Quantifying the aggregation-dispersion boundary condition in terms of saturated hydraulic conductivity reduction and the threshold electrolyte concentration

Dang, Aaditi; Bennett, John McLean; Marchuk, Alla; Biggs, A. J. W.; Raine, Steven R.

doi:10.1016/j.agwat.2018.03.005

Cited by 30 publications

(19 citation statements)

References 19 publications

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“…Practitioners and industry use government C TH guidelines (e.g., ANZECC, ) to make practical irrigation implementation decisions. The industry C TH guidelines are typically based on a generalized equation for the C TH , which is contradictory to the fact that C TH is soil specific and is only linearly correlated with SAR (Bennett et al, ; Dang et al, ). It seems that the P max is a better indicator for soil structural management, because P max is not only soil specific, but also includes the combined contributions of electrolyte concentration, SAR and EIP according to the theoretical calculations of P EDL .…”

Section: Resultsmentioning

confidence: 99%

Effects of interactions between soil particles and electrolytes on saturated hydraulic conductivity

Liu

Yang

et al. 2019

European J Soil Science

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Interactions between soil particles can strongly affect water movement in soil. In this study, a model to predict soil saturated hydraulic conductivity based on interactions between soil particles was proposed. Firstly, a model of ion−soil particle interactions at the soil/water interface was established taking specific ion effects into account. Based on the ion–soil interaction model, the theoretical relationship between the sodium adsorption ratio and the surface potential was derived, and the surface potentials were calculated at different sodium adsorption ratios and electrolyte concentrations. Secondly, a theoretical expression of midpoint potential between two adjacent soil particles in a mixed 1:1 + 2:1 electrolyte solution (e.g., NaCl + CaCl2) was derived. The midpoint potential was estimated based on the calculated surface potential. Thirdly, the interaction pressure (repulsive pressure) between soil particles was quantified based on the obtained midpoint potential. Finally, an empirical model of the relationship between measured saturated hydraulic conductivity and maximum net repulsive pressure was proposed. The surface potential, electrostatic repulsive pressure and net pressure between soil particles in the presence of Na+ is higher than that of Ca2+ because the effective charge of the former (1.18) is smaller than that of the latter (1.98). Although the soil saturated hydraulic conductivities were substantially different in Na+ and Ca2+ solutions, they can be described as a function of maximum repulsive pressure between soil particles. Employing this empirical relationship, saturated hydraulic conductivities might be predicted in other soils at different sodium adsorption ratios. This work implies that the sodium adsorption ratio and electrolyte concentration control saturated hydraulic conductivity through affecting the electrostatic repulsive pressure between soil particles. Highlights A model of ion–soil particle interactions was established considering specific ion effects. The theoretical relationship between sodium adsorption ratio and surface potential was derived. The interaction pressure between soil particles in mixed electrolytes was quantified. An empirical model of the relationship between saturated hydraulic conductivity and net repulsive pressure was proposed.

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Section: Resultsmentioning

confidence: 99%

Effects of interactions between soil particles and electrolytes on saturated hydraulic conductivity

Liu

Yang

et al. 2019

European J Soil Science

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“…The scaling factor r is a function of the soil solution pH, SAR, and EC, and the relative hydraulic conductivity K r is a function of the hydraulic pressure head:

K (h, p H, SAR, EC) = r (pH, SAR, EC) K_{normals} K_{normalr} (h)

where K is the hydraulic conductivity (cm d −1 ), h is the pressure head (cm), pH is the solution pH (−log[H + ]), SAR is the sodium adsorption ratio, EC is the total electrolyte concentration of the solution (mmol c L −1 ), and r is a scaling factor (a function of pH, SAR, and EC). Subsequently, the scaling parameter, r , is divided into two sub‐factors:

r (pH, SAR, EC) = r_{1} (SAR, EC) r_{2} (pH)

where r 1 is a function of SAR and EC, providing the disaggregation (inter‐ and intra‐crystalline swelling) and dispersion effects on the hydraulic conductivity, as described by Quirk and Schofield (1955), Dang et al (2018b), and Bennett et al (2019), while r 2 represents the effects of solution pH on the hydraulic conductivity (Suarez et al, 1984). The assumption is that the scaling parameters r 1 and r 2 can be applied for the entire range of pressure heads under unsaturated conditions.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…The use of marginal quality irrigation water is likely to cause deterioration in the soil structure; a change in the ratio of solids, water, and air within the soil; and reduced hydraulic conductivity due to clay disaggregation and dispersion processes (Bennett et al, 2019; Quirk and Schofield, 1955; Rengasamy and Olsson, 1991). A reduction in hydraulic conductivity often occurs as a result of excess Na within the soil solution (measured as the sodium adsorption ratio, SAR), which can result in both intra‐ and inter‐crystalline swelling, leading to clay dispersion (Dang et al, 2018b; Ezlit et al, 2013). The magnitude of the reduction in hydraulic conductivity depends on the electrolyte concentration (EC) in the soil solution (Quirk and Schofield, 1955; Shainberg and Letey, 1984).…”

