The sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils. It is an indicator of the suitability of water for use in agricultural irrigation, as determined from the concentrations of the main alkaline and earth alkaline cations present in the water. It is also a standard diagnostic parameter for the sodicity hazard of a soil, as determined from analysis of pore water extracted from the soil.[1]
The formula for calculating the sodium adsorption ratio (SAR) is:[2]
where sodium, calcium, and magnesium concentrations are expressed in milliequivalents/liter.
SAR allows assessment of the state of flocculation or of dispersion of clay aggregates in a soil. Sodium and potassium ions facilitate the dispersion of clay particles while calcium and magnesium promote their flocculation. The behaviour of clay aggregates influences the soil structure and affects the permeability of the soil on which directly depends the water infiltration rate. It is important to accurately know the nature and the concentrations of cations at which the flocculation occurs: critical flocculation concentration (CFC). The SAR parameter is also used to determine the stability of colloids in suspension in water.
Although SAR is only one factor in determining the suitability of water for irrigation, in general, the higher the sodium adsorption ratio, the less suitable the water is for irrigation. Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil.[3]
If irrigation water with a high SAR is applied to a soil for years, the sodium in the water can displace the calcium and magnesium in the soil. This will cause a decrease in the ability of the soil to form stable aggregates and a loss of soil structure and tilth. This will also lead to a decrease in infiltration and permeability of the soil to water, leading to problems with crop production. Sandy soils will have less problems, but fine-textured soils will have severe problems if SAR is greater than 9. When SAR is less than 3, there will not be a problem.[4]
The concept of SAR addresses only the effects of sodium on the stability of soil aggregates. However, high K and Mg concentrations have also negative effects on soil permeability. The effect of potassium can be similarly treated by means of the potassium adsorption ratio (PAR).[5] To take into account simultaneously all major cations present in water, a new irrigation water quality parameter was defined: the cation ratio of structural stability (CROSS), a generalization of SAR.[6][7]
^Reeve, R. C.; Bower, C. A.; Brooks, R. H.; Gschwend, F. B. (1954). "A comparison of the effects of exchangeable sodium and potassium upon the physical condition of soils". Soil Science Society of America Journal. 18 (2): 130. doi:10.2136/sssaj1954.03615995001800020004x.
^Oster, J. D.; Sposito, Garrison (1980). "The Gapon coefficient and the exchangeable sodium percentage-sodium adsorption ratio relation". Soil Science Society of America Journal. 44 (2): 258. doi:10.2136/sssaj1980.03615995004400020011x.
^DWAF (1996). "South African Water Quality Guidelines: Vol. 4: Agricultural Use: Irrigation" (PDF). Department of Water Affairs and Forestry, South Africa. pp. 141–153. Retrieved 21 June 2017.
^Rollins, Larry (1 October 2007). "Advanced topics in water chemistry and salinity". WateReuse Foundation. Retrieved 2 November 2016.
^Sposito Garrison (2008) The Chemistry of Soils. 2nd ed. New York. Oxford University Press.
^Rengasamy, Pichu; Marchuk, Alla (2011). "Cation ratio of soil structural stability (CROSS)" (PDF). Soil Research. 49 (3): 280. doi:10.1071/SR10105.
^Smith, Chris J.; Sposito, Garrison; Oster, J.D. (2016). "Accounting for potassium and magnesium in irrigation water quality assessment" (PDF). California Agriculture. 70 (2): 71. doi:10.3733/ca.v070n02p71.
and 26 Related for: Sodium adsorption ratio information
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate...
Desalination of water Desalination of soil: soil salinity control Sodiumadsorptionratio Measuring salinity Salinometer Salinity by biologic context In...
by the following two indexes: The sodiumadsorptionratio (SAR, ) The formula for calculating sodiumadsorptionratio is: SAR = [Na+]/√[Ca2+/2 + Mg2+/2]...
adsorption capacity. Sodium polyacrylate has a very high adsorption capacity and one of the highest adsorption capacities for sodium polyacrylate was found...
livestock. Its use for irrigation is limited by its relatively high sodiumadsorptionratio. Depending on aquifer connectivity, water withdrawal may depress...
crop irrigation, some waters are naturally high in salinity and sodiumadsorptionratio. There has been controversy on how to best manage these saline...
Renewable energy portal Algal bloom Soil pH Cation-exchange capacity Sodiumadsorptionratio RSC Index Soda lake Soil salinity Narmada Bachao Andolan "India:...
The Gibbs adsorption isotherm for multicomponent systems is an equation used to relate the changes in concentration of a component in contact with a surface...
salinity that would result in a reduction in yields. A normal sodiumadsorptionratio (SAR) must be within the range of 3 to 9 SAR. Total dissolved solids...
SiO2 • 9/2 H2O Silica-alumina ratio: SiO2/ Al2O3≈2 3A molecular sieves are produced by cation exchange of potassium for sodium in 4A molecular sieves. 3A...
softened to remove these ions. The softening process often substitutes sodium cations. For certain populations, hard water may be preferable to soft water...
surface area available for adsorption or chemical reactions that can be thought of as a microscopic "sponge" structure. (Adsorption, not to be confused with...
finely divided powders formed by the precipitation reaction of water-soluble sodium silicate (water glass) and a water-soluble magnesium salt such as magnesium...
bonding contribution. They have excellent hydrophobicity and are suited for adsorption of bulky, hydrophobic molecules such as hydrocarbons. In addition to that...
W. R. (January 1988). "Sulfur/sodium bentonite prills as sulfur fertilizers. 2. Effect of sulfur-sodium bentonite ratios on the availability of sulfur...
froth flotation, adsorption is a strong consequence of surface energy, since the small particles have a high surface area to size ratio, resulting in higher...
concomitant adsorption. The amount of expansion is due largely to the type of exchangeable cation contained in the sample. The presence of sodium as the predominant...
activated carbon and the carbon dioxide will adhere to the activated carbon [adsorption]. Once the bed is saturated it must then be "regenerated" by blowing low...
livestock. Its use for irrigation is limited by its relatively high sodiumadsorptionratio. A large amount of coalbed methane produced water from the Black...
for a wide range of adsorbent and catalyst applications including the adsorption of catalysts in polyethylene production, in hydrogen peroxide production...
voor Ondernemend Nederland (Netherlands Enterprise Agency) SAR - Sodiumadsorptionratio SBA (or SBM) - Swachh Bharat Abhiyan, Clean India Mission or Swachh...
Note: adsorption is a surface phenomena, absorption involves the entire material. Ex: Activated carbon an adsorbent, used for the adsorption of odorous...
by the continuous action of the sodium–potassium pump, which, with other ion transporters, maintains the normal ratio of ion concentrations across the...