I checked your math and I get the same result. It is good to do the math and I don't think it is a waste of time at all, but the real test is what the tuna cans say. You might need more time on one zone and less on another. I run each zone twice for 45 min each so that I get 1.5 hours total, which is what I need. I do this to make sure the water doesn't run off or pool.

The other thing to remember is that you ARE NOT doing this once a week! When your grass is tall and the roots are deep you might only irrigate once a month, or not at all if it rains in any appreciable amount. Warning: if your lawn isn't used to deep watering it won't be able to take advantage of it and you will have to water more frequently.

I tried the tuna can method but for some reason it takes like a whole day to fill it ...

LOL. Those are the cans I use. Index finger - first knuckle is 1 inch, second knuckle is 2 inches.

With my water pressure, hose, and turbo oscillator sprinkler it takes 8 hours to fill the cans. My neighbor's high flow in-ground system takes 20 minutes. Every system is different, but the amount per 1,000 square feet is always going to be 623.376623 US gallons.

Do you just put a few can in random parts of each zone and keep checking till they are all full?

Why one inch? Why not 1/2 inch or 1 3/4 inch? What's the rational?

I don't check for water volume, I use a 6 inch screwdriver and when it goes in all the way I'm done watering. Based on the amount of time it takes and volume of the sprinkler seems to be about an inch of water for me.

Yardtractor: if you use 1/2 or 1 3/4 then you'll have to aerate. With 1" you don't need aeration. :o)

How do you know when you've put down 623.2766233766 gallons of water per 1,000 sf?

There's more than one way to skin the same cat. You can use a tuna can, you can use a screwdriver, you can look at your water meter, the purpose of any of those is do determine when you've watered enough.

If you're confident your sprinkler heads will give you even coverage - 1 inch across the entire surface, not 1.3 in one area and 0.7 in another - then the water meter and math method will work fine. Otherwise, the tuna can method would give better results by measuring the exact amount of water per area and not an average across all areas.

I also think different soil types have different water absorption rates. It may only take 1/2 inch for some soils to get moisture 6 inches deep, while with others runoff will occur and you can put down 3 inches of water and not get anywhere. To me the goal is water 6 inches deep, so I don't care how much water I put down, I use the screwdriver to know when that goal has been achieved. For my soil it happens to be about 1 inch of water.

Do all of your nozzles spray the exact same amount of water from the nozzle out to 15 feet? How about where the spray pattern between two systems overlaps? Do they need a little springtime adjusting after going through the winter? I'm all for calculating but it is plain stupid not to distribute a few cans around the yard to double check the distribution (not calling you stupid :o) ). For that matter, how do you know you are getting the rated amount of water? Did you do a flow test when the system was installed? What pressure is your system regulated at and how does that compare to the rated flow? Seems like the cans provide a good way to test each nozzle if for no other reason.

I should add that last year I was getting excessive dryness in one particular part of the lawn. I redid my tuna can test and realized I had been watering for only 45 minutes instead of 1.5 hours. Maybe I could have caught that with a calculation but it was quick and accurate.

Each zone is pretty close. I also tested each zone separately. Of course there will be some overlapping and the possibility of each sprinkler head not putting out the "exact" amount, but I think it will be ok and narrowing it down to testing each zone will get it damn near close. I just preemerged through my sprinklers as well, it works great. I plan to fertilize, fungicide, and repel mosquitos this way too. I just wish they had liquid seed, hahaha.

September 2016:

"For some reason none of the seed is germinating in a 2 foot radius around my sprinkler heads".

wait a second, how are you applying product through your irrigation system? This sounds genius. Also, I like your water meter method, but I'm out on that one since I have well.

Yea I guess whatever works for someone is fine. The point of this thread was that I was under the impression that an inch of water can be obtained somewhere between 15-30min per zone and after I did the math I came up with 137min per zone. i had know idea it would take that long so I just wanted to make sure I wasnt misinterpreting the "1inch of water".
You can fertilize through your sprinklers using an inline fertigator that sucks up whatever liquid you want and mixes it into your system. I took a lot of heat on this forum once I started looking into it because I guess its not the norm, but I got tired of walking a half acre lawn with the spreader lol.

It just takes a lot of math and trial and error and timing of zones to make sure it is spraying chemicals correctly. I dilute mixture by 2 and run whatever liquid through sprinklers twice to be safe. I figure this will compebsate for overlapping. So far I did preemergent, the end of may will be the first time I run fertilizer through.

