Florida citrus grower Pete Spyke is staking the future of his citrus management company on an advanced hydroponics system designed to bring citrus trees into production and profitability early.


The revolutionary production system on trial at Arapaho Citrus Management Inc., Citra, was adapted from a similar system Spyke discovered while on tour in South Africa in 2006. In an era when canker and greening are limiting the long-term viability of Florida citrus groves, Spyke says he believes the high-density system and specifically timed and formulated daily pulses of water and nutrients will speed his return on investment and make citrus operations more profitable.


Spyke had removed about two-thirds of his 120 acres of citrus he grows for his retail fruit store in Citra and was looking to replant. 


“I wanted to replant, but we had greening in the area and I wanted to first see what growers in South Africa, where they have greening, were doing about the problem,” he says. “What we found they have been doing is using an approach we are calling open hydroponics systems and advanced production systems.”


This involves selecting scion-rootstock combinations and tree spacings to create managed high-density plantings that will bring groves into higher production earlier, says Bill Castle, a horticulture professor at University of Florida’s Citrus Research and Education Center at Lake Alfred. The groves are irrigated through an open hydroponics system, which uses short, regular bursts of drip irrigation to spoon feed water and specially formulated nutrients to the trees’ dense root zone.




Make a profit earlier


In 2007, Arapaho Citrus dedicated a 10-acre block of grapefruit and minneola tangelos to look at the variables of the two systems. Trees are planted on replicated blocks with 6-foot and 8-foot spacings and two different rootstocks. The trial also is set up to compare various drip schedules and nutrient mixtures. The idea is for growers to make their profits before the trees become vulnerable to canker or greening.


“The conventional orchard today is planted on 15-by-25 foot spacing; the modern orchard is 10-by-20 and the high density orchard we are talking about with [advanced production systems] is 8-by-15. So the system is taking us from about 100 trees an acre to 363 trees per acre,” Castle says.


In addition, growers using advanced production systems apply imidacloprid to control the Asian citrus psyllid—the main vector of citrus greening—and reduce disease losses the first three years. From there, dense spacing should help mitigate tree losses from greening, Castle says. Spyke says that since the trees for the trial were planted in November 2006, the company has only lost 10 out of 1,400 trees to greening. “So far, that is pretty good,” he says.


The hydroponic system within the advanced production system uses fully automated drip irrigation and fertigation systems to supply water and macronutrients, based on the trees’ growth stages. In a true hydroponic system, roots are maintained in a water and nutrient solution in a closed loop system.


The goal is to produce exceptional yields by the time the orchard is 3 years old and turn a profit by the time trees are no more than 5 years old, Castle says. By the time trees are 8 years old, growers would theoretically recover the cost of investment to set up the initial system. With the high cost of nursery trees, he says it’s imperative that growers manage the two systems to meet the eight-year financial targets if they want them to be economically viable.


“It’s a big investment in trees alone,” he says. “The drip system, we believe, will be less expensive in the end because it requires a smaller pump… and uses water more efficiently. And ag will also come out on the short stick for water, so this drip system offers distinct advantages by virtue of the way it’s managed.”


By comparison, growers during the Florida citrus heydays of the 1980s might expect to generate a net annual operating profit in about a decade and repay the loan on orchard establishment costs three to four years after that, Castle says.




Up-front investments


Spyke says the cost of establishing a grove with full open hydroponic systems and advanced production systems features can be two to three times higher than the estimated $1,000 to $1,200 per acre to plant new groves with lower tree densities and a manually operated microjet system. The main cost increase comes from the greater number of trees, with additional cost increases due to the more high-tech equipment. Once the grove is planted, Spyke says he is finding that costs in the first few years are much lower per-acre than conventional microjet blocks, and only about half the per-tree cost of conventional.


In later years, though, management costs will be higher because of some hand pruning and other hand labor requirements. However, Spyke says he believes growers can offset those extra costs by reducing herbicide use, eliminating broadcast fertilizer applications, automating irrigation operations, and reducing maintenance on micro-irrigation lines and emitters.


