The villagers in single player do not behave the same way as their multiplayer counter part. Example: Multiplayer villager farms and breeds, the single player version doesn't farm, pick up items, or even breed without aid. These villagers are spawned from a spawn egg in the 14w30c.

I was working on building a city for the villagers sort of like the Sims. The villagers were not reproducing at all giving it was an update I went out to new territory where the rabbits were spawning and went /gamemode 1 to build Docm77's infinite villager creation. It worked great for him but I needed a lot of villagers. I went to sleep to wake up to seeing the same 3 villagers (farmers) in the bottom pen.

A link to Docm77's video is: https://www.youtube.com/watch?v=iFL1K41yKUs&list=UU4O9HKe9Jt5yAhKuNv3LXpQ to build the contraption. The problem is as stated above the farmers are not farming the crops and they are not reproducing any offspring. This is in the single player version & I tested it out on a fresh new world and I get the same result.