What about back flow of chemicals into your water supply? How do you account for/prevent this?

It's called a backflow valve. It's code in most jurisdictions for in-ground water systems hooked to potable water.

It's code to have a double checkvalve backflow preventer on the supply side of the sprinkler system.

Edit: Yardtractor1 beat me to it lol.

So, no one knows why, you folks just follow the "1" rule" because you were told to, no questions asked. K.

So, no one knows why, you folks just follow the "1" rule" because you were told to, no questions asked. K.

It's because on average 1" of water will give you about 6" of soil penetration, which is the target depth. It's a rule of thumb, there's going to be variations.

It's because on average 1" of water will give you about 6" of soil
penetration, which is the target depth. It's a rule of thumb, there's
going to be variations.

That's the common sense explanation. I've used it here many times myself in a quick and dirty explanation of what it "likely" is intended to accomplish. However, I have never seen any studies that support it. Ever. All searches for the rule return citations from here or other lawn forums. Due to the "variations", I'd say it isn't a very accurate rule of thumb. Sorry, I just find it humorous when people spend so much effort calculating a rule of thumb.

Well, it's an easy test. Get a clear plastic bucket, fill it with dirt, calculate how much an inch of water is for the surface and pour it in, then measure how deep it went.

When I'm watering, it takes me 3.5-4 hours to cover 2000 square feet to 6" deep based on the screwdriver test. The sprinkler outputs 350 gph which amounts to about 650 gallons per 1000 square feet. That's about 1", so there's my anecdotal evidence.

I was in on the deep and infrequent rule as far as this forum goes. Waaaay back in about 2004 or so I got into a very heated discussion with a lawn care pro from Phoenix. My point was that watering every day was better than deep and infrequent. After about 2 weeks of skirting along the boundary of getting kicked off this forum, he finally convinced me that deep and infrequent would work better for several reasons. It seems to me that 1-inch was understood to be the definition of deep. That left the frequency as an open question. That issue was discussed for years on three different forums. Finally the temperature scale emerged as the dominating factor among all the different factors (air temperature, soil temperature, soil mix, organic matter, grass type, mowing height, grass density, wind speed, clouds/shade, direct sun, humidity, and probably other factors). I have a gardening text book from the early 1970s. I'll look to see what they recommend. I'm pretty sure they recommend infrequent watering, but what the depth is, I can't remember.

I can't get away with 1 inch a week for cool season grasses here in NC, I get drought stress after about 4 days with temps in the mid to high 80s. I posted on another forum but I pulled a patch of sod from the back to fix my front lawn after the electrical people dug into it and the grass roots went down about 6-8 inches, thus watering any deeper than that would be pointless.

I just water when I see signs of drought stress until my 6 inch screwdriver goes in all the way, don't really care about inches of water or set intervals. I think it's important to listen/watch what the grass is telling you rather than blindly follow one size fits all solutions.

J4 what kind of grass do you have?

It's a mix of TTTF(Speedway) and HBG(Spitfire).

I recall you said you're in a transition area so I guess the seed choice is very important.

.

Sorry tye. I didn't mean to hijack your topic.

J4c11,

Get a clear plastic bucket, fill it with dirt, calculate how much an
inch of water is for the surface and pour it in, then measure how deep
it went. When I'm watering, it takes me 3.5-4 hours to cover 2000 square feet to
6" deep based on the screwdriver test. The sprinkler outputs 350 gph
which amounts to about 650 gallons per 1000 square feet. That's about
1", so there's my anecdotal evidence.

Based on your statements, 6" is perfect for your lawn as your turf's roots are 6-8" deep. It appears that it isn't the 1" of water that is important to you, it's that the full depth of your root zone gets moistened which in your case happens to take 1" of water. Makes sense to me.

So, you fill a clear bucket with a foot of your soil and add an inch of water. You wait an appropriate time for the water to percolate so that the soil retains maximum moisture and is not water logged. You measure and sure enough, the 1" of water wetsexactly 6" of soil to maximum moisture content. I assume that if it measured 10", you would reduce the amount/depth of water until it wet 6" or if 1" had wet only 4" of soil you would increase the depth of water added to reach the desired 6" of moistened soil?

On to the implementation of the 1" rule.

