Drip Increases Yields, much of the time

Numero uno is one of the often poorly-understood concepts about drip irrigation.

There are many scientific studies which indicate that drip irrigation can improve growth and yields. For example, in 1981 T. A. Howell et al surveyed 50 research reports on crops grown with drip irrigation, and concluded: “Where trickle [drip] irrigation was compared with either no irrigation or other water-application methods, yields were equal or better in all cases; and the amounts of water applied were equal or less with only two exceptions.” (As summarized by D. A. Bucks and F. S. Nakayama and A. W. Warrick in “Principles, Practices, and Potentialities of Trickle (Drip) Irrigation,” Advances in Irrigation, Vol. 1).

Research in many different climates and states invariably supports the benefits and cost-effectiveness of drip irrigation. Art Gaus, an extension horticulture specialist with the University of Missouri at Columbia, MO, has had a drip system in his personal garden for nine years. One summer, his bush watermelons with plastic mulch and a drip system produced 32 pounds in a four-by-four-foot area, compared with 9–16 pounds in the same area with conventional irrigation. He reckoned a well-timed drip system “could mean a 100% increase in yields; during the droughts of 1980, ’83, and ’84, it meant the difference between having a crop or no crop at all.”

In a study of established pecan trees in Georgia, trees with drip irrigation added had a 51% increase in yields.

Michigan State University has documented a 30% yield increase in vegetable crops with drip irrigation, even in its humid, summer-rain climate.

A study in India in 2002, found that with chilies, water use was down 34–50%, while production was up 33–48%. The researchers attributed this to irrigation that kept the soil moist, not too dry.

A study in New Mexico found amazing differences in yields compared to [respectively] furrow and drip irrigation: 18 pounds versus 30 pounds with cucumbers, 69 to 156 pounds growing Swiss chard, and 64 versus 166 pounds with green beans—to quote a bit of the study. [It is interesting to note that broccoli, Brussels sprouts, and carrots didn’t have any greater yields in the drip irrigation plots. Yet, a study at Oregon State University found a 20% increase in carrots compared to plots with sprinklers.]

To be fair, the benefits of drip irrigation are not confirmed across the board in agricultural studies. There are a number of studies which show it to be less beneficial than sprinklers, especially with perennial and tree crops. One such example is found in a paper entitled “Growth and Yield of Rabbiteye Blueberry as Affected by Orchard Floor Management Practices and Irrigation Geometry,” by K. D. Patten et al. in The Society, September 1989, Journal of the American Society for Horticultural Science, Vol. 114 (5) pg. 724-728. This study found that 360-degree sprinklers created better plant establishment and growth than either one emitter or two emitters per shrub. This is one of many cases where agricultural limitations (such as having to keep the area between tree rows free of tubing and emitters so tractors can mow or disc) greatly restrict both the number of emitters which can be used and their placement. In my drip-irrigation book (Drip Irrigation for Every Landscape and All Climates, 2nd Edition, Metamorphic Press, 2009), I very specifically recommend that emitters be placed equidistant throughout the entire root zone—which would include the area equivalent to that between the rows. The results in the abovementioned study are only to be expected when a dramatically reduced proportion of the root zone is watered by a mere emitter or two.

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Let me know what you think. Visit my web site (www.robertkourik.com) to learn about my new book on drip irrigation and other gardening books. Thanks, Robert

Drip Tubing for Trees

Tree roots grow one and one-half to two and even three times the width of the foliage above. More amazingly, this ratio is maintained throughout the life of the tree, regardless of the rootstock, species and soil.

These two trees don't understand this basic rule of thumb. The one with two circles has the right idea that trees should be watered in circles. But at least the inner circle with the beige/brown tubing is too close to the trunk. This is at least a waste of tubing. With drought tolerant trees and many other water sensitive roots can receive enough water to cause root rot. Put the emitters further out, near the dripline of the canopy. (Based on the book Drip Irrigation- For Every Landscape and All Climates.)


