A Combined Salt Transport‐Chemical Equilibrium Model for Calcareous and Gypsiferous Soils

Robbins, C. W.; Wagenet, R. J.; Jurinak, J. J.

doi:10.2136/sssaj1980.03615995004400060011x

Cited by 67 publications

(40 citation statements)

References 16 publications

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“…The appropriate ortho-P ion pairs and activities were added to an existing iterative procedure to calculate Ca' and HPOz activities corrected for CaS0,1, CaCM CaHCW, CaH2 PO:, CaPOZ, Car2', MgSQ, MgC01, MgHPM MgH2P0:, and MgF + ion pairs and ionic strength (Robbins et al,1980). The Davies equation was used to estimate activity coefficients (Stumm and Morgan, 1970, p. 83) and ionic strength was estimated from EC (Griffin and Jurinak, 1973).…”

Section: Methodsmentioning

confidence: 99%

Phosphorus Forms and Extractability from Three Sources in a Recently Exposed Calcareous Subsoil

Robbins

Westermann

Freeborn

1999

Soil Science Soc of Amer J

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Irrigation-induced erosion and land leveling have decreased crop yields on -800 000 ha of south-central Idaho silt loam soils because of topsoil removal. Phosphorus availability is a known production problem after topsoil removal. This study evaluated the effect of three P sources on soil P solubility by three standard methods for calcareous soils. A long-term study was initiated on a Portneuf silt loam (Coarsesilty, mixed, superactive, mesic Durinodic X eric Haplocalcid) by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips. Phosphorus treatments applied across all strips were conventional fertilizer (applied according to soil test), dairy manure, and cheese whey. All treatments increased the freshly exposed subsoil bicarbonate extractable ortho-P concentrations up to or greater than the topsoil concentrations, which were more than adequate for economical crop production. The high-whey and manure treatments increased the subsoil saturation paste and 0.01 M CaCl2 extractable ortho-P concentrations up to or greater than the untreated topsoil ortho-P concentrations. The initial topsoil ortho-P solubility was along the II-tricalcium phosphate (j)-TCP) isotherm and the initial subsoil was well below the 13-TCP isotherm. The ortho-P solubility of the subsoil monocalcium phosphate (MCP) treatment remained just below the I3-TCP isotherm. The cottage cheese whey treatment increased subsoil P solubility up to the 0-TCP isotherm and the manure treated subsoil ortho-P solubilities were between the 13-TCP and octacalcium phosphate (OCP) isotherms. Most subsoil ortho-P concentrations by all three extraction methods decreased from spring to fall and then increased over winter in the subsequent spring samples. Soil solution ortho-P concentrations decreased with time in the subsoil treatments except immediately following treatment applications. The topsoil ortho-P extract concentrations by all three methods varied among samplings but remained about the same during the study period.

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Section: Methodsmentioning

confidence: 99%

Phosphorus Forms and Extractability from Three Sources in a Recently Exposed Calcareous Subsoil

Robbins

Westermann

Freeborn

1999

Soil Science Soc of Amer J

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“…Chemistry models and subroutines currently available for predicting lime and gypsum precipitation and dissolution in saline and sodic soils do not take into account the effects of exchangeable sodium nor soil solution electrical conductivity (EC) on soil pH (Tanji and Doneen 1966;Robbins et al 1980;Suarez 1982). Models using these calculation methods are also restricted to soils containing lime.…”

Section: Introductionmentioning

confidence: 99%

Calculating pH from EC and SAR values in salinity models and SAR from soil and bore water pH and EC data.

Robbins¹,

Meyer²

1990

Soil Res.

