The document discusses factors that determine the quality of irrigation water for maintaining soil and crop productivity. Poor quality water can damage soils by making them saline or alkaline due to salt accumulation, injuring crops. Key factors discussed include total soluble salts (salinity hazard), sodium adsorption ratio (sodium hazard), residual sodium carbonates, permeability index, and specific ion toxicities such as boron and chloride. Tolerances of various pulses and oilseeds to these factors are also provided.

2. GOOD QUALITY IRRIGATION WATER IS ESSENTIAL TO
MAINTAIN THE SOIL CROP PRODUCTIVITY AT A HIGH
LEVEL.
THE ESSENTIAL PREREQUISITE FOR QUALITY
IRRIGATION WATER IS THAT IT SHOULD BE SAFE FOR
USE TO CROPS AND SHOULD NOT DAMAGE SOILS
POOR QUALITY WATER DAMAGES SOILS USUALLY BY
MAKING THEM SALINE OR ALKALINE WITH SALT
ACCUMULATION THAT INJURES CROPS

3. PHYSICAL
CHEMICAL
BIOLOGICAL

4. Total soluble salts ( salinity hazard)
• This is directly related to quantity of salts dissiolved in the irrigation
water.All irrigation water contains potentially injurious salts and nearly all
the dissolved salts are left in the soil after the applied water is lost by
evaporation from the soil or through transpiration by the plants.
• Unless the salts are leached from the root zone,later they will accumulate
in quantities which will partially or entirely prevent growth of most crops.
• Electrical conductivity becomes a satisfactory measure of the salinity
hazard involved in the use of water for irrigation
•

5. Relative tolerance of pulses to salinity:
Mostly pulses are sensitive to salinity
1. Peas – 3.4 dS/m
2. Cowpea – 4.9 dS/m
3. Beans – 1.8 dS/m
4. Blackgram,Green gram,urd bean are moderately sensitive to salinity
5. Pigeon pea is sensitive to salinity

6. Relative tolerance of salinity to oilseeds
• Mostly,Oilseeds are tolerant to salinity
• Sunflower – 4.8 dS/m
• Rapeseed – 6.6 dS/m
• Toria – 4.7 dS/m
• Soybean – 2.0 dS/m

7. Sodium Adsorption Ratio (sodium
hazard):
• Sodium adsorption ratio (SAR) means a value representing the relative
amount of sodium ions to the combined amount of calcium and
magnesium ions in water

8. Relative tolerance of pulses to sodicity:
ESP RANGE CROPS
1. 10-15. Pigeon pea, lentils,peas,urdbean
2. 16-20. Bengal gram
3. 20-25. Cowpeas

9. Relative tolerance of oilseeds to sodicity
• ESP RANGE CROPS
1. 10-15. Safflower
2. 16-20. Bengal gram
3. 20-25. Groundnut
4. 25-30. Linseed
5. 30-50. Mustard, sunflower

10. Residual Sodium Carbonates(RSC):
• RSC is imporwater.Index for carbonate and bicarbonate rich irrigation
water. It indicates their tendency to precipitate Ca 2+ as CaCO3
• It is expressed in meq/L
• RSC index = [HCO3 + CO3] − [Ca + Mg]

11. Sodicity hazard in terms of RSC
• Safe - < 1.25 meq/L
• Moderate – 1.25-2.5 meq/L
• Unsafe - > 2.5 meq/L

12. Permeability index
• High sodium in the irrigation water can cause severe soil permeability
problem.Permeability Is affected not only by high Sodium in irrigation
water but also by Carbonates and bicarbonates content in water.

13. Specific ion toxicity hazard:
• Sodium
• Magnesium
• Chlorides
• Sulphate
• Potential salinity
• Total dissolved solids
• Total cations
• Boron
• Toxicities of boron and chloride for pulses and oilseeds are described here.

14. Relative crop tolerance to boron
• Cowpea is sensitive to boron (0.5-0.75mg/L)
• Beans,mung sensitive to boron (0.75- 1.0 mg/L)
• Pea is moderately sensitive to boron ( 1-2 mg/L)
• Mustard is moderately tolerant to boron ( 2-4 mg/L)
• Sunflower,sesame are sensitive to boron(0.75-1 mg/L)

15. Relative crop tolerance to chloride
toxicity:
• Sesame,sunflower are less sensitive to chloride (0.75-1 ppm) in
oilseeds
• Peas are moderately sensitive to chloride (1-2 ppm) in pulses
• Beans,peanut are less sensitive to chloride toxicity ( 0.75- 1 ppm) in
pulses

16. Thank you