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Table 8 Classification of irrigation water based on SAR values (College of Agricultural Sciences 2002; U.S. Salinity Laboratory Staff 1954)

From: GIS-based assessment of groundwater quality and suitability for drinking and irrigation purposes in the outlet and central parts of Wadi El-Assiuti, Assiut Governorate, Egypt

Level SAR Quality Class Hazard Use of water for irrigation
S1 0–10 Low sodium Excellent No harmful effects from sodium In all types of soil
S2 10–18 Medium sodium Good Problems on fine texture soils sodium sensitive plants, especially under low leaching conditions, but could be used on sandy soils with good permeability In coarse textural soils with high permeability and rich in organic matter
S3 18–26 High sodium Fair Harmful effects could be anticipated in most soils and amendments such as gypsum would be necessary to exchange sodium ions Requires good drainage and chemical amendments
S4  > 26 Very high sodium Poor Generally unsatisfactory for irrigation Very poor for irrigation, require low salinity water, good drainage and addition of gypsum