Field Estimates of Hydraulic Conductivity from Unconfined Infiltration Measurements

Abstract

Soil water infiltration exhibits spatial variability due to both intrinsic soil properties and management effects (e.g. wheel traffic and tillage). The description or prediction of field scale water and solute movement, therefore, requires that the spatial distribution of hydraulic properties be known. Practical measurement of hydraulic properties of unsaturated soil requires both a rapid field technique to sample the necessary number of sites and a straightforward analytical technique for interpreting data. We have designed precision automated tension infiltrometers that enable rapid determination of soil water infiltration. Tension infiltrometers were used to obtain unsaturated infiltration data for chisel-plow, no-till, wheel-trafficked, and non-wheel trafficked management zones. This paper reports means and coefficients of variation for hydraulic conductivities at multiple tensions derived from unconfined infiltration measurements. Mean hydraulic conductivities decreased as tension increased. Trafficked sites had lower values of hydraulic conductivity than non-trafficked sites. The tension infiltrometer is a useful tool for obtaining spatial measurements of field infiltration and unsaturated hydraulic conductivities.

Joint contribution from USDA-ARS and Iowa State Univ. Journal Paper No. J-13836 of the Agric. and Home Econ. Ext. St., Ames, IA. Projects No. 2659 and 2715.