I upgraded this instruction again with a new harvesting system and automatic collection of the farmed items (using hoppers).
This is what the farm is gonna look like when finished:
First these blocks are arranged linke an elongated solid staircase. The single layers are each 7 blocks long. Add a eighth block at the end of the upper layer.
Build a little frame around the irrigation system to avoid that later the water flows away:
Now a water-source is added at the top. The water should flow all the way down to the bottom, otherwise you built something wrong.
Now cover the irrigation system with a block of your choice. Beware, however, that the water flow is not interrupted! The water should still reach the bottom.
Add the field on both sides with a width of 4 blocks.
Again, add a border around the fields, so that later the water is not flowing sideways.
At the top (right next to the source of the irrigation system (I have the block removed for demonstration purposes)), 4 dispensers are now added on both sides.
Behind the dispenser the actual redstone system is built: Add repeaters behind the dispensers and connect them with redstone. You might add additional blocks for building the redstone. Finally, the control for the dispensers is added - a normal button.
Put a filled bucket in each dispenser.
Use a hoe to transform the dirt into soil.
This is the chest where we later all our harvested items will automatically be transported in. Put it right in front of the end of the irrigation system.
Attach a hopper to both sides of the chest. Make sure that the hoppers connect with the chest. Press and hold the “sneak key” (default: shift) to build the hoppers at the sides of the chest.
Complete the hopper rows on both sides. The new hopper must always be built on the site of the recently built hopper, to connect them in the right way (this is necessary for transporting the items in the chest) (and again, press and hold the “sneak key” (default: shift) to build the hoppers at the sides of the recently built hoppers).
Now we can plant our plants…for example carrots, potatoes, wheat…
Finally, the plants are grown. We can start the machine now to harvest them!
Just push the button at the back of the dispensers. The water begins to flow, the items are harvested.
The items are carried by the water stream to the hoppers, and are therefore transported into the chest.
The items are now in the chest.
To stop the water flow again, you can now simply press the button again and plant new plants.!