Water Quality: Is It An Issue? By Carrie Burns

It is a subject that comes up time and time again — water. In 2002 many growers in the United States had to overcome drought, trying to conserve water or altering crop selection by growing more drought-tolerant varieties. Though that is always an issue to keep an eye on, one other issue that has been popping up in the minds, E-mails and discussions of us at GPN is water quality. There are so many different sources of water throughout the country — city, retention ponds and, most common among greenhouse growers, wells. This just shows that different growers have different needs with water quality.

There has been lots of research showing what differences in water will do to a crop — clean water with the proper pH and EC can improve production; pathogen-filled water can ruin an entire seasonÉbut that's not the issue. The issue here is whether growers are doing anything about it and whether they need to. We visit a number of growers — small, medium and large — throughout the year and always make sure to check out their water situations. Through research, seminars and various information sources, we hear a variety of water-quality comments — growers need to test their water for numerous things such as alkalinity, pH, EC, calcium, magnesium, etc.; use treatment systems; don't reclaim water because of the pathogens present in it, and if necessary, use a filtration system; watch PGR effectiveness with water that is low in acid. All of these things, as well as many others can be issues, but are they issues for the average grower? We have seen, just by visiting growers, that many facilities are not using any kind of filtering system. "We've never had a problem," is the most common response we get. Then we get into the discussion of water quality, but that is just one grower at a time. We wanted to know more, so we distributed a survey via the Internet to get growers to answer a few water-quality questions.

An interesting result from this survey is that almost 60 percent of respondents indicated that water quality is of high concern to them, yet only about 45 percent use a water treatment system. Does this mean people don't want to pay for treatment systems or that after their water testing, they don't need it? Or does it mean something else all together?

Not in the Survey

A few questions within the survey allowed write-in answers, which are not in the figures shown. A few answers showed that growers are often testing for items more interesting than the normal nutrients (see Figure 3, left). Some of the most common answers included herbicides, pesticides, bacteria and sulfate. One respondent even wrote in gasoline. Apparently there was a big spill on a nearby property that he/she believed could've gotten into the water supply.

The question represented in Figure 5, left, gave respondents a list of water treatment systems and asked if they used any of them. Other answers we received included a water softener system, chlorination and pre-treated municipal.

Common factors

Just a quick refresher before you go on to read the results: Alkalinity, pH and hardness are the key components of water quality that growers need to understand, according to Paul Pilon, head grower at Sawyer Nursery, Hudsonville, Mich. The pH of a solution is the balance of the hydrogen ions and the hydroxides in it and measures the strength of an acid or base. The range of pH is from 0 (most acidic) to 14 (most basic). As the pH of the media increases, certain nutrients, such as iron and phosphorous, become less available for plant roots to uptake. At low pH levels in the media, certain micronutrient toxicities could occur. The media pH is directly related to the quality of water being applied to the crops.

Alkalinity is a measure of the total substances in the water that have "acid-neutralizing" ability. It is attributed mostly to calcium and magnesium carbonates and bicarbonates, which are major components of limestone (limestone is often used to increase pH levels).

Hardness is a measure of the combined content of calcium and magnesium carbonates in water. Hard water is generally associated with alkalinity. However, it is possible to have high levels of calcium and/or magnesium chlorides (often considered "hard") in the water and not have high alkalinity.

Take what you will from these surveys. While we know there are many more than 216 growers in the United States, this is a good start to capturing a perception of an ongoing issue.

Carrie Burns

Carrie Burns is managing editor of GPN. She can be reached by phone at (847) 391-1019 or E-mail at [email protected]

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