Agriculture requires more consistent energy inputs. In a similar vein, the Moon is poor in nutrients needed to sustain plant life. Certainly, most of the basic resources can be recovered from the Moon itself. Assuming recent measurements at the South Pole are accurate, water, oxygen and rocket fuel should not be a problem. The biggest obstacle is the cost effectiveness of a settlement project.
Launch costs make a lunar base prohibitively expensive.
Moreover, in most areas of the Moon, solar energy resources are feast or famine. Agriculture requires more consistent energy inputs. In a similar vein, the Moon is poor in nutrients needed to sustain plant life.