Effect of Undesired Compaction on Hydraulic Properties of Roadside Soils

Properties of roadside soils can be significantly affected by compaction caused by mowing operations. This undesired compaction can result in sediment loss, increased stormwater runoff, decreased infiltration and porosity, and limited root growth. This study examines how additional soil compaction impacts the hydraulic properties of soils and vegetation growth. Six-month pot studies were conducted at Michigan State University and the University of Maryland using topsoil and subsoil collected from Iowa roadways. Pots were prepared at 72% and 100% of their maximum dry unit weights to simulate loose and compacted field conditions following road construction. A total of 24 pots with different soil types, thicknesses, and densities were used, with half of the soil pots compacted to create additional compaction from heavy machinery. Root concentration and hydraulic conductivities of the compacted and uncompacted sides were measured separately. Results showed that mowing-simulated compaction reduced hydraulic conductivity by 15 times in low-density soils and by 1.5 times in high-density soils, while topsoil thickness increased root concentrations by up to 3 times.