If soil loses moisture from the surface down and 1" of water will wet 6" depth of this soil. wouldn't you have to wait until the top 6" has dried out before adding 1" of water to avoid losing water to percolation below the root zone. Not to mention if you waited until enough moisture had left the top 6" of soil (dry) before applying 1" of water, the turf would be dormant if not dead and the turf would give visual indicators of drought stress long before 1" of moisture had been lost. So even more likely that much of the added 1" of water would percolate below the root zone.

Wouldn't it be more efficient to measure the the amount of water lost and replenish that when the turf showed signs of drought stress? Once you correlated the amount of water loss that created drought stress, by keeping track of daily water loss, you could replenish the lost water before turf showed signs of stress. Seems like that would be a better system to impliment than the !" rule.

I assume that if it measured 10", you would reduce the amount/depth of water until it wet 6"

I would, unless there was evidence that watering to 10" deep would encourage grass to grow roots 10" deep. If your grass is going into summer with 60% deeper roots that's a huge win in my book. Otherwise it would be a waste of water since the grass wouldn't be able to take advantage of the deep water. This is the big question, how deep will tall fescue go for water? I may have to grow some fescue in a transparent container of some sort and find out.

or if 1" had wet only 4" of soil you would increase the depth of water added to reach the desired 6" of moistened soil?

Yes I would.

Wouldn't it be more efficient to measure the the amount of water lost and replenish that when the turf showed signs of drought stress? Once you correlated the amount of water loss that created drought stress, by keeping track of daily water loss, you could replenish the lost water before turf showed signs of stress.

Ideally, yes, but conditions (wind/sun/clouds/moisture) vary every day and so getting an accurate prediction is going to be tough. But I basically take this route and water when I see signs of drought stress rather than at fixed intervals.

I have given this issue some thought over the past year and the way to do it is to put a wireless moisture sensor in the ground at say 4" in each zone that talks to your irrigation controller. Once a certain configurable low moisture threshold is reached , it triggers watering for the zone . Once a certain high threshold is reached (enough water has been applied), it shuts off irrigation. This way you would use only the amount of water necessary to bring moisture back up and only when that moisture is needed.

No problem. I appreciate all the help. Can you explain what ypudo with the screwdriver test?

Sure. You take a 6" long screwdriver and you stick it in the ground. If it goes in easily all the way you're done watering.

The theory is that because water acts as a lubricant, wet soil will allow a probe (screwdriver) to penetrate soil easier. The difference between the resistance (and consequently the difference in the depth the probe can penetrate) before and after watering is an indicator of how deep the water penetrated. e.g, if you can push the screwdriver into the soil 2" before watering and then can push it into the soil 5" after watering, the water has wet the soil to at least 5"

I have given this issue some thought over the past year and the way to
do it is to put a wireless moisture sensor in the ground at say 4" in
each zone that talks to your irrigation controller. Once a certain
configurable low moisture threshold is reached , it triggers watering
for the zone . Once a certain high threshold is reached (enough water
has been applied), it shuts off irrigation. This way you would use only
the amount of water necessary to bring moisture back up and only when
that moisture is needed.

I believe they sell those, but quite expensive and not an option for many people. For those on a dime it would be cheaper and easier to get the daily water loss off the internet. And some of us can. Then all we need to do is plug in our turf factors, subtract the daily rainwater for the week and water our lawn the needed amount to make up the difference.

For those on a dime it would be cheaper and easier to get the daily water loss off the internet.And some of us can. Then all we need to do is plug in our turf factors, subtract the daily rainwater for the week and water our lawn the needed amount to make up the difference.

That is solution number 2, but an estimate vs an actual measurement. Probably good enough for most people. If you live in NC, the NCSU TIMS calculates water evaporation and input based on weather station data and send you alerts when it's time to water and how much. You then tell them how long you watered and they add that to your account. Really great effort from the NCSU team. I asked about an API - you could use something like a Raspberry Pi and some valves to build a controller for your irrigation system - but never got a response.

If you live in NC, the NCSU TIMS calculates water evaporation and input based on weather station data and send you alerts when it's time to water and how much.

Exacty! I'll bet it doesn't work out to a precise one inch very often.

An inch is an inch. No math needed, its not that complicated. We are talking about watering your lawn here. Put a can out, watch the clock on the wall. You are seriously over thinking it.

The point is.... it's not necessarily an inch and over 22K a quarter inch can amount to a savings of 3400 gallons per watering. Sometimes if a person was just a quarter inch taller things wouldn't go over their head. Right Daniel?

