Protect your equipment

Some growers become attached to their old fertilizer injectors to the point of not wanting to part with them, even when it becomes necessary to upgrade, according to Lela Kelly, vice president at Dosatron. She says they often tell her, “It’s the one we bought when we started this business.” Sentiments aside, it’s important that growers replace or upgrade their fertilizer injection equipment in a timely manner to ensure accurate delivery of nutrients and other chemicals.

Fertilizer injectors are the backbone of any greenhouse operation. Yet, this equipment doesn’t always get the attention it deserves. Sometimes, the inattention occurs during the selection process. Growers may choose the system on price alone. It may also occur during the maintenance phase, when growers don’t take the steps necessary to ensure continued accuracy of water and nutrient delivery.

When choosing fertilizer injectors, or a fertilizer injection system, there are several factors to keep in mind. Price is only one of them. Growers should also consider things like how accurate the injector is at delivering a product, how much automation they really need or want, and if the system’s company will be around when the injectors need to be serviced five to 10 years down the line.

“You should find out how long the company has been in business,” says Kelly. “I’ve seen a lot of companies come and go in my 36 years in this business.”

Determine your flow rate

Before you meet with an injector salesperson, determine the flow rate for your irrigation system. The flow rate is determined by adding up the gallons per minute (gpm) of water that is going to run to each of your lines, whether they be drip tubes, low-flow pressure compensated tubes or overhead spray nozzles. This number must be equal to or less than the gpm coming from the water source (a well or municipality). The injector has to at least match the flow rate. For example, if 100 gpm of water is coming from the source, your total gpm to each irrigation unit must add up to no more than 100 gpm. The fertilizer injector must be rated for at least 100 gpm to avoid damaging your injector, Kelly says.

“The flow rate of the water is crucial when deciding what system they want,” she adds.

How much are you willing to spend?

After you’ve determined flow rate, you’ll have to decide how many bells and whistles you need. Like buying a car, a Chevy van will get you down the road just fine. A Mercedes has many more features, which, of course, comes with a much heftier price.

The situation is similar for fertilizer injectors. For less than $300, you can purchase a nonelectric fertilizer injector that does just fine in a greenhouse where only one hose is being used with about 11 gpm delivery. The price goes up with the gpm of delivery and the number of lines you’re running in your greenhouse, up to around $2,500. The price takes a quantum leap if you’re interested in installing a full computer-based system with software that can run “multiple recipes” to different zones, monitor pH and nutrients in real time, and collect data for future use and comparison.

Fertilizer injector systems, like the folks at Argus Control Systems Ltd. are selling, can be customized to the size and function of a particular greenhouse. Starting at $38,000 for a rack mounted system, an Argus fertilizer injection unit comes in small, medium and large sizes to match the size of the growing operation, according to Morris Brink, business development representative with Argus.

“Every Argus fertilization panel is custom made to a customer’s specific needs,” Brink says. “It can do just [one] AB mix or have multiple AB mixes. More sophisticated growers might fertilize from raw salt, raw element and make up their own recipes. [Some have] multiple recipes to go down to multiple zones to irrigate and fertilize plants.”

A custom system with all the bells and whistles may be overkill for some growers, particularly those who don’t want something highly technical. But where precision monitoring is important, especially as evident in the emerging cannabis industry, it makes sense to take the leap and invest in a more advanced system.

“If you have very basic needs, like a couple of zones, an Argus system does not make sense,” Morris says. “If data logging, notification and reporting are important, then an Argus system does make sense.” He points to one cannabis grower in Colorado who was able to reduce his product usage from in the millions to tens of thousands of dollars with better monitoring and delivery of fertilizer and other inputs with one of their fertilizer injection systems.

Shop around

Just like purchasing a new vehicle, it’s a good thing to shop around and ask other growers what they’re using and what they like.

“When you talk to people, you get a lot of information,” says Kelly. “Talk to people you know, people you respect in business — this is especially true for new growers trying to figure it out.”

Maintaining a system

Kelly says some growers believe that because the injector is sucking liquid, it must be functioning properly. Yet, if the system hasn’t been properly maintained, it’s quite likely that it isn’t delivering the accurate amount of fertilizer, which ultimately costs the grower money. She says the maintenance steps are simple and should be done on a regular basis, kind of like car maintenance.

“When I speak to a group about fertilizer injectors I always ask this question: ‘Would you neglect to change the oil in your car when it is due?’ The answer is a predictable ‘no,’ yet many don’t take the necessary steps to maintain their fertilizer injectors.”

The injector filter is probably the cheapest and easiest maintenance step a grower can take. Kelly says if sand is allowed to get past the injector filter, over time the friction of the sand will enlarge the size of the nozzles, resulting in an increase in product delivery to the plants. It’s also important to periodically measure the amount of fertilizer being delivered with an EC meter to ensure everything is working properly.

Water hammer is another issue growers should pay attention to, particularly because irrigation is much more automated these days. Water hammer occurs when water moving in one direction suddenly hits a closed valve. That force will rebound at four times the pressure, possibly damaging the fertilizer injector. This can be prevented by installing a water hammer arrestor.

When you consider the amount of plant material you’re producing each year, it pays to purchase a quality fertilizer injector or injection system and properly maintain it.

“It’s one of the most important things you’re doing in the greenhouse: watering and fertilizing,” says Kelly. “So it should have the proper amount of attention.”

Neil is a horticulturist and freelance writer based in Sault Ste. Marie, Mich.