How to make an automatic agricultural farm

The beauty of this design is that you can make it as long as you wish. So make your platform of dirt. Make sure it is 6 blocks wide but you can make it as wide as you want.

Place your pistons and repeaters just like this. Make sure there are blocks under the pistons.

Wire it up to a lever underground.

Cover up the redstone and make these water pockets. Make sure you add a water pocket every 4 dirt.

Add the blocks above the water pockets, turn the lever on, and then add another water pocket behind the pistons.

Add hoppers leading into a chest. To connect one hopper to another hold shift and click the hopper you wish to connect to.

Fill with seeds.

Once your seeds have grown, get ready for the next step.

Flick the lever and watch the seeds and wheat flow into the hoppers.

Collect your wheat and seeds, retract the lever, and replant your seeds. Once the seeds are done growing, just click the lever again and collect your wheat and seeds again. Enjoy the surplus! :)