The title says it all, basically when I build a farm on the enhanced (+300%?) farming land, it did not get counted towards the total food production on my planet, which remained at 5 (from the original colony). I tried destroying and rebuilding the farm on the land multiple times, and it didn't work. I then built an additional farm on another spot, and wound up with 13 food production (5+8 for the upgraded farms I had at the time) which still didn't include the enhanced land farm.
Then I finally gave up and destroyed that farm to build something else there. When I checked back later on, I was now at -3 food production (that's right, *negative* 3) with the initial colony and the other farm. Clearly not working as intended. I have not verified this in another game, but it was true in the one I played last night.