Contact angle of soils as affected by depth, texture, and land management

Abstract

Water repellency can be a significant factor in soil physical behaviour, but little is known about the depth dependence of the contact angle of field soils. We investigated contact angles and wetting properties as a function of depth for a wide range of agricultural and forest soils in Germany. The agricultural soils ranged from silty to sandy texture (six profiles), and the forest soils ranged from sandy to loamy texture (eight profiles). Contact angles (CA) were measured with the Wilhelmy plate method (WPM). In most of the soils, advancing WPM contact angles were considerably greater than 0 and they varied irregularly with depth. In general, sandy soils had larger WPM contact angles than silty soils. From the relation of the contact angle with texture and pH the quality of soil organic matter (SOM) was considered as more important for the wetting properties than the total amount of soil organic carbon (SOC). Finally, it was found that for soils with intermediate sand contents either under agricultural or forest use, the kind of land use seemed not to influence CA. Coarse-textured sandy soils that were used only as forest sites were more hydrophobic than silty soils which were exclusively used as agricultural soils. We conclude that a coarse texture favours, in combination with other factors (mainly pH), hydrophobic SOM.

Occurrence and spatial pattern of water repellency in a beech forest subsoil

“…In a recent study by Diehl et al (2014) -treated samples could not be reproduced. On the other hand, in a study by Woche et al (2005), analyzing several arable and forest soils ranging from pH 3.0 to 6.8, a significant inverse correlation between CA and pH was found which is in agreement with the general tendency found for the topsoils of this study.…”

“…Bachmann et al (2008) showed that the availability and distribution of water in the soil matrix depends on soil particle wettability. WR occurs in soils of different texture, land use and under a variety of climatic conditions (DeBano, 1981;Doerr et al, 2000;Woche et al, 2005). Mineral surfaces are generally well wettable by water when they are free of any adsorbed organic substances.…”

“…The main objective of the present study was to investigate the impact of trees on the wettability pattern in forest top-and subsoils on an intermediate (m) scale. To unravel the systematic effect of tree abundance we extended the analysis to the deeper subsoil to depths of about 2 m. We chose a forest site with a moderate WR and soil development level to avoid a strong WR background as often observed for acid soils like podzolic soils under coniferous or heath vegetation (Woche et al, 2005).…”

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

“…It was shown (e.g., Blanco-Canqui and Lal, 2009;Goebel et al, 2008;Lachacz et al, 2009;Vogelmann et al, 2013) that soil water sorptivity decreased exponentially with increasing SOM content. Czachor et al (2013), Leelamanie and Karube (2007), Vogelmann et al (2013), and Woche et al, (2005) also reported a non-linear increase of the contact angle with SOM content.…”

Stabilization of soil hydraulic properties under a long term no-till system

“…We were aware of the fact that α could differ from 0º. Woche et al (2005) analyzed the dependence between the contact angle and the soil texture and observed small contact angles of 0º to 20º for silty loam soils. Moreover, α strongly depends on water content and probably approached 0º after sufficient infiltration time (Buczko et al, 2006).…”