It's true that your sandy soil won't retain water as long as clay soil, so you may need to increase irrigation frequency some. As you continue with your organic fertilizing regimen and follow good cultural practices by mulch mowing, leaving the clippings in the lawn, the amount of organic material in the soil will increase and so will water retention.

You just need to know when you need to water. Water when the grass needs it, then water an inch. OK that means you have to know what to look for. It is not hard, leaf curl is the best indicator and after you notice it a few times you can tell by just a glancing look by noticing the slight color change. You can also tell by walking on it. The grass should return quickly after walking on it, if it doesn't (if it stays trampled looking) then that's another way to tell. It could be once a week, every other week, or every other day in hot dry weather. Weather conditions such as wind & relative humidity also play a role here.

My 2 cents.....

Good day, Dan

Regardless of soil type, deep and infrequent irrigation of lawns encourages deeper root penetration. The deeper the roots penetrate, the more drought tolerant they become and the less water eventually will be needed.

The frequency is relative and as was very adequately explained in the previous response, will be determined by your weather, the soils and the type of lawn and its appearance. Just apply the needed amount all at once rather than in small increments. What you want to move away from is the type of watering that often occurs with automated sprinkler systems, where it comes on for 10-15 minutes daily. That is not accomplishing anything but the development of very shallow root system and little tolerance for any problems. And the wasting of a lot of water through evaporation.

dan, remember: it can take up to fifteen minutes for your irrigation water to even BEGIN to enter the soil.

Remember, hdayanan says the soil is sandy, not loam or clay. It won't take 15 minutes to get water into sand soil.

At a previous house, I had a lawn on soil that was mostly broken down granite - sandy. I found that watering deeply once a week did not help so I switched to less water more frequently. With sandy soil, the water quickly sinks down past the roots so the roots don't even "know" to go deep for water.

Michigan State has an excellent agriculture program and they have done studies on watering turf grass.

The link below has been past around before because it counters the common advise of watering deeply. The study states that during the warm season, the grass roots are short and watering deeply is of no use.

Now that I live in an area with high clay soil, I still don't water deeply because it just starts to run off after 15 minutes causing waste. With drip irrigation it makes sense because the water is released slowly. Not so with lawn sprinkers.

Here is a link that might be useful: MSU Turf Tips for the Home Owner

What is interesting about that link is that it contradicts virtually any other source on irrigating turfgrass, including publications from many University extension services, lawn care companies and even Tru Green, who I would not recommend for any other turf care suggestions - but at least they got that part right.

If one looks hard enough, they can always find something that will justify their own private methodology, but the consensus from the majority of horticulturists and turfcare specialists is that deep but infrequent waterings are far more beneficial to the long term health of an established lawn than are short frequent periods. And it has little do with soil types.

Here's just a sampling of a few of the many sources that support this thesis:
http://www.extension.umn.edu/distribution/horticulture/DG2364.html
http://www.urbanext.uiuc.edu/lawnchallenge/lesson4.html
http://www.extension.umn.edu/info-u/plants/BG530.html
http://www.american-lawns.com/lawns/watering.html
http://lawn-care.trugreen.com/cgi bin/trucare.cfg/php/enduser/std_adp.php?p_faqid=91

The first link mentioned actually does say it varies by soil type. It also states that run off is not good and that sprinklers often apply water at a faster rate than absorption. The second link is a proponent of infrequent irrigation "when possible".
The fourth link states it simply:
* On a loamy or silty soil, typically apply one inch of water once a week.
* Sandy soils typically have one-half inch of water applied twice a week.
* Clay soils may need water applied slowly or at several different times to allow time to soak in.
* Adjust watering amounts to account for summer rains.

Practicality was really my point. In an ideal situation, one would have loam soil that absorbs an inch of water from sprinklers. However, with clay, it doesn't happen because of run off, and with sandy, it does not stay around the roots anyway. That's not just what I am reading, but that has been my experience.

gardengal said, What you want to move away from is the type of watering that often occurs with automated sprinkler systems, where it comes on for 10-15 minutes daily. That is not accomplishing anything but the development of very shallow root system and little tolerance for any problems. And the wasting of a lot of water through evaporation.

That's my niece's husband. Can't tell him anything, either. He took care of my Mother's yard in California for years. Her soil was soggy all the time and just nasty!

If you are watering because your soil got hard before the week was up, that is NOT a reason to water again. The only reason to water again is if your grass plants wilt. Then you should water longer next time to make sure the water is in the soil to a deeper level, thus encouraging deeper growth of roots.

This type of watering also encourages fungal growth which is critical to water retention in non-clay type soil. Even pure white beach sand can turn black with humic acids and microbes.

"Then you should water longer next time to make sure the water is in the soil to a deeper level, thus encouraging deeper growth of roots."

So, even though deep watering does not work on my clay soil, my neighbors clay soil, or on the soil that the universities used in the studies mentioned above, your saying do it anyway?

As I said before, if I water "deep" the water runs off the lawn after 15 minutes. Less than a week later my grass plants wilt.

The readers of this forum should understand that the "water deep" drum beat that continuously gets pounded is not a one-size-fits all. Sure, it sounds logical, but it just doesn't always work. Not in my experience and not based on the studies.

What I challenge is for some of the regular posters of this forum to offer suggestions that can work for different situations.

"As I said before, if I water "deep" the water runs off the lawn after 15 minutes."

I have, or had, similar conditions. So I set my sprinklers to run for 12 minutes per station, then after it had gone through all the stations, it would repeat the process. Once it got through all of them again, it would repeat again.

This would allow the water to soak deeper into the soil and the soil would be able to absorb more water by the next cycle. In that way, I could apply water for 36 minutes without any runoff.

That's the "Wet Sponge, Dry Sponge" analogy. It does work for clay soils and is what I do when I HAVE to water. For sandy soils I'd agree with what David said about watering longer the next time around. Get the fungi going and we'll all be having a good time!

i can't help but wonder if applying mycorhizzal fungi to sandy soil will help form sponge-like soil to retain more water. I guess only one way to find out is to do half of yard with myco. fungi as experiment and other half as control. you'd need to core aerate the lawn to be able to get M. Fungi to the root zone.

At least that's what I'd do if i were in that situation.

Here's how you open up your clay soil for deep watering.

1. Get a soaker hose as long as your wallet can stand. Unroll it in a straight line at the highest part of your lawn.
2. Turn the faucet on to a trickle and connect to the soaker.
3. Leave it there for a full week running night and day. If you are still getting runoff, slow down the trickle.
4. After a week, move the hose 18 inches or so down hill and continue watering.
5. Repeat steps 3 and 4 until you finish.
6. Repeat steps 3,4, and 5 a total of three passes.

Here's what is going on with that. You're setting up a soil condition that favors beneficial fungi. These are the guys who will split apart the clay particles when they swell with moisture and shrink away when dry to allow the air and water to enter the soil. A lack of beneficial fungi is responsible for clay cracking and for runoff.

This works best with deep grass roots. Keep your mower at its highest for deepest penetration of the roots.