Fractal Analysis of Water Retention Data Collected with a Dew Point Water Activity Meter. (S01-kenst849534-oral)
Authors:
A.B. Kenst* - Univ. of Tennessee E. Perfect - Univ. of Tennessee
M. Diaz-Zorita - Univ. of Buenos Aires J.H. Grove - Univ. of Kentucky
Abstract:
We combined fractal modeling and the chilled mirror dew point method to facilitate rapid,
physically-based characterization of the water retention curve. Desorption curves (6 points per sample) were collected on disturbed soils in the tension (h) range 0.2 to 150 MPa using the gravimetric method to measure water content (w) and the chilled mirror dew point technique to measure h. Thirty-two samples were analyzed from a long-term tillage-nitrogen fertilization study on a silt loam soil. A new form of an established fractal water retention equation was derived: w = ahD-3-pw/ps, where a is a compound parameter including the bulk density and air entry value, D is the mass fractal dimension, pw
is the density of water and ps is the particle density. This model was fitted to the measured desorption curves using non-linear regression analysis. The a and D parameters were estimated with pw and ps fixed at 1.00 and 2.65 g cm-3, respectively. Convergence was always achieved and the equation fitted the data extremely well. The median residual sum of squares was 2.2x10-5, and adjusted R2 values from predicted versus observed relations were > 0.99. The estimates of a (0.62 to 0.74) and D (2.948 to 2.963) were physically reasonable and sensitive to the tillage and fertilization treatments. Additional research is needed to test this approach on other soil types, and to assess the impact of possible variations in ps on the parameter estimates.
Speaker Information: Andrew Kenst, Univ. of Tennessee, Dept. of Geological Sciences 1412 Circle Drive U, Knoxville, TN 37996-1410; Phone: 865-974-6017; E-mail: [email protected]
Session Information: Wednesday, November 5, 2003, 10:30 AM-11:30 AM Presentation Start: 10:50 AM
Keywords: Fractal analysis; Water retention; Organic matter; Tillage