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Let me know what you think. Visit my web site to learn about my new book on drip irrigation and other gardening books. Thanks, Robert

Get to Know Your Wet Spots

To test your soil and to understand how emitters work, buy a single emitter, use an emitter punch (which cuts a tiny circular hole) to pierce a hole near the bottom of an empty plastic one-gallon milk jug, and insert the emitter's barb. Fill the jug with water and place it on a dry spot in the garden. After the milk jug is empty (which may take 24 hours or more because it's not under pressure), dig a small trench next to the emitter to see the shape of the wet spot in your soil. This is the most graphic way to understand how the water from each emitter you install will move in your soil. (The shape of the wet spot will change, usually both wider and deeper, when the emitter is used under pressure.) The shape of the moist area is affected differently by each type of garden soil and ranges from long and carrot-like to squat and beet-shaped. Emitters with a higher rating, such as 2 or 4 gph, will cause the wet spot to be wider than 1/2 or 1 gph emitters.

A moist-but-not-too-wet spot that is the key to drip irrigation's superiority over all other forms of irrigation. With proper timing, a drip irrigation system provides moisture to the soil without overly saturating the pore spaces in the soil. The labyrinth of minute pore spaces helps the soil breathe. When a more aerobic condition in the soil is maintained by drip irrigation, the roots don't drown, the soil's beneficial bacteria can continue to release valuable nutrients, and harmful anaerobic fungi don't easily proliferate—thus, better growth and greater yields

The lower chart (From Drip Irrigation for Every Landscape and All Climates) and shows how the water can move in a theoretical soil. The darker the wet spot, the more it is anaerobic.


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Yikes, Don't do this at home!

There's a reason it's called "spaghetti" tubing. Here we see some breeding to make more of a mess in the garden. Avoid the mess with in-line emitter tubing. I favor it over all "spaghetti" for most landscape uses in my book Drip Irrigation, For Every Landscape & All Climates.

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Let me know what you think.Visit my web site to learn about my new book on drip irrigation and other gardening books. Thanks, Robert

Calculating your daily water needs

For referral to the previous post, here's a repeat of an earlier blog. Pick an ET rate (as given from your local Coop. Extension), follow the column down to the square footage of your planting area, and you'll be given the amount of water for each day. Click on the image and load into a page where you can enlarge the image. If this is too complicated, just buy my Drip Irrigation book from my website, www.robertkourik.com :)

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Let me know what you think.Visit my web site to learn about my new book on drip irrigation and other gardening books.NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert

He Fooled Around & Fell in Love with Plants

Elvin Bishop loves to garden. And though perhaps best known for his gold-record Rhythm-and-Blues classics like "I Fooled Around and Fell in Love,” Bishop, 62, is serious when it comes to growing things. For 27 years, along with his wife Cara and daughter Emily, he's been cultivating a medley of flowers, vegetables, herbs, berries and fruits around his Marin County, California home.
(See the photo on the left.)

He uses Toro’s brown-colored in-line emitter tubing in much of his garden. (As recommended in my book Drip Irrigation, Foe Every Landscape and All Climates.) The photo is a close up of his beans with in-line drip tubing.

Bishop's interest in Oriental vegetables was initiated by his marriage to Cara Wada, whose Japanese-American heritage and traditional cooking style brought more far-eastern vegetables into her husband's diet, then into his garden. “Cara's family made me aware of different tasty Oriental vegetables. I figure if it tastes good, then it’s worth growing. Besides, it’s nice to have vegetables to give away to the family.”

Many Oriental vegetables are members of the cabbage or crucifer family (Brassica spp.) and thrive in moderate weather. In the Marin-County "Mediterranean" climate, winter gardening makes good sense; plenty of winter rain keeps things moist and, after temperatures drop, the cold keeps most pests (including the aphids and root maggots which can thwart summer plantings, but not, unfortunately, slugs and snails) at bay.

The secret to a garden which can be harvested from mid-winter through the following spring is timing, and Bishop’s sense of the rhythm of the seasons is finely tuned. His brief recipe for cultivating Brassicas : choose seed for early-, mid- and late-season crops to spread the harvest. Seed everything on June 1st in six-packs, using sterile potting mix. In two to three weeks, transplant deeply into four-inch pots. Set out into the garden at the beginning of July. Shade for several days if the weather is hot. Water till the rains begin. Weed as needed and harvest when ready.

Reaping the Rewards
In addition to its other rewards, Bishop's garden offers an abundance of produce; each year he personally puts up about 300 jars of beans, corn, pickled beets, dill pickles, applesauce, apple juice, peaches, plums, pears, tomatoes and various jams, including kiwi.

