The policies of the United States Department of Agriculture (USDA) have had a tremendous affect on farming in our country. Their funding go to further the research at land grant colleges (like UT), and the advice is disseminated through the county extension programs. The way most farms are run is a direct result of this information.
Agriculture before the 20th century depended upon healthy soil. Farmers knew how to keep their soils light and fluffy, rich in humus and capable of long-term production. All farms had animals for power and food, and the waste products were composted to keep the land fertile.