Ethanol from stover
Mar 1, 2009 12:00 PM, By Lynn Grooms
Researchers are trying to identify ground covers that are compatible with corn
Corn stover could provide as much as 20% of the feedstocks needed for ethanol production by 2030. But is corn stover sustainable? Will growers be able to remove corn stover without harming productivity and soil and water quality?
These are questions being tackled by researchers at Iowa State University (ISU) and USDA's National Soil Tilth Laboratory. They are in the first year of a three-year study that focuses on ground-cover species, hybrids that tolerate ground cover and how to manage ground cover.
Ground-cover species
Ken Moore, ISU agronomist, is evaluating 36 species of ground covers. The challenge is to find species that do not compete with corn during corn's critical growth stages, but that provide enough cover through fall and winter to minimize loss of soil nutrients and to protect soil from erosion by wind and water.
The ideal cover crop would go dormant in the summer so as not to compete with corn, but then grow during the cool season. In addition, its root system ideally would not compete with corn roots in drought conditions.
Moore says that perennial ryegrasses look promising. They are summer dormant and also are associated with fungal endophytes. Endophytes live symbiotically within perennial ryegrasses and fescues and produce toxins that confer insect and disease resistance to the grass. They also could help suppress weeds, Moore says.
Another ground cover showing early promise is sideoats grama, a warm season grass that does not have much growth activity until mid to late summer, says Scott Flynn, an ISU agronomy graduate student. Corn may already be in the eight-leaf collar stage by the time sideoats grama begins growing. But the grass continues to grow well under the corn canopy, Flynn says. He adds, however, that the sideoats grama may not persist the following season.
Competitive genetics
In the second experiment, Kendall Lamkey, ISU agronomist, is evaluating the genetic characteristics of 50 corn hybrids grown using three different treatments: a control with no cover crop, a treatment with sweet clover, and a treatment with Kentucky bluegrass. All 50 hybrids are open pedigree hybrids with the glyphosate-tolerance trait.
At harvest, Lamkey observed a notable difference between the control corn and corn that was intercropped with sweet clover. Corn planted with sweet clover was 1 ft. to 1½ ft. shorter.
Over the next two years, Lamkey will evaluate the stages in the corn life cycle that are important to determining yield in the presence of ground covers. He also will evaluate the grain weight as well as the weight of the above-ground biomass, which are roughly equal.
Carbon balancing
Jeremy Singer, agronomist, USDA National Soil Tilth Laboratory, established the third experiment using four ground-cover treatments in fall 2006, which will remain in continuous corn. The ground covers were white clover, Kentucky bluegrass, creeping red fescue and a mix of white clover and creeping red fescue. The mixture could provide a good balance of carbon and nitrogen inputs with less competition between plants, Singer says.
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