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Converting to drip irrigation - how long to water?

Converting to drip irrigation - how long to water?

I'm almost done converting to drip irrigation.
Figured that I'll need it since my greenhouse is almost done. The green house measures 18ft long by 7ft wide by 8ft high. The long way is facing the south where the sun hits it the most to get the most heat. With the greenhouse, I figured that watering is going to be a headache for me. So I converted to drip irrigation.

I'm using 1/4inch dripline with holes spaced 6 inches apart on the line. I have all the drip line spaced in parallels 1 feet apart from each other. Each emitter hole on the line drips 1/2 gallon per hour.

Anyone know what is the optimum time duration and frequency to water? I estimate that I average about twentyfive
1/2 gph emitter holes per tree. So about 12.5 gallons per hour per tree.

I have sandy loam soil.

The following thread was started by Jonathan in San Francisco on February 22, 2008 at 4:36 am PST

Drip irrigation


I switched to drip three years ago, and it's been a total disaster for some plants. It simply doesn't work in my loamy soils. The water just finds micro-paths straight down and doesn't properly wet the soil. I ended up having so water longer, and therefore lost any savings on water quantity.

This year, I am switching my trees to micro-irrigation, the only way to go in loamy soil. That way I get greater surface coverage, which a lot of my tropicals need.

The drip has not been a problem at all with my deciduous crops, they seem to make deeper root systems.

So with sandy loam, you may want to rethink your strategy.

The above followup was added by Axel on February 22, 2008 at 9:11 am PST.

I am siding with Axel, I have a similar problem with my sandy silt soil

To add to that, I have hard pan generally down around 4 feet, but on the edges of my lot, 2 to 3 feet. Luckily it is not hard hard pan, and water does drain, but slower then the regular soil, but it does affect root penetration.

I was noticing the same thing with my soil as Axel, the water was pretty much just going down and not really spreading out and not really benefiting the top plus foot of the soil. If I water often enough, it does spread out, but that is only if the soil is still decently wet still.

For an example, some of my more heat sensitive bananas would stop growing when it got near to 100F. I figured that was just the way they were and I would just have to live with it. But after I put in a low emitter spray system to water better, I discovered the problem went away. The low volume 9 gph full circle mini sprayers started soaking up the surface, and not the the sub soil. To back up a bit, that was the reason I tried it, I was getting soggy subsoil with the sandy silty soil; you could dig down 18 inches and squeeze water out of the gummy wet soil, when the surface soil was fairly dry.

Not only did my heat senstive bananas now love and grow in the 100F temps, all of them greatly improved in growth in a season. The soil did improve too over time and that helped the bananas too, but I now get almost twice the growth from my banana trees in a season, then before the low volume sprayers.

It is not hard to switch over from drippers to low volume sprayers, the system is same in most cases the only difference are the application devices, the filters and hoses and pressure regulators are the same. The only change might be, larger hoses if you have a very large area to cover, but zoning and controls can take care of that.

I do know, if you keep your greenhouse somewhat humid, you will need much less water then you think on our plants. My temporary greenhouse has some potted plants like mango's, Dragon Fruits , and guavas in 5 gallon pots, plus some 1 gallon avocados which I just never got to moving out last year. This time of year it gets to 110 plus on a sunny day, and I have only watered them twice in the last few months.

In the summer I am sure it will change, just as it does for outside plants.


The above followup was added by DavidLJ48, Waterford CA, zone14 on February 22, 2008 at 9:59 am PST.

My thoughts and observations

Axel, this is the first time I've heard anyone say that drip irrigation did not work on loam soils. A loam soil will have approximately equal amounts of sand, clay, and silt particles and permiability and water holding capacity are characteristics that are ideal with loam soils. Drip irrigation is usually considered ideal for loam soils. In my university irrigation engineering class I remember seeing the wetting profiles of different soils and sandy soils can definitely be a challenge but drip can still be effectively used if adjustments are made. In some windy areas drip irrigation is still used on commercial orchards with sandy soils but more emitters are used and shorter durations. Even though I have moderate winds in my chestnut orchard much of the time, I still get by with micro-sprinklers which is what I assume you're talking about with the use of micro irrigation (drip irrigation is also a form of the broad term of micro irrigation). My choice to use micro sprinklers, though, was based on the large area I wanted to wet since chestnut trees can get quite large. Since I have to mow my orchard, especially during harvest, having drip lines around in large circles would not work although underground drippers could be an option. Also, some growers use one line on each side of the tree and pull the lines in close to the tree row during harvest which I could do also. I have actually considered switching from micro-sprinklers to drip for three reasons: (1) less wind drift which can get my tree trunks wet and potentially lead to fungal disease problems, (2) less weed growth and (3) not getting chestnuts wet which drop in-between the daily harvest which usually lasts for three weeks.

