Compaction is caused by the weight of the tractor tires pressing down on the soil. When operating tractors, farmers try to minimize compaction because it can hinder infiltration of water to crop roots and increase soil erosion and water runoff.
Thomas R. Way, an agricultural engineer with ARS's National Soil Dynamics Laboratory in Auburn, Ala., led the study in cooperation with Tadashi Kishimoto at the Obihiro University of Agriculture and Veterinary Medicine in Japan. In the study, the researchers used a tractor tire equipped with six sensors on its tread to study tire pressure on tilled and no-till soils. Surprisingly, they found that the pressure was least uniform on untilled clay soils, and was actually more uniform on tilled soils.
This research is expected to help manufacturers adjust the tire contact pressure and the size of tire lugs, which are the raised bars on the tread. The lugs have considerable contact with the soil and they also can affect compaction. Changing tire pressure and size could help minimize compaction on no-till fields, an important consideration because of the increasing popularity of no-till farming.
During the study, the researchers were also surprised by the similarity of another factor called "tractive efficiency" on tilled and no-till soils. This is a measure of the efficiency with which the tire converts the power that's applied to the wheel to useful work.
A tractor's fuel efficiency increases with its tractive efficiency.
Before the study began, the researchers thought that tractor fuel efficiency would be greater on no-till soils. But the study showed that tractive efficiency was the same on tilled and no-till soils, meaning there was actually little difference in fuel efficiency.
ARS is the U.S. Department of Agriculture's chief scientific research