Thanks. And by the way... do I really have to manually plant every time? Is there any way to automate them?
Select a farm using the "q" key. It should say something like Spring/Summer/Autumn/Winter, and list some different plants.
Each season, dwarves plant the farm with whatever crop is selected. You should notice that one of the plants is in white (selected), but the others are in light grey.
Dwarves will automatically replant and harvest the plants if they have the farming labours turned on (make sure at least one dwarf has the correct box lit in Dwarf Fortress). It's also a good idea to build a still (and maybe a farmers workshop) close to the farm. Then, dwarves should harvest the plants and immediately brew them into drink (or process them into food, respectively). Read
the wiki for more information on the different crops.
I suggest just going for plump helmets to start with. They can be both eaten raw and made into drinks. I wouldn't bother with crop rotation, either. It has no advantages and you can build several farms for several crops.
If no one is planting crops, its probably because they have other labours turned on (check Therapist). You can make any dwarf plant crops (and even dwarf children can harvest) but if they're also a mason then they'll probably prefer to spend most of their time in a workshop than messing around plants (that sort of crap is for tree-hugging elves).
L.