[Jeff_Brauer]

Alan,

I like your response.

It always bothers me when superintendents use the computer to replace ET 100%.  As noted in one post, ET is the main factor, but available moisture is the real component to determining irrigation need.

For most turfs, if plant moisture falls below 33% of field capacity, poor appearance, death (rye, bent) or dormancy (i.e. Bermuda and Blue) occurs. Thus, most superintendents won’t keep turf right on the edge, except when forced into it by improper water supply or drought.  In general practice, they maintain turf in a range between a minimum of 50% to 100% of available moisture.  Thus, there is no need in replacing ALL the ET.  It isn't necessary except for dessert climates! 

I can understand greens that are kept near field capacity for consistency, while tees and fairways may reach 25-50% depletion and roughs may tolerate 60% depletion, where the control system and sprinkler location allows.  But, increasing depletion allowances builds drought resistance and saves water.

Replacing all the calculated ET would result in a figure of close to100% of ET replacement.  But allowing turf to cycle through from full water capacity to something much drier saves a lot of water. 

For others -

 Available moisture is measured in inches per foot, so it increases with root depth. Manicured turf roots to 6-18 in., depending on species, soils, season and cultural practices. Watering practices that encourage deep rooting (i.e. deep, infrequent watering) actually improve water availability to turf, and slowly build resistance to drought.

Warm Season Grasses (bermudas, Paspalum and Zoysia can have roots 1.5-5.0' deep. 

Cool Season  Grasses (Bluegrass, Perennial Ryes, and turf type tall fescues have roots  0.5-1.5' deep.

Creeping Bents   and Annual Bluegrass  in soil average 0.1-0.3' deep. Properly managed, bent roots in sand greens can reach down nearly the full 12" of sand.
 
For the midwest, a course might have bent grass tees, greens, and fairways, with a Blue/Fescue mixture for roughs.  If we assume the superintendent will achieve average root depth with his maintenance practices, about 50% of the course will average root depth of less than 1 foot (bents) and half about 1.25 feet.

Root depth helps determine available water, and likely maximum days between irrigation to achieve best results. 

Available Water to the Turf is calculated by multiplying available water of the soil, typical root depth and allowable depletion. As an example, fairways with six inch roots in clay or silt loam soil with 1.8 in/ft of available water, and an allowable depletion of 50% of capacity have about 0.45 inches of available water:

1.8”in/ft X .5ft (root depth) X 50% (allowable depletion) = available water 0.45”.

When summer ET reaches about 0.22" per day, that fw can be watered every other day.  Even when a bit higher being short on water will be made up with natural rain in most climates.  In shoulder seasons, every 3rd night watering is possible when ET drops to .15” daily. 

Short Version - I think supers need to think in terms of checkbook water availability replacement, not 100% ET replacement. Replacing available root moisture should result in irrigation applications of 33-50% less than ET replacement for total water useage.  (I must stress, that is IN THIS EXAMPLE and UNDER PERFECT CONDITIONS)

But, I do know some superintendents who water their fw and greens every 4th day in summer with no ill effects. In part, its becasue they force deeper roots and water availability goes up.

[Craig Sweet]

Joe....I agree, thinking about daily water needs misses the point.  In the nursery business I was constantly reminding people that their lawns/shrubs/trees, would be better off with less frequent irrigation if they put enough water into the soil when they did water...and it helped if they would try and understand the seasonal water needs of their plants.

Is it possible that as a super becomes more aware of the problem areas on his course, and over time he becomes familiar enough with the water needs of his course, that fancy computers are not so necessary...

[Greg Chambers]

The computers make it such that adjustments to the irrigation can be made quickly.  Without the central control, setting up irrigation takes a long time, going from controller to controller.  However, I do agree that as one becomes familiar with how their course takes irrigation, the bells and whistles matter less and less.

[Pete Wendt]

A ton of great points on this thread.


        Food for thought.....  Playability should be the number one goal.  Deep infrequent at certain times of year on some soil types may be better for the turf, but we should be worried about what is best for golf.  Example:  Heavy clay soils in the summer- Deep infrequent Monday night on fairways and roughs.  Tuesday the golf course is a mud pit, Wednesday still plays somewhat wet, Thursday starts to play decent - possibly drying down.  Friday plays great - Water Friday night and the cycle starts again.  Is this scenario good for golf because it may be good for the turf?  Do we not want great conditions daily?  Certain times of year, certain soil types it could be possible all year.  Deep infrequent does work, but irrigation is art, science, qualified eyes on hoses and knowing every pocket of your property.

