Water and Solute Movement in an Undisturbed, Macroporous Column: Extraction Pressure Effects

Abstract

Abstract Undisturbed soil columns are commonly taken to conduct water and solute flow experiments. The proper boundary condition to impose at the bottom boundary of a soil column is most difficult to define and control. The objective of this study was to evaluate the effects of the magnitude of extraction pressure at the lower boundary of the soil column and the water application rate on the amount, distribution, and percentage 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 Eutrochrept). The soil column was placed on a collection chamber that allowed constant extraction pressures (0, − 1.3, or −2.0 kPa) to be maintained 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 partitioned into 100 cells. Flow of water and solute through macropores increased as the extraction pressure maintained at the lower boundary of the soil column increased, and as the application rate decreased. Extraction pressure had a greater effect on preferential flow than did application rate.