MF2576 Subsurface Drip Irrigation _SDI_ Components Minimum by dfgh4bnmu


									                                       Subsurface drip irrigation (SDI)     1. Pump. SDI systems generally
                                    systems provide water and nutri-           have low pressure require-
                                    ents directly to the plant root zone       ments. Only one pump is
                                    through built-in emitters on               needed, as is the case for most
                                    polyethylene tubes that are buried         irrigation systems in Kansas.
                                    below the soil surface. Experience         The pressure requirement is in
                                    in Kansas has shown that properly          the range of most low-pressure
                                    designed and managed systems can           center pivot sprinkler systems.
                                    maintain or potentially improve            The size of the pump depends
                                    yields, while saving water, fertil-        on flow rate and total head
                                    izer, energy, and money. However,          requirements. The total head
                                    these systems also require careful         requirements include pumping
                                    management to function properly.           lift, friction/losses, elevation
                                    A good first step toward maintain-         changes, system pressure and,
                                    ing a profitable SDI system is             for SDI systems, the pressure
                                    proper selection of the system             loss across the filter and other
                                    components.                                structural components, such as
                                                                               control valves, flow meter,
                                    This publication:                          check valves, main, and
                                    1. Lists the basic components for          submain supply lines.
                                        a subsurface drip irrigation
                                        system.                              • Considerations. The size of the
                                    2. Explains the important factors          pump will depend on the water
                                        to consider in selecting com-          supply capacity, system
                                        ponents.                               pressure needs, zone size (area

Subsurface                             Figure 1 shows the basic compo-
                                                                               to be irrigated at one time),
                                                                               and the filter and flushline
                                    nents of a typical SDI system and a        flushing requirements.
Drip                                general organization of the compo-
                                    nents. These basic components are       2. Filter system. The filter
Irrigation (SDI)                    required for any system.                   system removes suspended
                                                                               particles from water to prevent
                                    Required System
Components:                         Components
                                                                               emitter clogging. A group of
                                                                               filters can be installed in
                                        An SDI system can function             parallel to increase total flow
Minimum                             without all of the listed compo-           rate. A series of filters can be
                                    nents, but it may be difficult to          used to improve filtration.
Requirements                        manage and maintain and may
                                    perform poorly. Eventually, the          • Options. Screens, discs, and
                                    system may fail due to the lack of         sand media filters are com-
Danny H. Rogers                     cues to the manager on the status of       monly used depending on
Extension Agricultural Engineer     performance or insufficient emitter        water quality. Centrifugal sand
                                    protection. Usually there are several      separators are used when water
Freddie R. Lamm
Research Irrigation Engineer
                                    versions of each component; these          carries sand load from deep
                                    are listed as options below. A             wells. Settling basins to
Mahbub Alam                         specific option may or may not be          remove sediment load for
Extension Agricultural Engineer     acceptable for your application            surface water supply system
                                    depending on the specific site and         may be required in addition to
                                    system conditions. The major               regular filter system. A combi-
                                    factors that should be considered          nation of devices may be used
                                    when selecting each component are          to remove suspended particles.
                                    listed under considerations. Make          Many of these systems have
Kansas State University             sure the characteristics of your site      automatic backflush capability.
Agricultural Experiment Station     and system are specifically ad-
and Cooperative Extension Service   dressed in your SDI system design.
Manhattan, Kansas
• Considerations. Water quality,         3. Pressure-sustaining valve.             particulates into the water
  emitter requirements (maxi-               Depending on the type of               supply and are installed
  mum allowable particle size),             filtration, the unit may be            between the water supply or
  and system flow rate are                  equipped with a pressure-              pump and the chemical
  important filtering factors.              sustaining valve to facilitate         injection line.
  Water quality relates to the              flushing (automatic or manual).
  amount, size, and type of                                                      • Options. A physical air gap
  particles (organic or mineral)         4. Pressure gauges. The filter(s)         between waterline and
  to be removed. For example,               should have pressure gauges at         fertigation tank, an atmo-
  surface water typically has               the inlet and outlet points to         spheric vacuum breaker, a
  much higher organic matter                show pressure differential for         pressure vacuum breaker, or a
  content than groundwater,                 initiating flushing of the             double-check valve are options
  which affects the type of filter          filtration unit, either manually       to prevent backflow.
  that can be used. Filtration              or automatically. Follow the
  requirement is determined by              manufacturer’s recommenda-           • Considerations. The type of
  the emitter size or opening.              tion on the pressure differential      fluid that can backflow (toxic
  That information is provided              value at which flushing should         or nontoxic), and whether
  by the manufacturer and must              be initiated. It also is recom-        there can be back pressure or
  be followed to help ensure                mended to have pressure                back siphonage are important
  system longevity. In general,             gauges at the beginning of the         considerations. State and local
  filtration is provided to prevent         main delivery system and at            regulations and codes must be
  passing of particles 1⁄10 the size        the distal end of the system           followed.
  of the smallest passageway.               fitted on flushline. The flow
  Primary filters are grouped as            rate from the meter and the         6. Regulation valve. These
  screen, disc, or media filters.           pressure reading of the system         valves are used to help main-
  K-State Research and Exten-               provide cues to the operator           tain the proper pressure in
  sion publication, MF-2361,                about emitter performance and          irrigation lines.
  Filtration and Maintenance                clogging.
  Considerations for Subsurface                                                  • Considerations. The
  Drip Irrigation (SDI) Systems,         5. Backflow preventer. These              manufacturer’s emitter rating
  discusses filtration needs in             devices prevent the backflow           and the pipeline pressure
  more detail.                              of fertilizers, chemicals, or          losses during the delivery of

