The sodium adsorption ratio (SAR) measures the proportion of sodium ions relative to calcium and magnesium ions in irrigation water or soil extracts. A high SAR indicates that sodium will replace calcium and magnesium on soil clay particles, which degrades soil structure, reduces water infiltration, and harms crop roots. Agronomists use this value to determine if water needs treatment or if soil requires gypsum amendments.
Heard on the job
The well water tested out with a sodium adsorption ratio of 12, so we need to apply gypsum before it ruins the field drainage.
Insider tip
If the SAR is high but the overall salinity is low, the water can actually cause more severe soil crusting and infiltration problems than if the water were highly saline.
Also heard as
- SAR