Quality of irrigation water The suitability of irrigation water is mainly depends on the amounts and type of salts present in water. The main soluble constituents are calcium, magnesium, sodium as cations and chloride, sulphate, biocarbonate as anions. The other ions are present in minute quantities are boron, selenium, molybdenum and fluorine which are harmful to animals fed on plants grown with excess concentration of these ions.

Quality of irrigation is judged with three parameters:

1. Sodium Adsorption ratio water
2. Boron content

Total salt concentration Salt concentration of irrigation water is measured as electrical conductivity (EC). Conventionally, water containing total dissolved salts to the extent of more than 1.5 m mhos/cm has been classified as saline. Saline waters are those which have sodium chloride as the predominant salt.

Classification of irrigation water based on total salt content

C1 C2 C3

C4 C5

<1.5 1.5 – 3 3 – 5

5 – 10 > 10

Normal waters Low salinity waters Medium salinity waters

Saline waters High salinity waters

All soils Light and medium textured soils Light and medium textured soils for semi – tolerant crops Light and medium textured soils for tolerant crops Not suitable

Sodium Adsorption ratio Sodium Adsorption ratio (SAR) and residual sodium carbonate (RSC) are also the main criterion to determine the quality of irrigation water. Boron content Irrigation water which contains more than 3 ppm boron is harmful to crops, especially on light soils. Classification of irrigation water based on boron content