Understanding greenhouse irrigation system clogging

Features - Equipment

Here’s what growers need to know to handle a common problem that can present itself in three different ways.

October 25, 2018

Plants on the left are smaller because of frequent system clogs caused by a biofungicide.
Photo courtesy of Rosa E. Raudales

Many greenhouse operations rely on irrigation systems for their watering needs. While different growers use different types of systems, the purpose of each system is the same: to water plants efficiently and effectively.

But sometimes, irrigation systems can become clogged, causing production issues and negatively impacting plant growth. The good news is that it’s a manageable problem with viable solutions that growers can implement.

“We are all very aware of the importance of watering,” says Rosa E. Raudales, an assistant professor of horticulture and a greenhouse extension specialist at the University of Connecticut. “We’re also aware of the importance of not over-watering, but also [of] not stressing our plants. If you allow your system to clog, then you’re losing control because you can’t really estimate how much you’re going to water.”

Emitter in irrigation booms: The filter had crystals of calcium precipitates and the cover had biofilm with algae.
Photo courtesy of Rosa E. Raudales

The three types of clogging

According to Raudales, there are three kinds of clogging growers should be aware of: physical, biological and chemical. She says that each type has different causes and symptoms that when identified, allow growers to zero in on the problem afflicting their greenhouses.

For physical clogging, she says it involves a suspended solid backing up the system, thus preventing water from reaching the plants.

“Think of if you’re [a grower] recirculating water and if you’re carrying any type of remaining debris that’s coming back from the soil,” she says. “You would expect a physical [object] that would plug your system. Mostly that would be a concern for growers who are recirculating water or maybe growers who are using pond water as their water source because it tends to be a little dirtier than other sources.”

Biological clogging occurs when biofilm — commonly known as lime — builds up in an irrigation system’s pipes and slows or stops water flow, Raudales says. It is most often greenish-brown colored, giving growers a visual indicator that their pipes are clogged.

“[Biofilm] is mostly foreign debris caused by bacteria, but you can also think of it as a combination of bacteria and algae,” Raudales says. She adds that biological clogging can be the hardest type of clogging because there isn’t a comprehensive solution for it.

Lastly, there is chemical clogging to treat. Raudales says that this can be caused by different materials building up in the system, most notably iron. This type of clogging, she says, is often caused when a water source such as a well is contaminated and introduces harmful materials into the system. Calcium, manganese and other materials can also precipitate clogging.

Iron precipitates on the inside surface of a three- inch pipe
Photo courtesy of Rosa Raudales

Different treatments for different types of clogs

Raudales says treating physical clogging is straightforward and researchers know the most about it — making it the easiest type of clogging for growers to deal with. Often, the material clogging the pipe is something that can be blown out the front of the system and out of the greenhouse altogether. All a grower needs to solve this issue is pressure.

For biological clogging, Raudales says it can take a “big effort” to combat it properly. For instance, if a propagation house’s emitters are clogged with biofilm, growers must choose between a few different treatment strategies. One is to take the emitters down, replace them with clean ones and wash the clogged ones. Chemical treatments are also an option, although bacteria can become resistant to them over time.

As for chemical clogging, the process is like treating physical clogging. Raudales says that it requires using a large concentration of the chemical being used to clear out the pipe and the line being shut down. It also requires an empty greenhouse, or temporarily emptying a greenhouse, to avoid damaging plants.

The best way to combat clogging, Raudales says, is to be aware of the different symptoms of clogging.

The one significant factor that Raudales says links the different treatment options together is that unclogging irrigation systems is a labor-intensive process, and not all growers can take workers off other tasks in the greenhouse and assign them to the problem.

“If we don’t find a way where you can install a system that helps you treat the symptoms, treat the water as it goes and prevent the problem from happening in the end, then this is just going to happen,” Raudales says. “If they don’t have the alternative to do that, then it becomes something that’s very labor intensive. But they don’t have many alternatives other than [to] treat it or [to] spend the time cleaning. It's one or the other.”

Best practices to combat clogging

The best way to combat clogging, Raudales says, is to be aware of the different symptoms of clogging. Mum growers watering their plants with drip irrigation, for instance, should look for wilted plants and check them on a schedule. If a grower notices the wilting early enough and can fix the clogging issue promptly, then it might be early enough to fully salvage the crop.

There are also specific signs of the various types of clogging, Raudales says. For chemical clogging, growers can likely spot some residue in the piping before it is completely built up and causes damage.

“It’s pretty visual because of the way propagation houses are designed. There’s an overlap between the area that the mist is covering,” Raudales says. “You tend to just visualize when the systems are off. But you just see some plants being slightly drier than the others and then you go to check to see if the [pipes] are clogged.”

Raudales also recommends testing the greenhouse’s water supply to evaluate the possibility of it becoming contaminated, and backing up the system. She suggests starting an ongoing, low-dose chemical treatment that can reduce buildup over time in the system. She also recommends installing a water filtration system.

“When we think about the way we grow in greenhouses, it’s kind of an industrialized type of factory production,” Raudales says. “We want to have a product that’s pretty even and we want to be able to have control over timing. You think about clogging, the main problem is that you’re losing control.”