Farming used to disqualify you from enlisting voluntarily. My grandfather was told he couldn't enlist in early 1942 because he was a farmer. They let him in a few years later in time for him to fight in the Battle of the Bulge. With the change from mainly family farming to mainly corporate farming today, I doubt just being a farmer would get you out of serving today (except possibly in the situation mentioned in the article), especially if you want to serve.