Brian Lepore, Univ. of Wisconsin at Madison, 1525 Observatory Dr., Madison, WI 53703, Birl Lowery, University of Wisconsin, 1525 Observatory Dr, Madison, WI 53706-1299, and John Norman, University of Wisconsin, Dept. of Soil Science, 1525 Observatory Dr., Madison, WI 53706.
Experimental results intended for use in parameterizing
macropore components of soil water and solute transport models are
presented. These data include
infiltration and drainage flux densities, water content, soil tension, and
tracer breakthrough, both during and after ponded conditions. The experiments involved monitoring free
drainage during ponding and equilibrium tension
lysimeter measurements after ponding cessation. The
experiments were conducted in soil pits dug in a Plano
silt loam soil at the Univ. of Wisconsin-Madison Arlington Agricultural
Research Station, Arlington, Wisconsin. Two pits were in no-tillage plots and one in
chisel-plow. Under ponded conditions the
no-tillage plots maintained steady state infiltration and drainage flux density
in excess of 40 cm h-1.
Although only conducted for about 30 minutes before the pit wall
collapsed, chisel-plow rates were greater than 200 cm h-1. Preliminary solute data show nearly
instantaneous transport of Br- from surface pond to 1 m below,
implicating macropores as the primary flow path. These extremely high flux rates indicate the
potential of fine-textured soils with strong soil structure and earthworm
burrows to rapidly transmit nutrients and contaminants from the soil surface to
below the root zone and to groundwater.
This highlights the need to continue developing and improving methods of
parameterizing macropore routines in transport models.
Handout (.pdf format, 219.0 kb)