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confidence: 99%

A pH‐Based Pedotransfer Function for Scaling Saturated Hydraulic Conductivity Reduction: Improved Estimation of Hydraulic Dynamics in HYDRUS

Ali

Biggs

Šimůnek

et al. 2019

Vadose Zone Journal

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Soil‐specific pedotransfer functions can be incorporated into the HYDRUS model. Electrolyte concentration reduces the adverse effect of pH and Na on soil structural stability. Clay content is important in governing soil hydraulic reduction dynamics due to pH. Hydraulic conductivity is a key soil property governing agricultural production and is thus an important parameter in hydrologic modeling. The pH scaling factor for saturated hydraulic conductivity (Ks) reduction in the HYDRUS model was reviewed and evaluated for its ability to simulate Ks reduction. A limitation of the model is the generalization of Ks reduction at various levels of electrolyte concentration for different soil types, i.e., it is not soil specific. In this study, a new generalized linear regression model was developed to estimate Ks reduction for a larger set of Australian soils compared with three American soils. A nonlinear pedotransfer function was also produced, using the Levenberg–Marquardt optimization algorithm, by considering the pH and electrolyte concentration of the applied solution as well as the soil clay content. This approach improved the estimation of the pH scaling factor relating to Ks reduction for individual soils. The functions were based on Ks reduction in nine contrasting Australian soils using two sets of treatment solutions with Na adsorption ratios of 20 and 40; total electrolyte concentrations of 8, 15, 25, 50, 100, 250, and 500 mmolc L−1; and pH values of 6, 7, 8, and 9. A comparison of the experimental data and model outputs indicates that the models performed objectively well and successfully described the Ks reduction due to the pH. Further, a nonlinear function provided greater accuracy than the generalized function for the individual soils of Australia and California. This indicates that the nonlinear model provides an improved estimation of the pH scaling factor for Ks reduction in specific soils in the HYDRUS model and should therefore be considered in future HYDRUS developments and applications.

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“…For example, a given concentration of calcium has about 45 times more flocculating power compared to the same concentration of Na (see Equation (3)). Another debate on the derivation of TEC centres is about how much reduction in permeability or clay dispersion is permissible for different soil textures [7,38]. Table 2.…”

Section: Deficits In the Models Based On Quirk-schofield Concept On 'mentioning

confidence: 99%

“…It is now widely known that the TEC-SAR (or ESP) relationship is not universal, but unique for each soil. Several publications have revealed that many soil factors such as organic matter, clay content and mineralogy, cementing agents, and soil pH affect swelling, dispersion, and flocculation besides sodicity and salinity (e.g., [22,[38][39][40]). For example, Blackmore [41] and McIntyre [42] have shown that 'subplastic' soils in Australia with an ESP of 25-30 do not disperse, and the hydraulic conductivity of these soils was independent of ESP.…”

Section: Deficits In the Models Based On Quirk-schofield Concept On 'mentioning

confidence: 99%

Irrigation Water Quality and Soil Structural Stability: A Perspective with Some New Insights

Rengasamy

2018

Agronomy

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Abstract:The sustainability of irrigated agriculture depends on the quality of irrigation water used. The electrolyte concentration (EC) of irrigation water may lead to the accumulation of salts in the root zone layers and affect the physiological functions of the crop by osmotic and ion toxicity effects. Further, the cationic and anionic composition of the water may alter the exchangeable cation composition of the soil as well as its pH. Because of the dominance of sodium salts in many sources of irrigation water, parameters related to sodium such as exchangeable sodium percentage (ESP) of soils and sodium adsorption ratio (SAR) of soil solutions have been commonly used to study the effects of sodium in irrigation water on soil structural stability. Quirk and Schofield's concept of 'threshold electrolyte concentration' (TEC) has shown the importance of electrolytes in preventing the effects of sodium on soil structure. Based on this concept, several models have been proposed to relate ESP or SAR with EC to predict the possible impacts of irrigation water on soil structural stability. However, many research reports indicate that this relationship varies with soils, and a given model is not suitable for all types of soils. Further, the effects of potassium and magnesium in the processes leading to clay dispersion are disregarded in these models. This essay analyses all the factors involved in the structural failure of soils with different cationic composition, identifies the defects in these TEC models, and re-defines TEC on the basis of new insights on dispersive and flocculating charges of soils. This review does not deal with EC effects on crops nor the role of contaminant ions not involved with soil structural stability.

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Quantifying the aggregation-dispersion boundary condition in terms of saturated hydraulic conductivity reduction and the threshold electrolyte concentration

Cited by 30 publications

References 19 publications

Effects of interactions between soil particles and electrolytes on saturated hydraulic conductivity

Effects of interactions between soil particles and electrolytes on saturated hydraulic conductivity

A pH‐Based Pedotransfer Function for Scaling Saturated Hydraulic Conductivity Reduction: Improved Estimation of Hydraulic Dynamics in HYDRUS

Irrigation Water Quality and Soil Structural Stability: A Perspective with Some New Insights

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