Here is a growth comparison using plain charcoal vs. biochar, with the soil as a control.
Side by side of two cabbage plants, grown with biochar on the left, and without on the right.
Adding biochar helps. Adding biochar with fertilizer will give astonishing results.
Yield from a pea plant grown with biochar (right) versus one grown without (left).
Without biochar on the left, and with biochar on the right.
Corn grown with biochar (right) versus corn grown without (left). You can see not only the difference in plant growth, but the effect on the richness of the soil as well.
More yield with biochar!