A U.S. Department of Agriculture study suggests conventional tillage practices could actually hold back more carbon than a no-till operation. Researchers have found that below the surface, plowed fields hold just as much, if not more carbon than no till. However, they say no till fields will contain more carbon, if they are left that way. A common practice is to plow one year, and no till the next. Iowa State University Soil Scientist Mahdi Al-Kaisi says leaving crop residue has many other benefits, including a reduction in erosion.