Tuesday, November 14, 2006

Ponded Infiltration and Drainage of Water and Solutes in a Silt Loam Soil With Macropores.

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)