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Irrigation water quality

C62291821dac0dd5b7ef3b72a30cd137?s=47 Micah Woods
March 08, 2017

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.

C62291821dac0dd5b7ef3b72a30cd137?s=128

Micah Woods

March 08, 2017
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  1. Irrigation water quality Micah Woods 8 March 2017 Chief Scientist

    | Asian Turfgrass Center www.asianturfgrass.com
  2. 1. Salinity and sodium hazard

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

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

    Daily soil water balance
  5. Salinity

  6. The salt in the water is salinity

  7. The salt in the water is salinity

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

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

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

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

  14. None
  15. Yesterday at field day

  16. Yesterday at field day

  17. Salinity is managed by adding more water than the grass

    can use or the soil can hold.
  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?
  19. Leaching requirement LR = ECw 5(ECe) − ECw

  20. Using the leaching requirement After we have the LR, then

    we calculate the quantity of water to apply as: irrigation = ETc 1 − LR
  21. Example calculation, step 1 LR = 2.3 5(10) − 2.3

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

    = 4.2
  23. My favorite reference guide about water http://anrcatalog.ucanr.edu/pdf/8009.pdf

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

    irrigation water test results
  25. Even seashore paspalum dies when salinity is uncontrolled

  26. Sodium hazard

  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.
  28. Flocculation and deflocculation of clay

  29. Chemical compaction

  30. Check sodium hazard by SAR Sodium adsorption ratio (SAR) SAR

    = Na √ (Ca + Mg)/2
  31. Solve a sodium problem by adding gypsum

  32. Increasing the Ca solves the sodium problem

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

  34. Additional information

  35. Additional information

  36. Things not to worry about • bicarbonate

  37. Not a problem

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

  39. Soil water content

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

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

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

    field capacity 2. The VWC at the wilting point 3. The VWC now
  43. Measure with a soil moisture meter

  44. Measure with a soil moisture meter

  45. Daily soil water balance

  46. Bangkok, daily soil water balance

  47. Bangkok, daily soil water balance

  48. Phuket, daily soil water balance

  49. Chiang Mai, daily soil water balance