Over on Permies.com there have been a lot of people reporting on their various biochar experiments. One thing that I found interesting was that well-made biochar can hold its own volume in water, in a way that makes it very hard to dry it back out, but at the same time plants are able to access that water. A few people have even reported that it works to hold water in desert conditions, making it easier to undo some of the desertification in their area.
Might come in handy during a drought!