In Switzerland sugar beet are harvested primarily by two-row hauled or six-row self propelled vehicles. Time and again the multiple passes in the same wheel track caused by the hauled vehicles, the more than 10 tonnes wheel loads of the self-propelled harvesters and the generally unfavourable conditions with wet soils during the harvest campaign in autumn give rise to doubts about possible damages to soil structure by compaction. On a site with homogeneous soil conditions (deep sandy loam), two sugar beet plots with different tillage history were compared, one which has been managed with no-till for a long time, and one which has been plowed routinely before sowing sugar beet. During and after the passes of the two harvest vehicles described above, several measurements were done: Bolling probes were used for measuring soil stresses, undisturbed cylindrical soil samples were taken for the analysis of bulk density, porosity, air permeability and structural stability in the lab. Both harvest systems affected the structure of the plowed soil with its low stability of the arable layer at least down to 60 cm depth; however, between the two vehicles tested there could not be found any relevant differences. On the other hand the no-till system, applied for many years, showed a remarkable high degree of structural stability and could therefore make a valuable contribution to the improved traffickability of the soil.
Physical impacts on soil structure during sugar beet harvest