Micro-Irrigation for Home Landscape Plantings

Allen D. Owings  |  7/7/2008 8:51:54 AM

Micro-irrigation is a watering technique that delivers water in relatively small amounts slowly to individual or groups of plants. Such systems using polyethylene pipe, “spaghetti” tubing and emitters or porous materials provide water precisely to plant root zones and maintain ideal moisture conditions for plant growth.

In micro-irrigation, drip and low-volume spray emitters can reduce landscape water use for irrigating trees, shrubs and ground covers by up to 50 percent over traditional overhead sprinkler systems. The use of such systems also promotes water use efficiency because losses from evaporation and runoff are essentially eliminated.

By properly installing a micro-irrigation system and managing it correctly, micro-irrigation will provide ideal day-to-day water conditions for our plants, and that avoids overwatering.

Micro-irrigation has been applied on an ever-increasing basis in agriculture for a number of years, but it's only now finding its way to the home landscape. Component costs have dropped in the past few years, and some manufacturers provide design instructions and preassembled “kits” for do-it-yourselfers.

Benefits of Micro-Irrigation

  • Water volume savings of 50 percent or greater.
  • Improved plant growth, performance and appearance.
  • Ideal soil moisture conditions are maintained in root zone area.
  • Minimum foliar disease (leaf spot, etc.) problems.
  • Less concern over water-use restrictions.
  • Fewer weed problems because water is not being applied outside plant root zones where many weeds occur.
  • No runoff; less evaporation.
  • Specific emitter types, numbers and discharge rates can be tailored to individual plant needs.
  • Irrigation control is precise so people won’t be irrigated and buildings won’t be stained.
  • Systems can be expanded and modified without significant redesign.

Precautions with Micro-Irrigation

  • Systems require regular checks for clogging, leaks, etc.
  • Not effective for traditional turf areas.
  • Small orifice sizes can contribute to clogging because of algae, bacteria or dirt particles. Use of filters, anti-algae material and periodic flushing will help control these problems.
  • Use of pressure regulating component (or emitters that are pressure-compensating) will enhance uniformity of water discharge throughout the system.
  • Burying system components (except for emitters) will reduce chances of theft, vandalism or damage by rodents.
  • Control of the irrigated area around the plant is critical. Enough emitters must be designed per plant to cover the root zone area.
  • Like any emerging technology, some material can be of inferior quality. Check the reliability and reputation of the manufacturer and the warranty on materials and components.
  • Added costs?

Steps in Planning/Installing a Micro-Irrigation System

  • Gather all available information and make a plan. Your sketch should take into account the size of the area to be irrigated, number of emitters, water source and pressure, and obstructions.
  • Mark and classify plants according to canopy size.
  • Select emitters. Type will depend on type of plant(s), plant distribution, size, etc.
  • Determine spacing of lateral tubes and individual emitters and emitter flow rates.
  • Determine gallons per minute required for total system and compare to water available. You should be able to determine the latter through your utility company if you're on public water.
  • Lay out the main and sub-main pipes and emitter tubing. Determine pressure losses through system. Follow guidelines in planning and installation guide or manuals and/or consult with your equipment supplier.
  • Size main and sub-main pipes, making sure you have enough pressure to operate the last emitter in any zone.
  • Select an adequate filter assembly for the designed system. Can include master valve, backflow prevention devices, pressure regulator or control valve, pressure gauges on each side of the filter, fertilizer injector, valve manifold, pipe and fittings.
  • Complete the materials list. Major components are materials needed to tie into water source, the filter assembly, main line and sub-main pipe and fittings, emitters and tubing. Order some extra components.

Important Factors for Successful Micro-Irrigation System Installation

Installation consists of installing the filter assembly first (test it), mainline pipes and sub-mains (test and flush). Then connect emitters and tubing and flush again. Once installed, the system should be operated to replace moisture lost by the plant and not replenished naturally. Length and frequency of watering will depend on the plant, weather conditions, number, type and size of emitters, etc.

  • Use elbows for tight bends to prevent tube kinking.
  • Provide three to five percent more length of spaghetti tubes than actually required for distance.
  • Do not inject into system materials that will cause deterioration.
  • Make all cuts square.
  • Keep dirt out of emission lines by taping over ends until lines are installed.
  • Flush all main, sub-main and lateral lines before installing emitters. Run water at low pressure through lines during emitter installation.
  • Check pressure to see that emitters at the ends of lines (where pressure loss is greatest) are working. Pressure regulators or pressure-compensating emitters can eliminate problems.
  • If an automatic controller is used, run it through a test cycle to ensure it is operating properly.
  • Spot check emitters for adequate flow rate, using a bucket.

Micro-Irrigation System Maintenance

  • Check laterals and filters weekly. Flush monthly. Clean emitters when necessary.
  • Keep weed growth away from emitters.
  • Check tubing for leaks and kinking.
  • Check flow meter for correct flow rate.
  • Check pressure regulator (if used) for correct setting downstream.
  • Check controller program for proper operation. Adjust where necessary for climatic variations.
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