Why hurt your back putting cans out when you can just do the math and then just push sprinkler buttons lol?. Sounds like less work to me lol. Plus, math is fun!

Hi Yardtractor! Don't get me wrong, I appreciate considering alternatives and maybe better methods for watering. The discussion is good. However, I think there is more to the story than you are considering. The point of providing 1" of water is that the roots will go where the water is. In my thinking, I disagree that if you want 6" roots then you only need to water down to 6". Here's why: Let's say you dump 1" of water into the soil and through gravity and capillary action that water makes its way down to 6". Great. So at this point from surface down to 6" there will initially be a relatively uniform moisture profile, or gradient. As the days pass, water is evaporating from the surface and is also being drawn out through the roots. I think it is fair to say that the surface will dry out sooner than at the roots 6" down. So in dry weather we start to see a moisture gradient going from dry at the surface to wettest at the bottom of the roots. Now at this point if you provide another 1" of water, it will again percolate down to the 6" level, but there is already some moisture there, so it will go a little deeper than 6". This provides a reservoir of water just below the root level. When the surface begins to dry again, this reservoir will be drawn upward through capillary action towards the surface, and towards the roots at the bottom. So we are creating a moisture gradient where the greatest moisture is at the bottom of the roots, encouraging them to grow.

If instead of watering 1", we measure that there is still some moisture at the 6" level, and decide to water only 1/2 or 1/4" to reestablish an even moisture profile, I believe you will begin to see that profile get inverted so that you have more moisture nearer to the surface and less deep down as a reservoir for the roots. If the roots go where the water is, you risk encouraging shallow roots.

I'm sure it is more complicated, but I think the idea is to drench the soil so that you keep more moisture deep in the ground. If you trickle water in "as needed" the roots will have more even moisture more of the time and won't be encouraged to grow deep.

Or, I could be wrong, but this makes sense if the overriding principle is that the roots will seek out the water.

tye: I gotta tell you something. Judging from your inexplicable resistance to do something as simple as confirming your calculations with actual data (put out a few cans and measure the water), I can imagine that this next bit of advice may also go unheeded. On the other hand, you did come here for advice so it is possible you will listen to some of it.

Here it is: Never, never, never, ever, ever, never, ever, ever, never...ever (that's a bunch of "never ever's") attach poisons to your home's drinking (potable) water supply. I know the alternatives are more cumbersome, but please do not fall victim to the convenience of this "fertigation" system.

I don't know your background, but as a chemical engineer, I worked for 10 years in one of the largest plastics production plants in the world. Part of my job was designing process improvements which involved a lot of piping and valve considerations. Later, as a unit manager, I had to understand and help improve safety issues, including potable water considerations. So I believe I have something of an "expert" or at least well informed opinion on the subject.

Sometimes improvements are only made after an accident. For instance, it is not enough to throw the breaker on a piece of equipment before repairing it. Time has proven that somebody will come by and turn on the breaker, killing or injuring somebody else. So a lock and tag is attached to the breaker, and is logged into a book. As the years pass, general principles, or "do's and dont's", are developed. One of the greatest "do's" is too keep everything connected to potable water piping completely separate from any process piping. This keeps chemicals where they belong and clean water where it belongs. This same principal exists in the home. Just simply rule out the idea that you are going to connect any kind of chemical to your drinking water supply. Now, before you give me all the reasons why it is OK, let me try a couple of things out on you:

1. If a backflow or check valve is so foolproof, why does your town require two of them inline?

2. Think about this "thought" experiment: First, let's tap into your plumbing 6 inches upstream of your first back flow valve and put a tee and a sample valve there so we can sample the water. Then, hook up a bottle of cyanide, enough to kill 1000 people to your fertigation system and let it run. Flush the line as you said you've been doing. Don't use the water for 24 hours (ie, let your plumbing sit idle for a day) and then sample the water from the new tap. How many people do you have in your family? Let's say 4. Pour a glass for each and line them up at your kitchen table. One for the wife, the kids, and maybe a little for the dog. Tell them what you did. How many of them are going to drink the water? Would you bet your family's life that you've considered everything that could go wrong? Do this same experiment every day for a year. Nothing could go wrong ever, right? One check valve isn't perfect so the town requires two. Two check valves are perfect but one isn't? Do two check valves permit you to add chemicals/essentially poison to your potable water system? Call the town on that one. But you aren't using cyanide. OK, then how much pesticide is OK for your kids to drink, maybe even it's just a very little bit on a rare occasion?

