The Relationship of Field Geometry, Harvester Size, and Traffic Intensity during Wheat Harvesting

Investigations of soil compaction in agricultural land often deal with the deployment of heavy, high-performance machinery and their impact on soil structure and functions. The traffic intensity on the field considers the spatial distribution of the number of wheel passes and the wheel load of the machinery. The intensity can vary due to changing machine and field characteristics. However, these dependencies are not analyzed in detail yet.

To what extent the machine’s working size and field geometry influence the traffic intensities during wheat harvesting shall be presented in this contribution. A route planning system planned the routes of three different combine harvesters on 59 fields with varying field geometries. With these routes the spatial traffic intensities of the work process were modeled for all variants.

To represent the structure of the field geometry, eight shape-indices were calculated. The traffic intensities were divided into classes indicating the percentage area for different threshold values of wheel load and wheel passes.

The analysis of the three harvesters showed that the size of the machine has a significant influence on the total trafficked field area and the wheel load distribution. The larger the machine and working width, the more area is affected by high wheel loads, but less total area of the field is passed. Those relations are independent from the field zone (headland, infield or complete field area).

The analysis of the field geometry shows that there is a strong correlation between the passed area with more than 5 and 10 wheel passes in the headland and three shape indices. These shape indices are the interior edge ratio (IER), the interior area ratio (IAR), and the mean fractal dimension (MFD). Both the IER and IAR are dependent on the size of the field. It shows that the larger the field area relative to the perimeter and headland area, the bigger the proportion of area in the headland that has been passed more than 5 and 10 times. Analogously, the more complex the field structure, the greater the proportion of area with more than 5 and 10 passes. This increased traffic intensity is probably because a larger field requires more yield transportations from the infield across the headland.

The study shows that in wheat harvesting, the geometry of the field and the choice of the machine should be considered if high traffic intensities should be avoided to preserve the soil structure.