The document discusses the importance of crop rotation for preventing the depletion of soil nutrients and the buildup of pests and diseases. It explains that not rotating crops led to disasters like the Dust Bowl and Irish Potato Famine. Crop rotation involves growing different types of plants in the same area in successive years. This prevents any one nutrient or pest from becoming overly concentrated. The document provides examples of crop rotation plans and families of plants that should not be planted in the same area more than once every few years, such as the nightshade family.