Biochar is a type of charcoal that is produced from plant matter waste, including wood, agricultural waste, paper mill waste, etc. It is burned in a closed system, creating a stable form of carbon that is used to amend soil in agricultural practices, and is thought to increase yields. In arboriculture, we use it to improve the health of soil, and thus the roots of trees.
The inspiration for creating biochar comes from pre-Columbian practices in the Amazon rainforest. People would collect the charcoal from their hearths and return it to the earth. The soils, known as “terra preta” were dark, loamy, and contained higher levels of organic matter than surrounding soils. They also have higher nutrient availability, less compaction, and greater water retention, all of which contribute to better health for plants and their roots. Modern biochar was made in an attempt to recreate these effects.
How is biochar made?
The various waste materials are burned in a closed system via pyrolysis. In this process, carbon isn’t released as a gas via burning, but rather captured and stored in the final product. It is added to soil as an amendment as is considered a great way to sequester carbon. The final product will range in chemical and physical properties depending on source material, the heat at which it was produced, and the cooling and storage processes, but the final product will contain a more stable form of carbon. It is estimated that 50% of the carbon in the waste produce used become a highly stable, locking away that carbon for decades, or even hundreds of years.
Why use biochar?
Soil health is essential to tree health. It is the environment and the source of food and water that trees live in. Soils in our urban areas have properties that tend to be unwelcoming to trees. Urban soils have a history of disturbance due to construction, which disrupt the natural soil column and cause compaction. Compacted soils have less space for air, water, or microbes to exist. In addition, urban soils tend to be lower in organic matter, and tend to collect pollution, runoff, and excess salt buildup in northern climates. All of these issues make our cities and suburbs harsh environments for many trees to grow.
Adding biochar to soil produces several benefits to soil health, and thus the health of trees. Biochar amendments increase the moisture retention of the soil, slowing evaporation, increasing water infiltration, and helping plants through times of drought. It increases the cation exchange capacity, which dictates the availability of nutrients to tree roots. It also improves soil texture, by providing more pore space for air, water, and healthy microbes. Biochar also helps to break up soil compaction, which is a common issue in our urban soils.
Wide ranging effects of biochar are still being studied as agricultural and other green industries start to incorporate biochar into their practices. The source materials, the chemical and physical characteristics of the final product, and they way in which they are used will lead to different results. Be aware that biochar in too high of concentrations can be detrimental to plants.
Tree Health Management uses biochar in two ways:
- We use a coarse textured biochar as a soil amendment. We add it to the soil when we plant new trees as a way to increase the soil’s water and nutrient holding capacity. This helps to give new trees a welcoming space to develop new roots. Coarse biochar can also be spread in a thin layer on already-planted trees, like a mulch. This can be applied any time during the growing season or whenever the ground isn’t frozen. We sell bags of our biochar and compost blend, available year round.
- We use a micronized biochar blended in with our nutrient injections as a therapeutic treatment for new and/or stressed trees. We are able to apply small amounts directly into trees’ deep root systems underground using a soil probe. We tend to see positive results from soil injections the following season. We apply these injections throughout the growing season.
Contact Tree Health Management today if you are interested in biochar applications.