Dynamics and consequences of compaction process in agricultural soil under vehicular loading : High-sampling-rate measurements and structural analyses

Soil compaction induced by vehicle traffic on agricultural fields threatens soil health. Thus, stress caused by heavy machinery, and its effects on soil, have been widely studied by experimental and computational methods. This study presents a high-sampling-rate Bolling probe setup for dynamic soil stress measurements and a continuous Percometer measuring system to investigate the effect of a vehicular load on soil moisture. Both systems were implemented in a field test area where ten passes with an agricultural tractor were driven on a test track. The on-site measurements were accompanied by laboratory analysis of soil structure and strength analyses based on soil samples taken from the field test site before and after the vehicle passes. In addition to ten compaction passes, a high-speed vehicle pass was performed to test the capabilities of our experimental setup. Results of the Bolling probe and Percometer measurements showed new aspects on the dynamics of soil stress and the state of soil moisture caused by a vehicular loading. Measured stress and soil moisture values also indicated that soil was compacting due to vehicle passes, an effect which was confirmed by X-ray tomography imaging and laboratory analyses of soil samples. During the high-speed pass, our Bolling probe setup was able to measure oscillations of soil stress.