Testing infiltration run effects on the estimated water transmission properties of a sandy-loam soil

Testing factors influencing determination of soil water transmission properties by an infiltrometer method helps to better interpret the collected data and allows to develop appropriate sampling strategies for the intended use of the data. These factors include the soil water content at the start of the experiment, the height from which water is poured onto the soil surface, and the duration of the infiltration run. A sandy-loam soil was sampled with the BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization and two heights of pouring of water (0.03 and 1.5 m) on three dates differing by the initial soil water content, i (0.12 < i < 0.20 m3m-3). According to the BEST guidelines, relatively short infiltration runs (average run duration < 1.5 hours, depending on both the date and the height from which water was poured) were carried out. However, three long infiltration runs (10 hours) were also carried out when i was of 0.075 m3m-3. The saturated soil hydraulic conductivity, Ks, and the soil sorptivity, S, were estimated for each infiltration run with the BEST-steady algorithm. The means of Ks varied with the height of pouring of water and the date from 13 to 496 mm h-1, and low runs yielded 13 to 27 times higher means than the high runs, depending on the sampling date. An inverse relationship between Ks and i was clearer with the low runs than the high ones. The mean conductivity obtained with the long runs (15 mm h-1) was close to the means of Ks obtained with the high and shorter runs (13-19 mm h-1, depending on the date). The means of S varied from 35 to 126 mm h-0.5, with the low runs yielding 2.3 to 2.8 times higher means than the high runs. The high sorptivity obtained with the long runs (160 mm h-0.5) was in line with the low initial soil water content. In conclusion, the water application procedure and the duration of the infiltration run can have a noticeable effect on the estimated soil water transmission properties. High or long runs appear more appropriate than low runs to obtain data usable to explain surface runoff generation phenomena during intense rainfall events, especially when the soil is relatively dry at the time of sampling. In the future, the effects of both the height from which water is poured and the run duration on the measured water transmission properties with BEST should be tested for different initial soil water conditions in other soils. The usability of the height from which water is poured onto the soil surface as a parameter to mimic high intensity rain should also be investigated specifically.