Irrigation Scheduling: Q & A For Organic Practitioners

[Kiril]

This thread is for Q & A regarding issues surrounding irrigation scheduling and management. This topic is far to complex to just post some info, so the best way I can see to discuss the topic is Q & A.

That said ... anyone who schedules irrigation controllers should be intimately familiar with the following document. Most (if not all) modern day "smart" controllers use some form of the landscape coefficient method to determine landscape water use.

http://www.water.ca.gov/wateruseefficiency/docs/wucols00.pdf

Let the discussion begin.

[starry night]

Kiril or anyone with science education: Is there any detrimental effect of irrigating lawns with sulphur water (strong enough concentration that you can smell it when the irrigation is running.) ?

[Kiril]

Kiril or anyone with science education: Is there any detrimental effect of irrigating lawns with sulphur water (strong enough concentration that you can smell it when the irrigation is running.) ?

My most immediate concern would be the impact on soil pH. Beyond that, can't really comment without more info.

Have you had the water tested and have you identified the source of sulfur? If it stinks that much I can't imagine it being potable.

[OrganicsMaine]

Every spring, I have to re-program the irrigation systems on my customer's properties. They are always programed for watering every other day, for 20-30 minutes per zone.

What will it take to get these irrigation guys to learn these basic things? I have to say that I don't mind it, because it just makes me look better to my customers.

BTW....Most of these accounts have rain sensors, and they are re-programed by me to run 45 min to 1hr 2x per week. I can add an additional day if we get dry, but we get a very healthy amount of rain up here!

[Kiril]

Every spring, I have to re-program the irrigation systems on my customer's properties. They are always programed for watering every other day, for 20-30 minutes per zone.

What will it take to get these irrigation guys to learn these basic things? I have to say that I don't mind it, because it just makes me look better to my customers.

BTW....Most of these accounts have rain sensors, and they are re-programed by me to run 45 min to 1hr 2x per week. I can add an additional day if we get dry, but we get a very healthy amount of rain up here!

Need to know at the very minimum sprinkler type and/or PR (per zone), hydrozone requirements, system DU and AE or IE, soil type, average effective root zone for each hydrozone. That will provide the absolute minimum basic information required to comment on any scheduling.

Just so everyone is clear .... I am a strong proponent of deficit irrigation practices.

[OrganicsMaine]

OK Kiril, you have me here.....*trucewhiteflag*I don't take the time to find out what the heads are or what their output is. Its really not a part of my business. So if you could clarify what those acronyms are, I will try and give you a bit more info.

I know my system is not perfect, but it is better than just watering everyday or every other day for less time. I also call/email customers and tell them to turn off the system entirely if we have gotten too much rain....last two summers, just to let the lawns dry out a bit.

[Kiril]

PR = precipitation rate
DU = distribution uniformity
AE (or Ea) = application efficiency
IE = irrigation efficiency

[Landscape Poet]

OK Kiril, you have me here.....*trucewhiteflag*I don't take the time to find out what the heads are or what their output is. Its really not a part of my business. So if you could clarify what those acronyms are, I will try and give you a bit more info.

I know my system is not perfect, but it is better than just watering everyday or every other day for less time. I also call/email customers and tell them to turn off the system entirely if we have gotten too much rain....last two summers, just to let the lawns dry out a bit.


He has me too! I know most of them have rainbird brand control units. The heads are most likely to be whatever was cheapest that day. Most have rain sensors.
If I am asked to check the sprinkler system I usually do the following.
Set the zone off one at a time.
Ensure that the heads are covering the entire zone it was made too
I collect how much they are putting out by placing some old rusted tuna cans around various areas for each zone. After running for 15 minutes I collect how much water was in the cans on average. I then set that zone to the approximate time expected to be needed to get 1/2 inch of water.
I then program the timer to go off two days a week (already dictated by the St. John's water mgmt group).To obtain a total of 1 inch per week on Lawn areas.
I generally program to go off at 3 or 4 in the morning.

So with that said Kiril - you stated that it might be better to do more frequent lighter watering in FL. It is not possible if they are on reclaimed water supply as they only have access to water on two days. And does the thought of less frequent deeper watering hold true for FL? Are you stating that since the soil is so sandy that it may just end up going beyond the root zone? Tell me the reasoning behind your thoughts.
So does this approach I laid out sound decent in your opinion?

