In Cooking Better Biochar: Study Improves Recipe for Soil Additivewe learn that
...not all forms of biochar are the same. The researchers found charcoal produced at temperatures of 450 Celsius or higher was most likely to improve soil drainage and make more water available to plants, while charcoal produced at lower temperatures could sometimes repel water.
...the microscopic properties of biochar can vary widely depending upon how it's made. In the worst case, she said, improperly made biochar can harm soil rather than improve it. [emphasis mine]
Very informative. Enjoyed learning that.
Ruth, thanks for posting this. I had not heard the neologism "biochar" and was not aware that adding it to soil would be beneficial. It's interesting to read about it.