Introduction to Drip Irrigation

Richard L. Parish  |  11/19/2004 9:52:22 PM

We get a lot of rain in Louisiana, but it isn’t spaced out uniformly. Sometimes we get too much rain, and other times we have periods of drought.
Plants do better with a more uniform supply of water. To grow good plants, you will need to irrigate rather than taking what rainfall happens to occur. You can use sprinklers, hold a garden hose over the plants, carry water in buckets or use a drip irrigation system. A drip system is by far the most effective and efficient way to irrigate.

How Drip Irrigation Works
Drip (or trickle) irrigation systems meter a slow drip or spray of water at discrete intervals. Drip systems use either discrete individual emitters that you insert into plastic tubing (Figure 1) run along or among plants or plastic tubing with molded-in emitters at regular intervals (Figure 2). Each emitter drips water at a calibrated rate. Typical tube emitter spacings are 6, 12 and 18 inches. Discrete emitters are typically installed at each plant. The principle of drip irrigation is to slowly put down enough water in the plant root zone to supply the plants adequately without runoff and without wetting the soil between crop rows.

Drip irrigation minimizes weed problems and conserves water. Another advantage of drip irrigation compared with sprinklers is that drip does not wet the foliage and spread disease. Applying the water directly to the soil reduces evaporation compared with sprinkler irrigation.

What Do You Need
Obviously you will need hose and emitters or drip tape. You will also need a header line across the end to feed the drip lines, if you have more than one line. Drip tape is designed to run at only 8 to 12 psi and discrete emitters at 15 psi or so, therefore you will need a pressure reducer or regulator (Figure 3). Since the emitter orifices are very small and plug easily, you will need some type of filter. You will also need control valves and a way to connect the system to a garden hose or other water source.

Where and How to Buy
The easiest way to get started is to buy a kit from a home or garden center, hardware store or irrigation supplier. Separate kits are available for gardens or orchards and ornamentals. The kit should have all of the components listed above to get you started. You can then add additional lines or components purchased individually. Many home and garden centers stock individual drip irrigation components. You will often find these components in the plumbing section of a home center, not in the lawn and garden section.

Drip emitters have small holes. They are easily plugged by particles in the irrigation water. You must be sure the water entering the system is filtered. You also have to avoid contamination from dirt that gets into open hoses. 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. It is helpful to open the ends of the lines occasionally and flush the lines.

Drip Vs. Soaker Hoses
The 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, etc., but they do not put out a uniform amount of water, and they put out much more water per hour than a drip system. They are not a substitute for drip irrigation.

Safety Concerns
You should install some type of backflow prevention device in your system to prevent water in the drip system from backing up into your home water lines. Irrigation kits may contain a backflow preventer; if not, buy one separately and install it.

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