[OrganicsMaine]

Sorry, no can do! However, this could be the beginning of a good educational thread! What is the purpose of each, and how do I figure them out?

[Landscape Poet]

However, this could be the beginning of a good educational thread! What is the purpose of each, and how do I figure them out?

Kind of what I was hoping for, good educational thread!

[ecoguy]

Hey Kiril. Good thread here, I needed more info on this topic. Could you detail some of the consequences of over-watering? Many of my customers are on the every other day schedule too regardless if the grass needs it or not.

[ICT Bill]

I have spoken to several landscaping companies that believe setting their controllers correctly is the main reason that the sites do well
They will take over an account and immediately adjust the controllers to their areas spec's and Viola the site responds well and the owners think that their company is best they ever had

[ICT Bill]

Hey Kiril. Good thread here, I needed more info on this topic. Could you detail some of the consequences of over-watering? Many of my customers are on the every other day schedule too regardless if the grass needs it or not.

anaerobic soils
root andd crown rot issues
quicker to get fungal disease when the pressures are present
leeching of nutrients
run off
An unreasonably high water bill
less microarthropods and worms, they drown

[atouchofnature]

anaerobic soils
root andd crown rot issues
quicker to get fungal disease when the pressures are present
leeching of nutrients
run off
An unreasonably high water bill
less microarthropods and worms, they drown

Don't forget compaction!

[Kiril]

So with that said Kiril - you stated that it might be better to do more frequent lighter watering in FL.

Yes, as it applies to sandy soils. Increased infiltration rate and wetting depth can move water beyond the effective root zone and result in a net loss. You may apply 1", but if only 25% of that is plant available (application efficiency), you have wasted a bunch of water.

You also have less WHC (water holding capacity) in a sandy soil which can lead to a need for more frequent water application because you hit your MAD (management allowable depletion) quicker.

Toss in shallow rooting and hot weather, and your need to irrigate on a more frequent basis increases.

It is not possible if they are on reclaimed water supply as they only have access to water on two days.

Watering restrictions are what they are and you have to work with them. If you can only apply twice a week, then that is what you have to work with. I don't know where you live in FL, but when I lived there I could almost set my watch to the daily thunderstorms rolling in off the gulf. Two days a week should be more than enough with rain. If you find it is not, then you need to increase your SOM.

And does the thought of less frequent deeper watering hold true for FL?

Sure it does, as long as the water goes to a beneficial use (irrigation efficiency). Although some disagree with me, I believe it is important to water a couple of inches or so below the current effective root zone in order to allow for deeper root and for other soil related reasons. Note ... this deeper water does not include any leaching requirements.

For example, if you have a current root zone of 6", a potential root zone of 12", and no leaching requirements, you may want to irrigate to 8", then to 9", and so on until you get your desired rooting depth. As your effective root zone depth increases, your irrigation application depth increases, and your weekly schedule decreases (assuming you can replenish lost water in the time allotted) because your plant available water increases.

Keep in mind, generally speaking the majority of your water and nutrients will be withdrawn from the upper 50% of the root zone, so this is largely the region where you will be determining your MAD.

Are you stating that since the soil is so sandy that it may just end up going beyond the root zone? Tell me the reasoning behind your thoughts.

See above

So does this approach I laid out sound decent in your opinion?

Well, to be honest, no, but it is far better than guessing.

Not knowing how many catch cans you are using, I can only assume you are only getting a rough average PR. Problem is, in a catch can audit, the low quarter is the more important determination as it relates to scheduling.

Furthermore, you may not even need 1" of water. Without a determination of ET (by either calculation, soil moisture monitoring, or direct measure) you can't possibly know how much water you really need to apply.

I also try to start irrigation cycles early in the morning (resi/com) to minimize the impact of pressure fluctuations (assuming it is not regulated) on system performance, and to get all the water applied by 9-10 AM to reduce evaporative losses. Obviously there are cases where this is not possible.

[Landscape Poet]

Thanks Kiril,

Interesting input so far, I appreciate the answers. Thanks for putting your explanation into laymen's terms.

[Kiril]

Sorry, no can do! However, this could be the beginning of a good educational thread! What is the purpose of each, and how do I figure them out?


PR = precipitation rate = application rate of applied water, (in/hour)

DU = distribution uniformity = how uniform is the water applied in a given area

AE (or Ea) = application efficiency = how much applied water is plant available

IE = irrigation efficiency = various definitions, but generally how much of your water is put to a beneficial use.

