Washington, Dec 3 : In a new analysis, researchers from the University of Illinois in the US have determined that replacing corn with perennial grasses has a beneficial effect on soil carbon.
The research was undertaken by Illinois plant biology professor Evan DeLucia and his colleagues, who analyzed how land use changes associated with biofuels production affected soil carbon.
The researchers analyzed published estimates of changes in soil organic carbon in landscapes converted from natural or agricultural land to biofuel crops.
They focused on corn, sugar cane, Miscanthus, switchgrass and native prairie grasses. They also evaluated the impact of harvesting and using corn stover (the plant debris left over after corn is harvested) as a cellulosic biofuel source. Harvesting corn leaves and stems for use in biofuel production reduces carbon in the soil, the researchers found.
The more material harvested, the less carbon in the soil.
Their analysis showed that converting native land (grassland or forest) to sugarcane dramatically reduced soil carbon, creating a carbon deficit that would take decades to repay.
While perennial grasses add carbon to the soil each year, according to DeLucia, it could take up to a century for the sugar cane to rebuild soil carbon to former levels on native land.
Harvesting the corn residue for cellulosic ethanol production also reduced the carbon in the soil. The more plant residue was removed, the more the soil carbon declined.
But, it was found that planting perennial grasses on existing agricultural lands had the most beneficial effect on soil carbon.
Although there was an initial drop in carbon as fields were converted from corn to Miscanthus, switchgrass or native perennial grasses, the loss was fairly quickly offset by yearly gains in soil carbon as the grasses became established.
Unlike corn, which must be replanted every year, perennial grasses such as switchgrass and Miscanthus preserve and increase carbon stores in the soil.
These and other grasses have been proposed as high-energy alternative feedstocks for biofuel production.
"We began with the hypothesis that it might be good for soil carbon to put a perennial biofuel crop on the landscape instead of corn," said DeLucia.
"From a purely carbon perspective, our research indicates that putting perennial biofuel crops on landscapes that are dominated by annual row crops will have a positive effect on soil carbon," he added.