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May 242012
 

By Barbara Kessler
Green Right Now

Drip line irrigation is a great idea for gardeners who want to save water and grow plants successfully.

Our drip line system, set up at a community garden.

By soaking the ground with water, the drip line approach mimics the effect of a gentle drenching rain, instead of battering leaves with a harsh jet of water like so many sprinkler systems do. More importantly, by slowly delivering the water to the soil and plants and not spraying it overhead, a drip line system can better target, and thereby reduce, the water needed for landscape or edible plants.

You’ll be watering the tomatoes, not the neighbor’s fence, and the loss  to evaporation will be minimized.

We had no trouble installing a basic drip line system for about $30 in supplies. That would have been $50 to $60, if we’d kept the timer, a device that can add convenience to drip line system.

As it happened, the timer we bought proved to be a recalcitrant little rascal with mischievously flashing LEDs. It enjoyed clearing its memory instead of cooperating with our programming efforts. So we put Mr. Tricky Timer in time out.

The rest of the drip line installation was a breeze. We pretty much followed the advice of Texas Agrilife expert Dotty Woodson, who started us off with an equipment list, and the guidance of Frisco, Texas, irrigation and landscape experts, Mike Barth and Darrell Bagley.

By the way, yes, you can also attach drip line systems to your underground sprinkler system  to increase water efficiency in almost any landscaped area.  But our experts suggested that calling on an irrigation expert would be best in that situation, which involves a lot more water pressure and must be appropriately programmed.

The DIY system we’re talking about here is designed to hook up to a hose bibb or spigot. Here’s a basic rundown of what you’ll need:

1 – A backflow preventer. This will screw directly onto your hose line spigot. This piece of equipment does just what it says; it prevents backflow. Woodson says it’s vital, and so does everyone else. (Cost: A few dollars.)

Dotty Woodson displays the drip line irrigation equipment.

2 – A splitter. This is so you can run one drip line in one direction and another in another direction, or you can run a drip line system off one side of the splitter and keep a hose connected to the other. You can turn each side on or off independently.  Consider this optional.

3 – A filter. This is to keep out calcium so it doesn’t build up in your system and encrust inner parts, shutting it down.  It’s inexpensive insurance. On the other hand, it’s not strictly necessary if your system is hooked up to clean city water, according to Texas A&M University horticulture experts. But it’s recommended, and you should clean out the filter occasionally. Cost: About $10.

4 – A timer. This would screw onto your system at this point. Admittedly, this would be really nice to have. It would automate your system. A faucet battery-operated timer will be $30 to $50, depending on which model you choose. Our problem aside, several people on Amazon reported that the very same timer that confounded us (a DIG entry model) was easy to program. Woodson says you leave the spigot turned on, and the timer, once programmed, turns the water on and off to the system for days and duration you’ve set.

5 – No timer. On the other hand, if your garden is in your own backyard, you may be better turning the drip line system on and off manually, so you can check it every day to make sure there are no leaks or runoff problems, says Mike Barth, irrigation specialist for the city of Frisco. Barth says he’s convinced that the consumer market timers are a great idea, because they too often end up dripping or failing. “I’d rather people just turn on the faucet when they want to water, because it just makes me a little nervous to have the water turned on all the time,” he said.

6 – A pressure reducer. This is not just a nice to have. It will keep the water from bursting forth too briskly and causing problems down the line. It’s pretty important and inexpensive ($6 or so). You’ll be buying one that’s preset for 15-30 PSI at the hardware store, Woodson says, noting that this will not be required if you’re using a soaker hose with your system.

The backflow preventer, filter and pressure reducer altogether is known as your “head assembly.” Now you’re ready to attach the hose(s).

Dripline works because it delivers water directly to plants, such as these watermelon seedlings.

7 – Tubing or hose. You can choose different sizes, depending on your preference. We have ours on a vegetable garden so we used 1/2-inch tubing for good flow. Many people use ¼ inch micro tubing. Either can work. For potted plants or established perennials you’ll probably only need the micro tubing.

