Researchers from 13 USDA Agricultural Research Service locations, state universities and the U.S. Department of Energy are finishing the second season of field studies in a 5-year project to determine where, when and how much stover can be harvested for ethanol use without harming the soil.

The Renewable Energy Assessment Project (REAP), as it’s called, is being conducted as no-tillers face the prospect of harvesting stover for cellulosic sugars that can be fermented into ethanol. Stover refers to the stalks, leaves and cobs that remain in corn fields after the grain harvest.

Harvesting stover for sugars to ferment into ethanol could lessen dependence on crude oil imports. However, leaving stover in place reduces soil erosion, replaces lost nutrients and sequesters carbon in the soil, lessening carbon dioxide accumulation in the atmosphere as a greenhouse gas and its contribution to global climate change.

Wally Wilhelm, a plant physiologist in the ARS Agroecosystem Management Research Unit at Lincoln, Neb., coordinates the REAP research. Also, he’s working with ARS Lincoln scientist Gary Varvel on a 100-acre study on a privately run farm to examine the effect stover harvesting has on organic matter content, grain yield and carbon sequestration on high-, medium- and low-productivity soils.

REAP scientists in St. Paul, Minn., are conducting experiments with winter cover crops and living mulches like kura clover to determine whether they could help maintain soil health and productivity when stover is harvested.

Wilhelm says REAP aims to establish stover-management guidelines that would help no-tillers, ethanol producers and…