Florida soils are notoriously sandy with low nutrient- and water-holding capacities; this means that Florida citrus growers have to pay close attention to both. Nutrient management is especially important in the era of HLB; Florida growers interested in boosting productivity in their groves should utilize nutrient management and irrigation. See what UF/IFAS research says are the best ways to boost citrus productivity using nutrient management.
Nutrient Management and Citrus Productivity
Nutrient management recommendations are guided by the 4Rs—the right time, right place, right rate, and right source—which also help guard against over-fertilizing, saving both money and the environment.
Right Rate. UF/IFAS recommends that growers use the rate chart from the Nutrition of Florida Citrus Trees, 3rd Edition after conducting orange tree leaf analysis on spring flush leaves from non-fruiting twigs that are 4 to 6 months old.
Right Time. The type of fertilizers used is important for timing. Regardless of fertilizer type, however, growers should aim to make the majority of the fertilizer available to the citrus tree when the tree can uptake it the easiest and needs it the most; in Florida, this is usually spring and early summer.
Conventional granular fertilizers last about three months, so citrus growers should apply no fewer than four split applications a year, such as in February, March, May, and again in September to October. Minimize leaching of nutrients by breaking fertilizer applications into even more split applications.
Controlled-release fertilizers (CRF) last about six to 12 months. Their applications can be split into two or three split applications in a year. UF/IFAS also advises citrus growers using CRFs to use productions with polymer-coated micronutrients.
Right Source. The type of fertilization used also has an impact outside of timing. Liquid fertigation should be utilized in many small applications from February to October, such as weekly, bi-weekly or monthly, in order to “spoon feed” the nutrients to citrus trees with root systems weakened by citrus greening. However, UF/IFAS recommends using CRFs in the summer wet season to minimize leaching during heavy rainfall.
UF/IFAS also again recommends the use of fertilizer blends with macro and micronutrients such as calcium, magnesium, sulfur, and polymer-coated micronutrients like manganese, iron, boron, and zinc, to aid in improving tree productivity.
Right Place. Fertilizers must be applied in the right areas to effectively reach root zones. UF/IFAS recommends applying fertilizers 1 to 2 feet from the tree in the active root zone where microjets consistently wet the soil.
UF/IFAS also recommends using foliar fertilizers—both micronutrients and macronutrients like potassium and calcium—to correct short-term nutrient deficiencies in citrus trees. These deficiencies are generally identified through leaf testing. UF/IFAS recommends three or four foliar micronutrients applications a year with foliar potassium applications added in at the fruiting phase to boost fruit size and juice quality.