Tilled soil becoming untilled

[24k Ancient Fruit]

So we all know for a fact that for any tilled soil placed on your farm that does NOT already have a growing or wilted crop on them, there is a chance that it will become untilled soil the next day. So here's what I would like to know about this (assuming that the player never uses a Pickaxe on these tiles):

1) What is the approximate percent chance that a tilled tile with no crop will spontaneously become untilled the next day?
2) Are chances that the tilled cropless tile will become untilled the next day affected by the presence of Fertilizer (e.g. Deluxe Speed-Gro, Deluxe Retaining Soil, etc.) on that tile?
3) If the tile is watered and/or there is a Sprinkler in the vicinity that would water that tile each morning, does this affect the chances that the cropless watered tile will become untilled soil the next day?
4) How about in the Greenhouse? Can tilled soil become untilled there without using a Pickaxe?

 

[Draconifors]

4) How about in the Greenhouse? Can tilled soil become untilled there without using a Pickaxe?

In my experience, no.
I had a tilled, empty spot for I believe multiple seasons, and it never became untilled.

 

[FilthyGorilla]

Are chances that the tilled cropless tile will become untilled the next day affected by the presence of Fertilizer (e.g. Deluxe Speed-Gro, Deluxe Retaining Soil, etc.) on that tile?

Yeah iirc it's the same chance regardless of if there exists fertilizer on the tile

4) How about in the Greenhouse? Can tilled soil become untilled there without using a Pickaxe?

Nope, it'll always stay tilled unless manually changed

3) If the tile is watered and/or there is a Sprinkler in the vicinity that would water that tile each morning, does this affect the chances that the cropless watered tile will become untilled soil the next day?

I honestly can't remember at this point in time but that would affect the question about fertilizers, at least with retaining soils