PR and DU are generally determined by an catch can audit, at least that is what the IA signs off on. You can also estimate PR using nozzle and pressure data. There are also alternative methods for determining DU, but that is well beyond the scope of this discussion.

AE and IE are far more difficult to determine, and for most, beyond the scope of this discussion.

[OrganicsMaine]

Thank you Kiril, since the ground is a block of ice right now, I won't be able to really determine this until April. Many of my customers have told me that their water bills have been cut dramatically due to my adjustments. I'm sure that proper mowing height, and healthier soil go a long way in this as well. On a select few accounts, I have adjusted the rain sensors to the highest level....that is not to work unless it is extremely dry.

i am slowly working on all of my accounts to allow me to do this, but the ignorance of people tends to get in the way of progress!

[Kiril]

anaerobic soils
root andd crown rot issues
quicker to get fungal disease when the pressures are present
leeching of nutrients
run off
An unreasonably high water bill
less microarthropods and worms, they drown

Don't forget compaction!

............. and

shallow rooting (tight soils)
other nutrient problems not related to leaching
salt related problems from poor quality irrigation water

and .............

[starry night]

My most immediate concern would be the impact on soil pH. Beyond that, can't really comment without more info.

Have you had the water tested and have you identified the source of sulfur? If it stinks that much I can't imagine it being potable.

This is at a dentist's office who has a separate well for the irrigation. The building has city water. So it's not meant to be potable. Sulphur water around here is common. Have it at my own home
but with treatment equipment. I've been taking care of this property for about three years and the lawn just doesn't respond the way I would like. I only started using organics in general last year and have not moved all my clients to organics yet. I have the go ahead from the dentist to use organics this year.
I will be testing the soil so I'll be interested to see if your suggestion about the pH effect might be a factor.

[Kiril]

I will be testing the soil so I'll be interested to see if your suggestion about the pH effect might be a factor.

Test the irrigation water too. How much the sulfur impacts soil pH depends on how much is being applied via irrigation. Obviously the more you water, the more sulfur. Make sure you let the lab know this is irrigation water, so they can do the appropriate tests.

[Smallaxe]

I plan to use the 'stress-glasses' to hopefully see when the lawn needs watering. Here we don't even need to turn it on until after Memorial Weekend.

The only lawns that would - die, or go dormant - if left without water, for 2 weeks are the ones that are Over-fertilized and over-watered.

Perhaps, we could hear a comment, about the need for more water, created by an excess, of N. :)

[OrganicsMaine]

Same here SA, we usually don't need much water until mid June. That would be another great nugget of info.....how much more water synthetic lawns need to survive.

[starry night]

That would be another great nugget of info.....how much more water synthetic lawns need to survive.

I would think that salts would be the big factor in the synthetics.

[Kiril]

I plan to use the 'stress-glasses' to hopefully see when the lawn needs watering.

Do yourself a favor and get a moisture meter. Here is a cheap one that will do a fair job in soils that are not excessively high in salts.

http://www.forestry-suppliers.com/product_pages/View_Catalog_Page.asp?mi=3052

IMO, anyone responsible for setting irrigation schedules should have one, along with a brown probe and soil sampler (profile and core). These are the minimum tools required.

[Smallaxe]

Thatch and hydrophobic surfaces,, are also noteworthy, in dealing with, too much synthetic fert.
I like to 'plug' the turf after an irrigation event, just to see, how much of that water is, actually, soaking in. :)

[starry night]

Do yourself a favor and get a moisture meter.

I see in my Forestry Suppliers catalog there is also a Kelway soil pH and moisture meter for about $100. Do you know if that unit is worth the money?

[Kiril]

I see in my Forestry Suppliers catalog there is also a Kelway soil pH and moisture meter for about $100. Do you know if that unit is worth the money?

I have one ..... and no.

http://www.lawnsite.com/showpost.php?p=2092013&postcount=6

[quackgrass]

This one has worked well for me: http://www.specmeters.com/pH_Meters/SoilStik_pH_Meter.html

It is very useful in gathering multiple readings across the site without too much sample prep. Dry soils need to be moistened and it takes longer to get an accurate reading. Moist soils can be tested right from the soil sampler in seconds.

Order a second electrode because they break easily. Once you realize the breaking point its fine.