Rex’s Tips: Drip irrigation and water use

SOUTHERN UTAH – Water is one of three key elements to a successful garden (nutrients and sunlight being the others), but water is getting expensive, and if you have a large garden, it can pinch you a bit. Drip irrigation is easily the most water efficient method available. Drip irrigation is also convenient, and the system can be used for years. In the desert southwest, drip irrigation makes a lot of sense.

A drip system consists of a “header” and as many “lines” as you need. The lines can be placed as close or as far apart as you need. Rows of lettuce, radishes, onions, carrots and beets can be planted quite close together; but melons rows should be at least 6 feet apart. Drip allows you to customize your drip lines to your specific needs. And the following year, it’s easy to modify your header and lines to accommodate the rotation of your crops.

Drip irrigation system | Photo by Rex Jensen, St. George News

Drip lines come in rolls of tubing with drip holes every 6 inches or 12 inches. I’ve found the 6-inch lines to work best for all crops. A 12-inch gap between drip holes is a bit much for a row of carrots or beets, but is plenty adequate for corn, tomatoes, and melons.

With a couple of adapters, a drip system can be connected to a timer which will irrigate your garden precisely on schedule—whether you’re at home or on vacation for two weeks. This is a great feature I love about drip.

 

Drip also allows you to fertilize your garden while you’re irrigating (the best most sensible time to do so), using a water soluble fertilizer such as mono-ammonium phosphate, or Miracle Gro. The Miracle Gro type of dispensers will connect to your water supply and to your drip line so the water dissolves the fertilizer and carries it to every drip hole in your system.

The sequence of connections work this way: First connect your battery powered timer, then connect your fertilizer dispenser to the timer, then connect the drip line header to the fertilizer dispenser. Then set your timer to go on at whatever time you choose, and for as long as you choose.

One of the most common questions I am asked is: “How often should I water my garden.” This is not an easy question, but here are some considerations and guidelines.

When plants are young, just sprouting, or just up, the roots are very shallow, and the temperature is usually cool, so not much water is needed. But as the crops grow, become larger, and the temperature rises, more water is required.

Then you must factor in your soil type and how frequently you water. Sandy soil does not retain much water, clay soil retains a lot, and the amount of humus, or compost, you have in your garden is another factor, since humus will retain more water than soil without it.

The frequency of irrigation is as much a judgment call you learn from experience as it is science. In Orem, I had a flood irrigation turn that came once a week, so I watered once a week. But flood irrigation floods and soaks the entire garden, and you put a lot more water in the soil than you do with drip—but much of that water is also wasted.

With drip, you water only where the roots of your plants go. Visualize an inverted “V”, that is the way drip water spreads out as it soaks into your soil. If you have sandy soil, the “V” will be narrower, if clay soil, it will be a wider “V”.

So if you have young plants, in early spring, a shallow watering is all you need, perhaps only 10 or 15 minutes of watering. If it’s July and your crops are all full grown with deep roots, then you may want to water for an hour or two—depending on your soil type, and the plants you’re watering.

Drip Layout | Photo by Rex Jensen, St. George News

And then with home gardens you have the problem of some plants needing a lot of water, some plants needing less. If you have good drainage, this isn’t a big problem and you can water all crops the same. But you can buy a small, plastic shutoff valve that connects your drip lines to the header; and this can be used to shut off some rows that need less water, if you need to conserve water.

Melons prefer infrequent, deep watering. Corn will “burn” and the leaves and tassel will die if it lacks sufficient water. So if you’re going to err, err on the side of too much water in the summer, because the heat will dry out the soil quickly anyway and it will do no harm. The one caveat to this is if your soil has a high percentage of clay—then over-watering can be fatal to many plants. But a high content of compost will minimize this problem.

I prefer to create a shallow furrow for planting, and then lay the drip line down in the furrow. This keeps the water from running off and wasting. The furrow will also provide some protection for young, tender plants against the wind. But this isn’t necessary, you can plant on the flat and lay your drip lines on the flat if you prefer.

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Copyright 2012 St. George News.

 

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1 Comment

  • FERTIGATION May 9, 2012 at 12:01 am

    Drip irrigation is one such technology, which has assumed great importance in the recent times. In the present situation when the irrigated area is increasing, ground water table is dwindling and availability of surface water for irrigation is getting reduced, drip irrigation is the only answer to meet the growing demand of water.

    Drip Irrigation is the most modern technique of applying water directly to the root zone of the plant in right quantity at the right time and at the right place.

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