Hydrophobicity of Sparta sand under different vegetation types in the lower wisconsin river valley

Soil hydrophobicity is a characteristic that some soils exhibit where they repel water, and the plant community may play a role in its development. In the Lower Wisconsin River Valley (LWRV), some land with prairie has been planted with pines. There is an undetermined soil water repellency consequence of this land use change, as it was discovered that under pine plantation the soil was so desiccated at certain periods that it became extremely hydrophobic. The objective of this study was to determine the extent of soil hydrophobicity of Sparta sand (sandy, mixed, mesic Entic Hapludoll) in the LWRV under three vegetation types: prairie, pine plantation, and mixed prairie/forest (mixed vegetation). Soil samples were collected in 5-cm increments to a depth of 50 cm. Samples were analyzed using water drop penetration time (WDPT), soil wetted area (SWA), and molarity of ethanol (MED). Soil particle-size distribution (PSD), soil organic carbon (SOC), and soil water content were also determined. Additional surface samples were analyzed for chemical and particulate organic matter (POM) fractionation. Hydrophobicity was greater and extended to deeper depths in the pine plantation (35-cm depth) than in the prairie and mixed vegetations (10-cm depth). The greater water repellency in the pine resulted in drier soil conditions. This suggests there are strong plant-soil-hydrophobicity interactions for this soil. The PSD was not significantly different across vegetation, although it was across soil depth; this is expected since the soil parent materials were not different across sites. The SOC significantly decreased with depth but was not significantly different among vegetations. There were no relationships between water repellency, humic substances, and POM. A possible factor for the difference in soil water repellency among vegetations could be the quality of soil organic matter (SOM) produced by the different vegetation, with pine being the greater producer of hydrophobic material.