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Microirrigation

Microirrigation. Microirrigation. Delivery of water at low flow rates through various types of water applicators by a distribution system located on the soil surface, beneath the surface, or suspended above the ground

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Microirrigation

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  1. Microirrigation

  2. Microirrigation • Delivery of water at low flow rates through various types of water applicators by a distribution system located on the soil surface, beneath the surface, or suspended above the ground • Water is applied as drops, tiny streams, or spray, through emitters, sprayers, or porous tubing

  3. Water Application Characteristics • Low rates • Over long periods of time • At frequent intervals • Near or directly into the root zone • At low pressure • Usually maintain relatively high water content • Used on higher value agricultural/horticultural crops and in landscapes and nurseries

  4. Schematic of a Typical Microirrigation System

  5. Advantages • High application efficiency • High yield/quality • Decreased energy requirements • Reduced salinity hazard • Adaptable for chemigation • Reduced weed growth and disease problems • Can be highly automated

  6. Disadvantages • High initial cost • Maintenance requirements (emitter clogging, etc.) • Restricted plant root development • Salt accumulation near plants (along the edges of the wetted zone) 

  7. Salt Movement Under Irrigation with Saline Water Subsurface Drip Sprinkler/Flood Salt accumulation leached downward by successive water applications Salt accumulation leached radially outward from drip tubing

  8. Types of Systems • Surface trickle (drip) • Water applied through small emitter openings to the soil surface (normally less than 3 gal/hr per emitter) • Most prevalent type of microirrigation • Can inspect, check wetting patterns, and measure emitter discharges

  9. Point Source Emitters in a New Orchard

  10. Types of Systems Contd… • Spray • Water applied (spray, jet, fog, mist) to the soil surface at low pressure (normally less than about 1 gal/min per spray applicator) • Aerial distribution of water as opposed to soil distribution • Reduced filtration and maintenance requirements because of higher flow rate

  11. Types of Systems Contd… • Bubbler • Water applied as a small stream to flood the soil surface in localized areas (normally less than about 1 gal/min per discharge point) • Application rate usually greater than the soil's infiltration rate (because of small wetted diameter) • Minimal filtration and maintenance requirements

  12. Types of Systems Contd… • Subsurface trickle • Water applied through small emitter openings below the soil surface • Basically a surface system that's been buried (few inches to a couple feet) • Permanent installation that is "out of the way"

  13. Typical Subsurface Drip Tubing Installation for Row Crops 30 in Non Wheel- Track Row 12 – 14 in Drip Tubing Wetting Pattern 60 in 60-inch dripline spacing is satisfactory on silt loam & clay loam soils

  14. System Components • Pump •  Control head • Filters • Chemical injection equipment (tanks, injectors, backflow prevention, etc.) • Flow measurement devices • Valves • Controllers • Pressure regulators

  15. System Components, Contd… • Mainlines and Submains (manifolds) • Often buried and nearly always plastic (PVC) • Laterals • Plastic (PE) • Supply water to emitters (sometimes "emitters" are part of the lateral itself)

  16. Applicator Hydraulics • General • Need pressure in pipelines to distribute water through the system, but the applicator needs to dissipate that pressure • qe = emitter discharge • K = emitter discharge coefficient • H = pressure head at the emitter • X = emitter discharge exponent (varies with emitter type)

  17. Characteristics of Various Types of Emitters

  18. Emitter Type Coefficient, K - Exponent, X Emitter Discharge, gpm Operating Pressure 8 psi 12 psi 16 psi Porous Pipe - 0.112 1.00 2.07 3.1 4.14 Tortuous Path 0.112 0.65 0.75 0.97 1.17 Vortex/Orifice 0.112 0.42 0.38 0.45 0.51 Compensating 0.112 0.20 0.20 0.22 0.23 Emitter Hydraulics

  19. Estimating Emitter Exponent & Coefficient Requires discharges qe1, qe2 at two pressures h1, h2 • Emitter Exponent • Emitter Coefficient or

  20. Applicator Hydraulics Contd… • Emitters (Point Source) • Long-path • Orifice • Vortex • Pressure compensating (x < 0.5) • Flushing • Line-source tubing • Porous-wall tubing (pores of capillary size that ooze water) • Single-chamber tubing (orifices in the tubing or pre-inserted emitters) • Double-chamber tubing (main and auxiliary passages)

  21. Sprayers • Foggers, spitters, misters, etc • Relatively uniform application over the wetted area • Lateral hydraulics • Very much like sprinkler hydraulics, but on a smaller scale • Since there is usually a large number of emitters, multiple outlet factor (F)  0.35

  22. Other Design and Management Issues • Clogging • Physical (mineral particles) • Chemical (precipitation) • Biological (slimes, algae, etc.) • Filtration • Settling basins • Sand separators (centrifugal or cyclone separators) • Media (sand) filters • Screen filters

  23. There are many different types of filtration systems. The type is dictated by the water source and also by emitter size.