     Figure 1. Schematic of Subsurface Drip Irrigation (SDI) System. (Components are not to scale.)

                                                           Flowmeter Backflow Pump
                                                                      Device Station
                Main Line                        Injection

                                                                                      Air & Vacuum
                                                                                      Release Valve
         Dripline                       Zones
                                       1 and 2                                        Pressure Gauge
                                                                                      Flush Valve

                                                                                      Zone Valve
    the water to the dripline               chemical supply tank in case            water from the system head-
    connection point are important          of injector failure. This valve         works control to manifolds
    considerations. Emitters are            is often an integral part of an         connecting dripline laterals.
    typically rated by manufactur-          injector unit and can handle
    ers to provide a specific flow          both backpressure and                • Considerations. System
    rate if operated at a given             backsiphonage.                         pressure, required flow rates,
    pressure. The regulation valve                                                 water hammer, and pipe cost
    must be sized to provide this        • Considerations. State and local         are the consideration factors
    pressure while accounting for          codes must be followed.                 for consideration.
    pressure losses that occur
    between the valve and the           10. Zone valve. These valves are        14. Flushlines. The flushlines at
    emitter.                                opened or closed to control the         the tail end of the system serve
                                            flow to appropriate zones.              three purposes:
7. Chemical injector. A chemical            They can be automatically               1) Allow any sediment and
   injector precisely injects               controlled using an electronic          contaminants to be flushed
   fertilizers or pesticides into the       control system. In production           from dripline laterals at a
   irrigation stream.                       agriculture, these zone valves          centralized location,
                                            are often manually operated             2) Equalization of pressure in
 • Options. There are two types             where the zone size is appre-           the dripline laterals, and
   of chemical injection units:             ciably large.                           3) Allow positive pressure on
   1) Constant rate (positive                                                       both sides of a dripline break
   displacement): diaphragm,            11. Pressure regulator. Pressure            to prevent soil ingestion into
   piston, or gear pumps and                regulators are typically located        the dripline.
   2) Variable rate: venturi                on the manifold to help
   pressure differential injectors          regulate operating pressure for     15. Header manifold. The header
   or bladder tanks.                        emitters.                               manifold delivers water from the
                                                                                    submain to the laterals and links
 • Considerations. The types of          • Considerations. Manufacturer             a number of driplines together
   chemicals used, rate of injec-          emitter rating and line pressure         into one controllable unit. In
   tion, method of injection, and          losses are the major consider-           most agricultural fields, the
   the precision required are              ations. Emitters are typically           submain serves this function.
   determining factors in selec-           rated by manufacturers to
   tion of the best type of injector.      provide a specific flow rate if      16. Dripline. The dripline is the
   The required number of                  operated at a given pressure.            polyethylene tubing that
   injection systems and their             The pressure regulator must be           includes a built-in emitter.
   injection point location depend         sized to provide this pressure           Emitter spacing and rate are
   on the clogging hazard and/or           while accounting for pressure            selected to match crop de-
   the material being injected.            losses that occur between the            mands and soil water-holding
                                           regulator and the emitters.              capacity. They must be com-
8. Flowmeter. The flowmeter                                                         patible with the pumping
   measures the volume of water         12. Air and vacuum release                  pressure and flow capacity.
   moving through the system,               valves. These valves prevent            Driplines are available in a
   either as a flowrate or as an            soil or particulate material from       variety of wall thicknesses,
   accumulated total volume                 being sucked back into emitters         diameters, emitter spacings,
   basis. The flowmeter provides            when the irrigation system is           and flow rates. Most SDI
   the operator with information            turned off or when driplines are        systems in Kansas use
   on how the system is perform-            drained. They cannot handle             driplines with 8 (0.250 mm) to
   ing and how to schedule the              backpressure, only back-                15 (0.375 mm) MIL wall
   water application.                       siphonage. All high elevation           thickness. SDI systems for row
                                            points of system should have            crops tend to use large diam-
9. Chemigation line check                   air or vacuum relief.                   eter (7/8 inch or greater diam-
   valve. This valve, installed                                                     eter), thin-walled and low-flow
