|Casey, Francis - IOWA STATE UNIVERSITY|
|Horton, Robert - IOWA STATE UNIVERSITY|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 8, 1996
Publication Date: N/A
Technical Abstract: Hydraulic and preferential flow properties of a field soil play an active role in the transport of chemicals. In this study the hydraulic conductivity and the preferential flow parameters (immobile water content and mass exchange coefficient) of the mobile/immobile domain model are investigated. Forty field measurements were made. Hydraulic conductivity, immobile water content and mass exchange coefficient values were determined at four pressure heads of 10, -30, -60, and -150 mm using infiltrometers. Immobile water content and mass exchange coefficient values were determined by using a recently described in situ technique. The immobile water content decreased with lower water contents associated with the lower pressure heads. However, the immobile water fraction did not show a clear trend with pressure head or hydraulic conductivity. The mean immobile water fraction values were 0.40, 0.27, 0.22, and 0.35 for the respective pressure heads of 10, -30, -60, and -150 mm. The mass exchange coefficient decreased as pressure head decreased. The mean mass exchange coefficient values were 1.34 h**-1, 0.036 h**-1, 0.0044 h**-1, and 0.0033 h**-1 for pressure heads of 10, -30, -60, and -150 mm, respectively.