Long‐Term Effects of Compaction on Soil Properties Along the Mormon Trail, South‐Central Iowa, USA

The literature contains many studies addressing various aspects of soil compaction, but few of those studies address long‐term (>30 yr), natural recovery of the soil from compaction. Here, natural soil recovery over a 146‐yr period is investigated by comparing the properties of Sharpsburg soils in the Mormon Trail to those alongside the trail at a location in south‐central Iowa. Bulk density samples were collected using rings of known volume for the upper 20 cm of the soil in 5‐cm depth increments. Bulk soil samples were collected to a depth of 20 cm in 5‐cm depth increments, and additional samples collected to 45 cm with a 5‐cm‐diameter Giddings probe in 5‐cm depth increments. These samples were analyzed for total C, N, and particle size. The thickness of the A horizon was determined from core samples, and saturated hydraulic conductivity was measured using an Amoozemeter. Bulk density is lower in the 5‐ to 10‐, 10‐ to 15‐, and 15‐ to 20‐cm depth intervals in the off‐trail soils. Soil carbon levels and C/N ratios are higher in the off‐trail soils for all sampled depth intervals below the 5‐ to 10‐cm depth interval. A horizons were thicker and saturated hydraulic conductivity higher in the off‐trail soils. These results indicate the soils on the Mormon Trail have not recovered from compaction at this site.