May 20, 2020For many fruit growers, fertigation is becoming a mainstay
Soil and foliar-applied fertilizers have a place in specialty crops, but nutrients applied through drip irrigation or microsprinklers – also known as fertigation – are becoming very important.
Chris Lattak of St. Joseph, Michigan-based Trickl-eez Irrigation said some growers are adopting sooner than others. “While we don’t keep track, or have an actual number or percent, we have found that a surprising number of growers who have a complete trickle irrigation system, including automation and injectors for both pH modification and nutrient injection, do not use, or underutilize, their injection system,” Lattack said.
“Despite information on the benefits of being able to spoon-feed the nutrients needed by the plant, at key stages of the plant’s growth, there are a considerable number of experienced growers who still rely heavily on broadcast, salt-based fertilizers at the beginning of the season, and just want to make sure that they get water on the plant.”
Lattack compared it to growers who buy irrigation systems with electronics for automating their irrigation, but then operate it manually. Some are nervous about using the equipment correctly or may have had a bad experience in the past.
“I think a significant number of growers use the complete system less than they ordinarily might because of some bad experience with the nutrients they have used,” he said. “Trickle emitters require a minimum level of filtration to prevent emitters from getting plugged. We’ve seen issues when growers try to use nutrients of lesser quality, when the grower has used several products at the same time that react with one another, and I have personal experience where I, and growers that I have worked with are using products (often organic) that contain kelp/seaweed, fish emulsions, compost teas. These types of products, in general, are just too ‘large’ to get through the filter.”
Lattack said designing an irrigation system largely depends on the individual farm, but a grower could get the most basic siphon/Mazzei type injector set-up for about $100.
“It’s a manual system, but used by some of the larger vegetable growers,” he said. “It only builds from there with multiple levels of injector types and automation. A basic system will have backflow prevention, injector, filter, pressure gauges, flow meter and valves.” He recommends growers find a trusted Extension educator, crop consultant or experienced grower for advice and referral to an irrigation design and installation firm.
Large growers across the U.S. are using fertigation widely. OMEX Agronomy & Formulation Manager Francisco Rivera said nearly all tree fruit and nut growers in California use it either through regular drip irrigation, “double-line drip” – a drip irrigation line laid on either side of the tree. They’ll also use it in microsprinklers – emitters that spread as much as 10-15 gallons per hour. These irrigation systems are custom designed with the plant’s needs and their peak evapotranspiration (ET numbers).
“What they’ll do is they’ll design the system right to being able to irrigate a certain number of hours per week,” he said. “It deals with what’s my crop requirement, and how quickly do I put it on?” Drip irrigation, including microsprinklers, has been a major application for OMEX products such as its Size N fertilizer.
Lattack said irrigation has been a good way for growers to apply a variety of products, not just fertilizer.
“A number of big growers have been happy enough just getting the water on, with learning about efficient use of the trickle system for timely nutrient applications, maybe some PGRs (plant growth regulators), and pesticides (fungicides) as the next step,” he said.
Lattack added, though, that you can’t just apply anything through irrigation.
“You need a quality nutrient, and that often comes with a somewhat higher price tag per unit of nutrient,” he said. “Just like with your spray rig, you have to realize not every input works well with every other input, and one that is readily available to the plant.
“Doing it right involves taking the time to learn the operation, limitations and capabilities of the system and using that system to your greatest advantage. There is a learning curve, but the payoff is worth it. Soil applied applications seem to bookend the season and are best at getting the nutrients to the plant as it is breaking dormancy, to get the plant off to a strong start.”
Rivera said some of the common problems include having fertilizer “backflush” into their reservoir because they haven’t maintained the backflush feature of the irrigation system. Another common issue is having emitters lose their effectiveness over time, in part due to buildup of product.
“People are running into high bicarbonate issues in the water, and they don’t take that into account when they’re injecting calcium fertilizers,” he said. “If your bicarbonates in the water are over 140 parts per million, injecting calcium very quickly in an irrigation system with bicarbs that high will cause plugging of emitters. It won’t happen immediately sometimes … but it can happen over time.”
He said growers should regularly test their emitters to see if they’re applying at the correct rate. If they’re falling behind, a flush with chlorine to cleanse algae out, or even acid to clean up mineral buildup.
Lattack added that filters play an important role in heading off problems.
“An ounce of prevention is worth a pound of cure,” he said. “Start with an appropriate filter. If your system is going to plug up or have a related problem, let’s do it in one location that is easy to service – the filter being the shear pin of the system. (It’s) easier to deal with a filter than miles of plugged emitters. Iron and bicarbonates/total dissolved solids in the water are the other big problem when it comes to emitters. Again, prevention is much more effective than dealing with plugged emitters.”
— Stephen Kloosterman, associate editor