Temperature and Time of Day Influence on Double-Ring Infiltrometer Steady-State Infiltration Rates.

Steady-state infiltration rates (IRs) correlate well with temperature. They have been observed, however, to have values 1.5 to 2.5 times higher than predicted by viscosity, known as the t-effect. Many field studies that have observed the t-effect used continuous IR measurement systems. We measured 67 IRs using double-ring infiltrometers (DRIs) during the 2007 and 2008 autumn seasons in sand and loamy sand soils across a temperature range of 5 to 35°C. We found above-average to good correlation between temperature and IR. For loamy sand (n = 17), IR rate differences were accounted for by viscosity differences, but for sand (a = 30) the IR values were 2.0 to 2.9 times higher than the viscosity-predicted rate. Additionally, we found a difference in the IR temperature regressions based on the time of day of the measurements in the sand. Morning measurements were two times the viscosity-predicted IR, while afternoon measurements were nearly three times. This research corroborates other field studies that observed the t-effect using DRIs. [ABSTRACT FROM AUTHOR]