The counterproductive effects of reclaimed water

[Dennis_Harwood]

A few years ago a great number of courses in California and the southwest were forced to accept reclaimed water as its source of water supply for all but perhaps putting greens(forced since the authorities stated "convert to reclaimed or get no water at all")--

Although most of the course water supply contracts have standards for the water having certain levels of salt, minerals and other "impurities", that is usually stated as an average and recently, with less rain,  the experience seems to be such reclaimed water has been "lower quality" and delivered with an extremely large salt content--

Now we have drought conditions --And here is what I have heard is the effect--

With drought conditions in the southwest, and lack of rain to flush down the high salt content in the soil, plus the water being delievered having a high salt content, courses have found the only way to maintain any kind of condition and in order to give turf a chance to remain healthy is overwatering with reclaimed water--creating a vicious cycle--


I have also heard wet conditions are necessary to maintain any kind of grass condition with high salt content in the soil, but if the only water supply is high salt reclaimed water, the more you water the more salt you put in the soil--

The effect is more water use by courses in drought conditions because more reclaimed water is required to keep turf alive than potable water because of the "build up of salts" effect--

Can anyone verify this in your experience or area?

[Steve Okula]

Dennis,

In a word, yes.

I had a lot of experience with this sort of situation, known in the trade as "sodic/saline" conditions, as a GCS in the Canary Islands.

the quality of water coming out of treatment plants is notoriously suspect. Regardless of  what the contract says, the GCS has to water now and doesn't have time to go to court.

Common wisdom for irrigating with salty water is to continually flush. Theoretically, this doesn't build up the salt levels, but maintains them at a consistent, hopefully tolerant level, by moving excess salt down through the profile. This can work well on porous, sandy soils or not at all on heavy, clay ones.

There are several countermeasures. Aeration, to open up the soil and allow better water percolation is universally recommended. So is selection, where possible, of salt-tolerant turfgrasses. New varieties of seashore Paspalums have had success, but are restricted to warm climates. Gypsum applications, acid injection, and sulfur-burning water treatment apparatus can all be of some benefit in certain situations.

[Huff]

Gypsum may be counter productive unless it can actually be incorporated into the soil. A better scheme is to treat with calcium. Gypsum applications may actually seal the soil, grass plants will take up calcium cations instead of salt if enough calcium is present.

[Steve Okula]

Huff,

Gypsum may be counter productive unless it can actually be incorporated into the soil. A better scheme is to treat with calcium. Gypsum applications may actually seal the soil, grass plants will take up calcium cations instead of salt if enough calcium is present.

I beg to differ.

I refer you to the text of "Salt-Affected Turfgrass Sites" by Carrow & Duncan, page 120,

"Surface application (of gypsum) is important to maintain permeability of the soil surface for good infiltration. Gypsum... can be mixed into the soil prior to establishment but sufficient quantities shoud be applied to the surface to maintain infiltration and prevent crusting."

I have applied gypsum to very heavy, sodic soil and never have I seen any detrimental effect as you describe.

Can you describe situations where this sealing has occurred?

[A_Clay_Man]

I have been under the impression that gypsum helps breakdown the clay in the soil. Does it have other benefits? I live in an area where clay is dominate. Will dilegent applications help? How often should it be applied?

[Steve Okula]

Clay Man,

Gypsum is clacium sulfate. Both elements are essential to plants, so if the soil were deficient in one it might help. It has a pH of 6.5, ideal for most turfgrasses, so if the soil is either too acidic or too alkaline gypsum would have a moderating effect and might be beneficial that way.

I don't think it will change the soil structure. To over-simplify, in clay where there is an excess of sodium (salt), the pores in the soil become blocked and water percolation is reduced, (among other problems). By applying gypsum, the calcium replaces the sodium and alleviates the problem. But I don't think it will make any difference in non-sodic soils. On the other hand, gypsum never does any harm, either.

Gypsum is applied anywhere from 500 lbs to 15 tons/acre, and from twice a month to once a year, depending on soils, water, turfgrass, and what one is trying to accomplish.

[ian]

We have a number of clubs using an acid injection system with their watering systems to deal with poor quality water. Would this be for the same problem or another.

A number of city courses here in Toronto are haunted by poor water quality.

[Steve Okula]

Ian,

Acid injection systems are used to mitigate salinity, alkalinity, or both.

[Larry_Rodgers]

sorry I hit the wrong key. It is much easier to treat 325,850 gallons of water (acre foot) than it is to treat and acre of land 1 foot deep. Breaking up the calcium carbonate bonds on an acre of soil would take about 40,000 pounds of strong acid if the soil has 1% lime. Lime is insoluable and basically a rock. By removing the bicarbonate ions from the irrigation source will prevent the formation of lime and allow Calcium to occupy more exchange sites and displace the unwanted Sodium.

to eliminate Sodium, it must be replaced by Calcium or Magnesium and then leached out of the soil. Acidification of irrigation water is an accepted practice to eliminate the Bicarbonates. This can be accomplished by continuously acidifying the water with sulfuric acid or sulurous acid through SO gas.

When Gypsum is added to the soil and then irrigated, Gypsum (CaSO4) will slowly disolve into calcium (Ca) and Sulfate (SO4) ions. The calcium replaces the Sodium on the soil. Gypsum must be applied as a fine dust to the soil surface and thoroughly mixed in the top 1" of soil. 85% of the Gypsum must be fine enough to pass through a 100 mesh sieve. The rates of application varies as to the soil (ESP) echangeable Sodium Percentage, (CEC) cation exchange capacity, irrigation EC and adjusted SAR.

It is best to be testing the irrigation water frequently for chemical analysis by a reputable lab. Dave Wilber at: Dave@soil.com is an excellent source to start with, he then can specify a program to assist with your effluent water supply issues.

[ian]

Steve,
Thank-you, I never really thought to ask before.

[Mike_Young]

Larry rodgers is correct and he should be.  I have never used him being from the south but I hear he is exceptional with what he does.
Not to be advertising but I did a 478 acre wastewater golf project that is an Audobon signature a couple of years ago.  If you go to their website I think it will connect you to articles regarding salts etc that were being studied at the projecty by UGA and EPD.  www.cateechee.com
Mike