Jonathan, I think your best method for determining the duration and frequency needed is to hold off watering until your soil has dried out a bit. Then water and see how long it takes for the moisture to reach the lower range of your root zone and then turn off the system. Not all plants will require the same amount of water and you may end up having to use different zones or use fewer emitters on some trees. You should then monitor to see how long it takes for the soil to dry out again down several inches before watering again. You will need to check to make sure that the lower range of your root zone is not getting too wet or too dry, however. Sandy soils will require more frequent irrigation than loamy or clay soils since it has a lower water holding capacity. For my orchard I have moisture meters in three locations and each location has a meter at 15" deep and another at 30" deep. If I don't keep on top of my watering it will get dry at 30" and it is very hard to replace that moisture later in the season since it would require an excessive amount of water to reach that depth (you want to avoid saturated conditions, ideally).

I'm not sure about the effectiveness of using irrigation coefficients in greenhouses, but it's something you might look into. You can put out a pan of water and monitor the evaporation of the water from that pan. Their are published k-factors for many crops and if you have 2" of evaporation in a week you want to water to replace the established percentage for the crop you are growing. You can google for "k-factor" if this is something you want to try.

The above followup was added by HarveyC on February 22, 2008 at 10:47 am PST.

Harvey, help needed

Harvey, maybe one of these days you can come out to Santa Cruz and check out my drip system. Maybe it's not working the way it's supposed to. So far, I've not had good luck, basically, the drip would find paths straight down and didn't water a bulk of the root zone at all. I literally have trees where the root system was history because of drought. At the top, everything looked fine, but below, what happened is that the water penetrated a couple of inches, then found a way to escape down.

So for me, drip has been a complete failure, so bad that I had to hand water my entire citrus orchard to keep the trees from slowly declining.

My decidious orchard on the other hand did fantastically well. It's just the subtropicals that hate the drip irrigation, because they are surface feeders and therefore they need micro-irrigation.

The above followup was added by Axel on February 22, 2008 at 3:22 pm PST.

Sure, I'm hoping to make it over one of these days

I'm still planning on mailing your poms unless I deliver them in person. I'm always behind on my schedule it seems so I'm reluctant to say I'll ever have the time like I hope. Right now I need to put on a spray for my fruit trees as soon as we get a couple of dry days and then spray for weeds in my two chestnut orchards and pomegranate plot. Hope to get heat put in my greenhouse tomorrow since my flexible gas lines I ordered arrived today. Just got back from mowing a club's lot so people don't need to walk through wet grass at tomorrow night's crab feed. It might be better for me to come when you actually need to do watering, though!

I am trying to picture your soil structure and figure out why you would be having this experience. If the soil surface is allowed to dry out cracks can form obviously, but that should not go very deep. Preventing the soil from every drying out should avoid any significant cracks from forming. High organic matter also facilitiates lateral movement of water (some of our corn fields with peat soils have been irrigated simply by keeping trenches about every 50 feet filled with water).

One other handy irrigation method is using some of the small size of soaker hoses that can fit on the 1/4 inch feeder hose. I never see this stuff in the commercial stores but some retail stores carry it and I've found it handy for some smaller trees.

Don't get me wrong, I do like micro-sprinklers and they do have many benefits, but they are a little less efficient since more water is lost to evaporation and there is that weed problem. Nelson sprinklers has been promoting their sprinklers over drip emitters to walnut and almond growers because of reduced cracking, though. However, the cracking isn't a problem for irrigation directly but because nuts are missed by harvesting equipment.

As I think I mentioned to you, I need to head over your way one of these days because I want to go to the arboretum and buy a replacement Leucadendron 'Sunset Safari' that got destroyed by the early January storm after doing so well here for the past 10 years.

The above followup was added by HarveyC on February 22, 2008 at 5:01 pm PST.


Axel, thanks for the heads up. I decided to go 12.5 gph drip for plant, and 18 gph per plant using three 6 gph microspray.

