Time-dependent changes in distribution patterns of soil penetration resistance in a rangeland under overgrazing

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.