Sodium Absorption Ratio


Historical Information
  Determination of Essentiality
Function in Plants
  Metabolic Processes
  Fruit Yield and Quality
Diagnosis of Magnesium Status in Plants
  Symptoms of Deficiency and Excess
    - Symptoms of Deficiency
    - Symptoms of Excess
  Environmental Causes of Deficiency Symptoms
  Nutrient Imbalances and Symptoms of Deficiency
    - Potassium and Magnesium
    - Calcium and Magnesium
    - Nitrogen and Magnesium
    - Sodium and Magnesium
    - Iron and Magnesium
    - Manganese and Magnesium
    - Zinc and Magnesium
    - Phosphorus and Magnesium
    - Copper and Magnesium
    - Chloride and Magnesium
    - Aluminum and Magnesium
  Phenotypic Differences in Accumulation
  Genotypic Differences in Accumulation
Concentrations of Magnesium in Plants
  Magnesium Constituents
    - Distribution in Plants
    - Seasonal Variations
    - Physiological Aspects of Magnesium Allocation
  Critical Concentrations
    - Tissue Magnesium Concentration Associations with Crop Yields
    - Tabulated Data of Concentrations by Crops
Assessment of Magnesium in Soils
  Forms of Magnesium in Soils
  Sodium Absorption Ratio
  Soil Tests
  Tabulated Data on Magnesium Contents in Soils
    - Soil Types
Fertilizers for Magnesium
  Kinds of Fertilizers
  Effects of Fertilizers on Plant Growth
  Application of Fertilizers
Magnesium is also an important component in evaluating the sodium absorption ratio (SAR) of irrigation waters and soil extracts. The SAR is calculated as

SAR = (Na+) / √(Ca2+ + Mg2+)/2

In this equation, the concentrations of sodium (Na+), calcium (Ca2+), and magnesium (Mg2+) ions are expressed in meq L-1. When concentrations of magnesium, calcium, or both elements are increased, relative to sodium, the SAR decreases. Many soils in arid climates are affected by SAR in that as the SAR increases, the permeability of the soil decreases since the sodium reacts with clay, causing soil particles to disperse resulting in reduced water penetration into the soil (208). In most cases, a soil is considered sodic when the SAR>13 (209). However, at lower SAR values, some crops may still be susceptible to the adverse effects of sodium on nutrient uptake rather than to the physiochemical effects on soil permeability.


Primary and Secondary Minerals, Nonminerals, and Gems Containing Magnesium

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