of biochar is very stable and remains in the soil for thousands of years, binding and retaining minerals and nutrients, literally transforming poor quality soil into rich, fertile soil that retains its fertility over hundreds, or even thousands of years.

Deforested soils in the Amazon are typically productive for just a short period of time because of the poor fertility of the soil. This means that farmers must constantly move to new areas and cut down more of the Amazon forest to effectively grow crops, resulting in increasing deforestation.

Biochar “terra preta” soil, unlike unimproved Amazon soil, is less prone to nutrient leaching caused by heavy rains and floods because of the high concentration of charcoal, microbial life and organic matter. The charcoal holds, grabs and accumulates nutrients, minerals, and microorganisms.

Scientists estimate that some terra preta soils in South America created with biochar from the pre Columbian period were made by humans over between 450 BC and 950 AD. The dark, rich soil’s depth where biochar was made that long ago still reaches up to 2 meters deep even today.

Thousands of years after its original creation, this biochar enriched soil still regenerates itself at the rate of around 1 cm per year. It is highly sought out by local farmers in the Amazonian basin, who seek it for use in farming and also for sale as valuable potting soil.