The Cullars Rotation, established in 1911, is the oldest continuous soil fertility study in the South and the second oldest cotton study in the world. It began through the Alabama Agricultural Experiment Station on the farm of J.A. Cullars and John P. Alvis. In the late 1800s, J.P. Alvis and J.A. Cullars farmed this property, later known as the Alvis Field, and allowed Prof. F. F. Atkinson, a biologist at the Agricultural and Mechanical College of Alabama, to use the site to study cotton rust, a disease that causes cotton plants to shed leaves early. Atkinson's 1890 research found that cotton rust was caused by a potassium deficiency, leading to the start of the Cullars Rotation in 1911. In 1938, the Alvis Field was sold to Alabama Polytechnic Institute, which became Auburn University in 1960. The experiment includes 14 soil fertility variables in three blocks rotated with cotton followed by a winter legume, corn followed by wheat, and soybeans planted after wheat. Today, potassium fertilizers are used on cotton throughout the South.