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Titel |
Application of minidisk infiltrometer to estimate soil water repellency |
VerfasserIn |
Vincenzo Alagna, Massimo Iovino, Vincenzo Bagarello, Jorge Mataix-Solera, Lubomir Lichner |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250124078
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Publikation (Nr.) |
EGU/EGU2016-3452.pdf |
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Zusammenfassung |
Soil water repellency (SWR) reduces affinity of soils to water resulting in detrimental
implication for plants growth as well as for hydrological processes. During the last
decades, it has become clear that SWR is much more widespread than formerly
thought, having been reported for a wide variety of soils, land uses and climatic
conditions.
The repellency index (RI), based on soil-water to soil-ethanol sorptivity ratio, was
proposed to characterize subcritical SWR that is the situation where a low degree of
repellency impedes infiltration but does not prevent it. The minidisk infiltrometer allows
adequate field assessment of RI inherently scaled to account for soil physical properties other
than hydrophobicity (e.g., the volume, connectivity and the geometry of pores)
that directly influence the hydrological processes. There are however some issues
that still need consideration. For example, use of a fixed time for both water and
ethanol sorptivity estimation may lead to inaccurate RI values given that water
infiltration could be negligible whereas ethanol sorptivity could be overestimated due
to influence of gravity and lateral diffusion that rapidly come into play when the
infiltration process is very fast. Moreover, water and ethanol sorptivity values need to
be determined at different infiltration sites thus implying that a large number of
replicated runs should be carried out to obtain a reliable estimate of RI for a given
area.
Minidisk infiltrometer tests, conducted under different initial soil moisture and
management conditions in the experimental sites of Ciavolo, Trapani (Italy) and Javea,
Alicante (East Spain), were used to investigate the best applicative procedure to estimate RI.
In particular, different techniques to estimate the water, Sw, and ethanol, Se, sorptivities were
compared including i) a fixed 1-min time interval, ii) the slope of early-time 1D infiltration
equation and iii) the two-term transient 3D infiltration equation that explicitly accounts for
the effects of gravity and lateral expansion. According to Pekárová et al. (2015), the
combination of all the ethanol and water sorptivities was used to calculate an aggregated
repellency index, RIa, that accounts for the influence of spatial variability. Alternatively, the
plot of the water cumulative infiltration vs. square root of time, exhibiting a clear
“hockey-stick-like” shape, was used to estimate a single-test repellency index, RI∗, that
overcomes the limitations of the traditional approach given that information on both the
hydrophobic and the wettable states of soil are gathered from a unique infiltration
test.
The mean RI values were affected by the technique used to estimate Sw and Se. In
particular, the choice of a fixed time interval lead to overestimation of RI up to a factor of 3.2
as compared with the other techniques. The RIa yielded unbiased estimations of the mean RI
values and also allowed to quantify the variability of SWR within a given area. A statistically
significant relationship was found between RI∗ and RI but also between RI∗ and the water
retention cessation time, that is the time hydrophobic turns into wettable soil, thus
indicating that RI∗ is potentially able detect both the degree and the persistence of
SWR.
Pekárová P., Pekár J., Lichner Ľ. 2015. A new method for estimating soil water repellency
index. Biologia, 70(11):1450-1455. |
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