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ŠUMARSKI LIST 9-10/2016 str. 62     <-- 62 -->        PDF

Soil disturbances on skid road during a log skidding operation by a farm tractor were measured considering soil compaction and rut depth formation. Field measurements were made at 14 cross sections along the skid road. The results indicated that soil compaction and rutting increased as number of passes increased. During initial passes, the soils especially on the center of skid road became very dusty, and then dusty ground was removed from the skid road due to factors such as wind, rainfall, and operating vehicles. This process led to soil displacement and gully formation on the skid roads which potentially increased the risk of erosion (Pierzchala et al., 2014).
The results revealed that the amount of soil deformation was generally higher at the center of the skid road as compared to the control points at the edge of skid road. This situation was shown as deformation shape on skid road (Fig.4). Similar to previous studies, the rut depths on skid roads changed mainly depending on the number of passes (Akay et al., 2007a; Alexander, 2012). It was found that average rut depth did not reach to a critical level during the first five passes (4.0 cm); however, it was dramatically increased by the following passes.
The results indicated that rut depth became more significant after 4th, 8th, 12th, 16th and 20th passes for skid road, reaching a maximum of 2.6, 3.5, 4.1, 4.6 and 4.9 cm, respectively (Fig.5). In a similar study, Erdas (1993) reported average rut depth of 10-15 cm after 10-20 tractor passes during a log skidding operation.
In this study, every cross section was measured soil compaction values by penetrometer. Also, the compaction values on forest ground were measured to edge of each cross section. The soil compaction and soil disturbance were found to be on the skid road. The average soil compaction was found to be 0,97 kN/cm² on the center of skid road while the value of soil compaction was 0,54 kN/cm² on the forest ground (for 20th passes)(Table 2).
The average width of affected surface was found as between 30 and 220 cm on the skid road. Also, on the right and left sides of skid road were shown changes of soil depth during skidding operations. The results of this study showed that the rut depth and soil compaction developed with increasing of tractor passes. The exchange rate was more found first four passes. Then, this rate was lost (Table 3).
The soil displacement on the skid road was occurred on the each cross section. Dobek et al., (2011) also reported that