There's only one way to prevent unintended pregnancy that works 100% of the time, and that is abstinence.

3. Not to be overly morbid, but the largest plastics plant in the world was down the road and we had the second largest. The other plant was doing some routine maintenance, something they had done maybe 1000 times over many years without a problem. On this particular morning in October, 1989, as I was giving a tour to a visitor from our parent company, we looked to the west to see a wall of flames probably 200 feet high. It rose up and then slowly subsided. What had happened is that the 1001'th time they did the same procedure, it backfired. 22 people died at that moment and we then had the largest facility in the world. That one was mostly gone. It was national news that day and I recall calling my parents across the country to tell them, "It wasn't me!"

So maybe mixing chemicals in with your drinking water works today and tomorrow, but maybe not three years from now when something isn't quite right in your system and you don't realize it.

Again, I'm sure you can come up with a bunch of reasons to justify doing this. It sounds like you've already had arguments over it in the past. I'm suggesting that you put all that brain power towards finding an acceptable alternative. Maybe a 4 gallon battery powered sprayer? Do you have a rider mower where you could tow some kind of spray rig?

Lastly, if you won't listen to me, listen to the chemical manufacturers. The Tenacity label says, first, "It is a violation to use this product in a manner inconsistent with labeling" and then later says, "Do not apply through any type of irrigation system." It seems they have learned some general principals, too, and recommend against doing what you are doing.

Thanks for reading and considering the above.

I know I'm writing a ridiculous amount on this forum recently, but I had one other thought for tye. If you don't have a rain gauge, you can use a tuna can in an inconspicuous location to see how much rain you got any time rain is expected. Then you know how much to top off to get an inch if needed. For me, one index finger knuckle is about 1 inch.

I think there is more to the story than you are considering.

Actually, I did consider them. I chose not to discuss them so as not to overly complicate j4c11's "soil in a bucket" premise.

In broad strokes, I don't disagree with your statements about the desired affect of the 1" rule. (caveat later) I think the argument in favor of "deep and infrequent" is near indisputable. My concern is the 1". The 1' recommendation has become dogma. Don't get me wrong, I've recommended it myself, but I do not think that recommendation is justifiable, leave alone universal. At least not anymore. Case in point is the current OP, andit has become common for others here to match the 1" application. It's likely, in fact, more than likely, that the implementation of the rule is overkill for many people that results in a waste of water and unnecessary cost.

Ideally, if you theoretically start with soil water content at or very near maximum (likely to be the case at some point every Spring), then replenishing whatever amount is subsequently lost should maintain that level. I'm not suggesting that that be done on a daily bases for the same reasons you identified. In order to reap the benefits of "deep and infrequent" replenishment can be done weekly, give or take, based on turf stress. If you had a daily record of water loss, eventually, one should be able to determine the amount of cumulative loss that results in stress for your particular turf and soil and anticipate when to water. The end result would be to water efficiently and avoid waste.

ET data is becoming available in more and more regions and we should be implementing it and advising its use, rather than repeating the 1" dogma.

The previously mentioned aside:

Or, I could be wrong, but this makes sense if the overriding principle is that the roots will seek out the water.

With the exception of one Canadian University study ( I believe the plant was a legume and not a grass and the study, as usual, is no longer available on the internet viewing - I found their conclusions unconvincing) there is no basis for believing that grass, or any plant's roots can actively seek-out anything (although it would be interesting to see a study of any relationship between hypha and root growth direction). The consensus of turf specialists and agronomists is that when, through random growth, roots do enter an area of abundant moisture and/or nutrients, the growth of roots proliferates in that area.

Yard: I actually agree with everything you've said. I should say that I do not believe the roots actually grow through dry soil in search of water. What I mean to say, and I assume what most people mean, is that the roots will tend to populate moist locations.

I should say that I do not believe the roots actually grow through dry
soil in search of water. What I mean to say, and I assume what most
people mean, is that the roots will tend to populate moist locations.

I'll wager if you search my posts that I've said it too. I do disagree that that is what most people say when they don't mean it. I've decided to watch myself so I don't leave new people with misinformation. Otherwise people will be repeating a new dogma: "Water 1" because the roots seek out water and will grow deeper to find it." Lol