The only thing in the greenhouse are:

2 lemon strawberry guava
1 red strawberry guava
1 Osbourne Profilic Fig Tree

Since there are all top feeders going half way on microsprays does make sense to me.
Maybe with the micro sprays running to moisturize the surrounding areas, the drip will puddle out sideways more instead of going all the way down through the path of least resistance.

The above followup was added by Jonathan in San Francisco on February 23, 2008 at 2:32 am PST.

I also need ideas on a new irrigation setup

I am trying to setup a better irrigation system for my fruit trees and need some ideas. Anyone has some pictures of your setup to share?

Right now I have a drip system supplying about 5gal/hour per tree but I don't like the setup.


The above followup was added by Raul on February 26, 2008 at 8:40 am PST.


It would help if you would explain what you didn't like about your system, what you're trying to water, etc.

The above followup was added by HarveyC on February 26, 2008 at 12:52 am PST.

To many hoses


What I don't like about my system is the fact that I have to many 1/4in hoses feeding off a 1/2in hose. The main 1/2in hose runs parallel to the trees but about 2ft away so I had to run 1/4in hoses off the main and connect drip emitters to it. I have 2 drip emiters per tree connected to 1/4in hoses. Hope this makes sense

I am looking for a more convenient way to irrigate without running so many hoses.

I am trying to water tropical fruit trees such as Cherimoya, Green sapotes, Sapodilla, etc.


The above followup was added by Raul on February 26, 2008 at 3:00 pm PST.

With such hardy tropical trees, much better to use low volume sprayers, like in the commercial orchards.

Even many avocado growers have switched to these, the drippers in most cases just not wet the surface soil enough, as most of their roots are near the surface of the soil. They work fairly well for deeper rooted stone fruits and such though.

I have talked about my bananas before and my soil. My soil is sandy silt, and the water goes down fast like sand almost in much of my yard. And when I use a hose or a high volume sprinkler, the water mostly goes down and saturates the even more silty sub soil, with hard pan 2 to 5 feet below the surface. It was affecting the bananas deep roots, too much water and the surface roots, where most are, were not staying damp.

I installed low volume spray emitter system 9 gph to solve the problem of too wet of sub soil mainly, but solved the surface problem at the same time.

Now the surface soil soaks up with water and stays damp for quite a long time, and sub soil does not, and I cut down on my water consumption.

And in the processed solved another problem I didn't know I had control of. A few of my banana plants did not like hot temps near or over 100F, they would just stop growing completely and would take some time after a temp cool down to start again. After installing the low volume 9 gallon gph sprayers, that problem wet away too. How they do just fine in hot temps, just like the others, and the others even do better too.

I used to only expect 4 1/ to 5 1/2 feet of growth in one season, now I often get twice that, nothing to see a newly planted rooted 20 inch TC banana from a pot, grow to 8 to 9 feet in one season.

Sprayers can be placed every 5 to 10 feet depending on pressure, volume and type of sprayer.



The above followup was added by DavidLJ48, Waterford CA, zone14 on February 26, 2008 at 3:33 pm PST.

drip and micro-sprinklers

As I mentioned before, I use micro-sprinklers in my chestnut orchard and like they, but mostly because of the large area they cover as chestnuts become very large trees. There are problems with them that I don't have for the few situations where I use drip. Weeds are more of a problem with micro-sprinklers, though that is usually something that can be managed in a backyard situation fairly easy. Wind can also be a problem though, again, that may not be much of a problem in fenced yards. I use micro-sprinklers with a 270* pattern, placing one on either side of the tree so that I don't water the trunk and cause fungal problems, but that probably is not a problem for most tropical plants. If you have plants with many surface roots, micro-sprinklers are probably the way to go since lateral movement of water with drip emitters may not take place under quite some distance below the soil surface. Micro-sprinklers would certainly enable you to reduce the number of feeder hoses you use.

I have had more rodent damage with micro-sprinklers than drip but where I use drip I don't usually have feeder hoses. Rodents seem to enjoy chewing on my feeder hoses leading to my micro-sprinklers. My feet also like to trip over them when pruningm, harvesting, etc.

The above followup was added by HarveyC on February 27, 2008 at 7:31 am PST.

Watering Avocado Trees (10 acre)

which irrigation is better, dip or micro spray ?

The above followup was added by jeannie warnock on September 05, 2008 at 10:19 pm PST.

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