  24. Filtration Requirements for Drip Emitters Filter openings should be 1/7th – 1/10th the size of the emitter orifice 0.020-inch orifice

  25. Plugging Potential of Irrigation Water for Microirrigation

  26. Chemical treatment • Acid: prevent calcium precipitation • Chlorine • control biological activity: algae and bacterial slime • deliberately precipitate iron •  Flushing • after installation or repairs, and as part of routine maintenance • valves or other openings at the end of all pipes, including laterals • Application uniformity • manufacturing variation • pressure variations in the mainlines and laterals • pressure-discharge relationships of the applicators

  27. Subsurface Drip Irrigation Advantages • High water application efficiency • Uniform water application • Lower pressure & power requirements • Adaptable to any field shape • No dry corners (vs. center pivot) • Adaptable to automation

  28. Subsurface Drip Irrigation Disadvantages • High initial cost • Water filtration required • Complex maintenance requirements • Flushing, Chlorination, Acid injection • Susceptible to gopher damage • Salt leaching limitations

  29. Subsurface Drip-Center Pivot Comparison(¼-Section Field; ET = 0.25 in/day)

  30. Gopher Damage on Subsurface Drip Tubing

  31. Schematic of Subsurface Drip Irrigation (SDI) System Filtration System Backflow Prevention Device Flowmeter Pump Station Chemical Injection System Submain X X X X Air & Vacuum Release Valve Zones 1 and 2 Dripline Laterals Pressure Gage Flush Valve x X Zone Valve X X Flushline Diagram courtesy of Kansas State University

  32. Netafim Typhoon® Drip Irrigation Tubing (Clear Demo Tubing) 16-mm diameter, seamless, 13-mil thick extruded PE tubing Emitter outlet Turbulent flow PVC emitter welded inside tubing

  33. Netafim Typhoon® Drip Irrigation Tubing Flap over emitter outlet: - prevents root intrusion - prevents blockage by mineral scale

  34. Typical Drip Tubing Installation for Row Crops 30 in Non Wheel- Track Row 12 – 14 in Drip Tubing Wetting Pattern 60 in 60-inch dripline spacing is satisfactory on silt loam & clay loam soils

  35. Wetting Pattern of a Subsurface Drip Lateral Photo Courtesy of Kansas State University

  36. Wider dripline spacings may not work. Photo Courtesy of Kansas State University

  37. SDI System Maintenance • Lateral flushing schedule (sediment) • Chlorine injection schedule (biological growths) • Acid injection schedule (chemical precipitates & scaling)

  38. Salt Movement Under Irrigation with Saline Water Subsurface Drip Sprinkler/Flood Salt accumulation leached downward by successive water applications Salt accumulation leached radially outward from drip tubing

  39. Small research plots during supply line installation

  40. Plowing in drip tubing

  41. Trenching across the drip tubing ends for PVC manifold installation

  42. Drip tubing end after being sheared by the trencher

  43. Components for Drip Lateral-Submain Connection Stainless Steel Wire Twist Tie 21/32” Hole in Submain Neoprene Grommet 5/8” Polyethylene Supply Tube (Usually 2-3 ft long) Polyethylene Barb Adapter 5/8” Drip Irrigation Tubing

  44. Typical Drip Tubing Connection to Submain (1 ½ -inch Submains and Larger) Supply Submain or Flushing Manifold Stainless Steel Wire Twist Tie Neoprene Grommet Inserted in 21/32” hole in manifold 5/8” Polyethylene Supply Tubing 5/8” Drip Irrigation Tubing Polyethylene Barb Adapter Inserted in Grommet Identical connection on distal end for flushing manifold connection

  45. Flush Risers on Distal End of Research Plots Air Vent to Release Trapped Air from Laterals Ball Valve for Manual Flushing of Drip Laterals

  46. SDI Water Application Rates(inches/hour)(60-inch tubing spacing) Emitter Spacing Emitter Discharge

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