More Fruit, Less Fertilizer

08/01/2010 02:00:00 AM
Steve Heisler, contributing writer

For citrus grower Pete Spyke, the proof of his success with open hydroponics is in the pictures.

The owner of Fort Pierce-based Arapaho Citrus is quick to point to images of his 3-year-old Rock Bottom Grove on the company’s Website, Beyond the photos of growing trees are shots of densely packed root balls that Spyke says show one thing: Open hydroponics using drip irrigation promotes fast tree growth without great amounts of water and fertilizer.

And it may be one of the best solutions to citrus greening, also known as huanglongbing or HLB, Spyke says. He views two camps—those who try to live with the disease and those who understand they must live without it.

System helps spur early fruiting

Open hydroponics involves growing citrus on drip irrigation and spoon feeding trees nutrients through the drip. In theory, the system maximizes tree and crop uniformity.

In his 5-acre experimental Rock Bottom Grove, Spyke added an advanced production system that involves high-density plantings of 250 to 400 trees per acre, aggressive psyllid control, intensive pruning, and plant growth and flower set to achieve early fruiting.

Open hydroponics differs from growing trees on micro-jet sprinklers since you have more control over the trees on drip, he says.

“I have plenty of growers growing trees with micro-jets really, really fast, some outgrowing me,” Spyke says. “But what’s happening is it takes them four to six times more water and fertilizer. The point of doing the drip is about control of the trees and it’s about money.”

A young tree with a lean trunk on a micro-jet system spreads roots out evenly over a 12-foot radius, storing fertilizer to use as needed, he says, pointing to photos.

Trees on open hydroponics, on the other hand, have “pots” or root balls that are concentrated under emitters, a strategy that has proven to work best in densely spaced plantings.

Because the roots are concentrated in the wetting zone, nutrient uptake is improved and leaching is reduced, he says.

Growing trees quickly using drip is important, but the main goal is to bring them into fruit production as early as possible before they become infected with the citrus greening bacterium, Spyke says.

“You get them up and into production. And as they get greening, you get them out,” he says. “With drip, I can shift it from vegetative to reproductive. Trees don’t grow fast anymore, and they’re putting all their energy into producing fruit.”

Spyke bases his opinion on what he learned when visiting South Africa in 2006 and China in 2008, countries that both have the disease and have adopted a mandatory no-greening policy.

It’s a decision every Florida grower must make at some point once psyllid control has been exhausted and greening begins to set in.

“They need to capture as much equity in the groves as they can now,” he says, offering an example of a grower producing 500 boxes of Valencias. “You just keep doing that as long as you can. But at the point when you’re done and your existing grove has no more equity, if the decisions to keep going, then what you need to do is open hydroponics.”

The other main goal of his 5-acre test block was to gauge growth in Florida’s humid environment. Many of the techniques Spykes is using are adapted from Spain, which has an arid Mediterranean climate.

“Roots are totally dependent on what you’re dripping onto them,” he says. “But what we proved at Rock Bottom is we can achieve the same results in a high-rainfall environment. Because of Rock Bottom, everybody assumes we can do it and away we go—we’re onto the next phase, which is figuring out things for Florida.”

Putting the system to the test

Spykes’ production system caught the attention of Kelly Morgan, a soil and water scientist with the Southwest Florida Research and Education Center in Immokalee. He is experimenting with 8 acres of citrus on drip irrigation.

Morgan’s work in advanced systems is designed to address growers’ concerns about a tree’s lifespan being reduced to 10 to 15 years from 30 years. His work helped confirm that open hydroponics can work in Florida’s sandy soil, which doesn’t retain water and nutrients well.

“Growers never want to remove their trees,” he says. “They’re spraying leaves with micronutrients and nitrogen and potassium that seem to alleviate the [greening] symptoms.

“That’s a very hot debate. We’re not making the claim open hydroponics will even reduce the effects of greening. All we’re wanting to do is improve the business side of things for the grower.”

Arnold Schumann, a soil scientist at the Citrus Research and Education Center in Lake Alfred, also has looked at drip irrigation as well as micro-jets. His work showed that trees do grow faster and yield better with reduced water and nutrients.

The one issue with drip irrigation is it doesn’t provide frost protection like micro-jets do. But Schumann says if you consider drip saves 50 percent of fertigation compared with micro-jets, and micro-jets save one-third over conventional irrigation, the efficiency is hard to beat.

“You also recognize the savings of fertilizer could offset some costs of the system,” he says. “The hydroponic formulation is quite efficient regardless of how it’s delivered.”

For more information on Kelly Morgan’s research, visit

Contact Citrus + Vegetable at or (209) 571-0414

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