Elvin Bishop may sing the blues for a living, but in his garden, life is sweet.


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Wet Spots in Your Garden

The wet spot on the surface of the soil is misleading. The wet spots are at certain intervals, but don't represent what is going on. The photo on the left shows the misleading wet spots. The drawing on the right (from my book Drip Irrigation of Every Landscape and All Climates) shows that the wet spots beneath each emitter merge to form one continous zone of moisture. The soil for the entire length of the in-line tubing is moist some four to six inches beneath the surface, depending on the soil type. Sandier soils require tubing with the emitters pre-installed 12 inches apart. While heavier, clayey soils only need emitters every 24 inches.

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Proper Drip Irrigation Layout

In Drip Irrigation, For Every Landscape and All Climates, I recommend laying out parallel lines, or “laterals,” of tubing throughout the entire bed. I always stock the 1/2-gph, 12-inch-interval version because I install drip systems for different clients with different types of soil. The 1/2-gph tubing with the 12-inch spacing along the hose’s length is the only one that will water sandy soil. You can have your local irrigation supplier order tubing with 6-inch spacing in the drip hose. Yet, clay-loam soils can also be irrigated by turning on the system for a shorter period of time because the water easily spreads laterally. The parallel lines of tubing might be as close together as 6 or 12 inches in sandy soils and as far apart as 24 inches in heavy clay-loams. If you have a fairly heavy soil and want to save money, buy the tubing with 18-inch or 24-inch intervals between emitters, and you’ll save 25% or 40% respectively. Also, a higher flow rate, such as 1 gph, will help the water to spread wider than with the slower 1/2-gph emitter tubing. At worst, you’ll just have to run the system a little longer to get the wet spots to meet underground along the length of the tubing.

The photo on the left was taken at a winery here in Sonoma County. The one on the right I found at a museum in Paris, France. It's really catching on even though there is no French version of my book, as far as I know!

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Special Drip Irrigation Book Sale - the 2nd Edition

This Holiday Season, Give the Gift that Keeps On Giving

...one drop at a time.

Drip Irrigation for Every Landscape and All Climates

“Fun book, great info. Buy it and save the world’s water supply.”

— Jim McCausland, at Sunset Magazine’s blogsite “Dirt”

Special offer: Only $20 [lists for $24.95] No tax. Autograph included.

Includes Free Priority Mail!

Buy From the Source So Writers Can Keep on Writing®

Go to www.robertkourik.com to order via PayPal.

Or, send a check made out to Metamorphic Press to: Metamorphic Press, PO Box 412, Occidental, CA 95465

Information about the book:

As a celebration of its 25th anniversary, the highly respected newsletter Avant

Gardener published a list headed “The 25 Best Gardening Books of the Past

25 Years.” Up there on that list, at number seven, was the first edition of Drip

Irrigation for Every Landscape and All Climates. Great then, even better now.

Yes, Drip Irrigation for Every Landscape and All Climates, by Robert Kourik,

is now available in an updated second edition. It will give you the knowhow

to optimize your water use, survive a protracted drought, or work with the

unpredictable intermittent rains of certain climates. Its light-hearted approach,

step-by-step instructions and clearly drawn diagrams will allow you to construct

and streamline your own drip-irrigation system without the clutter of superfluous

widgets and gizmos.

Drip Irrigation for Every Landscape and All Climates also describes, in clear

and scientific terms, how drip-irrigation systems can be designed or reconfigured

to use less water while increasing yields of fruits and vegetables and improving

the growth of all plants. New in this edition are descriptions of how to use two

very important water sources—grey water and cisterns—as well as how to utilize

satellite control or a home-based weather station to irrigate your garden with

precision.

In short, this fully revised edition of the original ground-breaking book is designed to 1) help gardeners manage

precious water supplies with ease and efficiency, and 2) create sustainable water-efficient gardens and landscapes with the latest technologies of drip irrigation.

Page Count —192 (74 more pages than the 1993 edition)

Number of illustrations—89 B&W (21 new B&W illustrations)

Includes: A Bibliography, Glossary, Web sites to explore (new to this addition), and an expanded and detailed Index.

