The Role of Drop Volume and Number on Soil Water Repellency Determination

Hallin, Ingrid; Douglas, Peter; Doerr, Stefan H.; Bryant, R.

doi:10.2136/sssaj2013.04.0130

Cited by 18 publications

(32 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The water drop penetration time (WDPT) test was carried out by placing 30 drops of deionized water in different smoothed locations within the sampling area from a standard height of 10 mm and recording the time for their complete penetration, A medical dropper was used that yielded drops of uniform volume (70 ± 5 μL). Despite there is not a standard protocol for WDPT measurement, this drop size was close to the minimum volume recommended by Hallin et al (2013) to accurately account for soil microtopographical variability. According to these authors, the applied protocol allows estimating the mean WDPT value with an error of ±10% at 95% confidence.…”

Section: Methodssupporting

confidence: 50%

Application of minidisk infiltrometer to estimate water repellency in Mediterranean pine forest soils

Alagna

Iovino

Bagarello

et al. 2017

Journal of Hydrology and Hydromechanics

View full text Add to dashboard Cite

Assessment of soil water repellency (SWR) was conducted in the decomposed organic floor layer (duff) and in the mineral soil layer of two Mediterranean pine forests, one in Italy and the other in Spain, by the widely-used water drop penetration time (WDPT) test and alternative indices derived from infiltration experiments carried out by the minidisk infiltrometer (MDI). In particular, the repellency index (RI) was calculated as the adjusted ratio between ethanol and water soil sorptivities whereas the water repellency cessation time (WRCT) and the specifically proposed modified repellency index (RI m ) were derived from the hydrophobic and wettable stages of a single water infiltration experiment. Time evolution of SWR and vegetation cover influence was also investigated at the Italian site. All indices unanimously detected severe SWR conditions in the duff of the pine forests. The mineral subsoils in the two forests showed different wettability and the clay-loam subsoil at Ciavolo forest was hydrophobic even if characterized by organic matter (OM) content similar to the wettable soil of an adjacent glade. It was therefore assumed that the composition rather than the total amount of OM influenced SWR. The hydraulic conductivity of the duff differed by a factor of 3.8-5.8 between the two forested sites thus influencing the vertical extent of SWR. Indeed, the mineral subsoil of Javea showed wettable or weak hydrophobic conditions probably because leaching of hydrophobic compounds was slowed or prevented at all. Estimations of SWR according to the different indices were in general agreement even if some discrepancies were observed. In particular, at low hydrophobicity levels the SWR indices gathered from the MDI tests were able to signal sub-critical SWR conditions that were not detected by the traditional WDPT index. The WRCT and modified repellency index RI m yielded SWR estimates in reasonable agreement with those obtained with the more cumbersome RI test and, therefore, can be proposed as alternative procedures for SWR assessment.

show abstract

Section: Methodssupporting

confidence: 50%

Application of minidisk infiltrometer to estimate water repellency in Mediterranean pine forest soils

Alagna

Iovino

Bagarello

et al. 2017

Journal of Hydrology and Hydromechanics

View full text Add to dashboard Cite

show abstract

“…This trend is also observed in the results from 20-μl drops, but not to the same extent (Figure 4). In accordance with Hallin et al (2013), 20-μl drops show more variation in WDPT than 200-μl drops. This is probably because the smaller footprints of 20-μl drops sample surface heterogeneity better than the larger footprints of the 200-μl drops.…”

Section: Effect Of Drop Volume On Wdptsupporting

confidence: 72%

“…Previous research by Hallin et al (2013) tested mixtures of 90, 75 and 50% water-repellent soil with 10, 25 and 50% w/w wettable analogue soil, respectively. The same ratios were used for biochar:soil mixtures to enable direct comparisons with wettable soil.…”