“We are talking about revolutionizing how you are farming,” he says. “It’s much more management intensive and takes a lot more attention. The only similarity is in the plant material. Even the way you monitor and spray for pest and disease control is entirely different. But, in my opinion, it doesn’t make sense to plant a new grove any other way.”


They payoff should come with early yields, Spyke says.


“In a conventional grove, you are going to hit 300 to 400 boxes by year eight,” he says. “We expect to be yielding 300 to 400 boxes to the acre by the time trees are 3 years old. The advantage with open hydroponics and advanced production are going to be in year 3, 4, 5 and 6.”




Trials yield answers


In August, Arapaho Citrus harvested the fruit early on the Ray Ruby/Flying Dragon and Rio Red trees to give them more time to grow. According to the company’s harvest numbers that are posted online, the yields would have been about 73 boxes per acre for the Flying Dragon rootstock planted on a 6 by 20 row spacing, 92 boxes per acre for the Rio Red rootstock planted on a 8 by 20 spacing, and 121 boxes per acres for the Rio Red rootstock planted on a 6 by 20 spacing. This is using the assumption that the fruit would have averaged a size 40 when mature at about 24 months old.


Spyke says these yields are one or two years ahead of the per acre yields he would expect with trees planted using the modern 10 by 20 row spacing. “The more powerful thing than the amount of fruit you get is the cost. Basically, if you put more trees on an acre, two things happen. First you get more fruit per acre in the early years until the trees form a hedgerow. Second, the cost per box of fruit is less because when you mow, spray or do anything you are treating more trees,” he says.




Still in search of answers


Despite its promise, Castle says there are still questions about the system’s viability in Florida. Much of the information on specific fertility needs of trees is still an inexact science, he says, and the information from South Africa is proprietary.


Through test plots and additional research at the Citrus Research and Education Center, Castle says he hopes to eventually develop macronutrient recommendations for Florida citrus.


In addition, trees in these modern high-density orchards will be managed to not exceed 6 to 9 feet tall. Although some over-the-row pruning equipment can be used to manage the high-density hedgerow, Castle says growers will likely need to modify or purchase new over-the-top harvesting equipment. He already has been contacted by at least one equipment manufacturer to explore developing harvesting equipment specific to advanced production systems orchards.


There also are questions about adapting a system developed in arid regions to a more tropical climate like Florida’s and sacrificing frost protection from microsprinklers.


At Rock Bottom, Spyke says he doesn’t expect to need frost protection from a microsprinkler system. “For anyone in south Florida, this is the way to go. When you hit Orlando and above, then you might need to use microjets for cold protection. I really see this as a benefit in south Florida where they have so much greening and canker pressure and so many groves that need to be replanted,” he says. 


Questions also remain about the rootstocks, nutrient recommendations and management requirements to be successful. But Spyke says he hopes to answer these variables with his demonstration grove.


“So far, everything is working almost exactly like the South Africans predicted it would work. The trees are growing nicely, getting the root balls, the crop loads are progressing about how we expected. At this point, I see nothing to indicate there is any doubt about whether or not it is going to work,” Spyke says.


But he also cautions that there are a lot of subtleties to using such complex systems. He says it is much different from the fairly structured citrus production practices that are common among large scale operations. The practice of sitting down at the beginning of the year and planning how much fertilizer to buy, when to use it, etc., has been honed down over the years to simplify the decisions as much as possible.


“It has proven to be a profitable way to go about it because it is fairly predictable, at least before greening. But what has happened is we have gotten away from being true horticulturists where we are paying a lot of attention to what the trees are doing and how they are acting,” Spyke says, adding that open hydroponic and advanced production systems allow growers to pay attention and respond to scenarios to improve the growth and fruit production of the tree. “It rewards efforts to make the system as complex as possible.”


He says the company is spending a lot of time training people to develop a different set of observation skills and give them the ability to do what they think needs to be done.


“Everyone needs to buy into this whole idea of observing what is going on out there and making choices based on what they see,” he says.