I water about half of my fruit trees with mini-sprinklers while the other half is on drip irrigation. For example, the citrus trees along my driveway pictured above are all on drip. In this post, I’ll explain why I use drip on many trees, and I’ll give you my best advice for how to set up drip on your fruit trees as well as how to run it successfully.
What is drip?
Before moving ahead, very briefly let me say what I mean by drip irrigation for fruit trees. I’m using a narrow definition in this post. By drip, I mean a single orifice that emits some water. So you can have a black polyethylene tube that you punch drip emitters into or you can have a poly tube that has emitters built in (“inline” drip tubing, or “dripline”).
But I’m not talking about micro-sprinklers, bubblers, little sprayers, or adjustable octopus-type emitters.
Advantages and disadvantages of drip irrigation on fruit trees
Some of the advantages of using drip irrigation on fruit trees are that you can use water more efficiently because you are not losing much to evaporation (compared to sprinklers); you can run the irrigation at any time of day because the wind doesn’t affect it (compared to sprinklers); and it’s easy to calculate how much water you are giving each tree (count the emitters and multiply by the output per emitter).
A few of the disadvantages of using drip irrigation on fruit trees are that the emitters can clog, especially those in quarter-inch tubing (emitters in half-inch tubing clog far less, in my experience); your chickens scratch around the tubes and move them; and it can be more work to adjust drip as trees grow bigger (compared to adjustable micro-sprinklers).
Physical layout of tubing and emitters
Farmers and gardeners use various ways of laying out tubing under their fruit trees so the emitters are in the right places. I’ve used every one of these methods, and they all work.
If your fruit trees are in a line and close together, I’d choose the single or double lines layout. If not, then pigtails are probably best. I use mostly pigtails (or rings) on my trees.
How drip works
For me, it was not obvious that drip irrigation could work to effectively water a fruit tree when I first tried it. How could a tree be satisfied just getting water at a few points under its canopy?
But drip does work. That’s undeniable. I’ve watered so many trees for so many years successfully with drip that there’s not a shadow of a doubt left.
(There are also many large farms across the world attesting to the effectiveness of drip on fruit trees.)
It helps to understand what happens to the drips of water that come out of each emitter. They touch the dirt and then spread laterally. Many times I have measured the lateral spread of drip irrigation in my soil, and here is what it looks like:
So while from the surface it may look like dots of water, just below the surface a much larger volume of dirt is being wetted.
How many emitters
Remember this: your fruit tree needs a certain quantity of water more than a certain area wetted. In other words, what is most important is that you give a tree X gallons of water; what is less important is at how many points you are applying that water.
I once heard a farm advisor say that he had determined that roughly 60 percent of the soil volume under a tree’s canopy needed to be wetted in order for the tree to produce maximum fruit. I don’t know where he got that estimate, but I keep it in the back of my mind and it seems about accurate based on trees I’ve seen in various locations and other research I’ve read.
For example, a study in Israel on avocados found that “enlargement of the wetted soil volume from 25% to 75% increased root growth rate and improved tree water status and transpiration response to high evaporative demands.”
What this means for the number of emitters we use under our trees is that there’s a range of acceptability. There’s no single correct answer. But here’s a simple rule of thumb that will put you within that 60-percent plus range: use at least as many emitters as the tree’s canopy is wide (in feet). In other words, if the tree is ten feet wide, it should have at least ten drip emitters under it.
Following this rule of thumb has brought good results for the trees on drip irrigation in my yard.
Starting newly planted trees on drip
When I plant a new fruit tree, I usually give it a single drip emitter. If it’s a bigger new tree though, such as a bare-root fruit tree, I will give it two emitters.
For the small tree, the emitter must be placed right by the trunk, which is where the tree’s roots are. For the bigger new tree, the emitters can be placed on either side of the trunk, about 6-9 inches away from the trunk.
Adjusting the drip irrigation as a fruit tree grows
As a tree grows bigger it needs more water. This can be accomplished by running the system for longer, or it can be accomplished by adding emitters.
You can punch in more emitters, or if you’re using tubing with inline emitters then you can add emitters by using a connector and adding more inline tubing.
But here’s what I do for some young trees. I use inline tubing that’s longer than necessary at first – that is, it has more emitters than necessary – but I close off those extra emitters with a figure eight or other clamp. Then once the tree is bigger and needs more water, I just move the figure eight back so an additional emitter is running.
Here’s what NOT to do though. Do not change the layout of your tubing when you are adding emitters. Do not move the original emitters when you are adding new ones. If you move the original emitters, your tree is going to suffer because it has proliferated roots where the emitters have always been and now has no roots or not enough to drink the water in the new places it is being applied. If you need to change the layout of drip emitters, do so in the winter when rains are wetting the soil throughout.
Switching to drip
Similarly, do not switch from another irrigation method to drip in any season except winter, if you can help it. If you do switch in another season, it’s very important to continue giving the trees water where they had been getting it for about a month until they grow enough new roots where the new drip is applying water.
How often and how long to run drip on fruit trees
As with how many emitters to use, there is a range of effective water schedules for drip irrigation on fruit trees. For me, being twenty miles from the ocean and on a sandy loam soil, I’ve found these frequencies effective for summer (other seasons are less frequent): avocados every 2-3 days; citrus every 3-4 days; deciduous every 4-7 days.
But I’ve tried running my drip irrigation on various fruit trees as often as daily and as infrequently as every two weeks in summer.
As for how long to run the system, you have to do some simple math. If a tree has five emitters that each put out one gallon per hour, then you know you’re giving the tree five gallons every hour you run the system. Then you ask how much your tree needs.
Refer to this post to estimate: “How much to water a fruit tree in Southern California, roughly.”
Drip on slopes
There are two types of drip emitters. There are the cheap kind, and there are the expensive kind which are called “pressure compensating.” These PC emitters are the best choice for you if your yard is sloped because they will emit a more consistent flow despite the pressure changes caused by the elevation differences between your trees.
If you don’t use PC emitters on a slope, you’ll find that the trees high on the hill get less water while the system is running and the trees low on the hill continue getting some water after the system has turned off (because the water is bleeding out of the tubes through these low-elevation emitters).
Compensate for this by adding extra emitters on trees higher on the hill or by using pressure-compensating emitters. I use Netafim Techline CV tubing, which has PC emitters and check valves within the emitters so they don’t bleed out after the system has turned off. It is expensive but it is high quality. I’ve been using it for over five years and never had a single emitter clog.
But for some of my trees on a slope, where I don’t use the expensive PC emitters with check valves, I just use relatively fewer emitters on low-elevation trees.
You can buy cheap drip tubing and emitters at most nurseries and home improvement stores, but the expensive, high performance products like Netafim Techline CV are found at specialty shops like Grangetto’s in San Diego County and SiteOne Landscape Supply throughout Southern California.
An inspector with the California Department of Food and Agriculture was visiting my yard a couple weeks ago and said, “I love what you’ve got going here, but your water bill must be so high!”
He was wrong. I’ve yet to find anyone who gets more from production from a comparable yard for the gallons I use.
I’m not a perfect irrigator, that’s for sure. But I prize water, and I’m frugal. And drip irrigation allows a person like me to get the most bang for my water buck. You can grow a lot with relatively little water by using drip too.
Setting up a drip irrigation system: “The easiest automatic irrigation”
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