This seems to be a bug that they haven't fixed yet. You can compensate for now by using the mod Rainbeau's Fertile Fields. It's a bit more work to get the fertile areas set up. You have to gather the materials needed to create the soil and then to make it fertile, but at least you still have the option. Hope they fix this soon.

Alternatively, just don't smooth the floor you'll be using as soil. This has always been the case with the mod, ever since it was released. It's intended. But, to each their own.

@Ancient Aliens Guy I disagree. I have been having the same problem. In B18(or A17) you had to smooth the tile before soil could be placed on it.

+1 to this issue. Can't build tilled soil over stone of any kind, rough, smooth or brick. Before or after the research. Just a waste of a pawn's man-hours. also, (at least on 1.25x GUI scale) the research node is overlapping a vanilla node. Not a deal-breaker, but kinda unpleasant to look at.

After further investigation(and I am by no means a modder just a programmer) I am not sure it is possible to go back to the way it was unless the developer adds some C# code or has some other material required to make it. It looks like the defs changed and now when something is smoothed it is no longer the right tile type.

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

i_msd 님이 먼저 게시:

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

This worked perfectly.
Thanks!

i_msd 님이 먼저 게시:

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

+1 from me as well, was driving me mad. Thank you!

Also I have posted this workaround in the main mod comments, with credit to you.

i_msd 님이 먼저 게시:

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

Thank you you glorious bugger, this has been annoying me for a while now

{F-7} lone_wolf_wp 님이 먼저 게시:

i_msd 님이 먼저 게시:

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

Thank you you glorious bugger, this has been annoying me for a while now

There is much easier way. in dev mod you can change the terrain i.e. rough slate, so if you smoothed a large area you can just make it rough and then what ever you want then you can put soil over that. (the setting to get the change terrain is in the same as where you go to spawn item or change the weather etc.. Hopes This Helps.

Maybe use the terraforming mod?
To turn it into dirt or rough stone?

Can't build on sand either, which makes this mod almost useless in dessert.

i_msd 님이 먼저 게시:

It will not work propely, like it was at A 0.17- A 0.18, but it will work.

dir \Steam\steamapps\workshop\content\294100\725747149\Defs\TerrainDefs\

file Terrain_TS.xml
it need to find and to change line there:
<terrainAffordanceNeeded>SmoothableStone</terrainAffordanceNeeded>
to
<terrainAffordanceNeeded>Heavy</terrainAffordanceNeeded>

I'm sure I've seen this written somewhere before...