Wow, you guys are good. This is indeed the location of the infamous haybales roadblock from TAR6 and TAR15.
Here you see the road contestants arrived on:
The cluebox was just in front of the road sign:
And the clue picture I posted was of the background on the other side of the road:
The pit stop in TAR15 was just 100 meters down the road to the left.
This year the farmer has planted crops on the field. Also it might be worth to note that the number of haybales on that field during the roadblock was way more than a field of that size could produce so they had to have been brought in from other fields.
I hope you have had fun with this and well done to those of you who got it.