Brad Turner of Turner Family Groves in Lithia, FL, brews microbial inocula on the farm to encourage biological activity. Photo courtesy of Brad Turner
As a fourth-generation grower, citrus runs in Brad Turner’s blood. From an early age, he worked his family’s groves near Litha, FL, and continued to grow and work as a caretaker for citrus operations until 2016. For Turner, like many others, HLB took its toll on his groves, robbing valuable yields and quality from once productive trees. That set him on a path to study and investigate alternative means of production. His attention turned toward regenerative agriculture when his friend, Ed James, began using cover crops to rehabilitate a grove that had been given up for dead due to HLB. Turner will be the first to admit since that time he has gone down the regenerative ag rabbit hole, spending countless hours studying the field and traveling the country to attend seminars on the topic. In 2017, he purchased five acres of land and, along with his son, planted an experimental citrus grove utilizing regenerative practices. More on that work is available at SandtoSoilServices.com. Turner has been consulting with several commercial citrus growers interested in integrating regenerative ag into their production programs. For his efforts, he was among the 2021 winners of the Florida Agriculture Commissioner’s Environmental Leadership Award. “There is no cookbook for regenerative practices in citrus, and we are learning as we go,” Turner says. “But this is a passion for me, knowing these practices have to be practical for growers at the commercial scale.”
Cover Crops
The state’s citrus growers are giving cover crops a closer look because of their soil health benefits. They play an integral role in Turner’s approach to build organic matter and host microbiology in the soil. “Diversity above the ground equals diversity below the ground,” Turner says. “Every plant secretes specific exudates that summon specific microbes it needs to serve a certain purpose, like making certain minerals soluble. Each stage of root growth also is secreting different carbohydrates so the more diverse that plant species is, the more diverse your underground workforce is.” In his experimental grove, Turner says he doesn’t get too caught up in ratios of different plant species in cover crop mixes other than to avoid going too heavy with brassicas because they are non-mycorrhizal. When making up a blend for the growers he consults with, he will typically add in about seven to eight different species. Some of his favorites include partridge pea, buckwheat, hairy indigo, Alice clover, and a various assortment of greens.
Turner says diversity of cover crops above ground equals diversity of biology below ground. It also provides habitat for many species of beneficial insects. Photos by Brad Turner
“There’s research that says including different families of plants is beneficial,” he says. “In other words, having a grass, a cereal, a brassica, and a legume would be much better than four legumes in a cover crop mix. The less monoculture the better.” He says he’s still uncovering the cover crops benefits in his research, but no question there are fertility-saving benefits, soil microbiology is booming, and it’s a perfect habitat for all sorts of beneficial insects. In the last two years (using the same soil laboratory), his organic matter has grown from 2.5% to 3.5%, and his cation-exchange capacity has grown from 3.0 to 4.3. He made a change to his typical planting schedule after observing beneficial activity in the cover crops. “I had noticed that I had spiders all over the place in my cover crops that were eating adult diaprepes,” Turner notes. “When I terminated the cover, those spiders went away for a while. Then I started planting every other middle, every other month. I am really on a four-month turnover, which is planting three times per year, but I am always keeping something mature and flowering to maintain habitat for beneficial insects.” Turner adds that while he has diaprepes in the grove, he doesn’t have phytophthora. The spiders help combat the diaprepes, but he credits the lack of phytopthora to natural and applied beneficial fungal organisms in the soil. “I have a USDA psyllid inspector check the plot every three weeks,” Turner adds. “He tells me my counts are lower than any other stop on his route. In addition, Dr. Johan Desaeger, a Nematologist from the UF/IFAS Gulf Coast Research and Education Center, sampled our soils in April. He did not find any sting nematodes, which were present when we first planted. He did find high counts of beneficial nematodes making for a healthy-looking nematode population overall.” For those growers who just can’t get over the look of a “weedy” grove, Turner says just investigate the benefits. “The soil needs to be covered. The soil surface with a cover crop is about 80°F compared to 120°F to 130°F bare ground. Those bare ground temps just fry any biological activity in the soil.”
Biological Applications
Turner has applied compost, commercial microbial products, and his own recipe of inoculum to aid and maintain the development of biological activity in the soils. His homemade brew starts with vermicompost combined with the soil and fungal layer collected under wild citrus in wooded understory. He adds kelp and molasses as food sources and incubates for a month or longer. He has a machine that splits and replicates the microbes, and often toward the end of the brew, he adds commercial microbial inocula. Turner says he collects the fungal duff under the wild citrus in the forest because of the generations-old observations that the trees appear rather healthy despite being shaded from sunlight. In addition, those trees appear less impacted by HLB. He postulates that perhaps there is biological activity in that soil that is directing nutrients to the roots to improve photosynthesis and tree health. “In the first two years, I applied the inoculum mostly to the soil,” Turner says. “Now that soil biology is so rich, I am predominantly applying foliar inoculum with mineral inputs based on sap analysis results. Some research shows foliar-applied biology can stimulate stomata opening for better nutritional intake.” Between the cover crops and applied inoculum, Turner adds, the biological activity in his experimental grove is diverse and thriving. This has increased nutrient uptake and allowed for significant reductions of applied fertilizer inputs. Virtually no fungicides or insecticides are applied.
Going Forward
Turner understands this approach is a big leap from current conventional production but points out many of the practices are throwbacks to the way it was done a couple of generations ago. And considering the trajectory of current citrus production, which has been cut by more than 70% since HLB came along, all ideas should be worth a look. “For my entire citrus-growing career, I would get up in the morning, watch the weather on television to make the decision on what I was going to kill that day (weeds, mites, insects, fungi, bacteria, or nematodes),” he says. “Today I walk my research farm at dawn and see 5 acres that are full of life.”
Real-World Practice
What should commercial growers interested in regenerative practices expect in terms of the timeline to see results? Turner points to a commercial grower on the Ridge he has been working with for a year and a half who has been growing conventionally, applying compost. “The grower is working with some very good caretakers, and the groves look exceptional by today’s standards in this HLB-era, Turner says. “He is currently in a hybridized system with the goal to be fully regenerative. “In the spring of 2020, we began implementing some commercial microbial inocula and biostimulants. That summer we planted a multi-species cover crop, followed with a winter planting. We have followed up with a third planting this June. “For the past several years he has been fine-tuning the herbicide program by reducing rates, reducing bandwidths, and adding products to enable rate reductions. He is currently injecting (on a monthly basis) inocula and biostimulants into the soil. We also have been utilizing sap analysis and making some mineral adjustments to the foliar program. After harvest next season of the early varieties and Valencia, we will see how far we’ve moved the needle.”
