Drip, drip, drip
1 May, 2008 By: Jeffrey Knight Landscape ManagementWhen it comes to low-volume, drip or micro-irrigation, there is much deliberation surrounding the proper terminology. For many distributors, manufacturers, contractors and landscape architects, the debate continues.
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Contractors frequently identify "drip" as the term most often used in their day-to-day activities. No matter the terminology, the general consensus in the Green Industry is that drip irrigation offers many benefits — when properly installed in the appropriate applications.
Materials selection
Unlike traditional sprays and rotors, with flow rates measured using gallons per minute (gpm), drip irrigation is measured in gallons per hour (gph) and distributes water slowly over a longer period of time.
There are many drip irrigation product manufacturers to choose from, but there are essentially three basic forms of drip irrigation used in a variety of landscape and agronomic applications:
1. Microsprays, also known as microsprinklers, are similar to traditional sprays but have a much lower precipitation rate. These devices have an adjustable throw, but can be susceptible to wind and evaporation. Microsprays are often used in orchards, greenhouses, open fields, nurseries and landscape beds.
2. Point-source drip irrigation features single emitters that are attached to polyethylene tubing. The emitters can be placed at random intervals near individual plants to apply water directly to the plants' roots. Point-source drip irrigation is frequently used for sparse plantings, nurseries, vineyards and residential and commercial landscapes.
3. Line-source drip irrigation is similar to point-source drip irrigation, but the pressure-compensating emitters are built-in and pre-spaced. Easy to install, line-source drip irrigation wets an entire area indiscriminately and relies on the soil to distribute water to plants' roots. It is optimal for use with dense plantings.
No matter what drip irrigation materials you select for your project, be sure to incorporate proper filtration, pressure regulation, an air vacuum relief (or emitters with built-in check valves) and flush valves at the ends of the lines to rid your system of dirt and debris.
 Microsprinklers are designed for use in landscape beds. |
Typical applications
Drip irrigation is often considered for areas where water is scarce. On average, a typical irrigation system comprising sprays or rotors is only 50% to 70% efficient, whereas drip is 90% to 95% efficient. This means that the water applied is used more effectively. Drip irrigation can play an important role in reducing water waste and is most effective when combined with other water-saving technologies.
Many residential irrigation contractors choose to install spray or rotary heads in turf areas, and use drip line in adjacent landscape beds. Drip irrigation is an ideal solution for these sparse plantings because water can be applied precisely to the roots of a specific plant, providing a more efficient irrigation while reducing the growth of unwanted weeds in landscape beds. There are many U.S. cities that have ordinances preventing the installation of spray or rotary heads in turf areas six feet wide or less; in these cases, installers would use drip irrigation.
Drip irrigation is also optimal for shrubs, hanging baskets, row crops and orchards. It can be used successfully with most plant material, prompting some manufacturers to recommend the product for larger turf applications.
Despite the benefits of using drip line on landscape beds, many contractors still choose to install spray heads. Even if a contractor installs these heads on risers, the spray pattern will become distorted over time as plant foliage continues to grow and mature. Additionally, risers can become a tripping hazard when stationed in landscape beds near sidewalks or parking lots. They're also prone to vandalism.
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