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Currently used soil salinity models do not contain a mechanism for including exchangeable sodium effects on soil pH. A method is needed that allows pH calculation from the sodium adsorption ratio (SAR) or exchangeable sodium percentage (ESP) and electrical conductivity (EC) data. This study developed a simple method for calculating saturated soil paste and aqueous solution pH from SAR (or ESP) and EC data and compared the results with measured values from a number of soils and subsurface waters. The equation pH -A+{B*(SAR) 1/2 /(1+CEC)I estimated soil pH from EC and SAR or ESP values. When rewritten as: SAR or ESP = l(pH-A)(1+C'EC)/13} 2 , the SAR or ESP was estimated from pH and EC data. By using shallow bore (well) water and soil extract data from the Murray Basin, values were determined for the scalar terms A, B and C. These values differed among subsurface water and soil types, however, the range of each scalar was reasonably small. It was found that a range of at least 2 . 5 pH units in the calibration data was necessary to obtain reliable regression between predicted and measured pH and SAR or ESP values. When these conditions were met, the predicted results were satisfactory. These relationships provide a method for pH calculation in soil salinity models which takes into account soil EC and sodium effects. They also provide a rapid field method to estimate SAR or ESP from easily obtainable EC and pH data. Further research is needed to define the factors that determine the values of A, B and C.

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“…Soil and crop evaporation are estimated from pan evaporation data and crop cover data. The model moves the salt as individual ions within the soil profile and then calculates the electrical conductivity (Robbins et al 1980). The soil profile was divided into 13 layers, each 0.1 m thick.…”

Section: The Numerical Model (Nm)mentioning

confidence: 99%

Models for estimating capillary rise in a heavy clay soil with a saline shallow water table

Prathapar

Robbins²,

Meyer

et al. 1992

Irrig Sci

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Summary. Shallow saline water tables underlie large areas of the clay soils in the Murray basin of Australia. Accurate estimation of capillary rise is important in formulating management strategies to avoid degradation of such soils. Measured capillary rise from a saline water table was compared with capillary rise estimated by three mathematical models of varying complexity and input requirement. A quasi steady state analytical model (QS-SAM), a transient state analytical model (TSAM) and a numerical model (NM) were used. An undisturbed heavy clay soil core of 0.75 m diameter and 1.4 m deep was subjected to a static saline water table at 1.2 m from the surface. A wheat crop was grown on the core and the weekly capillary rise from the water table was measured. The electrical conductivity of a I : 2 soil : water extract was determined at 0.15 m depth intervals before and 21 weeks after the introduction of the saline water table. The QSSAM did not satisfactorily estimate the initial wetting of the subsoil and the estimated capillary rise was considerably lower than the measured values. Capillary rise estimated by the TSAM was reasonably close to the measured values, but the weekly rates fluctuated considerably. The NM estimated capillary rise quite satisfactorily throughout the experiment. Except near the soil surface, the electrical conductivity values estimated by the NM were close to the measured values. For estimating total capillary rise over large areas, the TSAM is preferred over the NM because of its fewer input requirements and shorter execution time.Salinisation of soil, the increase in soluble salts in the root zone, is influenced by climate, soil type, crop, irrigation water quality and management practices, and the depth to, and salinity of the water table. The ability to estimate the rate of salinisation is vital for the management of irrigated areas in the Murray basin of Australia, where salinisation of heavy clay soils is primarily caused by capillary rise from saline shallow water tables. Offprint requests to: S. A. PrathaparA description of water transport in the unsaturated zone of a non-hysteretic, non-swelling soil is given by Richards (1931). Analytical models to estimate capillary rise from a water table could be formulated either with a steady state solution or with a transient solution for Richards' equation. Subsequently, the rate of salinisation could be estimated by combining an appropriate analytical solution for diffusive and convective solute transport with the capillary rise calculation, or by multiplying the rate of capillary rise by the concentration of salt in the water table. Numerical models to estimate capillary rise and salinisation in an unsaturated soil profile solve Richards' equation and the diffusive and convective solute transport equation simultaneously.Analytical models to estimate capillary rise are efficient and easy to use when input data are sparse and uncertain. However, the analytical models are limited to certain idealised situations such as homogeneous and is...

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A Combined Salt Transport‐Chemical Equilibrium Model for Calcareous and Gypsiferous Soils

Cited by 67 publications

References 16 publications

Phosphorus Forms and Extractability from Three Sources in a Recently Exposed Calcareous Subsoil

Phosphorus Forms and Extractability from Three Sources in a Recently Exposed Calcareous Subsoil

Calculating pH from EC and SAR values in salinity models and SAR from soil and bore water pH and EC data.

Models for estimating capillary rise in a heavy clay soil with a saline shallow water table

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