No-till Shows Benefits when Switching from Grasses to Corn
May 27, 2009
The national push for biofuels may
encourage farmers to plant corn where environmentally friendly grasses are now
grown. But those making the switch can still sequester soil carbon and reduce
greenhouse gas emissions by not tilling the soil, according to
Agricultural Research Service (ARS)
Follett, a senior supervisory scientist at the ARS
Plant Nutrient Research Unit in Fort Collins, Colo., spent six years
monitoring levels of soil organic carbon in a Nebraska field where bromegrass
was grown for 13 years and the field then was converted to no-till corn.
The effort is one of the most comprehensive field studies yet to address a
major issue in agriculture: the effects of replacing native grasses with corn.
Bromegrass became a popular alternative in the 1990s for Midwestern farmers
trying to save erodible soils, enhance habitats and increase soil organic
carbon. Under conventional tillage, much of this carbon is released into the
atmosphere as carbon dioxide, a greenhouse gas that contributes to global
warming. Nationwide, there are 35 million acres of bromegrass and other plants
grown in exchange for $1.8 billion in annual payments as part of USDA’s
But as demand for biofuels raises corn prices and CRP contracts end, farmers
may replace grasses with corn.
Follett and his team used herbicide to kill the grass in the fall of 1998
and planted no-till corn the following spring. They collected soil samples at
three depths to analyze the total amount of soil carbon at each depth and
determine whether the carbon was previously sequestered by bromegrass or newly
sequestered by the corn.
Follett’s results, recently published in
Agronomy Journal, show the
benefits of no-till when making the switch. The researchers found yields were
decreased because of extended drought conditions, but the total amount of
carbon didn’t change. The rates of loss of soil organic carbon previously
sequestered in the top two depths by the bromegrass were offset by similar
rates of increase in newly sequestered carbon from the corn. There also was
little or no change in the amount of soil organic carbon from either the
bromegrass or the corn at the third depth.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.