George Washington Carver (1864 – 1943) – Crop rotation techniques
All three patents awarded to George Washington Carver were for cosmetics, paints, and stains. None of them were commercially successful. Carver’s discoveries were much more important than his inventions. He discovered that continuous cotton crops in the same piece of land depleted the soil’s natural nutrients. To avoid the damage, he experimented with crop rotation. Using peanut and sweet potato plants as the intermediates, he figured out that the system helped restore nitrogen in the soil, making the land healthy again. 
Now that the market had more peanuts than anybody could ever need, Carver found other product uses. Among the products were metal polish, glue, shampoo, soap, and face powder. As mentioned above, none of the inventions made him a wealthy man.