Biochar Pros and Cons in Horticulture

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The biggest handicap to growing crops in the Sandhills is the sandy soil. Acidic and low in organic matter, it does not hold water or nutrients. These ills can be modified by adding organic matter in the form of compost, cover crops or organic mulch, but the organic matter breaks down and needs to be reapplied every year. What if something could enhance the soil permanently? That is where biochar comes in. Biochar is a type of charcoal that is used as a permanent soil amendment to improve soil’s water and nutrient holding capacity.

To make biochar, organic materials such as timber waste or poultry litter are heated to a high temperature in the absence of oxygen. Such decomposition is called pyrolysis. The heating removes water and gases and leaves a stable, mostly-carbon substance. For use in farming, the char is ground into a powder that is applied to the soil. It provides many of the same advantages as compost, such as water and nutrient retention and a better microbial community. However, whereas compost breaks down within one year in a hot, humid climate, biochar can last for hundreds or even thousands of years. The most famous example is in the Amazon basin, where biochar added as far back as 6000 years ago still renders the soil darker and more fertile than the surrounding, nutrient-poor soil.

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