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| Titel |
An assessment of the BEST procedure to estimate the soil water retention curve |
| VerfasserIn |
Mirko Castellini, Simone Di Prima, Massimo Iovino |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148321
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| Publikation (Nr.) |
 EGU/EGU2017-12564.pdf |
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| Zusammenfassung |
| The Beerkan Estimation of Soil Transfer parameters (BEST) procedure represents a very
attractive method to accurately and quickly obtain a complete hydraulic characterization
of the soil (Lassabatère et al., 2006). However, further investigations are needed
to check the prediction reliability of soil water retention curve (Castellini et al.,
2016).
Four soils with different physical properties (texture, bulk density, porosity and stoniness)
were considered in this investigation. Sites of measurement were located at Palermo
University (PAL site) and Villabate (VIL site) in Sicily, Arborea (ARB site) in Sardinia and in
Foggia (FOG site), Apulia. For a given site, BEST procedure was applied and the water
retention curve was estimated using the available BEST-algorithms (i.e., slope,
intercept and steady), and the reference values of the infiltration constants (β=0.6 and
γ=0.75) were considered. The water retention curves estimated by BEST were then
compared with those obtained in laboratory by the evaporation method (Wind, 1968).
About ten experiments were carried out with both methods. A sensitivity analysis of
the constants β and γ within their feasible range of variability (0.1<β<1.9 and
of 0.61<γ< 0.79) was also carried out for each soil in order to establish: i) the
impact of infiltration constants in the three BEST-algorithms on saturated hydraulic
conductivity, Ks, soil sorptivity, S and on the retention curve scale parameter, hg; ii) the
effectiveness of the three BEST-algorithms in the estimate of the soil water retention
curve.
Main results of sensitivity analysis showed that S tended to increase for increasing β
values and decreasing values of γ for all the BEST-algorithms and soils. On the other
hand, Ks tended to decrease for increasing β and γ values. Our results also reveal
that: i) BEST-intercept and BEST-steady algorithms yield lower S and higher Ks
values than BEST-slope; ii) these algorithms yield also more variable values. For the
latter, a higher sensitiveness of these two alternative algorithms to β than for γ was
established. The decreasing sensitiveness to γ may lead to a possible lack in the
correction of the simplified theoretical description of the parabolic two-dimensional and
one-dimensional wetting front along the soil profile (Smettem et al., 1994). This
likely resulted in lower S and higher Ks values. Nevertheless, these differences are
expected to be negligible for practical applications (Di Prima et al., 2016). On the
other hand, the -intercept and -steady algorithms yielded hg values independent
from γ, hence, determining water retention curves by these algorithms appears
questionable.
The linear regression between the soil water retention curves of BEST-slope and
BEST-intercept (note that the same result is obtained with BEST-steady, due to a purely
analytical reason) vs. lab method showed the following main results: i) the BEST procedure
generally tends to underestimate the soil water retention (the exception was the
PAL site); depending on the soil and algorithmic, the root mean square differences,
RMSD obtained with BEST and lab method ranged between 0.028 cm3/cm3 (VIL,
BEST-slope) and 0.082 cm3/cm3(FOG, BEST-intercept/steady); highest RMSD values
(0.124-0.140 cm3/cm3) were obtained in the PAL site; ii) depending on the soil,
BEST-slope generally determined lowest RMSD values (by a factor of 1.2-2.1);
iii) when the whole variability range of β and γ was considered and a different
couple of parameters was chosen (in general, extreme values of the parameters),
lower RMSD values were detected in three out of four cases for BEST-slope; iv) the
negligible observed differences of RMSD however suggest that using the reference
values of infiltration constants, does not worsen significantly the soil water retention
curve estimation; v) in 25% of considered soils (PAL site), the BEST procedure
was not able to reproduce the retention curve of the soil in a sufficiently accurate
way.
In conclusion, our results showed that the BEST-slope algorithm appeared to yield
more accurate estimates of water retention data with reference to three of the four
sampled soils. Conversely, determining water retention curves by the -intercept and
-steady algorithms may be questionable, since these algorithms overestimated hg
yielding independent values of this parameter from the proportionality coefficient
γ.
(*) The work was supported by the project “STRATEGA, Sperimentazione e
TRAsferimento di TEcniche innovative di aGricoltura conservativA”, financed by Regione
Puglia - Servizio Agricoltura.
References
Castellini, M., Iovino, M., Pirastru, M., Niedda, M., Bagarello, V., 2016. Use of BEST
Procedure to Assess Soil Physical Quality in the Baratz Lake Catchment (Sardinia, Italy).
Soil Sci. Soc. Am. J. 80:742–755. doi:10.2136/sssaj2015.11.0389
Di Prima, S., Lassabatere, L., Bagarello, V., Iovino, M., Angulo-Jaramillo, R., 2016.
Testing a new automated single ring infiltrometer for Beerkan infiltration experiments.
Geoderma 262, 20–34. doi:10.1016/j.geoderma.2015.08.006
Lassabatère, L., Angulo-Jaramillo, R., Soria Ugalde, J.M., Cuenca, R., Braud, I.,
Haverkamp, R., 2006. Beerkan Estimation of Soil Transfer Parameters through Infiltration
Experiments–BEST. Soil Sci. Soc. Am. J. 70:521–532. doi:10.2136/sssaj2005.0026
Smettem, K.R.J., Parlange, J.Y., Ross, P.J., Haverkamp, R., 1994. Three-dimensional
analysis of infiltration from the disc infiltrometer: 1. A capillary-based theory. Water Resour.
Res. 30, 2925–2929. doi:10.1029/94WR01787
Wind, G.P. 1968. Capillary conductivity data estimated by a simple method. In: Water in
the Unsaturated Zone, Proceedings of Wageningen Syposium, June 1966 Vol.1
(eds P.E. Rijtema & H Wassink), pp. 181–191, IASAH, Gentbrugge, Belgium. |
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