So basicly i was thinking a more ways to improve the quality of soil, and then i remembered this old washion fertilization project called Slash-and-burn which long story shorter is,
you burn down a forest to increase the fertility of soil. This could work in game like if you burn down a tree in a few block area around it has a chance that soil will improve for example like.
From poor to medium could be like 50% change and from medium to high could be like 25 or even 10% change. or it could make a new kind of soil that is like a medium soil but looses fertility slower.