Sodium adsorption ratio

Sodium Adsorption Ratio (SAR) is a measure used to evaluate the suitability of water for use in agricultural irrigation. It is an important parameter in soil science and agronomy as it helps in assessing the potential for sodium to accumulate in the soil, which can affect soil structure and crop productivity.

Calculation

The Sodium Adsorption Ratio is calculated using the concentrations of sodium (Na⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) ions in the water. The formula for SAR is:

\[ \text{SAR} = \frac{[\text{Na}^+]}{\sqrt{\frac{[\text{Ca}^{2+}] + [\text{Mg}^{2+}]}{2}}} \]

where the concentrations are typically expressed in milliequivalents per liter (meq/L).

Importance in Agriculture

High SAR values indicate a greater risk of sodium accumulation in the soil, which can lead to soil dispersion, reduced infiltration, and poor soil structure. This can adversely affect plant growth and crop yields. Managing SAR is crucial for maintaining soil health and ensuring sustainable agricultural practices.

Soil and Water Management

To mitigate the effects of high SAR, several soil and water management practices can be employed:

• Gypsum application: Adding gypsum (calcium sulfate) to the soil can help displace sodium ions and improve soil structure.
• Leaching: Applying excess water to leach sodium ions below the root zone.
• Crop rotation: Growing salt-tolerant crops to manage soil salinity levels.

Related Concepts

• Soil salinity
• Irrigation
• Soil structure
• Water quality

See Also

• Soil science
• Agronomy
• Gypsum
• Leaching
• Crop rotation