Investigating soil dynamic behaviour through multi-height beerkan experiments

The multi-height beerkan (MHB) infiltration experiment allows investigating in the field short-term dynamics of soil hydrodynamic properties by distinguishing between wetting and water mechanical impact effects on infiltration rates. In this investigation, wetting alone and wetting plus water impact effects were separately determined in a loam and a silty-clay-loam soil by the MHB method with six heights of water pouring (0.03 ≤ H ≤ 2 m). Without mechanical perturbation, the coarser soil was three times more sorptive and more than one order of magnitude more conductive than the finer soil. Final infiltration rates decreased by nearly one order of magnitude with larger H values in the loam soil (from 641 to 58 mm/h), but they varied with H non monotonically and by about two times in the silty-clay-loam soil (between 84 and 46 mm/h). A nearly unique relationship between infiltration rates and gravitational potential energy of the applied water was detected in the coarser soil for H ≥ 0.25 m. Perturbing infiltration runs (H ≥ 1 m) yielded relatively similar final infiltration rates in the two soils (58–84 mm/h). Therefore, water impact effects were appreciable in the loam soil but not in the silty-clay-loam soil probably because the coarser soil had more unstable macropores than the finer soil. The lowest possible infiltration rates for a soil represent a hydrologically relevant information for understanding surface runoff. The MHB method appears potentially usable to confidently interpret and numerically simulate hydrological processes by explicitly considering water impact effects on the soil surface.