Lessons From "Our" Droughts

As winter approaches, gardeners in the west now have three things on their minds—water, water, and water. Or, rather, the lack of it. The pale, arid shadow of a dusty drought now extends over much of the American west and southwest.

The drought, which has settled into much of the west over the past three years, doesn't make much noise. You can't hear the sound of the mud drying in the bottoms of empty reservoirs. You don't hear any noise from the leaves as they turn brown and fall off the trees in mid-summer. And you can't hear anything coming from the countless wells which have run dry.

The first drought for me, after moving to California, was the so-called Big Drought of 1975-1977. Our current drought, which has lingered for three long, parched years, has had its impact on wild lands, suburbs, and cities. Now, I get to improve my skills with gray water systems, drip irrigation, and xeriscape (drought resistant) planting techniques.

My first experiments with gray water systems—collecting water from sinks, showers, and laundries to irrigate fruit trees and ornamental landscaping—were during the 1970's drought. The systems I installed in the basements and crawl-spaces of clients throughout Marin county in those days were, in retrospect, a rag-tag, baling-wire collection of bizarre-looking gizmos. Now I’ve learned a lot more. See the photo on the left of a system designed with current “technology”.

In my experience, gray water is not a crisis-intervention scheme, but one of the many "tools" which allows my garden to flourish. The overwhelming feedback, and my personal experience, has been: "My plants are growing better with gray water than with any other water source."

I knew nothing about drip irrigation until the drought of the 70's. Again, the "Big" drought introduced me to a new gardening tool which has become commonplace in the 1990's. The technological advances in drip irrigation since I first started messin' with drip irrigation in 1975 have practically exceeded that of the revolution in the computer industry.

After experimenting with countless drip irrigation widgets and gadgets I've settled on my favorite emitter technology—in-line emitters. (As described in my updated edition of Drip Irrigation, For Every Landscape and All Climates. 2009) Unlike the more common punched-in emitter, which you buy separately and insert into a hole you've punched into solid drip irrigation tubing, in-line emitters come pre-fabricated inside the one-half inch drip irrigation hosing. On the right, see the interior of several emitters that become encased in ½-inch tubing. There is also a clear piece of tubing to reveal the emitter. All the real tubing is black or brown. Old-fashioned, punched-in emitters get brittle in the heat and sunlight and easily snap off during routine garden maintenance—which leads to tedious hours of repair. In-line emitters have nothing exposed to break off, are securely housed inside a sturdy one-half inch plastic tubing that'll take to abuse of weeding, gardening, and mulching, and are far less time-consuming since the emitters are preinstalled. With in-line emitters, I avoid the so-called "spaghetti" tubing which seems to somehow mysteriously move and knot itself and ends up resembling its namesake, a heap of tangled noodles.

The drought of the 1990's taught me how to plant so as to practically eliminate the need for drip irrigation. I've come to discover many ornamental Mediterranean plants are actually more drought-resistant than a lot of California native plants. There are small 18-year-old test plantings around my house which were planted at the beginning of our fall rainy season, and never irrigated again.

The first drought for me was the so-called Big Drought of 1975-1977. (By the way, how can a reduced amount of rain, be "bigger"? How can you have more of less?) Anyway, there have been plenty of "bigger" and longer droughts over the past 400 years. Tree ring analysis in the central portion of Santa Barbara county, the Santa Ynez Valley, indicates two periods of 60 years of drought (below "average" rainfall) since the 1500s

So, watch out, don’t count on a break in the drought.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert

Winterize Your Drip

It got down to 36F here last night. So, it's almost that time of the year when light frosts begin to glaze the flowers. Soon many parts the country will be having hard freezes.

I've outlined how to get your drip system as described my book Drip Irrigation for Every Landscape & All Climates. Here's an excerpt.

A proper drip irrigation system is too valuable to leave neglected like an abandoned garden hose at each winter’s nippy return. Shut off your system’s water supply at a point inside the house where the water supply is protected from freezing. Loosen all unions at each main assembly to drain all water out of the pipes, filters, pressure regulators, and check valves. Make sure you don’t loose the O-ring which seals each union. Be sure to open the flush ball valve on the Y-filter so the filter chamber doesn’t crack. Better yet, bring the filter or the entire main assembly indoors. Also bring inside any battery-powered controllers which you have attached to faucets.

