By Brad Turner
From a family with deep Florida roots, I have over 40 years of experience in commercial citrus production. I learned the industry from the ground up by working in the family groves while studying citrus production at Florida Southern College. I have owned a citrus nursery, my own groves and a citrus caretaking business. I have also worked in production for Lykes Citrus Management Division, and most recently worked as ranch manager and production manager for Welcome Ranch and Groves.
Due to the challenges of the conventional citrus production model, I was forced to walk away from growing citrus commercially. In February of 2017, I began studying soil biology, chemistry and physics and how they affect plant nutrition and citrus tree health. In December of that year, I purchased 5 acres of land in Lithia and planted multiple varieties of citrus.
Because of my prior experiences and the unending challenges across the citrus industry with disease and insects, I chose to implement regenerative concepts in my grove to prove to myself there was more than one approach to dealing with the pest management problems that plague the industry and grower profitability. This began my trials, experimentation and research to better understand how regenerative principles and processes could be implemented into commercial citrus production, and how those processes would benefit soil health, tree health and grower profitability.
PRACTICES YIELDING POSITIVE RESULTS
In pest management, it is necessary to focus on beneficial insects and microbes, as well as optimal tree nutrition. At my research farm, I have found that beneficial insects and microbes (both above and below ground) are attracted and housed by the continual propagation of diverse cover crops.
I have developed a cover cropping rotation strategy keeping at least half of my grove in mature and beneficial living green plants all year long. This ensures beneficial insects are in the grove continually.
I apply biostimulants and inoculums on a regular basis to both the soil and foliage to feed and diversify the natural occurring biology and also to help keep pathogens in check. Many lower order of problem pests (aphids, thrips, whiteflies, mealybugs, all forms of scale, rust mites, spider mites and psyllids) are at extremely low populations or non-existent.
University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) nematologist Johan Desaeger sampled my soils, as well as the roots of trees and various cover crops last spring. He did not find any sting nematodes, which had been present before regenerative practices were implemented. Desaeger said there were “high counts of non-parasitic nematodes (bacterial and fungal feeders), which makes for a pretty healthy-looking soil overall.”
There are three insects/pathogens that remain a concern in my research block.
The diaprepes root weevil adults in my experimental block are being suppressed by at least three species of predatory spiders. One is the green lynx spider, which UF/IFAS entomologist Lauren Dieprenbrock identified in the research block as early as 2018.
Another method of diaprepes control has been referenced by Larry Duncan, UF/IFAS nematologist, in a past Citrus Industry magazine article. He stated that there are native entomopathogenic nematodes in some citrus soils that will attack and consume diaprepes in the larval stage. For research purposes, I have chosen not to apply commercial nonindigenous nematode products to address these larvae. I am, however, finding some larval stage diaprepes dead in the soil. While there are areas of root feeding in my research block, there are no phytophthora issues typically associated with this root damage.
Algal spot (Cephaleuros virescens) has been a problem for some varieties of my trees and appears to have no natural predators. Foliar inoculums have been trialed with no success. I am getting satisfactory control of algal spot with foliar phosphite applications in rotation with chlorine. Chlorine will volatilize off soon after application. Because the chlorine also obliterates all the beneficial biology on the trees, I follow up with a foliar inoculation of biostimulants and diverse microbes.
Leafminer continues to be a problem and appears to have no natural enemies yet. What I have found is there is a direct correlation to leaf Brix. In general, the trees with the highest leaf Brix levels have the least problems with pests. Trees testing with a leaf Brix of 11 or higher show minimal to no leafminer damage.
LEAF AND SOIL TESTING
I Brix test the leaves to monitor general health of the trees (how well photosynthesis is functioning) and take regular sap analysis of the leaves for more precise monitoring of nutrition management. This enables me to address mineral levels in the tree (deficiencies/excesses) and take appropriate corrective action to increase leaf Brix levels.
For comparative purposes, I continually monitor a grove of wild citrus trees in the neighboring forest that have no apparent insects or pathogens affecting them. Soil mineral and biological tests show that the biggest difference between the soil of the wild citrus grove and the soil of surrounding farms is the biology.
This becomes evident in the wild citrus grove soil’s high organic matter content along with the microbial diversity — specifically, the fungal component. Because of this, calcium, magnesium, phosphorus and boron, the main mineral drivers of photosynthesis, are continually found at luxury levels in the plant sap analysis. In addition, the sap testing results indicate the biology has made it possible to maintain total nitrogen at optimum levels while nitrate levels are low or even non-detectable in these soils where no nitrogen fertilizers are applied. These nitrogen levels are typical in the trees at the research farm also. With this total nitrogen to nitrate ratio, the nitrogen in these trees is in the protein/amino acid form. Protein nitrogen is the form of nitrogen desired by trees as it requires very little energy for the plant to utilize.
The benefits of the soil biology continue to unfold, but one especially important benefit is reducing excessive nitrates in the tree that can cause other mineral antagonisms and imbalances, drive down Brix and increase water consumption.
THE PROCESS OF PROMOTING LIFE
Transitioning to regeneratively growing citrus is a process; it is not just about products. Many salespeople representing companies with a “silver bullet” knock on my door, strongly encouraging me to use their product. My experience is first and foremost to figure out why their product would/should work. If the salesperson cannot explain how their product will benefit the process, then I am not interested.
Much is yet to be discovered and researched about regenerative principles. Growers need to focus on plant diversity above ground and microbial diversity below ground. Nothing grows in nature as a monoculture, and neither should our perennial agriculture food systems. As a conventional citrus grower and caretaker for 35 years, I felt the need to control and conquer everything in my path. That agricultural philosophy is built on the basis of killing or eradicating. Now I spend my time, energy and money in systems designed to promote life. Often it is best to get out of our own way and watch nature’s miracles unfold.
Brad Turner is a citrus grower and operator of Sand to Soil Services in Lithia, Florida.