Improve Garden Soil with Biochar
Gardeners are always looking for ways to improve the soil they have for better results. Whether you want to increase your vegetable yield or have healthier soil to grow beautiful flowers, biochar is a great option for the home gardener with several advantages. Hopefully this article will provide you with an overview of what biochar is, the advantages it has and its environmental benefits.
What is biochar?
Biochar is a fine-grained charcoal left behind by pyrolysis, the heating of organic material to a very high temperature (over 900 degrees F) in the absence of oxygen over several hours. The organic material can be anything from livestock manure, crop residue or biomass waste materials. Converting these materials to biochar instead of burning or letting them decompose prevents the release of carbon and methane into the atmosphere. The resulting charcoal has a very high carbon content, is a very porous matrix (imagine a coral reef structure) and has unique ability to hold nutrients. One gram of biochar has the equivalent surface area of 2000 square feet. These characteristics are what make biochar very attractive as a soil amendment.
First carbon content. By not releasing carbon to the atmosphere this process decreases greenhouse gases sequestering the carbon in a very stable form that does not degrade quickly. Biochar’s inert matrix prevents it from breaking down like other organic soil amendments and resists chemical and biological degradation resulting in extremely long persistence in soil so only one application is needed.
Secondly the porosity of the physical structure. This has several advantages, increasing water holding capacity, creating a habitat for beneficial bacteria and fungi and enhanced soil tilth. Increased water holding capacity results in less watering and some drought resistance as the structure gives water a place to go instead of just draining away (acting kind of like a sponge). Beneficial bacteria convert nitrogen from its unusable form of N2 to NH3(ammonia) or NH4(ammonium) which plants can then use. They also do many other things but that’s for another article. Beneficial fungi (Mychorrizae) develop a symbiotic relationship with plant roots delivering minerals and nutrients from the soil in exchange for water and carbohydrates. Again, they do much more than just this.
Thirdly is nutrient holding ability. Nutrients with a positive electrical charge like potassium, calcium, magnesium, and ammonium are attracted to the negatively charged surface and are released into the soil in the presence of hydrogen. That is why initially when biochar is applied there may be an increase in soil pH. Biochar can also act as a reservoir for nitrogen and phosphorous. This results in not having to use as much fertilizer for your plants.
How is biochar applied? Biochar is suggested to be applied at a rate of 5-10% by volume to the top 4-6 inches of soil. This results in 0.5 cu ft for an 8×4 foot raised bed using the 5% rate. Biochar is available in big box home stores, online, and garden outlets at a cost varying from $40 – $60 per cubic foot depending on the source. Because of the potential of pH increase use biochar conservatively with acid loving plants such as blueberries and rhododendrons.
Having to water less, fertilize less, and increasing soil diversity, having a look at biochar as a soil amendment might be right for you.
This article was original published win the August 2024 Ocean Observer.
