When a farmer tills a field, some carbon dioxide in the
soil escapes to the atmosphere. Agricultural
Research Service (ARS) scientists in Auburn, Alabama, are seeking
methods of reducing this CO2 loss because the loss of carbon
in this gas form may be harmful to the environment and to soil productivity.
Plant physiologist Stephen A. Prior and agricultural engineer
Randy L. Raper are the leaders of this project at the National Soil
Dynamics Laboratory. The main factors they scrutinized were time of
year (spring vs. fall tillage) and implements used. The scientists looked
at loamy sand soil in east-central Alabama to see how much CO2
escaped during plowing of a grain sorghum field.
With fall tillage, the amount of CO2 lost depends
specifically on the type of implement used. Disking caused more CO2
release than chisel plowing because disking causes greater soil mixing.
Plots of land that were not tilled had low levels of CO2
loss similar to the fields that were chisel-plowed because less residue
was incorporated into the soil.
"Our research shows that fall tillage equipment that
maintains surface residue and minimizes soil disturbance helps reduce
CO2 loss," Prior explains.
Simply waiting until spring to till also reduced CO2
flux. Leaving crop residue in place over the winter months and postponing
tillage until spring slows residue decomposition and protects the soil
during winter rains.
Sequestering carbon reduces the rate at which the atmosphere's
CO2 concentration increases. Carbon dioxide and several other
gases trap heat near the Earth's surface and may contribute to global
This work fits into Raper's research to develop implements
and cropping systems that minimize residue burial. He has also found
that the amount of residue buried increases substantially for disks
as speed or depth of tillage increases. His advice? "Park the disk
and use the chisel, if you have the choice."By David Elstein, Agricultural
Research Service Information Staff.
Stephen A. Prior
and Randy L. Raper are with
the USDA-ARS National
Soil Dynamics Laboratory, 411 South Donahue Dr., Auburn, AL 36832;
phone (334) 844-4741 [Prior], (334) 844-4654 [Raper], fax (334) 887-8597.
"Reducing CO2 Loss From Tillage" was published
in the March
2004 issue of Agricultural Research magazine.