Evaluating the Contribution of Soil Organic Carbon to Improved Water-Holding Capacity Through Increased Compaction Resistance: Progress Report

This BIOAg progress report examines whether soil organic matter indirectly enhances plant available water by improving resistance to soil compaction. Research was conducted at a long-term field site with replicated biosolids amendment rates (0, 2, and 4.5 dry tons per acre), a conventionally fertilized control, and an unfertilized control, resulting in clear differences in soil organic matter content.

A simulated 0.27-inch rainfall event was applied across all plots, followed by controlled tractor passes to induce compaction in designated strips. Intact soil cores were collected from compacted and uncompacted areas for analysis. Preliminary results show that compaction treatments significantly increased air-dry bulk density, while biosolids amendments significantly lowered bulk density overall. However, soils with higher organic matter were not more resistant to compaction based on bulk density measurements alone.

Ongoing analyses include saturated hydraulic conductivity and full soil moisture release curves to evaluate pore structure, infiltration, and plant available water. Results will clarify how organic amendments influence soil structure and water dynamics under compaction stress.