Richard L. Parish | 4/4/2006 8:28:36 PM
Louisiana gets a lot of rain, but it isn’t spaced out uniformly. Sometimes there’s too much rain, and other times there are periods of drought. Plants do better, however, with a more uniform water supply.
"To grow good plants, you will need to irrigate rather than taking what rainfall happens to occur," says LSU AgCenter engineer Dr. Dick Parish. "You can use sprinklers, hold a garden hose over the plants, carry water in buckets or use a drip irrigation system. But a drip system is by far the most effective and efficient way to irrigate."
Parish says drip irrigation works by metering a very slow drip or spray of water at discrete intervals. Drip systems use either individual "drippers" – called emitters – inserted into plastic tubing run along or among plants, or plastic tubing with molded-in emitters at regular intervals. Each emitter drips water at a calibrated rate.
Typical tube emitter spacings are 6 inches, 12 inches or 18 inches, while discrete emitters typically are installed at each plant.
"The principle of drip irrigation is to slowly put down enough water in the plant root zone to adequately supply the plants without runoff and without wetting the soil between crop rows," Parish says.
The LSU AgCenter engineer says advantages of drip irrigation include minimizing weed problems and conserving water.
"Another advantage of drip irrigation compared with sprinklers is that drip does not wet the foliage and spread disease," Parish says. "Applying the water directly to the soil reduces evaporation compared with sprinklers."
Parish says the basics of a drip irrigation system include hoses and emitters or drip tape coupled with a feeder hose across the ends of the rows if there’s more than one watering line.
"Drip tape is designed to run at only 8-to 12 pounds-per-square-inch pressure, and discrete emitters use 15 psi or so," he says. "Therefore, you’ll need a pressure reducer or regulator."
Parish cautions that the emitter orifices are very small and plug easily, so the water line should include some type of filter. The system also needs control valves and a way to connect the system to a garden hose or other water source.
"The easiest way to get started is to buy a kit from a home or garden center, hardware store or irrigation supplier," Parish says. "Separate kits are available for gardens or orchards and ornamentals."
The LSU AgCenter expert says a kit should have all of the components he’s mentioned to get started. Additional lines or components can be purchased individually.
"Many home and garden centers stock individual drip irrigation components," Parish says. "You’ll often find them in the plumbing section of a home center – not in the lawn and garden section."
Drip emitters have very small holes that are easily plugged by particles in the irrigation water.
"You must be sure the water entering the system is filtered," Parish says. "You also have to avoid contamination from dirt that gets into open hoses."
He also warns that algae growth may be a problem.
"Since the inside of the lines always stay wet, algae can grow inside the tubes and plug the emitters," he says. "It’s helpful to open the ends of the lines occasionally and flush them."
Parish says rubber "soaker hoses" that "sweat" out water along their full length should not be confused with drip irrigation. Soaker hoses can be useful for temporary watering of flower beds, shrubs and other plants, but they don’t put out a uniform amount of water.
"They put out much more water per hour than a drip system," Parish says of soaker hoses. "They’re not a substitute for drip irrigation."
The engineer also strongly recommends installing some type of backflow prevention device in a drip irrigation system to prevent water in the system from backing up into home water lines.
"Irrigation kits may contain a backflow preventer;" he says. "If not, you should buy one separately and install it."