Comparing Two New Nutrition Programs Utilizing Controlled-Release Fertilizer
Posted August 2025
Researchers: Davie Kadyampakeni, Jude Grosser
Contact: Davie Kadyampakeni, UF/IFAS CREC dkadyampakeni@ufl.edu
Summary:
Huanglongbing (HLB)-affected citrus trees in Florida exhibit severe deficiencies of all secondary and micronutrients (not NPK), especially in the roots. These deficiencies must be corrected to regain normal vascular system function as needed for high yields of quality fruit. Most grower practices to correct this problem provide oscillating levels of the affected nutrients, allowing trees to go below the required thresholds at different times of the year, apparently reducing tree performance. Simple increases in fertilization rates have also altered important NPK/secondary/ micronutrient ratios. We have also generated considerable evidence that continued use of controlled-release fertilizer (CRF) with coated secondary and micronutrients can stop fruit drop and produce pre-HLB quality fruit, regardless of rootstock. The project compares two new programs that are designed to provide a constant supply of elevated secondary and micronutrients to the roots year-long (mimicking real soil) to a selected standard commercial program. The first program is a four soluble dry application program where the second and fourth applications are the complex mix containing CRF (5-1-7). The second program is a four-time application soluble dry program, designed to test the Diamond R 5-1- 5 CRF 180-day product along with a more affordable source of NPK. Both programs target 150 lbs. N/acre/year. The control standard nutrition program for comparison is a quarterly 180 lb N program. Data collection on tree growth and soil nutrient variables for young trees and tree growth and fruit yield for bearing trees is underway and will be shared in due course.
Take Home Message:
- No differences have yet been observed in fruit yield and quality in bearing trees.
- Greater canopies observed in young trees receiving CRF and conventional blend.
- CRF would help offset the need for multiple fertilizations and help improve tree performance over time.
