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About Drip Irrigation
Drip irrigation is an efficient and economical method of watering. Used commonly
in dry regions with scarce water resources, the use of drip irrigation is increasing
in the Northeast. This irrigation method is typically more than 90% efficient
at allowing plants to use the water applied. Unlike other forms of irrigation,
such as sprinklers that are only 65-75% efficient, drip irrigation reduces
runoff and evaporation. Drip irrigation applies the water slowly at the plant
root zone where it is needed.
Drip irrigation has more commonly been used in commercial nursery and agricultural
operations, however, homeowners are beginning to take advantage of its uses and
benefits. As a homeowner, you can use drip irrigation in your vegetable and perennial
gardens, and to water trees and shrubs. You can see examples of drip irrigation
at the URI Cooperative Extension Master Gardener Demonstration Vegetable Gardens
located at the URI Learning Landscape and at URI East Farm.
The
above graphic and information contained in this factsheet
is partially adapted from Drip Irrigation Design Guidelines.
Jess Stryker. http://www.irrigationtutorials.com/dripguide.htm |
Drip Irrigation Benefits
Drip irrigation involves placing tubing with emitters on the ground along side
the plants. The emitters slowly drip water into the soil at the root zone.
Because moisture levels are kept at an optimal range, plant productivity
and quality improve. In addition, drip irrigation:
• Prevents disease by minimizing water contact with the leaves, stems,
and fruit of plants.
• Allows the rows between plants to remain dry, improving access and reducing
weed growth.
• Saves time, money, and water because the system is so efficient.
• Decreases labor.
• Increases effectiveness on uneven ground.
• Reduces leaching of water and nutrients below the root zone.
Drip Irrigation System Design and Components
The main components of a drip irrigation system include the mainline, valve,
sub-main, backflow preventer, pressure regulator, filter, tubing adapters
and fittings, drip tubing, emitters, and end caps. The mainline is the pipe
that runs from the water source – typically your outdoor faucet - to
the valve; and the sub-main runs from the valve to the point where the drip
tubing is connected. Generally, sub-mains are used only when there are multiple
lines of drip tubing and zones feeding off of the same mainline water source.
The combined length of the mainline and sub-main should not exceed 400 feet.
The valve controls water flow into the system and can be set for either automatic
or manual control. Backflow preventers are necessary to ensure that irrigation
water does not flow back into the pipes and contaminate your main water source.
Pressure regulators are only necessary if your water pressure is over 40
pounds per square inch. If you do not know your water pressure it is a good
idea to install one just in case.
Filters keep dissolved substances in your water from clogging the emitters
over time. Install filters either at the emitters or at the water source to
protect both the valve and pressure regulator in addition to the emitters.
It is best if the filter has at least a 150 mesh screen or higher. Tubing adapters
and fittings are used to attach the drip tubing to the rest of the system.
It is important that these are the right size for the tubing to prevent them
from blowing apart under pressure.
Drip Tubing and Emitters
Drip tubing is a polyethylene tube with emitters placed along the plants. The
emitters release the water from the drip tubing. Drip tubing and emitters
come in various types and diameters depending on your needs. The length of
a single drip tube should not exceed 200 feet from the point where water
enters the tube. You will need to stake the tubing to keep it from moving.
As a rule, don’t bury the drip tubing and emitters, even if they are
designed to be. This helps to prevent clogging and rodent damage.
Emitter Spacing and Design
Emitters can be spaced evenly for row crops, and this design is known as an
emitter hose. Emitters can also be spaced intermittently for plants spaced
further apart, such as trees, shrubs and perennials. With an emitter hose,
the emitters will generally be spaced about 18 inches apart. When watering
trees and shrubs, there should generally be two emitters per plant. Emitters
typically have a flow rate of 1 gallon per hour, though a flow rate of ½ gallon
per hour may be better for maximum efficiency. The end cap is placed at the
end of the drip tubing to prevent water running out the end.
Basic Operation and Maintenance
Drip irrigation can be set to run automatically, like sprinklers, or controlled
manually. Manual operation allows you to take advantage of rainfall before
applying unnecessary water. For more information on proper watering, view
our Water Wisely factsheet.
Because small amounts of water are applied slowly, drip irrigation is designed
to run daily unless it rains. How long to run the drip irrigation system will
depend on how much water your plants require per day and the flow rate of your
emitters. Water is applied either once or twice a day. Early morning is the
best time to water because there will be less evaporation. Watering in the
evening increases the plant’s susceptibility to disease.
You should check filters and emitters on a regular basis to ensure they are
functioning properly and not clogged. To prevent winter damage, you should
take up the drip irrigation system at the end of each gardening season.
Most suppliers/manufacturers of drip irrigation systems will provide specific
design, installation, operation, and maintenance specifications and guidelines
that should be carefully followed.
The cost of a drip irrigation system will vary depending on the size of the
area to be irrigated and the type of emitters and tubing used. However, regardless
of the size of the area being irrigated there is an initial upfront cost for
standard items such as the valve, pressure regulator, and backflow preventer.
Typically, a drip system for a home garden area will cost between $200 and
$600. For example, the drip irrigation system at the Demonstration Vegetable
Garden at URI’s East Farm irrigates 4,300 square feet in three separately
controlled zones, and cost about $500 in materials.
Soaker Hoses
Soaker hoses are another irrigation alternative. Soaker hoses require less
equipment and are easier and cheaper to install than drip irrigation. A soaker
hose is a porous hose that can be connected to an outside faucet, garden
hose, or rain barrel and laid out along the base of the plants. The hose
allows water to slowly seep out along its length. This system works well
with plants that are close together, like ornamental beds with clumped flowers
or groundcovers. However, a soaker hose should not be used to irrigate plants,
trees, or shrubs that are spaced far apart because the area in between the
plants will be unnecessarily watered.
Online
Suppliers
Digital Drip Directory. http://www.microirrigationforum.com/new/directory/
The
Drip Store, http://www.dripirrigation.com 866-682-1580
DripWorks. http://www.dripworksusa.com/ 800-522-3747
The
Gardener’s
Supply Company. www.gardeners.com 888-833-1412
Harmony
Farm Supply. www.harmonyfarm.com 707-823-9125
The Natural Gardening Company. www.naturalgardening.com 707-766-9303
The Urban Farmer Store. www.urbanfarmerstore.com 415-661-2204
Web Resources
Drip Irrigation Design Guidelines. Jess Stryker. http://www.irrigationtutorials.com/dripguide.htm
An Introduction to Drip Irrigation. Clinton C. Shock. Malheur
Experiment Station. Oregon State University. http://www.cropinfo.net/drip.htm
Drip Irrigation for Home Gardens. I. Broner. Colorado State
University Cooperative Extension. http://www.ext.colostate.edu/pubs/garden/04702.html
Books on Drip Irrigation
Drip Irrigation for Every Landscape and All Climates: Helping
Your Garden Flourish, While Conserving Water! Robert Kourik
and Heidi Schmidt. 1993. Metamorphous Press.
Ortho’s
All About Sprinklers and Drip Systems. Ortho Books. 1998.
Garden Watering Systems. Susan Lang. Sunset Books. 1999.
Watering Systems for Lawn and Garden: A Do-It-Yourself
Guide. R. Dodge Woodson. Storey Books. 1996.
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