With this system you can plant reagents to use in your macros or commercialize them with npcs or players.
To start tour farm, go to a Farmer Npc and buy one of the 3 deeds available (3x3, 5x5, 7x7) , after buying it choose a place to build it, be careful to built it (it is not like house).
When your farm ok, go back to Farmer and buy some seed that you'd like to plant.
Now go to your farm and dclick the seeds (30.0 or more is needed of herding and a shovel), after choose a part of the farm that is free to plant this seed.
Alright, now is only wait 8 hours to the seed grow completely and you be able to reap it.
The amount of reagents that you will get depends of your herding.
Hint: If you put a scarecrow on your farm, it will increase the amount of reagents that you reap.