Controlled-release fertilizers (CRFs) may help improve leaf nutrition in citrus trees affected by huanglongbing (HLB), but choosing the right fertilizer program is critical to maintaining yields, according to new research.
A University of Florida Institute of Food and Agricultural Sciences study compared two CRF programs with a conventional fertilizer program in mature Valencia sweet orange trees growing in Florida’s sandy soils. All trees were affected by HLB, also known as citrus greening.
HLB damages citrus roots and reduces their ability to absorb water and nutrients, making fertilizer management an important tool for maintaining tree health and production.
Researchers found that one controlled-release program, CRF1, increased leaf levels of magnesium and sulfur while maintaining fruit yields comparable to conventional fertilization throughout the study’s yield comparisons. The other program, CRF2, produced higher potassium productivity relative to the amount of potassium fertilizer applied, but yields fell below those of the other two programs in 2026.
Neither CRF program significantly improved juice quality. Measures including juice content, sugar levels and acidity were generally similar across the three fertilizer treatments.
The findings suggest that CRFs are not interchangeable, and that higher nutrient-use productivity does not necessarily mean higher fruit production.
For Florida growers managing greening-affected groves, fertilizer decisions should consider leaf nutrient levels, fertilizer costs, nutrient inputs and sustained production — not just the potential for improved nutrient efficiency.
The researchers also cautioned that results may differ based on rootstocks, growing conditions and fertilizer formulations. The study focused on mature Valencia trees on Swingle citrumelo rootstock. Weather-related stresses may have influenced yields during the research period.
The takeaway is that CRFs may offer nutritional benefits, but growers should evaluate specific programs over multiple seasons before making changes to their grove fertility practices.
Jonas Pereira de Souza Junior, Davie Mayeso Kadyampakeni and Jude W. Grosser of the Citrus Research and Education Center conducted the study. Read the full research article in Frontiers in Plant Science.
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