Precision Nutrient Management to Rejuvenate Huanglongbing-affected Sweet Orange
Posted August 2025
Researchers: Tripti Vashisth
Contact: Tripti Vashisth, UF/IFAS CREC tvashisth@ufl.edu
Summary:
Effective fertilizer management is critical for healthy tree growth and maximum yield. Historically, nutrient management for healthy citrus trees involved annual leaf sampling of 4-6-month-old spring leaves in July to August, with subsequent fertilization plans based on single nutrient analysis. The widespread prevalence of huanglongbing (HLB) in Florida needs improved approaches for fertilizer management through regular leaf sampling. Thus, this study was conducted to improve and revise leaf nutrient sampling guidelines for HLB-affected trees by optimizing sample collection methodologies and frequency per year. Emerging spring and summer flushes on mild and severe HLB-symptomatic ‘Hamlin’ and ‘Valencia’ trees were tagged in central Florida for two consecutive years, with leaves sampled four times yearly for nutrient analysis. Two years of evaluation indicate that fertilization based on leaf nutrient analysis improved tree health and productivity with good canopy growth and less decline in both varieties of the HLB-affected trees. Spring leaf nutrient levels correlated to canopy density and yield. High leaf nitrogen and iron levels promoted tree canopy growth early in the season. Later in the year, leaf potassium and boron levels became more crucial for yield. Overall, this study shows that at least two leaf samples (June and September) are needed to improve the canopy and fruit growth of HLB-affected trees. Interestingly, a random leaf sample can also be collected, as a randomly collected leaf sample is comparable to the spring flush in June and September.
Take Home Message:
- Frequent fertilization based on frequent-timely leaf nutrient analysis can improve tree health and productivity.
- At least two leaf samples (June and September) are needed to adjust the fertilizer program to improve the canopy and fruit growth of HLB-affected trees.
- Spring leaf nutrient levels correlated to canopy density and yield, and random leaf samples can also be collected.
