The dispensers have water in them, they are hooked up to a button via redstone.One press of the button releases the water which is placed by the dispenser as a source block.the water pushes the wheat to the walkway.once all wheat has been moved I press the button again and the dispenser collects the water source block back into the bucket.I then go and collect the wheat and seeds from the walkway.unfortunatley I have to plant the seeds my selfIf your interested on how I built it and seeing it in action feel free to check out the video on You Tube [link] This video is quite long sorry but you can skip through it right