Root Nutrient and Fertilization Guidelines for HLB-Affected Trees

Daniel Cooper Nutrition, Tip of the Week

Yellow veins are possible HLB symptoms.
(Photo courtesy of UF/IFAS)

By Davie Kadyampakeni, Lorenzo Rossi and Alan Wright 

Huanglongbing (HLB) disease lowers tree performance by reducing water and nutrient uptake as a result of root loss. HLB-affected trees have a fibrous root loss of about 30% to 80%, which increases as disease symptoms develop in the canopy. Investigating optimal nutrient concentrations in citrus roots thus improves the understanding of HLB dynamics concerning root nutrition and fertilizer application methods.

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers looked at nutrient uptake via soil fertilizer applications for 5- to 6-year-old HLB-affected Valencia orange trees on Swingle rootstock at Ridge and Flatwoods sites. Macronutrients and micronutrients were applied at varying fertilization rates via fertigation according to UF/IFAS guidelines. The standard fertilizer program was compared with elevated macronutrient and micronutrient fertilization programs. Soil and leaf samples were collected for nutrient concentration analysis in spring and fall of 2019 and summer of 2020.


No significant differences among treatments were observed for tissue and soil nutrient concentrations due to nutrient interactions. Fruit yield between 2019 and 2020 harvest seasons increased with increased nutrient availability.

At higher fertilization rates of standard fertilization + 40 pounds/acre calcium + 40 pounds/acre magnesium + 220 pounds/acre potassium + 20 pounds/acre iron + 20 pounds/acre manganese + 20 pounds/acre zinc + 4 pounds/acre boron, HLB-affected trees showed increased nutrient uptake and root growth, improving overall tree performance. 

  • Higher macronutrient and micronutrient fertilization rates led to higher fruit yields and faster root growth. 
  • Soil fertilizer application for micronutrients was more effective in increasing canopy size and root growth than foliar fertilization. 

Acknowledgment: This project was funded by the UF/IFAS Citrus Initiative funded by the Florida Legislature, the U.S. Department of Agriculture and the Citrus Research and Development Foundation.

Davie Kadyampakeni is an associate professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred. Lorenzo Rossi is an assistant professor, and Alan Wright is a professor, both at the UF/IFAS Indian River Research and Education Center in Fort Pierce.

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