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Updated citrus nutrition guide helps growers deal with greening

Florida citrus growers hit hard by the citrus greening disease can benefit from UF/IFAS expertise in an updated book — the third edition of the Nutrition of Florida Citrus Trees.

Greening, known scientifically as huanglongbing (HLB) has caused significant damage to Florida’s citrus industry, and UF/IFAS scientists and Extension faculty have updated the guide to help farmers better cope with HLB.

Although the book still contains some data from the 2008 edition, that information remains sound for healthy trees, said Davie Kadyampakeni, assistant professor of soil and water sciences at the UF/IFAS Citrus Research and Education Center and co-editor of the latest citrus nutrition guide.

“Much of the information provided in this document on nutrients, application methods, leaf and soil sampling and irrigation scheduling also helps greening-affected trees,” he said.

Research conducted since greening was detected in 2005 has necessitated changes in many production practices, including nutrient application rates, irrigation scheduling, soil pH management and the use of Citrus Under Protective Screens (CUPS), Kadyampakeni said.

He cited the following as key updates:

  • Chapter 2 highlights the importance of soil pH and soil organic matter management to improve tree performance in the era of HLB. Soil pH measures acids or bases in the soil that can affect the presence and availability of nutrients. Growers add compost or animal manure to the tree irrigated zones to improve organic matter. That’s because Florida citrus is grown in soils with less than 3%  organic matter, Kadyampakeni said.
  • Chapter 6 describes the importance of what Kadyampakeni calls “spoon-feeding” HLB-affected trees. Growers can do this by using controlled-release or liquid fertilizers, so nutrients go move easily from the soil into the tree. Greening-affected trees have limited capacity – a compromised root structure — to take up nutrients. “So, we recommend a balanced and constant supply of nutrients in the root zone to make those nutrients available throughout the year,” he said. Controlled-release fertilizers are coated to make sure environmental conditions such as temperature and rain don’t speed up the breakdown of the fertilizer on nutrient leaching. Liquid fertilizers are injected in the irrigation system, about once a week to once a month. They make nutrients readily available to the tree and are known to boost nutrient uptake, tree growth and eventually, yield.
  •  Chapter 8 describes new findings drawn from several years of experiments on improving tree performance through balanced soil nutrition. In the same chapter, the authors describe improved soil pH moderation practices and root-health management for increasing productivity of HLB-affected trees.
  • Chapter 9 shows the importance of managing water differently for HLB-affected trees. Such trees have limited capacity to absorb water. Recommendations include frequent irrigation to increase water in the root zone in the soil beneath trees.
  • Chapter 11 includes an innovation in citrus production called the Citrus Under Protective Screens (CUPS). The CUPS strategy grows trees in screen-enclosed structures. The screening system keeps the Asian citrus psyllid off citrus trees. The psyllid is the pin-sized insect that transmits the pathogen that causes citrus greening.

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By: Brad Buck, 813-757-2224 (office); 352-852641(cell); bradbuck@ufl.edu

The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS)
is to develop knowledge relevant to agricultural, human and natural resources and to make
that knowledge available to sustain and enhance the quality of human life. With more than
a dozen research facilities, 67 county Extension offices, and award-winning students and faculty
in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions
to the state’s agricultural and natural resources industries, and all Florida residents.

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