The drip irrigation hose can stay in place in the landscape, but as much water as possible should be drained out. The photo on the left shows draining a system with a figure eight closer device. Open the end-closures on all lines, let all water drain out, and close. Start at the highest elevation and work downhill. I prefer to use threaded end caps because the Figure-8 end closures (The photo on the left. Not my finger nails.) will quickly wear out the kinked end of the hose. I prefer the threaded end cap for its strength. (The photo on the right.) It’s essential that the water is drained from every low point of the system.

A deep mulch will help protect in cold winter climates. You don’t want anyone stepping on cold plastic tubing, but since many drip systems are primarily located in perennial plantings, the risk of trampling the tubing is low. Some compulsive people do lift out the entire assembly of header and lateral lines, roll up the tubing and store it in the garage for the winter. Porous pipe and in-line emitter tubing make this a lot easier than hose with emitters punched in or hose with, God forbid, spaghetti tubing with emitters.

If possible, lay out your drip irrigation lines so they can all be drained from the low ends. Otherwise, install your drip lines so they naturally drain to various low spots, install an access box at the lowest spot in each line of the system for the winter. Install a manual drain-down valve a simple ball valve. Each fall, the metal drip irrigation ball valve should be opened to fully drain the line.

Lonnie Zamora, a former rooftop-gardener and irrigation designer in New York City, used drip irrigation for over four years on most of his jobs, even in the flower boxes for a penthouse on the 27th floor of a Manhattan apartment building. To winterize his client’s drip irrigation systems each fall, he would:

l Drain the pressure regulator.

l Close the faucet at the home’s wall.

l Attach a 110VAC air compressor with the necessary fittings to the female hose thread at the beginning of the drip system.

l Set the timer to run each line or zone for five to seven minutes.

l Run the air compressor pumps at 25 psi or less to blow out all the lines.

l Manually drain all lines on multilevel, terraced gardens.

l Open the Y-filter’s ball valve to drain the filter cartridge chamber.

Finito!

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Wet Spots & Flavor

It's summer time and the time for a refresher. (From my book Drip Irrigation for Every Landscape and All Climates)

In this illustration, in-line emitter tubing moistens the soil the entire length of the line but slightly below the surface, where the bulbous-shaped wet spots come together to form one nearly continuous moist zone. The emitters come pre-installed in tubing with 12-, 18-, 24-, 36-, and 48-inch spacings [they can be custom ordered at just about any interval—for an extra fee], but the type most commonly sold to gardeners is the 12-inch interval. The emitters inside the hose are rated to dispense either one-half- or one-gph [actually 0.6 and 0.92 gph]. The cost ranges from$22 to $30 for a 100-foot roll depending on the emitter [its emitters flow rate and whether or not it’s pressure compensating.]

If you've grouped your veggies by similar water zones it's time to think about reducing the amount of water a bit to enrich the flavor. Tomatoes are a great example. Over watered 'maters have nothing over store bought. But if tapered off of water once fruiting, the reduced water in the flesh concentrates the flavor. In some climates, you can gradually reduce the water all together by August for the best flavor as the roots are well established after growing throughout the continuous zone of moisture at the beginning of the season. Experiment!


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Drip irrigation does increase yields

I'm working hard to finish my 2nd edition of Drip Irrigation, For Every Landscape & All Climates. (Thus the lack of entries on this blog. Spring is springing, yet water supplies are down 40-50%. Thus the need for drip irrigation.) I stumbled across some very exciting data that shows the reduced application of water via drip irrigation can actually lead to higher yields compared to furrow irrigation.

A study in Sri Lanka in 2002, found that with chilies, water use was down 34–50%, while production was up 33–48%. The researchers attributed this to irrigation that kept the soil moist, not too dry.

A study in New Mexico found amazing differences in yields compared to [respectively] furrow and drip irrigation: 18 pounds versus 30 pounds with cucumbers, 69 to 156 pounds growing Swiss chard, and 64 versus 166 pounds with green beans—to quote a bit of the study. [It is interesting to note that broccoli, Brussels sprouts, and carrots didn’t have any greater yields in the drip irrigation plots. Yet, a study at Oregon State University found a 20% increase in carrots compared to plots with sprinklers.]

