Variability of topsoil hydraulic conductivity along the hillslope transects delineated in four areas strongly affected by soil erosion

Soil hydraulic conductivities of topsoils were studied at 5 points of the hillslope transects delineated at 4 geomorphologically diverse areas, where the original soil types (Chernozem, Luvisol and two Cambisols) were due to erosion transformed into different soil unites. Hydraulic conductivities of saturated soils and for a pressure head of –2 cm were measured directly in the field using a Guelph permeameter (K_s,GP) and mini disk tension infiltrometer (K_h=–2,MDI), and in the laboratory using a multistep outflow method (K_s,MSO, K_{h= –2,MSO}). While K_s,GP ≈ K_s,MSO in the Chernozem and Cambisol (sandy loam) regions, and K_s,GP < K_s,MSO in the Luvisol and Cambisol (loam) regions. The K_s values obtained using different methods showed different trends along the hillslope transects. The K_{h= –2} values obtained using different methods showed similar trends along the transects in the Chernozem and Luvisol regions. These trends could be explained by the position within the transects (i.e., different stages of erosion/accumulation processes). No relationships were found between the K_h=–2 values in the Cambisol regions. The pressure head at an inflection point of the a soil-water retention curve was the main parameter, which appeared to associate (negative correlation) with K_h=–2 and K_s,MSO in the Chernozem and Luvisol regions.