Section: Preliminary Studiesmentioning

confidence: 99%

The effect of addition of a wettable biochar on soil water repellency

Hallin

Douglas

Doerr

et al. 2015

European J Soil Science

Self Cite

View full text Add to dashboard Cite

Summary The potential of biochar to ameliorate soil water repellency has not been widely studied. Previous studies have focused on the potential for biochar to induce or exacerbate existing water repellency rather than alleviate it. This study investigates the effect of adding wettable biochar to water‐repellent soil by comparing the water drop penetration times (WDPTs) of a control and biochar‐amended soil. The potential of wettable biochar to act as a physical amendment to water‐repellent soil was evaluated by mixing coarsely‐ground biochar (CGB, particle size range 250–2000 µm) or finely‐ground biochar (FGB, particle size range < 250 µm) with one strongly and one severely naturally water‐repellent soil in various quantities, and then measuring the WDPT for each mixture. When biochar particles did not fall within the size range of existing soil particles, an initial increase in both mean WDPT (WDPTM) and variation in WDPT was observed with small additions of biochar. These effects possibly result from increased surface roughness and inhibition of infiltration by the suspension of drops above the average soil–air interface at a few hydrophobic points. Both CGB and FGB reduced soil water repellency, FGB more effectively than CGB. The addition of 10% w/w FGB reduced soil WDPT by 50%, and 25% FGB eliminated repellency. Direct absorption of water by biochar and an increase in soil surface area in contact with water are the predominant physical mechanisms involved. This exploratory study suggests biochar has the potential to amend water‐repellent soil.

show abstract

“…This type of distribution was also reported in Orfanus et al (2014) who used the same non-parametric tests as this study due to non-Gaussian distribution in hydraulic conductivity measurements across a range of unburned soils. This is in contrast to Hallin et al (2013) who utilized parametric tests in their laboratory analysis of drop number and volume on sieved, washed, homogenous soils. Hallin et al (2013) note that heterogeneity is expected in situ, which may influence the number of drops required for an accurate estimation of mean WDPT.…”

Section: Discussionmentioning

confidence: 94%

“…In the literature, estimates of the spatial variability in WR are typically provided by reporting on mean WR class with standard deviations (Hallin et al, ; Moody and Schlossberg, ). Reporting on mean Class (from mean WDPT, Table ) is potentially misleading for sandy WR soils when small sample sizes are used.…”

Section: Discussionmentioning

confidence: 99%

Does fire alter soil water repellency in subtropical coastal sandy environments?

White

Lockington

Gibbes

2016

Hydrological Processes

View full text Add to dashboard Cite

Irregular wetting, water repellency, and preferential flow are well‐documented properties of coastal sandy podzols, though little is known about the effect of fire on unsaturated zone processes in this environment. This study investigates water repellency at and below the soil surface in two coastal sandy podzols following bushfire. Water drop penetration time tests were applied to burned and unburned soils at a high dune field site in South East Queensland, Australia. It was found that the mean water drop penetration time of the burned soil was four times that of the unburned soil, but both soils were largely non‐repellent. Post‐fire repellency peaked below the surface in a patchy layer, in contrast to the laterally extensive layer reported in other studies, and high organic matter content in the soil did not appear to significantly influence repellency post‐burn. Non‐parametric statistics were used to quantify the high spatial variability in water repellency, which was ultimately insufficiently captured by atypically large (n = 1000 drop) datasets. This study confirms the presence of naturally occurring repellency and patchy infiltration in sandy soils while demonstrating that conclusively describing the influence of fire is challenging in a soil with heterogeneous infiltration characteristics. With respect to this uncertainty, it appears that fire does not increase soil water repellency such that infiltration and runoff processes due to fire‐induced water repellency would differ post‐burn.

show abstract

The Role of Drop Volume and Number on Soil Water Repellency Determination

Cited by 18 publications

References 20 publications

Application of minidisk infiltrometer to estimate water repellency in Mediterranean pine forest soils

Application of minidisk infiltrometer to estimate water repellency in Mediterranean pine forest soils

The effect of addition of a wettable biochar on soil water repellency

Does fire alter soil water repellency in subtropical coastal sandy environments?

Contact Info

Product

Resources

About