Water smarter

Greenhouse Management: What are the most common problems in irrigation water that you see?

Bryan Swistok: Clearly, the most common issues we see are the high pH, high alkalinity and high hardness levels that can create a variety of problems not only for the irrigation equipment, but for the actual health of the plants. We have less common issues with things like metals; iron and manganese are probably the two most common that can also cause problems for plants. They can also clog up equipment.

GM: What prompted you to create this factsheet?

BS: We get a lot of questions from people who get their water tested for irrigation. One of the first questions they have is, “What do these numbers mean?” It’s kind of like if you go to the doctor and get your blood tested, they hand you a bunch of numbers and they don’t mean anything until somebody interprets them. It’s really important that we give people some idea of whether these numbers are bad or good. It gives them some sort of background about what are the typical values that we see, where do we think problems might be and what can be done about some of these issues.

GM: How did you gather the information presented in the factsheet?

BS: There are a number of resources out there that we put in the reference section that come from other universities. [We also referenced] information that was available from past publications here at Penn State.

One of the issues that you have is — unlike drinking water — it’s very easy to just look up [data]. When it comes to things like water for irrigation or livestock or for agricultural use, it gets into more of a grey area. You even get into differing opinions about research that’s been done because there hasn’t been nearly as much research as there has been with drinking water. So we really tried to look through a bunch of different references and get differing ideas, and it’s important to give references for people to be able to look up what others are saying.

We [also] did an irrigation water study last year across Pennsylvania, so we used some of that data in this factsheet to provide information about the frequency of problems, and what are the typical values that we see.

GM: What parameters are difficult to remove from irrigation water?

BS: Very rare organic contaminants, man-made materials that might need to be carbon filtered, or salt in the water [are] very difficult, [or] a high fluoride concentration. It’s very difficult to remove [those components] because it has to be done with reverse osmosis or distillation units that are very expensive to use.

Some of the easier ones are some of the most common, for examples, water that has a high pH or high alkalinity. Thankfully, those are some of the easier problems to deal with.

GM: What is the biggest mistake you see growers make when it comes to their irrigation water?

BS: The one big mistake is that they don’t test the water at all. There’s often an assumption that you can put any water on there and it’s going to be fine. And unfortunately, sometimes they find out down the road after problems are already occurring, that they may have wanted to test the water up front.

GM: How often should growers test their irrigation water?

BS: For things like pH, alkalinity and hardness, there are simple meters and test strips [you can use on site]. It’s a good idea to have those on hand and be testing pretty frequently because they are such important parameters and they can change pretty consistently with weather and season. They [growers] may want to have some of those simple meters, [along with] a conductivity meter, [which are] very inexpensive things to have on hand to generally look at the water quality and make sure things aren’t changing drastically.

But a good, thorough, water test at an accredited lab should be done at least annually, and that doesn’t even deal with things like GAP [Good Agricultural Practices] testing for bacteria, which needs to be done very routinely, especially if it’s a surface water supply. That would also have to be done at an accredited laboratory.

Editor’s note: This interview was edited for length and clarity.

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