Exchangeable sodium percentage

This is defined as the relative concentration of sodium to calcium plus magnesium, and is represented by a parameter known as the sodium adsorption ratio (SAR). The absolute concentration values of the different cations in irrigation water are not adequate for estimating probable hazards. An important consideration is the extent to which the exchangeable sodium percentage (ESP) of the soil will increase as a result of adsorption of sodium from the irrigation water. The higher the ratio, the... 

Soils properties are very sensitive to the type of exchangeable ions. Calcium imparts favorable physical properties to the soil, while adsorbed sodium causes clay dispersion and swelling. It is generally recognized that an exchangeable sodium percentage of 10 is sufficient to cause soil dispersion, reduction of soil permeability and impaired growth of some crop plants. On the other hand, excess salt concentration prevents the dispersive effect of adsorbed sodium. 

Fig. 8.26 Exchangeable sodium percentage (ESP) along a Burleson soil column, as a function of the sodium adsorption ratio (SAR) of irrigation water. The values were obtained by percolating the soil columns with sodic water (total electrolyte concentration of 11 meq/L). Each curve corresponds to a given applied volume of solution (Thomas and Yaron 1968)...

TABLE 10.1. Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) Values Associated with 20% Reduction in Saturated Hydraulic Conductivity (SHC) for Pembroke Soil (10- to 30-cm Incremental Depth) at Three pH Values... 

Exchangeable sodium percentage is related to the relative ratio of Na to Ca1/2 in the solution phase, which is referred to as the SAR (see Chapter 4). An empirical relationship between SAR and ESP, representing soils of the arid west, was developed by the U.S. Salinity Laboratory Staff (1954) ... 

The SAR magnitude reflects the quantity of sodium on the exchange sites of the soil. Most arid-region soils with SAR values of 15 have approximately 15% of their CEC loaded with sodium. This sodium load is known as the exchangeable sodium percentage or ESP. Soils with an ESP greater than 15 would be considered unproduc-... 

Frenkel, H., J. O. Goertzen, and J. D. Rhoades. 1978. The effect of clay type and content, exchangeable sodium percentage, and electrolyte concentration on clay dispersion and soil hydraulic conductivity. Soil. Sci. Soc. Am. J. 42 32-39. 

Gardner, W. R., M. S. Mayhugh, J. O. Goertzen, and C. A. Bower. 1959. Effect of electrolyte concentration and exchangeable sodium percentage on diffusivity of water in soils. Soil Sci. 88 270-274,... 

Oster, J. D and G. Sposito. 1980. The Gapon coefficient and the exchangeable sodium percentage-sodium adsorption ratio relation. Soil Sci. Soc. Am. J. 44 258-260. 

Equivalence points, 29 Equivalent Fraction, 202 Exchangeable sodium percentage (ESP), 379,395... 

A soil is equilibrated with a solution of SAR = 20. Based on the Gapon equation, what would be its equilibrium exchangeable sodium percentage (ESP) If the soil had instead been equilibrated with the same solution diluted fivefold with salt-free water, what would have been the corresponding SAR and ESP values ... 

The traditional classification of salt-affected soils in the United States has been based on the soluble salt (EC) concentrations of extracted soil solutions and on the exchangeable sodium percentage of the assodated soil. The dividing line between saline and nonsaline soils was established at 4 dS m-1 for water extracts from saturated soil pastes. Salt-sensitive plants, however, can be affected in soil whose saturation extracts have ECs of 2 to 4 dS m l. The Terminology Committee of the Soil Science Sodety of America has recommended lowering the boundary between saline and nonsaline soils to 2 dS m-1 in the saturation extract. 

Two parameters are used to measure and evaluate the effects of excess sodium in soils. These are the sodium adsorption ratio (SAR) and the exchangeable sodium percentage (ESP). SAR is a parameter used to describe the composition of irrigation water or existing soil solution and is used to predict the ESP. SAR is defined by the equation... 

Dispersive erosion depends on the mineralogy and chemistry of soil on the one hand, and the dissolved salts in the pore and eroding water on the other. The presence of exchangeable sodium is the main chemical factor contributing towards dispersive clay behaviour. This is expressed in terms of the exchangeable sodium percentage, ESP ... 

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