From drips to bounty.

Note: I somehow lost the usual section "Post a comment". To leave a comment, simply click on the area/button that says "___ Comments" below. Or,clicking on the title of a Post under "Blog Archive" also gets you to a view that gives the option of leaving a comment. Robert


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Frequent Irrigation Can Use Less Water

Most drip systems are up and running by now. Yet, do you know where to start to get the proper amount of water on your flowers and/or vegetables? I'm working on a revised edition of my 1995 classic (so I'm told) Drip Irrigation, For Every Landscape and All climates. Here's an excerpt:

Daily irrigation doesn’t mean using countless gallons of extra water. In fact, with infrequent irrigation, it takes a certain amount of water just to rehydrate the soil before the plant can even make use of the moisture. Oddly enough, infrequent waterings can use more water than the same planting would receive with frequent, even daily, irrigation.

Years ago, for example, I planted a drought-resistant landscape, with plants such as lavender, santolina, rockroses, and rosemary, for a neighbor. The day after planting, the timer was set to irrigate each zone for 15 minutes. After the risk of transplant shock was over, the irrigation lines were turned on each day for only eight minutes. The plants flourished, even though each one-half-gph emitter was distributing the paltry amount of seven tablespoons of water-per-emitter each day. Contrast this with a nearby garden with a similar soil and lavender plants arbitrarily watered only twice a month for four hours. This amounts to two gallons per emitter for the two-week period, or just more than 18 tablespoons of water per day—more than twice the water used in the flourishing landscape.

No matter how you use drip irrigation, frequently or every once in a while, it will always be more efficient than any sprinkler you’re currently using. All sprinklers, except the most modern of micro- or mini-sprinklers, apply water faster than many silty and clayey soils can absorb it. This leads to anaerobic puddling and runoff, especially on steep slopes. Every sprinkler is vulnerable to wind- and sun-induced losses, with as much as 25% of the water wasted. In general, sprinklers are rated at an overall efficiency of 75% to 80%, compared with drip irrigation’s 90%. [Furrow irrigation can have an efficiency rating as low as 50%.]

How Long to Water

There are two general approaches to watering, the empirical and the more analytical, which uses the evapotranspiration rate as a guideline. Each works, but the ET-rate-based approach can be far more accurate and water conserving.

The most immediate, or empirical, way to understand your soil’s response to drip irrigation, and to determine how long to leave the system on, involves digging. Even after doing your experiment with the milk jug, you should test for the drip system’s underground pattern of moisture. Turn on the drip system for an hour, then turn off the hose and dig a number of small holes in the flower bed to see how deep and to what width the water has soaked in. Then turn the system on for another hour, to equal a test total of two hours, and check to see how much farther the water moves. Do this for several more intervals of time and observe vague changes in the wet spot. This test will reveal the shortest length of irrigation time to produce the widest wet spot, based on which test hole revealed the widest spread of the wet spot during the elapsed time. Without doing this test, you’ll just be guessing in the dark.


ET-Based Irrigation

Another approach involves using the ET figures for your local climate. Your local Cooperative Extension office should be able to tell you either the current week’s ET rate or the month’s average rate; both are expressed in inches per day or month. If they don’t know, fire them. (Click on the chart to get a bigger version.)

WARNING: Math Ahead.

The chart above shows the daily water use for ten different ET rates. Remember, the amount of water needed to replace the ET losses depends upon the amount of soil covered [like a shadow] by the planting’s foliage. If the plants are young, the ET rate is less, corresponding to the smaller area of coverage. With a mature flower border, the coverage is complete and all you need to determine is the total square footage of the border. For example, a five- by 20-foot border [100 square feet] uses 18.7 gallons of water per day during a hot day when the ET rate is equivalent to nine inches of water per month. If you still prefer to water once a week, multiply the daily ET rate by seven to determine the total amount for the weekly watering.

