Living in the era of HLB, growers clearly understand that the days of managing groves like the generations that came before them are over. They’ve already begun adjusting production to include aggressive foliar nutrition and intensive psyllid control to live in the presence of the disease.
While these steps are important, more radical approaches are being considered like advanced citrus production systems (ACPS). This style of production incorporates elements of open hydroponics or intensive fertigation, high planting density, and a suitable rootstock capable of developing a compact tree and an efficient root system in the fertigated soil zone.
The driving force behind ACPS is the idea of bringing a new grove into commercially viable production quicker than traditional plantings. This will be increasingly important as HLB threatens to shorten the productive lifetimes of trees and groves. Only a handful of growers have tried the system, including Pete Spyke who was featured as Florida Grower’s cover story in October 2008.
UF/IFAS has been collaborating with other growers to build data on ACPS and its potential in Florida. According to Dr. Arnold Schumann, a soil and water scientist with UF/IFAS, the practice is showing some significant early yields in trials.
In one trial with Gapway Groves in Auburndale, trees that turned three years old in December yielded 220 boxes per acre using this system. Typically, trees are four to five years old before they begin producing similar yields in a traditional configuration.
The economic advantage of early, high production and return on investment with drip open hydroponics and high-density planting is significant. About one to two years of production costs are saved with ACPS. Economic break-even can occur much earlier (e.g., eight years) with high-density ACPS than with conventional citrus production (13 to 18 years), assuming that trees are kept healthy.
The Auburndale site is located on typical Ridge soils at an elevation of about 160 feet above mean sea level. It was previously used for a traditional low-density citrus grove with a standard production system using old fully grown trees with resetting.
Several densities of trees were planted in the grove with a conventional spacing planted as a control. Densities included: 10×20 feet (218 trees per acre), 8×18 feet (303 trees per acre), and 8×15 feet (363 trees per acre). All rows are orientated north-south with four replications in a randomized complete blocks design, covering a 14-acre block.
“To make a credible economic comparison requires full analysis of all establishment costs, the production costs for three years, and the fruit yield and quality for two seasons,” says Schumann. “We are in the process of conducting this analysis. In the interim, it is fair to say that by growing trees faster, the time saved in years are therefore savings of production costs, too. For example, if ACPS gets the trees to a productive size in three years, equivalent to 4½-year-old trees grown conventionally, then the method has saved the grower one and a half years of production costs.”
“I think this grove trial has demonstrated that we can bring a grove into production quicker,” says John Strang, Gapway’s grove manager. “Thus far, the 8×18 (302 trees per acre) looks good to me. I think as long as you have a rootstock that will make a smaller tree, this spacing might be a good compromise between early yields and something that can be maintained and harvested with existing equipment.”