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

Abstract

Testing factors influencing determination of soil water transmission properties by an infiltrometer method helps better interpretation of the collected data and allows the development of 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) under three different initial soil water content, θi (0.12 ≤ θi ≤ 0.20 m3 m− 3), conditions. According to the BEST guidelines, relatively short infiltration runs (average run duration ≤ 1.5 h, depending on both the date and the height from which water was poured) were carried out. However, three long infiltration runs (10 h) were also carried out when θi was of 0.075 m3 m− 3. The saturated soil hydraulic conductivity, Ks, and the soil water sorptivity, S, were estimated for each infiltration run with the BEST-steady algorithm. The mean values of Ks varied with the height of pouring of water and θi from 13 to 496 mm h− 1, and a low height from which water was poured yielded 13 to 27 times higher Ks means than a high height, depending on θi. An inverse relationship between Ks and θi was clearer with the low height of pouring of water than the high one. The mean saturated hydraulic 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 θi). 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. Long duration runs or runs carried out with a high height of pouring of water appear more appropriate than short duration runs with a low height of pouring of water 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 water transmission properties measured 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.