Water transmission properties of a sandy-loam soil estimated with Beerkan runs differing by the infiltration time criterion

The Beerkan method consists of a ponded infiltration experiment from a single ring inserted a small depth into the soil. Fixed, small volumes of water are repeatedly poured into the ring to maintain a quasi-zero head on the soil surface. According to the standard Beerkan infiltration run, a new water volume is poured on the infiltration surface when the previously applied volume has completely infiltrated and the soil surface is entirely exposed to air (t_a criterion). However, water could also be applied when the soil exposition to air begins (t_o criterion) or half the soil surface is exposed to air (t_m criterion). The effect of the infiltration time criterion on determination of the water transmission properties of a sandy-loam soil was tested. As compared with the standard t_a criterion, the two alternative criteria (t_o, t_m) yielded higher and/or more variable estimates of soil water transmission properties. The saturated soil hydraulic conductivity, K_s, was the most sensitive property to the infiltration time criterion. However, statistically significant differences for K_s were not practically substantial since they did not exceed a factor of 1.7. Infiltration time effects likely occurred due to differences between ponding depth of water, soil water pressure head gradient, air entrapment and soil mechanical disturbance. The standard t_a criterion was suggested for performing a Beerkan experiment in the field since it appears to yield the most reliable estimates of a mean value. However, the t_o criterion could be considered in dual permeability soils to maintain macropores active. Factors that could appear minor in the context of an experiment can have statistically relevant effects on water transmission properties.