By Tacy Callies
Citrus grower Sonny Conner recently hosted a group from the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) for what he called his “Clint Eastwood tour of the good, the bad and the ugly.” While some of his trees are too far gone from citrus greening (the bad and the ugly) to be resuscitated, many more are thriving and productive (the good) despite being diseased.
According to Steve Woodruff, regional agronomist with NRCS, the purpose of the tour was to get a firsthand view at alternative approaches growers are taking to combat citrus greening.
“We want to look at sustainable, biological options,” said Woodruff. “This was a meeting of the minds between producers and NRCS. We are at the point of no return in citrus and need to find alternative ways to manage greening. This was the starting point of the conversation.”
At 84 years old, Conner is still actively managing a 20-acre Valencia grove in Lake Jem, Florida. Many growers are battling greening with up to nine insecticide sprays per year, but they still have psyllids in their groves, Conner told the tour group. Instead, Conner has taken a softer approach that relies, in part, on recycled materials. He attributes the combined use of compost and cover crops to the lack of psyllids in his grove and improved plant health.
PUTTING WASTE TO WORK
About three years ago, Conner began making an annual application of compost that consists of treated biosolids mixed with yard waste. He saw improved soil health and tree health after the first application. He saw even better results after upping the amount of the second application.
Conner learned that a manure spreader works much better to apply the light, fluffy compost than a fertilizer spreader. He noted that the compost does not have a foul odor; it simply smells like dirt.
The grower said a major added benefit of using compost is that it prevents biosolids and landscape waste from going to limited-capacity landfills. “Dade County is shipping biosolids to Georgia landfills, and in New York, biosolids are being sent to Alabama,” said Conner.
Interestingly, he reported that a soil test result of the compost showed it had no to very little nutritive value. “That is because the nutrients are tied up in the organic matter. Once the compost is applied, the microbes in the soil go to work on it to release the nutrients,” said Conner.
COVER CROPS
As for cover crops, Conner has tried different varieties over the last several years with varying results. This summer, after harvest, he intends to plant sunn hemp in half his grove and hairy indigo in the other half to see which performs better.
“Sunn hemp is very vigorous and easy to grow. My father used hairy indigo as a cover crop in the 1940s. The cover crops throw shade on the compost and keep it from oxidizing,” explained Conner. He added that the cover crops are mowed and disced into the soil, resulting in an increase in soil organic matter.
Another big benefit Conner has seen from cover crops is an abundance of predatory insects like green lacewings and ladybeetles that feed on psyllid nymphs. The cover crops provide a habitat for the predators.
“We are going to pick our best crop since greening arrived,” said Conner in April, just prior to harvesting. While his Valencias are contracted for juice, he said the fruit quality this season would have been good enough for the fresh market.
Products Conner applies to his grove include a low-dose systemic fungicide/bactericide (2 gallons per acre) combined with active iron three times per year. A foliar supplemental nutrient is applied once or twice per year. No granular fertilizer applications have been made for three years. Herbicides are used as needed.
MORE PRODUCTIVE SOILS
Conner says results of his cover crop/compost program include a high cation exchange capacity (CEC), which is a measure of how well the soil holds nutrients.
“CEC values range from basically 0 to over 300. Typically, sandy soils with low organic matter have very low CEC values below 2,” explained UF/IFAS Extension agent Brandon White, who coordinated the NRCS visit to Conner’s grove. “These types of soils and CEC values are common in Florida citrus. Generally speaking, real good CEC values for fertile, productive agricultural soils would be around the 10 to 15 range. Excellent numbers are 15 and above. So, the fact that Conner says he got 15.9 is a big deal for a Florida citrus grower.”
According to White, CEC is a key indicator of soil fertility, and soil fertility is an integral part of overall crop health and productivity. “Soil health is an important thing to understand and invest in. For Florida citrus production soils, the more you can increase CEC, the better,” he said.
Woodruff believes that if growers understand how soil functions, they will be more likely to stick with a soil health improvement program. He said NRCS programs are in place to assist growers with funding through the Environmental Quality Incentives Program and the Conservation Stewardship Program, but first “we want growers to understand the process of improving soil health and how it works. We have to figure out specific scenarios that work best for citrus.”
Seeing what’s working for Conner and other citrus growers is a step toward meeting that goal. In addition to visiting Conner’s grove, NRCS staff also paid a follow-up visit to Ed James’ grove, which they first visited in 2020. James is well known in Florida citrus circles for his extensive experimentation with cover crops that has led to greatly improved plant and soil health.
“Soil health is very applicable for the current state of citrus,” said White. “It’s just one part of a solution to citrus greening but is not an immediate fix. However, it is not as long and complicated a process as people tend to think in order to start seeing benefits. Improved soil health by simple, more sustainable practices leads to overall better tree health and can potentially reduce costly chemical inputs, which combined could be a sizeable part of the answer.”
