The best crop in our area is the weed! Seems most of the US has had a strange growing season. When we have a good year people often plant fall crops to protect and feed the soil over the harder seasons.
According to Rutgers University they change what they plant to encourage the soil for the following year's crops. They do not plant the same things in the same area year after year, and sometimes let the land set so it can regain its health.
When they planted corn next to our field one year, the next year they planted beans. Over the winter they planted winter wheat. For small farms broccoli or cauliflower is a good fall crop.