Hey all brilliant discussion. My thoughts.
Anyone who burns wood for heat in temperate zones should make a point of damping down the stove and allowing enough ash to build up that there are small yet frequent bits of char. It would be foolish not to add this to your do do or what have you and spread around our land to feed this to the soil for eternity. When ash and bits of char are added to the mulch the ash leaches away quickly to the roots of the plants while the char will become bio-char in the top dressing were it will not compete with deep rooted crops, while absorbing nutrients all year round.
Moderation is always key.
Especially when adding wood ash. Remember Fukuoka said he stopped using it because it maid the spiders go away. I've noticed worms detest it too, and a ring of wood ashes can keep slugs away from plants, wile making them grow like mad. We know it raises the ph of the soil, which is better then importing lime. But I wouldn't cover fields with either. And be sure to add some greens because there is no N in wood ashes.
As far as charged up bio char, If you need to double dig (so you need not till again) why not add a little to the sub layers if none is present. After all natural forces set bigger fires then we throughout history and before. Nature is constantly adding char to the soil, I frequently pass a burnt out gap were most of the charred trees are still standing, over the years all that char is absorbing nutrients from the rainfall and bird do and all other life activity around the spot before even hitting the ground. Now the site is full of shrubs, young trees and still many herbaceous plants among the standing dead.
We mimicked nature when burning, in the past because we found burn sites full of edible fruit and veg.
But i don't think anyone should be burning old growth to till corn fields. Maybe in a hundred years of proper management we might start clearing sites making char on site and planning the succession for peek productivity. But right now we have to much damaged soil to heal and trucking in bio char or anything else is wrong. Just plant the right seeds step back and let her do it.
When considering the removal of aerial fuel loads from forests ripe to burn. If you have the will to turn it into bio-char, I think a few pounds in the naturally occurring pits or small dug pits (with the corresponding mound planted with nitrogen fixers and dynamic accumulator understory species) covered with leaves and maybe some do do in the rainy season, would not be to disturbing, or pose a ground fire risk, but would hold lots of moisture and nutrients. Eventual the tree roots and there mycorize would be in there digesting away. And build a few morel beds. Wouldn't that be awesome.
Good luck to you all