Turf & Rec

Features Agronomy
Left untreated, irrigation water can do more harm than good


February 11, 2013
By Mike Jiggens


Topics

The difference in quality between natural rain water and sources for
irrigation water can be like night and day, and turfgrass will reflect
that difference, often in a profound way.

Irrigation water isn’t as pure as its natural counterpart and can sometimes do more harm than good if left untreated.

Speaking in November at the Master’s Turf Supply Ltd. 10th annual seminar series for golf course superintendents at the Flamborough Hills (Ont.) Golf Club, Warren Schafer of Illinois-based Growing Solutions Inc. suggested irrigation water be tested from time to time because its quality affects both nutrient availability and uptake and affects soil structure.

“You really need to take everything into consideration,” he said.

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Testing a golf course’s water gives the superintendent a better understanding of what is happening in the soil and provides information for the best choice of fertilizer, Schafer said.

Things to look for in a typical water test include its pH level, conductivity, sodium absorption ratio, adjusted sodium absorption ratio, cations, pHc and bicarbonates content. It will also provide information on water hardness, which is an indication of calcium content.

Water pH is a measure of the concentration of hydrogen ions in the solution, affecting the availability of micronutrients and macronutrients, but it’s the micronutrients which are especially important in the pH, Schafer said.

“In my opinion, pH is not an indicator of water quality. It will tell you a little bit about whether your nutrients are available or not, but you need to look at all the different factors in your water rather than just looking at pH and saying it’s high so I need to treat it. That may not be the case.”

It’s vital that superintendents acidify their spray tanks, he advised, adding, “If you’re not doing that, even if you can’t afford to treat your water, you need to do it.”

Insecticides are sensitive to pH, “so read the label of what you’re spraying and adjust accordingly.”

The more salt which is present in irrigation water, the greater the conductivity. Some salts can enhance water quality while others make it less favourable for irrigation purposes.

“If your soil is higher in salt, then you have a moisture deficiency, but also the nutrients can’t get into the plant, so you have a double problem.”

It’s a ratio between beneficial calcium and magnesium and detrimental cation sodium, Schafer said. If there is a lot of sodium, it will disperse soil particles, causing them to seal over and making it more difficult to get water to the soil.

He said the pHc on a water test is an indicator of whether irrigation water is to be classified as a “stripper” or a “precipitator.” If the number is greater than 8.4, it will be classified as a stripper, meaning as the water goes through the soil profile it will dissolve the calcium and magnesium nutrients. The nutrients are stripped out, making them soluble.

If the pHc number is less than 8.4, it deposits, so as the water comes through (a precipitator), the bicarbonate grabs the calcium. As it dries up, and is taken up by the plant, it becomes a solid, plugging up the soil, and is calcium carbonate.

If it’s 8.4 or higher, it’s going to solubilize, making everything available, and will strip all the nutrients.
“In that case, you’re going to watch your soils to make sure you keep enough nutrients there. If not, you need to do a lot of foliar application to keep the nutrients available if you have a water that’s classified as a stripper because it can take nutrients out pretty fast.”

Schafer said most of the water he deals with would be classified as a precipitator.

Desirable content ranges include calcium (40 to 120 parts per million), magnesium (6-24 ppm), potassium (.5-10 ppm), and sodium (up to 60 ppm, although some will suggest less than 40 ppm).

Alkalinity is the buffering capacity of water. The higher the alkalinity, the more product it will take to bring pH levels down.

Often, a light water is so light that it won’t infiltrate into the soil. By treating it, more weight is added, enabling it to infiltrate better, rather than having it simply sit atop the soil.

Usually, there is no carbonate seen in the water until the pH level goes above 8.5.

Once calcium is not available, then sodium is likely to build, Schafer said.

“It will take quite a while, but it’s eventually going to build in the soil.”

If a golf course’s irrigation water source is a river, or if an irrigation pond is being filled by a river, there will be ample suspended solids, and the superintendent should ask for his total solids to be tested on a water test, he suggested.

Rainwater pH, by comparison, usually ranges between 5 and 5.5 with scarcely any bicarbonates (perhaps 8-10 ppm). The information is important to know when a superintendent is comparing his irrigation water to that of what Mother Nature is supplying, Schafer said.

When irrigating with poor quality water for five to seven straight days, turf begins to lose its colour and vigor and starts to tie up nutrients because of the bicarbonates. When water is treated, it infiltrates into the soil because it is being opened up and thus releases calcium. When soil is opened, water infiltrates much faster.
Schafer said that in the golf industry, it’s the symptoms which tend to be treated and not the problem. An obvious symptom of poor quality water is its reduced colour and vigor due to reduced nutrient availability. In cases of localized dry spot, more fertilizer tends to be applied as well as the use of wetting agents. In such situations, it is the symptoms which are being treated and not the problem which is poor quality water.
“All we’re doing is making a band-aid approach to what the problem is. When treating the symptom, you have to keep treating and treating, and never get to the problem.”

Schafer said almost everyone he has worked with has reduced his fertilizer use after treating his water.
“It just makes your nutrients more available. They’re not getting tied up in the soil, so you’re using that rather than losing it in the soil.”

When treating irrigation water, it’s rendered to work more like rainwater, he said.

Treated water results in the turf looking better, the soil has opened up, localized dry spot is reduced, better water infiltration is achieved, and irrigation is more efficient.

“Most guys say they’ll shorten their runs times when they start treating their water because it opens the soil and they don’t have to overwater.”

It also makes pumps operate more energy-efficiently, he added.

Schafer offered up a little trick for his audience to consider if they should begin treating their water. When golf turf is aerified, golfers often complain about the disruption and unevenness of the playing surface.
“You can turn the pH down and they normally say turn your water to 6.5 on a daily basis, but, after aerifying, set it down to 5.5 and make those nutrients available. What we’ve seen and have determined is that it cuts your healing time about in half. Make the nutrients available, the holes heal over a lot quicker, and the playing surface is smooth again a lot faster.”

The higher the alkalinity, the more product it takes to bring the pH down. When treating the water, the main thing being accomplished is the destruction of bicarbonates. It hits the bicarbonate and splits it into carbon dioxide gas and water. The pH is brought down and nutrients are made more available.

When treating at 6.5—depending on the pH level at the outset—30 to 50 per cent of the bicarbonate load will be destroyed, Schafer said.

Growing Solutions’ product is called pHirst, which is urea and sulfuric acid. Reacting the two together causes an exothermic reaction, and the product acts as a “buffering” acid. Unlike sulfuric acid, which will burn human skin, pHirst is not harmful when coming into contact with it, yet it will burn through clothing.

Schafer said some people might ask, why not simply use sulfuric acid to treat water?

Although it’s hazardous, it will destroy bicarbonates, yet it’s used up immediately. Once it does its job, it’s gone, he said.

pHirst is a time-released material which works in the soil for 25 to 28 days.

“A regular sulfuric acid is spent and is gone right away.”

Phosphoric acid, by comparison, isn’t concentrated enough and isn’t strong enough to bring pH levels down, Schafer said. One would have to use so much of it that it would not be cost-effective.

Best results are realized if the superintendent is consistent and runs the product in his system all the time rather than doing it and then not using it, Schafer said.

“If you maintain your course consistently, it’s going to be in better shape than by doing different things all the time.”