USGA greens were built for deep infrequent cycles.  That doesn't mean throw the hoses out.

E.T. -  In some parts of the country, the desert being a good example, ET is a great tool.  In others, watering off of ET would bring on every disease imaginable.  It is a tool like many other things to help improve the golf course.

Pete

[Don_Mahaffey]

Yes some good points, but lots of generalizations as well.
Deep infrequent does not mean you turn your golf course into a mud pit.
That's idiotic, not deep, infrequent, but it is an argument often used against deep watering.
Deep, infrequent done right is matching your irrigation programming to your soil infiltration rates and timing irrigation cycles so your soil will take the water.

It's a lot easier to just set up the computer to replace ET each night, but you'll never convince me that's the best way, at least not with the soil and grasses I'm used to working with.

JS,
I understand what you’re trying to do but I just don't see your equation being that great for comparing different courses with different grasses in different regions. What I do think its good for is your own course and tracking your irrigation efficiency to see if all your practices are helping reduce water use.

[Pete Wendt]

Don,

"A mud pit" - That is an exaggeration.  I guess I should have spelled that out!

When you are trying to produce daily playability, deep infrequent on certain soil types is not always the best solution.

Is the goal to grow the healthiest grass possible, or produce the best conditions?  The two are not always one and the same.  We can argue that growing the healthiest plants possible will be the best for playablity because you can push them further, but that is common sense.

[Don_Mahaffey]

Pete,
I'm a golfer, I want good golfing turf.

I don't want shallow rooted junk that requires constant chemical remedies (one good exaggeration deserves another, no?)

How you get there can be argued forever, but it's either dry and firm or not, and I've yet to see a course that waters every night play fast...but it's all in the definition of fast.

I believe there are many, many benefits to deep and infrequent…but above all, I like roots and soil that has some air and can take water. Can you do that with everyday irrigation based on ET, maybe if you’ve got course soils, and you’re paying attention. One of the beauties of deeper irrigation is you can’t go to sleep at the wheel.
To each his own.

[Pete Wendt]

Don,

Who said anything about watering every night?  That would be a recipe for disaster in my neck of the woods.

 We both obviously agree that there are huge benefits to deep/ infrequent irrigation, and we have seen the results.  You obviously did not understand my point on playability.  I would think that shallow rooted junk would play poorly too!! Hence, managing to playability should be the number one priority.  Grow the longest roots possible so you can push the plant harder.  But.. don't sacrifice playability trying to get there.

IMO - In the transition zone on cool season grasses, daily ET based irrigation would not work well at all.  You would end up over watering your golf course.

Gotta run and think of a constant chemical remedy.  I'm thinking vodka tonic, with a twist of lime!

[Don_Mahaffey]

Pete,
For me its all about the game. I get your point on playability. I just didn't like your deep infrequent example.  You had the golf course playing well one day out of five, and although I know you were trying to make a point, I disagree with your example. But I do agree that no matter the method, poor irrigation management hurts playability.

"Grow the longest roots possible so you can push the plant harder.  But.. don't sacrifice playability trying to get there."

In complete agreement

[Steven_Biehl]

One of the misconceptions that has come up is that watering from ET means you are watering every night.  That is not universal for people using ET. I do water everything except greens from ET. I do prefer watering with deep and infrequent cycles. The programs can be set to run when a minimum ET has been reached. For example(from Mr. Brauer's post), a program can be set to run when the available water of 0.45" in the soil has been depleted. The program will not run until the ET accumulates to 0.45", be it 2 days of an ET of 0.23", or 5 days of an ET of 0.10". So, the programs can be set to run deep and infrequently.

Having said that, I run fairways and roughs from ET every night. Not ideal for how I want to water, but here is why. I could go three days between irrigation cycles on fairways and roughs. That ET would accumulate to around 0.50". Returning that ET to 90 acres would require 1 million gallons to be pumped in one night just on fairways and roughs. The majority of systems can't handle that capacity. 100% of ET is not returned either. A allowable depletion is used, like Mr. Brauer addresses, to prevent the turf from being overwatered.

I will water deep and infrequently on tees and greens because the irrigation system can handle the requirements of the smaller areas. In the summer time, I can regularly make it 5 days between cycles on greens and have gone as long as 10 days in July. In the fall, I can go 14 days between cycles on greens.

