Thats our devs, jumping from one extreme to the other.
yup confirmed, you can have a tree growing in your field witch is placed in the deep forest on a sharp slope, you can't however have a field on a perfectly flat, freshly leveled (plowed?) ground.
Can some one explain the logic here?
edit:
I remember the remains of a semi large base build some 5-6 months ago, the ground there hasn't regenerated completely even now (and nothing has been paved), since apparently not even one of the 16 tiles that make up the field can be "scared" that means if you build a base and wait half a year you can still find it impossible to plow fields. Great idea devs.