Soil Resistance and Resilience to Compaction As Affected by the Clay-Organic Carbon Relation.

Soil stability has been expressed as a derivative of its resistance and resilience to human and environmental stresses. The objective of the study was to investigate the influence of clay saturation by organic carbon on soil physical resistance and resilience to compaction using void ratio, e, air-filled porosity, ε, and air permeability, k_a, as functional indicators. Three arable soils of similar texture and different organic matter contents (variable clay saturation status) were used. One of the soils had more organic carbon relative to clay [MFC] while the other two soils had varying amounts of excess clay in relation to organic carbon [MCC and CCC]. Soil cores were subjected to uniaxial confined compression (200 kPa) at -100 hPa followed by a period of natural recovery and wet-dry, freeze-thaw cycles. The resistance of the soils to compaction, quantified by both the compression index and a proposed resistance index, was significantly higher for the MFC soil compared to the other two soils. Plastic reorganization of the soil particles immediately after compaction, prior to removal of the load, was highest for the high organic soil. Resilience following natural recovery was significantly lower for the CCC soil for all three indicators (k_a, e, and ε). After two wet-dry cycles, the MCC soil showed a significantly higher resilience for all three indicators (k_a, e and ε). Resilience (k_a, and e) after three freeze-thaw cycles was significantly lower for the CCC soil than the MFC and MCC soils. A significant correlation between resistance and resilience was observed for k_a and e but not for ε.