As stated earlier, everyone has their own preferences, and if it works then keep using it. I like using ET, and would prfer not to go back to guessing how much water to put down. The more science I can use, the less human error is involved. From my experience, the courses I have seen that run their system from ET, have firmer conditions that those who water by feel. 

[Jeff_Brauer]

Steven,

There are post length limits, or I would have added that soils have varying infiltration rates that prevent too infrequent watering.

In general, coarse soils have higher infiltration rates, while cohesive clay soils have lower infiltration rates.  Actual infiltration also varies with soil moisture and surface slope.  Dry soil has high initial infiltration rates, which decrease as soils approach saturation.   In general, steeper slopes lower the infiltration rate. 

Irrigation should be applied at a rate less than the soil’s infiltration rate. The estimated infiltration rate of clay soils might be as low as .07-.17 inches/hour, so a .25 nightly application must be applied in multiple cycles over 1.5-2.5 hours (.25 divided by .07 and .17) to avoid runoff.  Most sprinklers irrigate at about .5 - .6 In./hour, suggesting “alternate wetting cycles” to maximize irrigation and minimize runoff.

Low percolation soils often prevent infrequent, deep watering. Longer periods between irrigation mean more water must be applied at a given time. If you let outer fescue roughs go, and they develop 3' deep roots, then wetting that root zone really takes about 5 inches of actual irrigation.  At perc rates of 0.2”/hour, watering must be spread over 25 hours (5 divided by .2) to avoid runoff.  That usually isn't practical, even twice a month, so watering roughs 2-3 times weekly often fits better in an overall watering schedule.

I like your approach of 90% science, 10% superintendents intuition!

[Larry_Rodgers]

I work with formulas often and am amused at what some of the manufacturer's are claiming their weather staions will produce. The other unknown that has deserves some discussion would be water quality and composition. The salinity and temperature monitoring equipment is one of the most interesting alarms I have seen in a long time and am excited to see it used on some of my upcoming projects.

It is good to start with all the formula's to produce a value and it is even more important that the users are aware of the inefficiencies of their systems, so you can start to make them better. The basics of uniform spacing, good distribution patterns and perfectly positioned sprinklers will make the system more efficient with minimum capital investment.

The best efficiency I have seen in a controlled environment is 91% distribution uniformatty, in the real world with which most of you operate wind, soils, and angle of throw from a crooked head will reduce efficiency to below 75% quickly.

Good Post.

[Steven_Biehl]

I agree about the infiltration rates, but the programs know that also(if you enter the data). Irrigation programs have a feature called cycle and soak. This feature compensates for different infiltration rates and prevents the system from putting out too much water and causing runoff. This feature can be set differently for every station on the course as well. If a cycle time is set for 6 min. and a soak time of 15 min., the head will only run for 6 min. at a time, then shut off for 15 min., before it will turn on again. Thus, compensating for infiltration rates. So, if the system figures that head needs to run for 19 min. to return ET, it will run for 6 min., shut off for 15 min., run for 6 min., shut off for 15 min., run for 6 min., shut off for 15 min., then run for 1 min. to finish the cycle.

So, this feature allows soil to be watered at less than their infiltration rates.

[Craig Sweet]

Maybe it's just me, but this total micro managing of your irrigation system...the fancy computers and all, have the potential to remove the human element from growing good turf....and the potential to detach one from the mission at hand.

[Joe Perches]

if the system figures that head needs to run for 19 min. to return ET, it will run for 6 min., shut off for 15 min., run for 6 min., shut off for 15 min., run for 6 min., shut off for 15 min., then run for 1 min. to finish the cycle.

Would it be better to use increasing delay intervals?
Something like: On 6, Off 15, On 5, Off 30, On 4, Off 60, On 4

[Donnie Beck]

Using ET sounds good in theory but I don't care how much your spent on your system it is going to have flaws. Last time I checked golf courses are not consistent sizes and shapes. There are going to be areas that get more water than others and other areas that don't get enough. Forget about the spacing issues for a few minutes and start to think of all the micro climates around the golf course. Sun, Shade, Trees, Wind, exc... Way too many variables to factor in. IMO there is no way around dragging a hose. It may be more labor intensive but I feel it still provides the most consistent playing conditions.

