• Quality irrigation water is an essential resource for better growth of
• Concentration and composition of dissolved constituents in water
determine its quality for irrigation use
• Irrigation purposes the water quality is assessed on the basis of the chemical
The quantities of salt dissolved in
irrigation water are usually
expressed in terms of electrical
conductivity (EC) mg/L (ppm)
Alkalinity / sodicity
Absolute and relative
concentrations of specific
cations and anions
Presence of toxic ions Boron,fluoride,nitrate,
• If TSS was high in irrigation water it leads to mild chlorosis of the
foliage, later progressing to a necrosis of leaf tips and margins.
• There will be yield loss if the salinity value is higher than the
TSS in irrigation water
Sodium Adsorption Ratio(SAR)
• Sodium adsorption ratio (SAR) is an important irrigation water
• It is a measure of the amount of sodium relative to the amount of
calcium and magnesium in a water sample.
Crops moderately tolerant to SAR and typically handle SAR values of 20-50
Crops tolerant to SAR and typically handle SAR values of 50-100 includes:
• ESP measures the proportion of cation exchange sites occupied by
• Soils are consideres sodic when ESP is above 6.And highly sodic
when the ESP is greater than 15
• The residual sodium carbonate (RSC) index of irrigation water or soil
water is used to indicate the alkalinity hazard for soil.
• When dissolved sodium in comparison with dissolved calcium and
magnesium is high in water, clay soil swells or undergoes dispersion which
drastically reduces its infiltration capacity.
RSC value (meL-1) Waterquality
< 1.25 Water can be used safely
1.25 - 2.5 Water can be used with certain
> 2.5 Unsuitable for irrigation purposes
• Apart from the salinity or the sodicity hazard, the constituents of
much irrigation water may cause toxicity problems when taken up
by the plants in excess amounts.
• The toxic constituents of major concern are sodium, chloride and
• The chloride ion can be taken up by plant roots and accumulate in
• Excessive accumulation may cause burning of the leaf tips or
margins, bronzing and premature yellowing of the leaves.
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