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
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
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