Farmbot is an open-source CNC farming machine that -- while not exactly a 3D printer -- is a great use of 3D printing technology.
How one social enterprise in Yangon, Proximity Designs, is teaching Myanmar's farmers to 3D print their own agricultural tools.
Crops and the Internet of Things; a high-tech, 3D printed pellet called BeanIOT can help farmers better monitor their stored crops. And perhaps even provide home security!
Democratized, open source agriculture sounds like an unusual concept, but that's exactly what FarmTools3D hopes to achieve with 3D printing.