In old forestry,we dont need fertilizer to maintain farms,so I really think it is counter-intuitive to require aptite,a non-renewable resource as part of agriculture automation.
However here is catch,even if you allow compost to be alternative,you still have no way getting Dirt or Podzol with manual working,so here is suggestion.

1.make Humus no longer accept Podzol as alternative to Dirt.(in crafting table)
2.replace leave with sapling in Podzol recipe.(in moistener)
3.replace seed with Podzol in Mycelium recipe.(in moistener)
4.add recipe turn Mycelium into dirt(like smelting it into dirt?)
5.allow compost be used in mutifarm as alternative.

by these changes,it turn sapling+wheat->dirt,so dirt is now a full automational renewable resource,and by doing this part,the role of Moistener no longer ignorable,because you can cut the aptite entirely if you setup your automation right(tho you need 2 mutifarm setup to have such luxury).