Abstract:
Soil penetration resistance as an indication of soil compaction affects on soil infiltration and runoff. Overgrazed
rangelands are under severe erosion risk because of compaction. The objective of this study was to determine
changes in soil penetration resistance with time in a high altitude rangeland. A 5 ha rangeland (200x250 m) was
transected with 25 m intervals, and soil penetration resistance was measured at every 5 m in each transect for 20
cm surface soil layer in three different time periods (15th of July, August and September). Undisturbed soil
samples were taken for determining soil bulk density and soil moisture-penetration calibration tests, and these
samples also were used to obtain fundamental soil characteristics. Exponential semivariogram models were fit to
explain spatial variance in soil penetration resistance values. Distribution patterns of soil penetration resistance
were defined using kriging values produced by the punctual kriging. Results indicated that soil penetration
resistance was higher than the critical penetration resistance (3 MPa) for root growth in all measurement points.
The mean soil penetration resistance increased about 9 % in August as compared with July and it was more or
less constant in the following month. There were good agreements among the distribution patterns of soil
penetration resistance obtained for different time periods.
