Reducing CO₂ Loss From Tillage

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 warming.

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.