Mario Flores1, Birl Lowery1, James G. Bockheim1, Cynthia Stiles1, and Grizelle González2. (1) Univ of Wisconsin, Dept of Soil Science, 1525 Observatory Dr, Madison, WI 53706, (2) Int'l Institute of Tropical Forestry (USDA-FS), Jardín Botánico Sur, 1201 Calle Ceiba, San Juan, PR 00926-111
Nonwetting conditions have been found to decrease water
infiltration into the soil, particularly sandy soils and under certain plants.
Hydrophobic conditions have been documented for potato crops grown on sands in Wisconsin. Preliminary data suggest
hydrophobicity in Sparta sand under a pine plantation in the Lower Wisconsin River Valley. At this site groundwater quantity and flow of the Wisconsin River
could be negatively impacted by hydrophobicity. We are evaluating the effects
of soil hydrophobicity on soil water infiltration under prairie, native forest
and prairie (mixed vegetation), and pine plantations. Time domain reflectometry
probes, rain gages, monitoring wells and throughfall collectors were installed
to evaluate water infiltration. Soil samples were collected every 5 cm from
0-50 cm and hydrophobicity tests performed using water and ethanol drop
penetration. In addition, undisturbed soil samples were collected for measuring
bulk density and saturated hydraulic conductivity. The hydrophobicity tests
showed more cases of water repellency for all vegetations from 0 – 15 cm
compared to 15 – 50 cm. The prairie and mixed vegetation sites did not have
water repellency at depths lower than 15 cm, although the pine sites had water
repellency to depths of 50 cm. There was no significant difference in saturated
hydraulic conductivity and bulk density. There was no difference in rain
throughfall between pine and mixed vegetation, but these were both
significantly lower when compared to prairie. It appears that the groundwater
table is lower in the pine plantation than prairie. Preliminary data show that
the prairie and mixed vegetation had greater soil water content and flux than
pine plantation after rain events. We anticipate that hydrophobic soils
will negatively impact groundwater recharge, however
hydrophobicity might be reduced by the use of a surfactant. Land use that
negatively impacts groundwater recharge should be altered given the potential
impact on groundwater quantity.