Sustaining Citrus Production in the HLB Era

The virtues of daily irrigation and increased micronutrient applications were among key points researcher Davie Kadyampakeni made in an Aug. 13 discussion of citrus production in the HLB era. Kadyampakeni is a University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) associate professor of soil, water and ecosystem sciences at the Citrus Research and Education Center in Lake Alfred. 

Kadyampakeni opened his presentation by listing what he called the five Rs of citrus production for HLB-affected trees: 

1.  Right water management
2.  Right fertilizer placement
3.  Right fertilizer source
4.  Right nutrient rate
5.  Right timing

His conclusions and take-home messages included:

• Frequent irrigation is key to optimal tree performance.
• Daily irrigation results in improved nutrient uptake.
• Use of sensors is key to determining water needs of trees.
• Fruit yields, juice quality, canopy size and development were enhanced with a balanced nutrition approach with effective crop protection for HLB-affected citrus.
• Root health and overall plant health and immunity were strengthened with elevated rates of micronutrients compared to current recommendations where micronutrients were kept at current UF/IFAS guidelines.
• A manganese rate of 8 to 10 pounds/ac^-1 for young HLB-affected trees appears to be appropriate.
• Increases were observed in root growth, canopy size and yield over time for trees fertilized with elevated doses of micronutrients.
• Consideration should be made to revise and increase current micronutrient recommendations for HLB-affected trees.

Multi-county citrus Extension agent Mongi Zekri, who works in Southwest Florida, hosted Kadyampakeni’s presentation and provided additional information about micronutrients. According to Zekri:

• The use of most micronutrients (manganese, zinc and boron) is recommended at least three times a year. 
• Copper should not be included in dry fertilization if copper sprays are used for disease control and if the grove soil test shows adequate copper.
• Molybdenum deficiency occurs on soils that have been allowed to become very acidic.

Zekri said foliar sprays of micronutrients are a more effective, more economical and quicker application method than soil application, when included with post-bloom and summer foliar sprays at about full expansion of the new leaves. He noted that sulfate forms are less expensive, and nitrate forms appear to facilitate the uptake of micronutrients.

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