scholarly journals Closed‐form hydraulic conductivity equations for multimodal unsaturated soil hydraulic properties

2021 ◽  
Author(s):  
Katsutoshi Seki ◽  
Nobuo Toride ◽  
Martinus Th. van Genuchten
Keyword(s):  
Hydraulic Conductivity ◽  
Closed Form ◽  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic

scholarly journals Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

2018 ◽  
Vol 66 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Camila R. Bezerra-Coelho ◽  
Luwen Zhuang ◽  
Maria C. Barbosa ◽  
Miguel Alfaro Soto ◽  
Martinus Th. van Genuchten
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Measurement Techniques ◽  
Richards Equation ◽  
Water Retention Curve ◽  
Soil Hydraulic Properties ◽  
Evaporation Method ◽  
Soil Hydraulic

AbstractMany soil, hydrologic and environmental applications require information about the unsaturated soil hydraulic properties. The evaporation method has long been used for estimating the drying branches of the soil hydraulic functions. An increasingly popular version of the evaporation method is the semi-automated HYPROP©measurement system (HMS) commercialized by Decagon Devices (Pullman, WA) and UMS AG (München, Germany). Several studies were previously carried out to test the HMS methodology by using the Richards equation and the van-Genuchten-Mualem (VG) or Kosugi-Mualem soil hydraulic functions to obtain synthetic data for use in the HMS analysis, and then to compare results against the original hydraulic properties. Using HYDRUS-1D, we carried out independent tests of the HYPROP system as applied to the VG functions for a broad range of soil textures. Our results closely agreed with previous findings. Accurate estimates were especially obtained for the soil water retention curve and its parameters, at least over the range of available retention measurements. We also successfully tested a dual-porosity soil, as well as an extremely coarse medium with a very high van Genuchtennvalue. The latter case gave excellent results for water retention, but failed for the hydraulic conductivity. In many cases, especially for soils with intermediate and highnvalues, an independent estimate of the saturated hydraulic conductivity should be obtained. Overall, the HMS methodology performed extremely well and as such constitutes a much-needed addition to current soil hydraulic measurement techniques.

Hyphal colonization of Rhizophagus irregularis increases unsaturated hydraulic conductivity of a loamy sand distant from roots

2021 ◽  
Author(s):  
Michael Bitterlich ◽  
Richard Pauwels
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Hydraulic Properties ◽  
Volumetric Water Content ◽  
Rhizophagus Irregularis ◽  
Loamy Sand ◽  
Soil Hydraulic Properties ◽  
Unsaturated Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
Root Exclusion

<p>Hydraulic properties of mycorrhizal soils have rarely been reported and difficulties in directly assigning potential effects to hyphae of arbuscular mycorrhizal fungi (AMF) arise from other consequences of AMF being present, i.e. their influence on growth and water consumption rates of their host plants that both also influence soil hydraulic properties.</p><p>We assumed that the typical nylon meshes used for root-exclusion experiments in mycorrhizal research can provide a dynamic hydraulic barrier. It is expected that the uniform pore size of the rigid meshes causes a sudden hydraulic decoupling of the enmeshed inner volume from the surrounding soil as soon as the mesh pores become air-filled. Growing plants below the soil moisture threshold for hydraulic decoupling would minimize plant-size effects on root-exclusion compartments and allow for a more direct assignment of hyphal presence to modulations in soil hydraulic properties.</p><p>We carried out water retention and hydraulic conductivity measurements with two tensiometers introduced in two different heights in a cylindrical compartment (250 cm³) containing a loamy sand, either with or without the introduction of a 20 µm nylon mesh equidistantly between the tensiometers. Introduction of a mesh reduced hydraulic conductivity across the soil volumes by two orders of magnitude from 471 to 6 µm d<sup>-1</sup> at 20% volumetric water content.</p><p>We grew maize plants inoculated or not with Rhizophagus irregularis in the same soil in pots that contained root-exclusion compartments while maintaining 20% volumetric water content. When hyphae were present in the compartments, water potential and unsaturated hydraulic conductivity increased for a given water content compared to compartments free of hyphae. These differences increased with progressive soil drying.</p><p>We conclude that water extractability from soils distant to roots can be facilitated under dry conditions when AMF hyphae are present.</p><p> </p>

scholarly journals Use of field and laboratory methods for estimating unsaturated hydraulic properties under different land uses

2015 ◽  
Vol 19 (3) ◽  
pp. 1193-1207 ◽  
Author(s):  
S. Siltecho ◽  
C. Hammecker ◽  
V. Sriboonlue ◽  
C. Clermont-Dauphin ◽  
V. Trelo-ges ◽  
...  
Keyword(s):  
Land Use ◽  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Rubber Tree ◽  
Measurement Methods ◽  
Soil Parameters ◽  
Forest Site ◽  
Land Uses ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic

Abstract. Adequate water management is required to improve the efficiency and sustainability of agricultural systems when water is scarce or over-abundant, especially in the case of land use changes. In order to quantify, to predict and eventually to control water and solute transport into soil, soil hydraulic properties need to be determined precisely. As their determination is often tedious, expensive and time-consuming, many alternative field and laboratory techniques are now available. The aim of this study was to determine unsaturated soil hydraulic properties under different land uses and to compare the results obtained with different measurement methods (Beerkan, disc infiltrometer, evaporation, pedotransfer function). The study has been realized on a tropical sandy soil in a mini-watershed in northeastern Thailand. The experimental plots were positioned in a rubber tree plantation in different positions along a slope, in ruzi grass pasture and in an original forest site. Non-parametric statistics demonstrated that van Genuchten unsaturated soil parameters (Ks, α and n) were significantly different according to the measurement methods employed, whereas the land use was not a significant discriminating factor when all methods were considered together. However, within each method, parameters n and α were statistically different according to the sites. These parameters were used with Hydrus1D for a 1-year simulation and computed pressure head did not show noticeable differences for the various sets of parameters, highlighting the fact that for modeling, any of these measurement methods could be employed. The choice of the measurement method would therefore be motivated by the simplicity, robustness and its low cost.

Unsaturated Soil Hydraulic Properties Identification using Numerical Inversion and In-Situ Experiments from Mnasra Area, Morocco

2019 ◽  
Vol 23 (11) ◽  
pp. 4949-4959
Author(s):  
Hamid Qanza ◽  
Abdellatif Maslouhi ◽  
Said Abboudi ◽  
Hachimi Mustapha ◽  
Abderrahim Hmimou
Keyword(s):  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Numerical Inversion ◽  
Soil Hydraulic Properties ◽  
In Situ Experiments ◽  
Soil Hydraulic

Unsaturated Soil Hydraulic Properties according to Double-Ring Infiltration of Saline Water

2020 ◽  
Vol 53 (11) ◽  
pp. 1596-1609
Author(s):  
M. Amini ◽  
H. Ebrahimian ◽  
A. Liaghat ◽  
H. Fujimaki
Keyword(s):  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Saline Water ◽  
Soil Hydraulic Properties ◽  
Double Ring ◽  
Soil Hydraulic
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