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Index : Watering
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- 16. Make Irrigation Changes Now - Top
- I really don't know of anyone who enjoys making changes to their drip irrigation system. It always involves a lot of hunting for irrigation lines and tubes, and worst of all, lots of digging! But having said that, now is the time to make changes in your drip system. The weather has been cool and rainy, so plants can take the disturbance with little adverse effect.
One of the most common changes needed for drip systems is to add more emitters around plants. When landscapes are installed, drip emitters are put in sparingly. Usually, just two or three emitters are placed around trees, and only one per shrub. That's fine for the first year, but after that the roots need to grow out much farther. They have a hard time expanding out if water isn't available.
I recommend putting enough emitters around trees to water the area from the trunk, out to a few feet beyond the ends of the branches. The same holds true for shrubs. Determining the number needed for the space depends on your soil. If, like most of us, you have a heavy soil that's hard to dig in, then you'll need to space the emitters about 3 feet apart to achieve a uniform watering of the area. If you live along a wash and have relatively sandy soil, then the emitters should be spaced closer - about one foot apart.
Trees benefit most from the addition of emitters. To keep the frustration level down, just do one tree at a time. First, you'll need to find the main polyethylene supply line. Do this by carefully digging down around on the small quarter-inch poly tubes that your emitters are connected to. When you've located the main half-inch tubing, dig out around it to expose enough tubing to connect another quarter-inch "spaghetti" tubing and emitter. Garden centers and hardware stores have the hole punch and barb connectors needed to add new spaghetti tubing and emitters.
You can connect several spaghetti tubes relatively close together on the main line. This will save from digging down to the main line for every individual new tube and emitter you add. Then it's just a matter of running the tubes to the locations around the tree to achieve the proper spacing. I do recommend putting the emitters above ground, on the end of the spaghetti tubing. When the emitters are above ground, they're easier to check for clogs or breaks.
Along with adding drip emitters to your system, it's also the best time to change from basin to drip irrigation. Basins are often placed around trees, especially citrus, for the practice of flood irrigation. This is a perfectly acceptable way to irrigate, however, it may not blend well with other landscape plantings. With basin irrigation, the water is distributed evenly over the roots. So when it is converted to drip, it's critical to have drip emitters well spaced to evenly water the area. Don't skimp on the number drip emitters. If you do the tree will suffer next spring. Also, after converting to drip, check to make sure your watering deep enough. Trees should be watered to a depth of three feet, and for shrubs the depth should be 18 inches.
The best way to determine the depth of wetting is to use a metal rod pushed down through the soil. The rod will push easily through moist soil but stop when dry soil is encountered. Sometimes the rod will hit a buried rock, so it's advised to push the rod down in several locations to be sure the measurement is correct. If water isn't getting down far enough, adjust the irrigation run time up to get the water down deeper. A piece of concrete reinforcing bar, available at home supply stores, is great to use for measuring the depth of wetting.
Finally, this is also the time to do a complete renovation of your irrigation system. Standard drip systems begin to fail after 10 years. The soft poly tubing in the ground slowly degrades, and leaks begin to occur. It's best to install a new irrigation system, one which has more than one line or zone. At the minimum, I would recommend two zones; one for the true desert plants and one for those plants that need more frequent irrigation.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: November 23, 2004
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