   between the injector and the         13. Main line, submain. The main            driplines, which are sometimes
   water source, prevents                   line and submains are the               referred to as driptapes. Larger
   backflow of water into the               delivery pipelines that supply          diameter and lower flows
    allow longer length of runs and                           dripline connection or may                          to minimize initial investment
    larger zone size that are                                 receive a supply tube that is                       costs whenever possible is a
    appropriate for the typical field                         attached to the dripline. The                       practical goal. However, cost
    sizes in Kansas. Pressure-                                dripline connector options are                      reductions should be attempted
    compensating driplines are                                wired, clamped, or interference                     only if system design and operat-
    available, but are generally not                          (compression) fit.                                  ing integrity are not compromised.
    used in Kansas due to higher                                                                                  Cost cutting that results in a poor
    cost. Water quality also may be                     Optional Automatic                                        design or a difficult to manage
    a consideration in the choice of                    System Control                                            system may increase operating
    emitter size and spacing to                            Automatic control may be                               costs, decrease system perfor-
    avoid clogging. K-State                             useful for precise delivery of water                      mance and increase the chance of
    Research and Extension                              and nutrients according to design                         system failure.
    publication, MF-2578, Design                        or crop need. This also reduces the
    Considerations for SDI                              need for manual control.                                  Additional Resources
    Systems, discuss these consid-                                                                                   MF-2361 Filtration and Mainte-
    erations in more detail.                               Automatic controls. Pumps,                             nance Considerations for Subsur-
                                                        valves, and injectors can be turned                       face Drip Irrigation (SDI) Systems
 • Considerations. Tubing wall                          on and off or opened and closed to                           MF-2242 Economic Compari-
   thickness, emitter spacing,                          allow automatic timing and                                son of SDI and Center Pivots for
   discharge rate, soil texture, and                    sequencing of irrigation zones.                           Various Field Sizes
   soil water holding capacity are                      These may be linked to automatic                             MF-836 Irrigation Capital
   considerations because these                         timers, soil water sensors, or                            Requirements and Energy Cost
   affect plant root zone water                         weather-based models to determine                            MF-2578 Design Considerations
   content and distribution.                            when irrigation system should run.                        for Subsurface Drip Irrigation
                                                        Computer control and monitoring                              MF-2590 Management Consid-
18. Connectors. Connectors are                          is an option, but not required for                        eration for Operating a Subsurface
    needed to attach the dripline to                    automation.                                               Drip Irrigation System
    the manifold or submain. The                                                                                     MF-2575 Water Quality Assess-
    number and type depend on                           Summary                                                   ment Guidelines for Subsurface
    system layout. There are many                          SDI systems have higher initial                        Drip Irrigation
    types of connectors. Connector                      investment costs compared to
    options include glued, grom-                        traditional types of irrigation                             K-State Research and Extension
    met, barb, and compression.                         systems used in Kansas, so efforts                        SDI Web site
    These can have a direct                                                                               

Acknowledgment: This material is based upon work supported by the U.S. Department of Agriculture Cooperative State Research Service
under Agreement No. 00-34296-9154. Any opinions, findings, conclusions or recommendations expressed in this publication are those of
the authors and do no necessarily reflect the views of the U.S. Department of Agriculture.

             Brand names appearing in this publication are for product identification purposes only. No endorsement is intended,
                                        nor is criticism implied of similar products not mentioned.
                 Publications from Kansas State University are available on the World Wide Web at:
                  Contents of this publication may be freely reproduced for educational purposes. All other rights reserved.
             In each case credit Danny H. Rogers et al., Subsurface Drip Irrigation (SDI) Components: Minimum Requirements,
                                                    Kansas State University, July 2003.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service
MF-2576                                                                                                                                                   July 2003
It is the policy of Kansas State University Agricultural Experiment Station and Cooperative Extension Service that all persons shall have equal opportunity and
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