[Jeff_Brauer]

Craig,

The superintendents job is becoming more science and less art all the time, I agree. I haven't noticed any detachment on the part of the vast majority of superintendents. It merely lets them focus on other things.

But, as Donnie has just mentioned, and as one old and respected superintendent told me as well, a great super will still have the guys hand water, particularly on greens.  The sprinklers are still 70' apart and there can be micro contours (or big honkin humps) in your greens that simply are smaller than the combined sprinkler area and its possible control variations. 

I used to judge a superintendent by how little I could get him on the phone in the shop.  That has changed with cell phones, but the need to be constantly on the course, and not in your office will never change, despite any new technolgy.

Steve,

I know the computer knows all that (if the super who uses it can program all that - not all have gotten that sophisticated and used every feature our friends at Toro and Rainbird have put in there, much like I use only a limited portion of what my software can deliver)  

Just out of curiosity, do you also program for valleys and hills, shade and sun on every one of your stations?

Joe,

In the old days, a wise old head took me over to his office plant.  He put water in and it went right through.  He spritzed it with a mister.  Then he put more water in and it percolated slowly, because the light application adjusted the surface tension.

Old supers used to water 3-6 minutes - one or two complete rotations (mister bottle) and then come back with their full application.  So, if anything, the first cycle should be the small one and the others longer.  As to the rest of the cycles, it really depends on the math, which as Steve says, can now be done by the computer for you!

[Don_Mahaffey]

Steven,
I think we all use ET, but I use it as a guide and factor in other condiditons as well. I can get away with a irrigating at 30-40% of ET if I'm coming out of a wet period and that number climbs as I get into droughty conditions. But, I still keep it at 70% or less and I do think using deep infrequent helps with that.

Craig,
The computer is a tool and it does some very nice things for you. First, the flow management part really helps to protect your system as it keeps velocities and flows in line with your pipe size.  Record keeping is a lot easier especially if you've got it communicating with your pump station. It's a lot more than just turning water on and off. If your in an area with high electricity costs and especially demand costs, the computer can help to make sure you stay within the limits so you're not spending $$$ because you trigger some demand charge.

But, like Donnie said, it's not going to do it all for you and if you try and let it you'll end up with a wet, uneven golf course. The newer centrals have outstanding control and features that can save time like the PDA you can drive the course with and then sync with the central. But hose dragging will always be a part of the equation.

[JSPayne]

I'm glad the topic has brought up a lot of good conversation.....I think it's fairly obvious that irrigation is still very much an art as many involved in this discussion, at the end of the day, will have to agree to disagree at least on some aspects of how to effectively irrigate a golf course.

But we've strayed from my real intention.

Look....maybe this is only siginificant for us here in California, but the reason I brought up the original idea was because water worries, reductions and restrictions are getting VERY scary here in California, and only look to get worse with the kind of weather we're having this winter. We can all be sure that as some of the largest water users, we will be looked at, evaluated and taken to task if Joe Public thinks we are wasting the new "golden resource." Likewise, even if availability of water is something you don't have to worry about, we as an industry still use alot of it, and it behoves us to demonstrate, proactively in my opnion, that we are some of the best managers of water that you will find in ANY industry.

But how are we to effectively evaluate the efficiency of a golf course, and compare it with others around the globe? Say the US government steps in and really wants to know if golf courses are using water as well as they say they are. How will they go about evaluating it in true government fashion, which is to try and find the easiest, simplest measure that the general public can understand so they can publish the results?

For example, one course could say they use 80 million gallons of water annually over 100 acres, while another two states away uses 40 million over the same acerage, or even more acerage. Using only this, Joe Public is going to wonder why Course One uses twice as much water as the other. But using the equation I've put up here, the variables of site-specific weather and total course size (irrigated acerage) would be pulled out as variables.....and it could be entirely possible that both are watering at 75% of annual ET, which could be a good indication of effciency if many other courses are found to be watering at 90+% of ET. ET can be relatively easily explained and it makes sense to the public when trying to describe why we irrigate and how much. Going on and on and on about all the other factors and variables does no good in helping someone who only has minimal interest understand our practices.

Just by COMPARING ourselves to ET does not mean that we are, or have to, irrigate by ET. How you irrigate is up to you, but ET is a tool....a mere scientific benchmark by which you can adjust irrigation practices according to weather. In my eye, going into your computer and changing your fairways to run for 15 minutes instead of 10 at the end of the day is no different than having the computer set up such that if the ET increased by a certain amount when the computer downloaded it from the weather statin, the run time of your fairways then increases by 5 minutes without you having to even touch the computer. THAT is how to effectively use ET.

