1. MANAGEMENT OF POOR QUALITY WATER FOR IRRIGATION
Submitted by:
B.THIRUMALAI,
BSA

2. Quality and suitability of irrigation water
Total salt concentration
Relative proportion of sodium to other cations
Carbonate and bicarbonate concentration
Boron concentration

3. Total salt concentration in irrigation water
Total concentration of soluble salts is the most important single criterion of irrigation water quality
The harmful effects increases with increase in total salt concentration
EC - the standard method of evaluating irrigation water for total salts
EC is the reciprocal of the electrical resistance (dSm-1),
equal to one millimhos cm-1
EC serves as a guide to know the extent of soluble salts in irrigation water.

4. Classification of irrigation water according to salinityEC
(dSm-1)
Suitability
Low C1
< 0.25
Can be safely used for most crops on most soils
Moderate C2
0.25 – 0.75
Can be used for all but extremely salt sensitive crops
Medium C3
0.75 – 2.25
Can be used on soils of moderate to good permeability. Regular leaching may be needed. Crops with moderate to good salt tolerance should be grown.
High C4
2.25 – 4.00
Can be used only in soils of good permeability. Special leaching is needed. Salt tolerant crops are suitable
Very high C5
4.00 – 6.00
Undesirable for irrigation and should be used only in highly permeable soils with frequent leaching and with plants of high salt tolerance
Excessive C6
> 6.00
Unsuitable for irrigation

5. Classification by STL of Tamil Nadu
Quality of water
EC (dSm-1)
Suitability
Good
< 1
Suitable for irrigation
Critical
1 - 3
Suitable on proper management
Injurious
> 3
Not suitable

6. 2. Relative proportion of sodium to other cations
    Sodium Adsorption ration (SAR)
It measures the sodium cations in relation to the calcium and magnesium ions present in a solution and is expressed as Na
SAR =
 Ca + Mg 2

7. Classification of irrigation water based on sodium hazards
SAR
Suitability
LOW S1
0 – 10
Can be used on all soil with little danger of accumulation of exchangeable sodium
Medium S2
10 – 18
Can be used in all soils with good permeability; appreciable sodium hazards in soils of high clay and low organic matter.
High S3
18 – 26
Tends to cause harmful sodium accumulation in most soils: needs good drainage, high leaching and organic matter addition.
Very high S4
> 26
Generally unsatisfactory for irrigation

8. Exchangeable sodium percentage (ESP)
Exchangeable sodium percentage is closely related to sodium adsorption ratio and gives the degree of saturation of the soil / water exchange complex with sodium and is given by
Exchangeable sodium
ESP = x 100
Cation exchange capacity

9. Sodium percentage
Sodium percentage (SP) refers to proportion of sodium in relation to total cations in water and the sodium percentage is calculated as follows. Na
SP = x 100
Na + Ca + Mg + K
If the SP is more than 60, the use of water for irrigation is questionable

10. 3. Carbonate and bicarbonate contents
The term Residual Sodium Carbonate is used to indicate the relative proportion of carbonates and bicarbonates in relation to calcium and magnesium in water.
  The RSC is expressed as
RSC = (Co3 + Hco3) – (Ca + Mg)
RSC < 1.25 me/l : Good
me/l : Fair
2.50 me/l : Bad

11. Limits of boron tolerance of some crops
    4. Boron concentration
Limits of boron tolerance of some crops
Tolerant
(4 ppm)
Semi-tolerant
(2 ppm)
Sensitive
(1ppm)
Palm
Date palm
Onion
Turnip
Cabbage
Lettuce
Carrot
Potato
Radish
Field bean
Sweet potato
Lima bean
Walnut
Plum
Grape pear
Orange
Grape fruit
Avocado
Lemon

12. Problem with poor quality water
Salinity
Soil permeability
Toxicity
Physiological effects
Nutritional effects
Soil microbes
Miscellaneous effects

13. Management of Saline Water for irrigation
 Application of organic manures
Application of gypsum to the irrigation water to increase the proportion of calcium.
Combined use of poor quality water with good quality water
Raising green manure crops and incorporation.
Scheduling irrigation with small quantity of water at more frequent intervals
.Optimum use of manures and fertilizers
Providing better drainage facilities
Adopting ridges and furrow and drip methods of irrigation.
Deep ploughing to break the impervious layer
Mulching with locally available plant materials
All soil management practices that improve the infiltration rate and maintain favourable soil structure reduce salinity hazard

14. Salinity tolerant crops
Degree of salt tolerance
Good
Turnips
Beet root
Date palm
Moderate
Lettuce
Tomato
Asparagus
Carrot
Spinach
Onion
Pepper
Clove
Fig
Grape
Olive
Poor
Peas
Celery
Cabbage
Egg plant
Sweet potato
Potato
Green beans
Plum
Pear
Apple
Orange

15. Sludge Sewage water Management
Besides salinity and alkalinity hazard of water, some industrial effluents and sewage water are also problem water that can be reused by proper treatment.
Sewage
Sewage is the mixture of both liquid and disintegrated solid waste without giving any treatment.
Effluent
Effluent is the filtered liquid portion of the sewage
Sludge
Sludge is the anaerobically decomposed organic matter present in sewage water. This is used as a source of organic manure.

16. Using sewage water for irrigation
    
The sewage water contains heavy metals like Ni, Cr, Cd, Si
The sewage water is rich in N (2 to 2.5 %) mostly in the form of NO3 and causes nitrate toxicity
T Sewage farm should be located in sloppy lands
·        Drainage should be provided to drain the excess effluent
·        Avenue trees, silk cotton, coconut can also be grown
·        Crops like elephant grass, bhendi, radish, brinjal, agathi can be grown since they do not accumulate heavy metals
·        Sewage farms are encouraged for social forestry
·        Irrigating effluent water mixed with good quality water is advantageous
·        Stagnation of water should be avoided. The field should be dried for few days at least once in a week

17. THANK YOU