saplings that have grown on rich soil immediately convert it into regular dirt.

Trees are not meant to grow on rich soil, only farmland. (Wheat, carrots, potatoes, etc.)

Trees are not meant to grow on rich soil, only farmland. (Wheat, carrots, potatoes, etc.)

Wrong.

Trees are not meant to grow on rich soil, only farmland. (Wheat, carrots, potatoes, etc.)

in 1.1 i had an automated spruce tree farm growing on rich soil and it never converted

try growing a cherry blossom tree on it.

That may be part of the problem, I think there is another issue with Forbidden and Arcanus saplings crashing servers. Try growing just Vanilla saplings on the rich soil.

there goes my big money idea of selling cherry tree wood, guess i'll have to sell bread instead

I also have a tree farm using rich soil right now in version 1.2 and it doesn't convert into dirt.