Microirrigation Management in Grapes Mike Kizer, Extension Irrigation Specialist

1. Microirrigation Management in Grapes Mike Kizer, Extension Irrigation Specialist

2. Grape Microirrigation Management Issues • Water Supply Quality Issues • Chlorination • Acid Injection • Filtration • Irrigation Scheduling • Regulated Deficit Irrigation

3. Microrrigation Water Quality Issues • Biological Growth Control • Chlorination • Mineral Precipitate Control • Acidization • Particulate Control • Filtration

4. Chlorination Chlorine is a strong oxidizing agent that prevents water contaminants from fouling microirrigation systems. • Dissolved minerals (iron, manganese, etc.) • Biological growths (bacterial slime, algae)

5. Chlorination Modes • Continuous • Intermittent • Superchlorination

6. Continuous Chlorination Used when water treatment is the goal (iron or manganese precipitation) • Concentration: 1 – 5 ppm • Injection Time: Continuous

7. Iron & Manganese Precipitation • Chlorine injection must occur before the filter • Mn precipitates much slower than Fe • (Mn treatment may require chlorinating the well) • Inject 1 ppm free Cl for each 0.7 ppm Fe • Fe and Mn are more soluble at lower pH

8. Intermittent Chlorination Used to prevent or kill biological growths (algae or bacterial slime) • Concentration: 10-20 ppm • Injection Time: 30-60 minutes • Frequency: Depends on severity of the problem

9. Superchlorination Used to dissolve organic buildup blocking emitters (algae or bacterial slime) • Concentration: 300-500 ppm • Injection Time: Until all lines are filled; Shut system down; Leave standing 24 hours; Flush system • Frequency: As needed for remediation

10. Chlorination and pH The water pH determines if free Cl2 becomes hypochlorite (OCl-), or hychlorous acid (HOCl) which kills organisms 40-80 times more effectively.

11. Chlorine Sources • Calcium hypochlorite: Ca(OCl)2 • granular “swimming pool” chlorine bleach • 45-70% Cl2 • Sodium hypochlorite: NaOCl • liquid household bleach • 5.25% Cl2

12. Chlorine Injection Rate IR = Q x C 167 x S where: IR = chlorine injection rate, gph Q = irrigation flow rate, gpm C = chlorine concentration required, ppm S = strength of chlorine source, %

13. Example An irrigator wants to inject 20 ppm free chlorine into his 50 gpm irrigation system using household bleach (5.25% Cl2) as the chlorine source.What is the required injection rate? IR = Q x C = 50 gpm x 20 ppm = 1.14 gph 167 x S 167 x 5.25%

14. Venturi Chemical Injector throttling valve Bypass venturi injection device for injection of liquid chlorine, liquid fertilizer or acid. Cutaway of a venturi injector cross-section. chemical suction port

15. Hydraulic Powered Chemical Injector drive water exhaust port drive water inlet & filter chemical solution injection port chemical solution intake

16. Chemical Injection Pump positive displacement piston pump

17. Acid Injection • Acid injection can prevent precipitation of dissolved minerals in water • Acid injection can dissolve mineral scale clogging emitter orifices • Injection rate varies (titrate to determine) • pH goal • Concentration of acid • Buffering capacity of the water

18. Acid Injection Options • N-Phuric acid (liquid urea-sulphuric acid mix) • Provides nitrogen fertility and sulphur • 10-0-0-18S, 15-0-0-16S & 28-0-0-9S formulations • Phosphoric acid (H3PO4) • Provides phosphorous fertility • Muriatic (Hydrochloric) acid (HCl)

19. Acid Injection Cautions • Hazardous solutions – Corrosive & Toxic • Hazardous vapors – Ventilate properly • Eye-wash/Shower requirements by OSHA • Corrosive to metals (even 316 SS in some cases) • Use only PVC, PE or Polypropylene fittings (No Nylon fittings)

20. Filtration Filtration removes solid contaminants (suspended solids, precipitates, organic particles) from the water supply • Filtration should be the last treatment process before the water goes to the irrigation system (after acidization, chlorination and fertilizer injection) • Match filter system to the irrigation system size and the water contaminant load

21. Sand Media Filter For water with heavy load of organic (algae) or inorganic ( silt, clay) contaminants. To back-wash properly, the upward flow of water must be high enough to “float” the top portion of the filter sand.

22. Sand Media Filter Sizing

23. Sand Filter Maximum Flow Rate(gpm per tank)

24. Sand Media Types and Sizes

25. Minimum Backwash Flow Rate(gpm per sand media tank)

26. Backwashing Using two or more small filter units allows the use of filtered water from one or more units to backwash other filter units individually.

27. Grooved Disc Filters For moderately dirty water. A series of grooved, plastic discs held together by spring pressure removes particles. Spring pressure on the discs can be relieved for back-washing.

28. Disk filter bank with two 2-inch filter units

29. Screen Filters For water with light load of suspended solids, a plastic or metal screen removes particles.

30. Grape Water Requirements • Weather • Sunshine, Temperature, Wind, Humidity) • Stage of Growth • Management Aims • Regulated Deficit Irrigation (RDI) • Control Vine Growth • Improve Cold Hardiness • Improve Fruit (Wine) Quality • (Arizona researchers recommend “some degree of water stress after the onset color change”)

31. http://agweather.mesonet.org

33. Regulated Deficit Irrigation • Allow root zone moisture to be depleted to some degree • Maintain deficit by irrigating to only partially replenish • Australian RDI Examples

34. Regulated Deficit

35. Regulated Deficit

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