Soil water repellency changes with depth and relationship to physical properties within wettable and repellent soil profiles

Abstract

This study explored the effect of soil water repellency (SWR) on soil hydrophysical properties with depth. Soils were sampled from two distinctly wettable and water repellent soil profiles at depth increments from 0-60 cm. The soils were selected because they appeared to either wet readily (wettable) or remain dry (water repellent) under field conditions. Basic soil properties (MWD, SOM, θ v ) were compared to hydrophysical properties (K s , S w , S e , S ww , S wh , WDPT, RI c , RI m and WRCT) that characterise or are affected by water repellency. Our results showed both soil and depth affected basic and hydrophysical properties of the soils (p <0.001). Soil organic matter (SOM) was the major property responsible for water repellency at the selected depths (0-60). Water repellency changes affected moisture distribution and resulted in the upper layer (0-40 cm) of the repellent soil to be considerably drier compared to the wettable soil. The water repellent soil also had greater MWD dry and K s over the entire 0-60 cm depth compared to the wettable soil. Various measures of sorptivity, S w , S e , S ww , S wh , were greater through the wettable than water repellent soil profile, which was also reflected in field and dry WDPT measurements. However, the wettable soil had subcritical water repellency, so the range of data was used to compare indices of water repellency. WRCT and RI m had less variation compared to WDPT and RI c . Estimating water repellency using WRCT and RI m indicated that these indices can detect the degree of SWR and are able to better classify SWR degree of the subcritical-repellent soil from the wettable soil.

Impact of secondary succession in abandoned fields on some properties of acidic sandy soils

“…Vegetation change can also induce soil water repellency (SWR), which parameters are influenced by soil temperature (Novák et al, 2009), moisture (Leelamanie and Nishiwaki, 2019;Oostindie et al, 2017), texture (Benito et al, 2019), pH (Diehl et al, 2010), soil organic carbon (SOC) and clay (mainly kaolinite) content (Lichner et al, 2002). SWR may affect soil properties with depth (Orfánus et al, 2016;Sepehrnia et al, 2017) and time (Orfánus et al, 2014;Moret-Fernandez et al, 2019), and has positive effects on the stability of soil aggregates (Fér et al, 2016). Soil compaction may reduce SWR mainly as a consequence of decreased surface roughness (Bryant et al, 2007), but the hydrophobic conditions are readily restored a few days after removal of compaction load.…”

Development of a universal microinfiltrometer to estimate extent and persistence of soil water repellency as a function of capillary pressure and interface chemical composition

“…Ultrapure degassed water was used to reduce air bubble formation in the system and to enable long-time measurements (i.e., > 24 h) under higher tensions (i.e., -20 and -40 cm) of the testing liquids; a very important difference to previous approaches (Hallett et al, 2003;Sepehrnia et al, 2016Sepehrnia et al, , 2017Tillman et al, 1989). Water and ethanol (Normapur, 96 vol-%, VWR Chemicals, France) infiltration tests were performed under different slight pressures (+0.5 and 0 cm) as well as under different tensions (-2, -5, -20, -40 cm) on soil cores repacked to their field bulk density.…”

“…Soil water repellency (SWR), as a transient property of soil particle interfaces, often has high temporal and spatial variability that makes water infiltration measurements and predictions of hydrological processes complex (Bauters et al, 2000;Cosentino et al, 2010;Dekker et al, 2001Dekker et al, , 2005Sepehrnia et al, 2017). An accurate prediction of soil hydraulic properties is difficult as SWR changes over the time of infiltration (Bachmann et al, 2007;Clothier et al, 2000).…”

Natural colloid mobilization and leaching in wettable and water repellent soil under saturated condition

“…To evaluate RI, the cumulative liquid infiltration rate I of water and ethanol were measured for the time interval < 180 s with a microinfiltrometer (Sepehrnia et al, 2016(Sepehrnia et al, , 2017. The infiltrometer was placed on top of the samples and the results were plotted against t 0.5 .…”