Tillage prepares soil for planting, controls weeds, incorporates manure or fertilizer that has been spread on the soil surface, mixes crop residue into the soil, and encourages soil warming for early planting. In recent decades, however, farmers have steadily reduced tillage or eliminated its use altogether (no-till). This keeps crop residue on the soil surface, which helps reduce erosion and conserve soil moisture. Recent ERS research shows that roughly half of U.S. corn, cotton, soybean, and wheat producers used either no-till or strip-till at least once between 2012 and 2016. Twenty-one percent used no-till or strip-till every year during the same period.