I don’t really see the point.

What if every square is already occupied? Or can you destroy existing things on squares to place rocks there?

Also, this rule contradicts itself, in that it states that something (having three rocks) is true, and then implies that it can be false for an extended period of time. This also leads to utter bizarreness if a plot somehow ends up with four or more rocks. You should probably just change it to something like this:

Squares may contain Rocks. A Square containing a Rock cannot contain anything else, nor can anything else occupy or pass through that Square. If any Plot has not contained at least three Rocks at any time within the previous 48 hours, then any Farmer may place Rocks on it, destroying anything else on the squares they are placed on in the process, until it contains three Rocks.

It also needs some method for initialization, so that there isn’t a free-for-all 48 hours after the proposal passes. (Most plausibly, just let Farmers place Rocks on their own Plots even without the 48-hour deadline.)

.  The method for ‘fixing’ having 4+ rocks is to place more.

S/K because this sucks for the foregoing reasons

Another point: Any farmer may put Rocks to every Plot? Don‘t like that.

This rocks.
(Yes I know it’s selfkilled)
I’d vote yes if fixed and with only 2 rocks.

Note that this is Self killed.