Assessment of Crawler Tractor Effects on Soil Surface Properties


1 A. Najafi*1, A. Solgi1 and S.H. Sadeghi2 1- Dept. of Forestry, Faculty of Natural Resources. Tarbiat Modares University, Noor, Mazandaran, Iran 2- Dept. of Watershed ManagementEengineering, Tarbiat Modares Universiy Noor, Mazandaran, Iran * Corresponding author?s E-mail:

2 A. Solgi1*, A. Najafi2,


Skidding operations can cause considerable and wide spread soil disturbance. The objective of this study was to evaluate the effects of ground skidding operations on soil compaction, moisture content, and total porosity at different levels of slope and traffic frequency. Four levels of traffic intensity (3, 8, 13, and >13 passes of a Crawler Tractor Onezhets ? 110) and three levels of slope (<10%, 10%-20% and > 20%) were applied to assess soil disturbance. The soil samples from the depth interval 0-10 cm were collected with a soil hammer and rings. Results showed that dry bulk density, moisture content and total porosity were affected considerably by slope and traffic frequency of skid trails. Bulk density was drawing near to the critical value after 8 passes in the trail with the slope >20%; when the number of machine passes increased from 8 to 13 passes, the additional bulk density increment was negligible. Irrespective of traffic frequency, dry bulk density increased significantly in the slope >10% compared to the slope <10%; however there was no significant difference between slopes 10-20% and >20% . Minimum moisture content was measured as 27% on the skid trail versus 47% in the undisturbed area. A negative correlation was found between moisture content and dry bulk density. Total porosity was measured as a maximum 58% to a minimum 44% on the skid trail treatments, and 65% in the undisturbed area. Soil disturbance was extended dramatically on the treatments with slopes >20%, so dry bulk density on the treatments with 8 passes and slopes >20% (1.38 g cm-3) was significantly higher than on the treatment with 13 passes and slopes <10% (1.32 gcm-3). Results showed that slope >10% increased soil disturbance quite dramatically.