Soil deformation during field traffic

Under moist soil conditions, high wheel loads and repeated wheel passes due to intensive field traffic, e.g. at sugar beet harvest, significantly increase the risk of soil compaction and harmful soil structure damages. The tires of the machines induce loads into the soil via the tire soil interface. The pressure is transmitted into the soil and may induce soil deformations. Plastic soil deformation lead to soil compaction with multiple effects on soil parameter (e.g. dry bulk density, air capacity), soil structure and soil pore system.

A measurement device is presented to measure soil pressure and soil deformation simultaniously in different soil depth. It was applied for different field traffic situations and techniques at silage maize and sugar beet harvest, as well as for the application of digestates on a stagnic Luvisol in northern Germany. Under moist soil conditions, almost every wheel pass leads to plastic soil deformation in the topsoil. Depending on soil loads and conditions, the subsoil can also be deformed. In all measurements, the first wheel pass induces the highest deformation, but every further wheel leads to further soil deformation. Therefore, in addition to the wheel load, the number of wheel passes also plays an essential role in evaluating field traffic and soil compaction processes.

Undisturbed soil cores were collected before and after field traffic in different soil depth (20, 35, 50 cm) and analyzed in the soil physical laboratory. With increasing plastic deformation the total pore volume decreases, wider soil pores were reduced and finer soil pores generally increase. Hence, mainly parameters like dry bulk density, air capacity and saturated hydraulic conductivity react negatively to increasing soil deformation.