Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 1999
Publication Date: N/A
Technical Abstract: Tension disk infiltrometers often are used to estimate soil hydraulic properties from cumulative outflow measurements obtained from unconfined flow. Interpretation of outflow data may be problematic for soils that exhibit large variations in physical properties near the surface. Such features will reduce the reliability of the predicted infiltration rates using parameters estimated from tension infiltrometer measurements. Unsaturated infiltration rates at a tension of 150 mm H2O were measured using a disk infiltrometer on a fallowed no-tillage field. Soil water contents were measured below the disk using TDR probes and gravimetrically using cores obtained immediately after each infiltration measurement. Soil hydraulic parameters were estimated using cumulative outflow measurements in conjunction with least squares parameter optimization from the numerical inversion of the Richards' equation. The validity of estimated parameters is evaluated by comparing simulated water contents with measured water contents below the disk using TDR probes and gravimetric samples.