Interpreting Tension-infiltrometer Data for Quantifying Soil Macropores: Some Practical Considerations

A tension-infiltrometer offers a practical means for obtaining information on soil infiltration characteristics at low soil moisture tensions in the field. This study examines interpretation of tension-infiltrometer results. Saturated hydraulic conductivities (Ks) calculated from unconfined tension-infiltrometer measurements were not statistically different from conductivity measurements made with a velocity-head permeameter. Ks values determined with the tension-infiltrometer were greater than conductivities measured with a Guelph permeameter. Tension-infiltrometer measurements of infiltration made through a 20-mm layer of sand were an order of magnitude less than ponded infiltration measurements at the same location. Increases in antecedent soil moisture decreased infiltration values, but parameters for equations fitted to the hydraulic conductivity versus tension curve were similar. Unconfined infiltration rates when adjusted to give vertical conductivity did not change appreciably the values of parameters fitted to a hydraulic conductivity versus soil moisture tension curve.