To get friends for your farm you need to earn individual rep with the inhabitants of Halfhill and the surrounding area. There are ten friends that you can get and each will add something to your farm. In addition to the Tillers dailies that give rep for these people, you can aquire gifts for them and make their favorite food.
You can give five of their favorite food to each friend per day.
These are either found in Dark Soil or occasionally when you harvest vegetables. You can give as many gifts as you have, this is not a daily thing. Many of the potential friends will accept many of the gifts but each has a favorite which gets you the most rep.