Your tubing will likely be polyethylene plastic. The upside is that this is a fairly inert plastic, so it won’t break down when the hose gets hot in the sun or you apply fertilizer. The downside: It won’t breakdown when it gets hot in the sun or you apply fertilizer. It’s not biodegradable. The day is coming when we’ll have plant plastic that we can use to water our plants. That would be some nice eco-symetry. But we’re not there yet.

You won’t have to pay a lot for this polyethylene tubing, a few dollars to maybe $20 for 200 feet. But do get enough so you can snake it around the bed. (See our 50-foot line in the picture here. A couple passes through a 15-foot garden is all you get.)

8 – Emitters. These are little plugs that you can install over the holes in your hose. It helps the water drip out instead of running out. You’ll want these. Dripping the water out is after all what drip line irrigation is all about! You want to gently soak the soil.

Experts suggest that for general purposes, holes should be spaced 12 inches apart. But some home irrigation kits or plain tubing from the hardware store will allow you to set your own openings based on where your plants are.

Bagley explains that there are two kinds of drip line emitters, those that are built into the tubing and those that allow you to punch your own holes.

The idea with the pre-installed emitters is that you’re going to wet the soil everywhere in the garden, he said. “You lay out the tubes and hook it into a looped pattern where it’s all tied together, turn it on and it goes.”

For more specific advice on drip line irrigation for differing types of uses, vegetable gardens, decorative gardens or trees see this Texas A&M article.

9 – Stakes. You’ll want to hold your drip line in place, especially if you’ve got seedlings going. Our hose kit came with a ridiculous minimum number of stakes. But you can view this as a recycling opportunity, a job for an old hanger or another widget from your garage. Many things can be fashioned into stakes.

A soaker hose, by the way, is a suitable alternative to plastic tubing,  and one that Woodson endorses. Soaker hoses, like drip line hoses, water the soil, not the air, so fait accompli.

Now for the tricky part, how much and how often to water.

A soaker hose also works for dripline systems; no pressure reducer is needed.

First, to be precise: It depends. Are you watering squash or strawberries, or hardy perennial flowers like salvia or Turk’s cap? If you’ve got native perennials that have been in the ground for more than a year, you only need to water them once a week. And that’s a good thing, because many Texas and Southwest cities, for instance, are on water restrictions that limit watering to once a week for lawns.

But veggies are much greedier imbibers, and the law allows homeowners to water them as needed.  As Texas A & M horticulture experts explain, edibles benefit when they are watered often, daily in some cases, and not allowed to dry out. A cycle of watering and water deprivation can be hard on them. Efficient drip line irrigation affords you the opportunity to give your growing vegetables a frequent water feeding.

Bagley says one rule of thumb is to keep the ground moist, but not saturated. In Frisco, Austin and many other cities, residents can keep track of soil moisture using sensors their utilities or cities offer for free.

Another way to think about watering plants is the old-fashioned method: Look at them. If they look like they need a drink, water them. Then repeat.

“People used to water that way, they’d walk around and water if the plants looked a little limp.…Now with automatic systems we’ve gotten away from being attuned to the plants,” says Bagley, a native landscape expert.

Woodson notes that a vegetable garden will require watering for seedlings every day for a week or two, with decreasing frequency as the plants mature. A vegetable garden can get by with a soaking every other day, or a three- or four-day a week watering if the gardener is careful to thoroughly wet the soil, and keep it moist with a heavy cover of mulch or straw.

“Mulch is a key to making this work,” says Woodson, noting that a vegetable garden is “dynamic” with plants being harvested and replanted, depending on the region, up to year round. So irrigation must be carefully considered. Installing a drip line system can be a step toward success.

Here are those A&M experts again:

The basic concepts behind the successful use of drip irrigation are that soil moisture remains relatively constant, and air, as essential as water is the plant root system, is always available. In other watering methods there is an extreme fluctuation in soil water content, temperature and aeration of the soil….

With drip irrigation the water soaks in immediately when the flow is adjusted correctly. There is neither flooding nor run-off, so water is not wasted. With a properly used drip irrigation system, all of the water is accessible to the roots. Watering weed patches, walkways and other areas between plants and row is avoided. Wind does not carry water away as it can with sprinkler systems, and water lost to evaporation is negligible….

As for that timer…guess we’ll read the manual.

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