The Influence of Hydraulic Nonequilibrium on Pressure Plate Data

Gee, Glendon W.; Ward, Anderson L.; Zhang, Fred; Campbell, Gaylon S.; Mathison, Jon B.

doi:10.2113/1.1.172

Cited by 32 publications

(36 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…We assume that shrinkage caused a loss of hydraulic contact between soil and pressure plate. These findings corroborate results of previous studies, which also proposed blocked pores in the ceramic plate caused by soil dispersion as additional source of error (Gee et al, 2002; Cresswell et al, 2008; Bittelli and Flury, 2009; Solone et al, 2012). The pressure plate method provides precise (repeatable) but inaccurate (biased) values despite 4 wk of equilibration time and should therefore not be used to determine WP.…”

Section: Discussionsupporting

confidence: 92%

“…According to Soil Science Society of America (1997), the permanent wilting point is “… often estimated by the water content at –1.5 MPa soil matric potential”, which corresponds to pF 4.2. Traditional pressure plate extractors can be used to drain small samples to this potential (Dane and Hopmans, 2002a), but thermodynamic equilibrium may not be reached (Campbell, 1988; Gee et al, 2002). This can be caused by the loss of hydraulic contact between the sample and the plate and soil dispersion which causes blocking of the pores in the ceramic plate (Cresswell et al, 2008).…”

mentioning

confidence: 99%

“…As an alternative, the chilled‐mirror dewpoint technique yields reliable data at pressure heads around the permanent WP. It has been used as a reference for evaluating methods to determine water potentials in the dry moisture range (Gee et al, 2002; Bittelli and Flury, 2009; Bechtold et al, 2018). This method is limited to low water potentials, as it is based on measuring the relative humidity of soil air, which is close to unity for water potentials greater than –10 4 cm.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Determination of the Soil Water Retention Curve around the Wilting Point: Optimized Protocol for the Dewpoint Method

Kirste

Iden

Durner

2019

Soil Science Soc of Amer J

View full text Add to dashboard Cite

Soil water retention curve over the entire moisture range with high accuracy. Combination of evaporation method and dewpoint method. No a priori knowledge on soil texture needed. Experimental methodology that is reliable, efficient, and easy to use. Accurate knowledge of the soil water retention curve (WRC) is essential for various hydrological and plant‐physiological studies. Currently, there is a lack of a uniform protocol for measuring the wilting point water content (WP) with the dewpoint method (DP), despite its ecological relevance and frequent use to calculate available water capacity. We present a new protocol for measuring the WP with the dewpoint method. In contrast to existing methods which add or remove specific amounts of water to moist, air‐dry, or oven‐dry soil, we propose to apply the dewpoint method after the evaporation method in which tensiometers measure the pressure head of the soil. We suggest to stop the evaporation experiment when the air‐entry of one tensiometer cup is reached, to slice the soil core into slabs, and to apply the dewpoint method to subsamples of the slabs. We test the method by numerical simulations and laboratory experiments on five soils covering a broad range of texture. We investigate the accuracy, robustness, and practicability of the new method and compare it to the existing protocols for the dewpoint method and the pressure plate technique. We find that the proposed method allows a precise determination of the WP and the WRC across the full moisture range. It is easy to perform, robust, accurate, and does not require any a priori guess about the amount of water to be added or removed. By fitting a retention curve to the measured data, any water content, including the WP, can be obtained with great confidence.

show abstract

Section: Discussionsupporting

confidence: 92%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Determination of the Soil Water Retention Curve around the Wilting Point: Optimized Protocol for the Dewpoint Method

Kirste

Iden

Durner

2019

Soil Science Soc of Amer J

View full text Add to dashboard Cite

show abstract

“…Progress in developing definitive models of the dry end of the SWC [ Rossi and Nimmo , 1994; Ross et al , 1991] was hampered by data scarcity and experimental challenges using standard pressure plate devices with prohibitively long equilibration times at potentials lower than ‒1.5 MPa [ Gee et al , 2002]. Additionally, the introduction of residual water content as a fitting parameter in most SWC models often obscures the physical representation of key processes in the low potential range.…”

Section: Introductionmentioning

confidence: 99%

Water films and scaling of soil characteristic curves at low water contents

Tuller

2005

Water Resources Research

287

249

View full text Add to dashboard Cite

[1] Individual contributions of capillarity and adsorptive surface forces to the matric potential are seldom differentiated in determination of soil water characteristic (SWC) curves. Typically, capillary forces dominate at the wet end, whereas adsorptive surface forces dominate at the dry end of a SWC where water is held as thin liquid films. The amount of adsorbed soil water is intimately linked to soil specific surface area (SA) and plays an important role in various biological and transport processes in arid environments. Dominated by van der Waals adsorptive forces, surface-water interactions give rise to a nearly universal scaling relationship for SWC curves at low water contents. We demonstrate that scaling measured water content at the dry end by soil specific surface area yields remarkable similarity across a range of soil textures and is in good agreement with theoretical predictions based on van der Waals interactions. These scaling relationships are important for accurate description of SWC curves in dry soils and may provide rapid and reliable estimates of soil specific surface area from SWC measurements for matric potentials below À10 MPa conveniently measured with the chilled-mirror dew point technique. Surface area estimates acquired by fitting the scaling relationship to measured SWC data were in good agreement with SA data measured by standard methods. Preliminary results suggest that the proposed method could provide reliable SA estimates for natural soils with hydratable surface areas smaller than 200 m 2 /g.

show abstract

“…When thermodynamic equilibrium is reached, however, the equilibrium w should not be significantly affected by the artificial elevation of u a . To minimize experimental errors, the test duration should be long enough for the soil specimen to achieve thermodynamic equilibrium (Gee et al, 2002).…”

Section: Results and Interpretationmentioning

confidence: 99%

Comparisons of Different Suction Control Techniques by Water Retention Curves: Theoretical and Experimental Studies

Zhou

Leung

2015

Vadose Zone Journal

View full text Add to dashboard Cite

The axis-translation (ATT), osmotic (OMT), and vapor equilibrium (VET) techniques are widely used suction control techniques for investigating the hydraulic and mechanical behavior of unsaturated soils in the vadose zone. Yet there is still debate in the literature regarding their validity and consistency. In this study, four purposely designed experiments were carried out to measure the water retention curves (WRCs) of a compacted silty sand at different densities using the ATT and OMT. The four WRCs obtained from this study, together with extensive existing data published in the literature, were then analyzed using newly derived thermodynamic equations. The aim and novelty of this study were to apply the thermodynamic theory to verify and explain the validity and consistency of WRCs obtained by the three commonly used experimental techniques. By allowing for some possible experimental errors, the analyzed results reveal that the WRCs obtained from the three techniques are remarkably consistent. These consistent results can be explained by the derived thermodynamic equations, which illustrate that the inal soil water content at the thermodynamic equilibrium state should be the same regardless of the suction control technique used, even though the techniques involve different processes of moisture exchange.

show abstract

The Influence of Hydraulic Nonequilibrium on Pressure Plate Data

Cited by 32 publications

References 0 publications

Determination of the Soil Water Retention Curve around the Wilting Point: Optimized Protocol for the Dewpoint Method

Determination of the Soil Water Retention Curve around the Wilting Point: Optimized Protocol for the Dewpoint Method

Water films and scaling of soil characteristic curves at low water contents

Comparisons of Different Suction Control Techniques by Water Retention Curves: Theoretical and Experimental Studies

Contact Info

Product

Resources

About