Citrus growers discuss production practices to improve root health.
By Tacy Callies
What began as an experiment in Ben Krupski’s 10-acre grove in Howey-in-the-Hills, Florida, is now a common practice he uses as production manager for Lennon Grove Service.
Four years ago, Krupski started testing the use of compost in his small leased block of Hamlin trees. In the first year, he picked 60 boxes per acre. This year, he expects 300 boxes per acre. Due to this success, he and Bill Lennon, owner of Lennon Grove Service, are now using compost on a couple thousand acres of citrus that they caretake in Lake, Orange, Polk and Marion counties. A spreader is used to broadcast the compost throughout the groves, primarily under the trees.
“The compost does several things for us,” explains Krupski. “It aids in water retention and keeps nutrients in the roots.” He says the compost contains nitrogen that releases slowly over several years. It also contains “trace to good amounts of calcium, potassium, manganese, boron and other nutrients.”
While the use of conventional fertilizer is still necessary, Krupski says compost has allowed him to reduce nitrogen applications by up to 30 percent. While the fertilizer savings may not be this great in the first year after applying compost, he has been able to decrease the amount of nitrogen input from granular fertilizer, and even more so with controlled-release fertilizer.
According to Krupski, visual inspections of root samples reveal how compost improves root growth. “You can see the roots are growing up toward the compost,” he says. Krupski applies compost one to two times per year, ranging from 2 to 10 tons per acre. He recommends using as much compost “as your budget will allow.”
Another advantage of compost is that “it is a great medium for soil microbes to thrive in,” Krupski says. He injects microbes on top of the compost four to five times per year to further increase root health.
In addition to compost, Krupski believes daily irrigation can significantly improve citrus roots. He says he used to water trees three times per week for four or more hours at a time. Then he began irrigating daily for an hour at a time. Now, in some cases, he is watering twice daily for 30-minute durations. “We’ve gone from 12 to 15 hours of watering per week to 7 hours per week.”
He’s not only seeing healthier roots; other advantages are apparent. “We’re saving water, there’s less leaching of fertilizer and less stress on the trees,” Krupski says. “Less electricity or diesel is also being used to pump the water.”
David Wheeler of Wheeler Farms also attributes more frequent irrigation to better root health in his groves. Wheeler grows Florida citrus in Glades, Hendry, Highlands, Osceola and Polk counties.
“We’re irrigating more often but for lower intervals,” Wheeler says. “At times, we’re irrigating every day of the week for about an hour per day, as opposed to every three days for three hours at a time.”
Although Wheeler is experimenting with compost on a small scale, his preferred method for improving root health is the use of humic and fulvic acid materials to increase soil organic carbon.
Krupski is also a proponent of using humic acid, which he says improves root health as well as water retention. As far as the frequency of humic acid applications goes, he says “it can be whatever your time and budget allows, but three to four times per year is ideal.”
Liquid fertilizer injections, along with sulfuric acid to lower pH, are other practices Krupski employs for better root health.
Wheeler agrees with Krupski. “Treating the irrigation water with sulfuric acid to lower the pH is helping us a lot,” says Wheeler. “So are liquid fertilizer injections that feed the trees more often. We also apply a lot of phosphorous to help with root disease.”
Krupski adds that “aggressive pruning, hedging, topping and skirting can get the root-to-shoot ratio in balance.”
“There’s no doubt that more emphasis on the dirt and less emphasis on what we are spraying on the tree is needed,” says Krupski. “I am less convinced every day that there is anything you can spray on a tree to noticeably improve its health.”
Krupski subscribes to the philosophy he attributes to “old-timer” citrus grower Skip Wilson: “The good Lord never intended for a citrus tree to get nutrients through its leaves. He put the roots there for a reason.”
“I’m convinced the answer is in the ground,” concludes Krupski.