This will benefit the organisms and nutrients, although will not be as environmentally friendly as Biochar.
The great benefit of Biochar is that is does not need to be reapplied to treated soil.
Yes if you carefully scrape back the soil around mature trees and plants you can add enriched Biochar at the 10-15% rate.
Enriched Biochar can be added all year. As it helps with prevention of disease and Biochar retains up to 5 times its weight in moisture it can benefit the plants both in the cold and hot periods.
Mix into soil so that the Biochar is equally distributed. Ideally add 10% of small gravel to the mix which will also help with aeration.
Yes, applying Biochar to a rate of more than 50% to the soil can have negative effects. Ideally stick to an application ratio of 10-15%?
It is only necessary to add compost when applying pure Biochar, i.e. not already enriched with nutrients.