What are the orgins of biochar?
Today’s methods of using biochar are updated versions of the methods of the native peoples of the Amazon Basin, where thousands of years ago they supported their growing populations by improving the very poor jungle soils. They found by adding carbon from cooking fires and purposeful placing of charcoal in the ground resulted in as much as a fourfold increase in fertility. These dark soils, called terra preta, continue to be fertile today and still retain large amounts of carbon. They are sometimes dug up and used as potting soils.
Why is biochar so good for the soil?
Biochar has a unique physical and chemical nature. A single gram can have an astounding 500-1000 square yards of surface area! This large surface area provides the perfect habitat for soil microorganisms, some of which form symbiotic relationships with plant roots and improved uptake of nutrients by plants. The sponge-like nature of biochar has the unique ability to attract and hold moisture and nutrients. Biochar is especially good at retaining hard-to-hold nutrients like nitrogen and phosphorous, greatly reducing fertilizer runoff and at the same time reducing the need for valuable fertilizer by using it more efficiently. Recent research has shown biochar enriched soils reduce carbon dioxide and nitrous oxide emissions by 50-80%.
How long does it last?
Most organic matter applied to the soil must be added again every year to replace it as it is consumed in plant growth. Biochar persists in the soil for thousands of years, and is a permanent soil upgrade. This means that the benefits are permanent, and after the ideal char to soil ratio is attained no more needs to be added. Since it is relatively inert, it resists chemical and microbial degradation.
Does biochar affect soil ph?
Biochar is basic in ph and thus acts as a “liming” agent. It will reduce soil acidity but does not actually add nutrients, although the exception is biochar made using manure will still have some nutrients. In our opinion manure is better used directly as compost in the garden. It is possible to move the ph of biochar toward neutral by putting diluted vinegar on it and mixing. You should do this in small batches, testing as you go until you have determined how much is needed.