Is charcoal a good soil amendment?

Hand holding biochar
Photo credit: Marcia O'Connor

Do you have published, current, projected , research in the effects of charcoal amendment to agricultural soils/forest soils?

- Multnomah County, Oregon

There is quite a bit of research going on around the country on biochar including some in Oregon. Three seem to be three major research directions - actual use of biochar in ag, forest, stormwater, or other settings; recoverable value from wood waste that would otherwise be left to rot or needs to be removed to reduce fire concerns; value of biochar in carbon sequestration to help reverse the impact of human CO2 emissions on climate change.

As you might guess, it is a complicated. To produce biochar efficiently, the raw material to be charred has to be collected, trucked to a facility, and then subjected to extremely high temperatures (>700 degrees Celsius), all activities with a high energetic (carbon footprint) cost. The material then has to be trucked back out to the application site, applied, and worked into the soil as appropriate.

So, with that in mind, the cost and value of the carbon sequestration has to be compared with other means (and their respective costs and benefits) to achieve the same sequestration end, i.e. growing cover crops and tilling them in or composting wastes and adding them to soils. The cheapest method and that with the lowest carbon footprint will probably be incorporating cover crops, at least in annual cropping situations. There probably will be specific situations where some of the unique characteristics of biochar will stimulate its use but it is unlikely to become more generally used, at least in field crop agriculture unless the costs get much lower. And with all that trucking and heating, that is hard to imagine. But specialized horticulture settings with a high gross income per acre (vegetables, small and tree fruit, nursery, etc. might find value if some disease suppression characteristics or other production values can be confirmed by high quality research.  

Here are some biochar links of research done in Oregon and/or reported here and a few other international papers. There appears to be some interest in using biochar to "activate" compost. Still, farming practices that are using "green manures" i.e. plants that are sown in between crops or over the winter and tilled in fix a lot of carbon over time.

Chip Bubl
Extension Specialist Agriculture
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