Irrigation water quality

I used these slides for a presentation about irrigation water quality at the Sustainable Turfgrass Management in Asia 2017 conference. I then showed various calculations of the daily soil water balance.

Transcript

1. Irrigation water quality
   Micah Woods
   8 March 2017
   Chief Scientist | Asian Turfgrass Center
   www.asianturfgrass.com
   

   View Slide

2. 1. Salinity and sodium hazard
   

   View Slide

3. 1. Salinity and sodium hazard
   2. Soil moisture content
   

   View Slide

4. 1. Salinity and sodium hazard
   2. Soil moisture content
   3. Daily soil water balance
   

   View Slide

5. Salinity
   

   View Slide

6. The salt in the water is salinity
   

   View Slide

7. The salt in the water is salinity
   

   View Slide

8. As salinity increases, water uptake (growth) decreases
   

   View Slide

9. As salinity increases, water uptake (growth) decreases
   

   View Slide

10. The salt in the water is the most important
    water quality parameter.
    

    View Slide

11. Salinity is measured in two ways
    Total dissolved solids
    By evaporating the water, and measuring what remains, one
    gets total dissolved solids (TDS), reported as mg/L, or ppm.
    

    View Slide

12. Salinity is measured in two ways
    Electrical conductivity
    When there is more salt in the water, it can conduct more
    electricity. The electrical conductivity (ECw
    ) is in units of dS/m.
    

    View Slide

13. Converting from TDS to ECw
    1 dS/m ≈ 640 ppm
    

    View Slide

14. View Slide

15. Yesterday at field day
    

    View Slide

16. Yesterday at field day
    

    View Slide

17. Salinity is managed by adding more water than
    the grass can use or the soil can hold.
    

    View Slide

18. This is called a leaching fraction
    2 step process
    First, calculate the leaching requirement (LR). Second,
    calculate the quantity of water to apply.
    Let's imagine we have a water with a TDS of 1,500 ppm. And we
    expect the grass to use (ETc
    ) 4 mm. How much water is
    required for irrigation?
    

    View Slide

19. Leaching requirement
    LR =
    ECw
    5(ECe) − ECw
    

    View Slide

20. Using the leaching requirement
    After we have the LR, then we calculate the quantity of water
    to apply as:
    irrigation =
    ETc
    1 − LR
    

    View Slide

21. Example calculation, step 1
    LR =
    2.3
    5(10) − 2.3 = 0.05
    

    View Slide

22. Example calculation, step 2
    irrigation =
    4
    1 − 0.05 = 4.2
    

    View Slide

23. My favorite reference guide about water
    http://anrcatalog.ucanr.edu/pdf/8009.pdf
    

    View Slide

24. My favorite reference guide about water
    From Harivandi's Interpreting turfgrass irrigation water test results
    

    View Slide

25. Even seashore paspalum dies when salinity is uncontrolled
    

    View Slide

26. Sodium hazard
    

    View Slide

27. If there is too much sodium in the irrigation
    water, the sodium causes deflocculation of the
    soil clay particles. This is not a problem on
    sand rootzones.
    

    View Slide

28. Flocculation and deflocculation of clay
    

    View Slide

29. Chemical compaction
    

    View Slide

30. Check sodium hazard by SAR
    Sodium adsorption ratio (SAR)
    SAR =
    Na
    √
    (Ca + Mg)/2
    

    View Slide

31. Solve a sodium problem by adding gypsum
    

    View Slide

32. Increasing the Ca solves the sodium problem
    

    View Slide

33. From Harivandi's Interpreting turfgrass irrigation water test results
    

    View Slide

34. Additional information
    

    View Slide

35. Additional information
    

    View Slide

36. Things not to worry about
    • bicarbonate
    

    View Slide

37. Not a problem
    

    View Slide

38. Things not to worry about
    • bicarbonate
    • water pH
    

    View Slide

39. Soil water content
    

    View Slide

40. Know three numbers
    1. The volumetric water content (VWC) at field capacity
    

    View Slide

41. Know three numbers
    1. The volumetric water content (VWC) at field capacity
    2. The VWC at the wilting point
    

    View Slide

42. Know three numbers
    1. The volumetric water content (VWC) at field capacity
    2. The VWC at the wilting point
    3. The VWC now
    

    View Slide

43. Measure with a soil moisture meter
    

    View Slide

44. Measure with a soil moisture meter
    

    View Slide

45. Daily soil water balance
    

    View Slide

46. Bangkok, daily soil water balance
    

    View Slide

47. Bangkok, daily soil water balance
    

    View Slide

48. Phuket, daily soil water balance
    

    View Slide

49. Chiang Mai, daily soil water balance
    

    View Slide