Why is it good for farmers to switch off between growing peanuts and growing cotton?

Cotton is a plant that makes huge demands on soils and area resources. Peanuts are members of the legume family. That means that they're nitrogen fixers. So they're able to change nitrogen from a form that's present but inaccessible within the soil, into a soluble form that's available for use by plant roots and the organisms of the soil food web. Therefore, peanuts build back up the soil that has been ravaged by cotton production. For it makes nitrogen available. And nitrogen is one of 17-18 elements that are essential for healthy soils, soil food webs, and plants. It's one of what are called the macro and secondary nutrients, for their use in larger quantities by soils. And it's therefore one of the three major elements that's found in artificial, commercial, conventional, fast-acting, synthetic N-P-K fertilizers. For the N stands for nitrogen, the P for phosphorus, and the K for potassium. And the bag of fertilizer always indicates their proportions within the total mix. For example, a popular choice is 10-10-10, which means 10% each of each of the big three elements.