I actually put together an artificial soil mod together on my own after asking. It's unpublished because it's unfinished - was thinking of adding soils for all of your agri mods, but didn't get around to it :)
https://www.dropbox.com/scl/fi/tpp72exvaasp6elisz2z8/AgriculturalSoils_1.0.0.zip?rlkey=ufumodcxdsrn7p2lgtv4z4hjv&st=a0kc5j6u&dl=0
I doubt it's going to be useful to you, and some of the stuff in there is placeholder from Alchemistry (thumbnail, changelog, graphics kind of), but I thought it worked pretty well. While the soil available for Stingfrond is very widely available, it's pitted with Highland Rock and Cracked Lichen soils, which actually drastically reduces the practical farming space available. The Agri tower needs 3x3 tile sectors, so a little 2x2 blotch of Cracked Lichen can block 4 entire sectors. Even with this soil, you still have to contend with rock intrusions and other terrain, but at least your planting fields can be made smoother.
Let me know if you're interested in doing actual soils for your mods, of if I should just publish what I have.