Worldwide standard evaluation methods for golf course irrigation use efficiency are coming......likely sooner than later. Mine was simply one idea of a way to measure in attempts of levelling the playing field. If it really doesn't work, I'd like to hear why. If we'd get more numbers, then at least we'd have something to talk about. I'm at 85%, two other supers are at 54% and 43%......how big is the variance or am I truly an outlyer? Are the numbers we are using accurate (i.e. has rainfall been removed from the ET used by the lower percentages?)? What kind of grasses are we growing? The questions left after using this equation seem a lot fewer and easier to answer and talk about than abstractedly going on and on about the variables of actually getting the water into the soil.

[Craig Sweet]

Don....I fully agree with what you and Donnie have added....I asked those questions to draw this discussion deeper into what is happening with irrigation these days....it often seems that  "automated irrigation" is a bad word on this board....but a smart Super utilizes it as one of several tools in growing good turf...

We use ET...but in a very limited way....first of all, our weather station is on the roof of the maintenance shop        And we know that there are many variables through out the course....soils, sun, wind, topography, vegetation, gaps in the system, pipe size, head size. etc, etc.   But over time the Super has become aware of this, and he's more comfortable with the irrigation system...we know that every summer the same greens will have to be hand watered....we know that certain areas will become over watered if we aren't careful and paying attention.....it still boils down to having as many knowledgeable eyes on the course as possible....thus, it is still an ART.

[Jeff_Brauer]

JS,

I understand your intention.

Craig,

If we want this board to embrace technology, all we have to say is that it was always intended by Toro to be a better way to play firm and fast - in theory, superintendents should be able to keep courses closer to the edge of dryness.

[Greg Chambers]

JS,

72.18%

[Scott Furlong]

I’m with Pete on this one.  In our neck of the woods, mid-Atlantic, if we watered deep and infrequent during a hot and humid summer on our clay and rock we would be a mud pit!   That’s with every head on the course micromanaged to a specific output.  The only exception is a drought year when humidity levels on average are lower.  Because of our annual rainfall, sub-tropic zone, most irrigations systems are designed to help grass survive in between rain events.  The opposite is true in arid regions; they rely solely on their irrigation system.  Furthermore, they are always dealing with sodium issues that require flushing and deep watering.  Irrigation heads and systems have made their greatest advancements in this region and the rest of the regions have benefited from it.  I’m not saying we never water deep and infrequent, but when it’s humid and hot, give it enough to fight the battle tomorrow.  In my situation, ET it for a week, stay away from the first tee for a week.     

[Don_Mahaffey]

JS,
You may want to visit AZ dept of water resources for more info as they have been doing what you’re trying to do for about 40 years. You might have to dig around a bit but I'll bet you can find their methodology for golf irrigation.

BTW, my number is .4911

TX gulf coast
95 acres of turf with 75 acres of close cut fwy.
Non-over seeded bermuda kept lean and dry as possible.
Off color turf is acceptable
Almost all N applied through fertigation.
This was the first full year of irrigation as course was planted previous late summer and fall. I hope to use less water this year.
Poor irrigation water quality,  High bicarbs and Na

(When it does rain here in the summer it comes in buckets...not all rain is the same and fine tuning your equation may require measuring effective rainfall. Rain that falls at a rate higher than infiltration is lost and skews the equation…as does rain that falls in the winter in your area when you don’t need it…comparing regions is tough)

[JSPayne]

Don and Greg,

Thanks for the data. For those who are attempting the exercize, can you add what grass types you're growing? I think that would help to compare apples to oranges. Seems like close to 60-80% would be a decent range for cool season grasses (that makes mine high, but after my first year on this property I'm still learning the ropes a bit and at least it was a better number than last year). 40-60% sounds close for a good warm season number. Won't know without more data though.

Don,

I agree with your explaination of effective rainfall. But if you are closely recording the numbers, ETa should be calculated everyday, so if it rains more than there is ET, the lowet number you can get is 0, no negatives. So finding total ET for the year, then subtracting total rainfall doesn't quite work. You need a total of daily ETs, less any rainfall FOR THAT DAY, with the min value being zero. That will cancel out the effects of any excessive rain events.

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