To determine the length of each day’s watering, take the total amount of water the flower border requires and divide by the total flow of the drip irrigation system. Consider a theoratical five- by 20-foot border with a daily ET rate of 18.7 gallons. Since the total length of in-line emitter tubing in the bed is 84 feet [this figure is reached by adding together one header four feet long and four 20-foot laterals], the sum flow of the system is 52 gph [84 one-half-gph emitters times their actual flow of 0.62 gph]. Thus, dividing the daily water need of 18.7 gallons by 52 gph yields 0.36 hour, or 22 minutes per day 0.36 of an hour times 60 minutes. If you want to water once per week, then multiply 22 minutes per day times seven days to get a weekly watering time of 154 minutes, or nearly three hours.

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Note: I somehow lost the usual section "Post a comment". To leave a comment, simply click on the area/button that says "___ Comments" below. Or,clicking on the title of a Post under "Blog Archive" also gets you to a view that gives the option of leaving a comment. Robert

Simple Drip Emitter Tubing

It’s irrigation season on my friend Chester’s garlic farm. The garlic has been growing all winter but now needs irrigation until July or so. That's him to the left, 85 and still growing and eatin' garlic.

About 18-years ago, I helped put in a simple drip irrigation system for each of his 4-foot by 10-foot planter boxes. I insisted on in-line emitter tubing.

In-line emitters are still probably the least well-known drip irrigation technology, but afford the best mix of efficiency, ease of installation, and resistance to clogging. The tubing is 1/2-inch in diameter with an emitter pre-installed inside the tubing at regular intervals.

These internal emitters seldom clog because they utilize what is known as a "tortuous path,” which forms a continuous vortex, a kind of horizontal tornado that keeps any sediment, sand or silt in suspension until it passes out of the emitter. (See the illustration above or in my books Drip Irrigation for Every Landscape and All  Climates or in Roots Demystified - Change Your Gardening Habits to Help Roots Thrive. Click on the illustration for a bigger image) In-line emitters even work with well water high in soluble iron-oxide or other minerals. In-line emitter tubing moistens the soil the entire length of the line, but slightly below the surface where the bulbous-shaped wet spots come together to form one nearly continuous moist zone.

The emitters come pre-installed in the tubing, which is most commonly sold in pre-spaced, 12-inch intervals—but also comes in intervals of 24- and 36-inches. The emitters inside the hose are rated to dispense either ½ or 1 gallon-per-hour (gph) and the hose is available in both non-compensating and pressure-compensating versions.

We used ½ gph pressure-compensating emitters on 12-inch spaces along the tubing. We placed three equally-spaced lines running down the length of every box. (See upper-left photo. Taken before the straw is added.) Each box has the three lines connected to the water supply and the other ends connected to a drain-down manifold to flush the system at the beginning of each irrigation season. That’s what Chester is doing in the right-hand photo above. The garlic has grown considerably during the rainy winter months.

The benefits of pressure-compensated in-line emitters are: it's easy to install, simple to snake around your existing plantings, it is easy to put together a simple array of tubing which can be readily removed from the vegetable beds for seasonal cultivation, suffers less clogging than porous tubing and most punched-in emitters Chester stopped using the filter several years back and still only a handful of plugged emitters. Even with iron-based irrigation water only a few emitters in the thousands of feet of tubing have clogged over the past 18 years, and not cracked or leaking. Warranty says 10 years, but this tubing is always under six inches of mulch, works at the greatest range of pressures (9-25 psi), provides consistent rates of irrigation without regard to slope or length, has no external parts to snap off (a premier advantage over all punched-in emitters), and the compression fittings don't leak and seal better than the hose clamps used with porous hose.

The regular interval of the emitter makes it easy to irrigate the entire root system of all vegetables—in this case, garlic—and ornamentals by simply running parallel line of tubing throughout these raised beds or any garden. This will insure the greatest yields when compared to any other irrigation method—even sprinklers.

The drawbacks are few: it requires extra planning for plants placed very far apart and at very odd intervals, it can't turn a sharp radius, and it’s not carried by very many retail outlets.

You can get by mail from Harmony Farm Supply & Nursery, Peaceful Valley Farm & Garden Supply, and DripWorks (one word). Google them for what’s sold on their web site. You may have to order from one of their printed catalogs.

Let me know if you’ve tried in-line emitter tubing. How did it work for your garden?

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Labels: Chester Aaron, drip irrigation, emitters, gardening, garlic, in-line emitter tubing, irrigation, raised beds

Plants Really Drink and Eat Near Our Toes.

