This is my final Wheat farm and it combines my previous piston and water farms into one, which can be extended as far as you want using a Daisy Chain type system which requires you to connect each farm section with just 2 repeaters as show in the video here http://www.youtube.com/watch?v=2BIw9uSVmQY.

The download contains the main farm and a add on section to extend the farm as shown in the video. The same piece can also extend to the right but you will need to break into the side to expose the redstone.

Additional Notes

Excuse my redstone work as I do believe it could be better or more compact, and I would love it if someone could post telling me how.