Testing a full-range soil-water retention function in modeling water potential and temperature

2000 ◽  
Vol 36 (10) ◽  
pp. 3081-3089 ◽  
Author(s):  
B. J. Andraski ◽  
Elizabeth A. Jacobson
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Retention ◽  
Full Range ◽  
Retention Function ◽  
Soil Water Retention

Wet-range physical realism in a model of soil water retention 

2021 ◽  
Author(s):  
John R. Nimmo
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Full Range ◽  
Soil Water Retention ◽  
Data Set ◽  
Soil Matrix ◽  
New Model ◽  
Trapped Air ◽  
Middle Range ◽  
Blowing Up

<p>Most models of soil water retention represent the wettest range simplistically, reflecting a high priority on facilitating computation without recognition of the active physical processes. Commonly the wet range is misleadingly represented by a straight line of zero slope, or by default using the same formulation as for the middle range, even though the mechanisms of water retention are different for the wet and middle portions of the range. Though adequate for some purposes, such treatment causes problems for applications that are sensitive to wet-range processes. It prevents accurate prediction of critical but challenging wet-range phenomena such as domain exchange between preferential flow paths and soil matrix. It limits the choices available for quantifying flow problems, for example a blowing-up of derivatives on approach to saturation prohibits the use of diffusivity-based formulations.</p><p>A new model addresses these issues for the important case where the medium is soil matrix material exclusive of macropores, thus having a well-defined air-entry value, and the moisture dynamics are the typical wet and dry cycling that achieves maximum wetness at field saturation, with a presence of trapped air at zero matric potential. The range between the air-entry value and field saturation is dominated by trapped air expansion in response to pressure change, as well as a process that increases the sensitivity to changing matric pressure. This enhanced sensitivity may be related in part to a collapse of liquid bridges between air pockets as they expand. For this wet range, the new model incorporates the Boyles’ law inverse-proportionality of trapped air volume and pressure, amplified by an empirical factor to account for the additional processes. To cover the full range of possible moisture, this wet-range formula is supplemented by two others. The middle range of capillary advance/retreat and Haines jumps is represented by a new adaptation of the lognormal distribution function. The adsorption-dominated dry range is represented by a logarithmic relation used in earlier models. Joined together with a continuous first-derivative constraint, the overall formulation recognizes the dominant processes within three segments of the full range. Optimization of five parameters can fit the model to a full data set.</p><p>Tests have demonstrated excellent fits, using measured data that have many closely spaced points in the wet and middle ranges. With their basis in process, the model’s parameters have a strong physical interpretation, and potentially can be assigned values without fitting, from knowledge of fundamental relationships or individual measurements. This basis in process also may permit accommodation of hysteresis by a systematic adjustment of the relation between the wet and middle ranges, and with minimal additional data may serve to facilitate estimation of other properties such as hydraulic conductivity, diffusivity, and sorptivity.</p>

scholarly journals Predicting the Campbell Soil Water Retention Function: Comparing Visible-Near-Infrared Spectroscopy with Classical Pedotransfer Function

2018 ◽  
Vol 17 (1) ◽  
pp. 170169 ◽  
Author(s):  
Zampela Pittaki-Chrysodonta ◽  
Per Moldrup ◽  
Maria Knadel ◽  
Bo V. Iversen ◽  
Cecilie Hermansen ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Soil Water ◽  
Near Infrared Spectroscopy ◽  
Water Retention ◽  
Near Infrared ◽  
Retention Function ◽  
Pedotransfer Function ◽  
Soil Water Retention

scholarly journals Modelling Soil Water Retention for Weed Seed Germination Sensitivity to Water Potential

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
W. John Bullied ◽  
Paul R. Bullock ◽  
Rene C. Van Acker
Keyword(s):  
Seed Germination ◽  
Water Potential ◽  
Soil Water ◽  
Water Retention ◽  
Soil Water Potential ◽  
Residual Soil ◽  
Similar Data ◽  
Weed Seed ◽  
Soil Water Retention ◽  
Minimum Threshold

Soil water retention is important for the study of water availability to germinating weed seeds. Six soil water retention models (Campbell, Brooks-Corey, four- and five-parameter van Genuchten, Tani, and Russo) with residual soil water parameter derivations were evaluated to describe water retention for weed seed germination at minimum threshold soil water potential for three hillslope positions. The Campbell, Brooks-Corey, and four-parameter van Genuchten model with modified or estimated forms of the residual parameter had superior but similar data fit. The Campbell model underestimated water retention at a potential less than −0.5 MPa for the upper hillslope that could result in underestimating seed germination. The Tani and Russo models overestimated water retention at a potential less than −0.1 MPa for all hillslope positions. Model selection and residual parameter specification are important for weed seed germination by representing water retention at the level of minimum threshold water potential for germination. Weed seed germination models driven by the hydrothermal soil environment rely on the best-fitting soil water retention model to produce dynamic predictions of seed germination.

Effect of long-term organic amendments on the full-range soil water retention characteristics of a Vertisol

2020 ◽  
Vol 202 ◽  
pp. 104663
Author(s):  
Hu Zhou ◽  
Chong Chen ◽  
Daozhong Wang ◽  
Emmanuel Arthur ◽  
Zhongbin Zhang ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Full Range ◽  
Organic Amendments ◽  
Soil Water Retention ◽  
Retention Characteristics
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