WATER AND SOLUTE MOVEMENT IN AN UNDISTURBED, MACROPOROUS COLUMN - EXTRACTION PRESSURE EFFECTS

Undisturbed soil columns are commonly taken to conduct water and solut e Bow experiments, The proper boundary condition to impose at the bott om boundary of a soil column is most difficult to define and control. The objective of this study was to evaluate the effects of the magnitu de of extraction pressure at the lower boundary of the soil column and the water application rate on the amount, distribution, and percentag e of leachate and solute drained through the soil column. Water and Cl - were applied to a 325 by 325 by 339 mm undisturbed soil column of a Nolin silt loam soil (fine-silty, mixed, mesic Dystric Fluventic Eutro chrept). The soil column was placed on a collection chamber that allow ed constant extraction pressures (0, - 1.3, or - 2.0 kPa) to be mainta ined at the lower boundary of the soil column. Water containing solute was applied at rates of 5, 10, and 15 mm h(-1). The leachate was part itioned into 100 cells. Flow of water and solute through macropores in creased as the extraction pressure maintained at the lower boundary of the soil column increased, and as the application rate decreased. Ext raction pressure had a greater effect on preferential flow than did ap plication rate.