I consider those ever-popular metal tree root deep-feeders as virtually useless and mostly harmful.

Spring has been warmer than past years up here “on the mountain”. Friends are thinking about watering. I hope they think carefully. (My plants and trees receive no summer irrigation. But that’s another blog altogether.)

The roots of many plants, it turns out, don't really get most of their water and nutrients from the deep regions of the soil. Rather, most plants, tree and shrubs gather all the moisture and nutrients they require from the top 12- to 36-inches, depending on the plant. The first foot is the most critical. Here is where the soils are most aerobic and this facilitates the exchange of nutrients from the minerals into soluble form that plants can absorb. Feeding root hairs actually grow up toward those first moisture-laden nutrients. (The lettuces pictured here can send roots as deep as four feet--if you don't have gophers! This is why boxes with wire bottoms should be 24-inches high instead of 12 inches. To give the roots "room to move". Yet the lettuces still get much of their "food" from the top 12 inches. So careful irrigation is a must.)

The roots of many plants, it turns out, don't really get most of their water and nutrients from the deep regions of the soil. Rather, most tree and shrubs gather all the moisture and nutrients they require from the top 12- to 36-inches, depending on the plant. The first foot is the most critical. Here is where the soils are most aerobic and this facilitates the exchange of nutrients from the minerals into soluble form that plants can absorb. Feeding root hairs actually grow up toward those first moisture-laden nutrients. (I describe this in more detail in my newest book - Roots Demystified, Change Your Gardening Habits to Help  Roots Thrive.)

An old adage advises gardeners to water trees deeply; this often means infrequent, but lengthy irrigation. Increasingly, drip irrigation has been used as a tool for deep, occasional irrigation. Infrequent, deep irrigation tend to produce two points in the total irrigation cycle where the soil life and root hairs are damaged enough to reduce plant growth—during both the drying stage and when the soil is too wet. Dry soil kills off the tender root hairs as they can’t survive too much air. When the ground is flooded, root hairs die and noxious gases can’t escape nor pure air enter—or as pure as it may or may not be.

The metal probe of a typical deep root feeder is 18- to 24-inches long. This means that the application of the water begins below almost the entire zone of maximum water and nutrient uptake.

Good pore space makes for healthier plants. An ideal mineral/humus/pore structure balance results in a crumbly soil that allows water to percolate down, harmful gases to vent out, and refreshing air to permeate the soil. Soil breathes 24/7 at a lumbering, beneficial rate we cannot see. A soil with a healthy structure allows for easy and deep root growth and will produce the best-looking lawn, garden and tree growth.

Root feeders flood the pore space of the deeper soils, which quickly becomes flooded and anaerobic. Sometimes the deep soil saturates and the irrigation water backs up toward the surface so that more shallow soils actually get waterlogged. It's a bit backwards to send the water through a 24-inch deep probe just to apply the water 6- to 12-inches deep!

I recommend you just toss your root feeder—actually, recycle the scrap metal parts. (China could use them.) A good sprinkler can do a better job. And a drip irrigation system will promote the best growth possible—better than any other method of watering.

One garden’s “deep” soil is another garden’s “shallow” soil. Another hidden assumption about tree roots concerns the depth of your garden's soil. There are places where glacially-deposited topsoil extends for dozens of feet, but these are more the exception than the rule. If you have such a deep, loamy soil, then rejoice, but remember that the majority of moisture and nutrient absorption by trees still happens in the top two feet of the soil. Typically, most suburban yards have a very shallow layer of topsoil, if there's any left at all after construction. If, for example, there is a continuous layer of rich-orange clay some 12 inches under the ground, then the 12-inch layer of topsoil is, for all practical purposes, the only place your plant’s roots will be feeding.


Most heavy clays, whatever the color—and dark blue or pale white-gray are the worst—are relatively worthless to feeding tree roots. While clayey soil has plenty of nutrients, their availability is locked up in its tight, anaerobic structure and strong chemical bonds. Tree roots can, over many years and decades, grow somewhat into clay soils, but the number and extent of roots in the looser topsoil in far greater and more important to tree nutrition.

Please post a comment - I want to know what you think.


All rights reserved, Copyright 2008

Visit my web site to learn about my gardening books.

NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert