In the HLB era, research has shown that nutrient management is critical, and that includes micronutrients, according to UF/IFAS. Micronutrients such as manganese (Mn), zinc (Zn), boron (B), iron (Fe) and copper (Cu) are not required in large quantities like the “big three” of Nitrogen (N), Phosphorus (P), and Potassium (K), but they are essential for improved tree performance. They should be a part of every Florida citrus grower’s tree management strategy.
Benefits of Micronutrients for Citrus
Micronutrients have many benefits for citrus trees, based on research. Boron has been shown to help the mobilization of nitrogen throughout the tree. Iron has proven to be important in the tree’s food-making process. Manganese and zinc work to improve metabolism and tree immunity. Copper has been shown to help the tree combat diseases.
Florida citrus growers should aim to keep micronutrients readings at optimal levels all year round. This is so that citrus trees can operate at optimal levels in responding to stressors and going through the production cycle under the constraints of HLB.
Micronutrient Analysis
UF/IFAS experts advise Florida citrus growers to utilize both leaf and soil analysis to guide their applications of micronutrients. A leaf analysis that shows a low level of a specific micronutrient could point to a deficiency; if the soil analysis shows a deficiency as well, then the micronutrient can be applied.
However, if the soil analysis shows a high level of the micronutrient in the soil when the leaf analysis shows a low level, then there is something keeping it from being available to the plant. Maintaining the soil pH between 5.8 to 6.5 will allow the micronutrients to be readily available in the soil.
If both the leaf and the soil analysis show a high level of a micronutrient, then the application of that micronutrient can be skipped.
Tips for Micronutrient Management
UF/IFAS recommends the following tips for utilizing micronutrient management for optimal tree health in the HLB era:
- Use both foliage and soil applications for micronutrients as trees affected by HLB have limited foliage and a smaller root mass compared to pre-HLB trees.
- Split applications of micronutrients into four or more applications throughout the year. Generally, the more the applications are split, the better the uptake of the micronutrient.
- Split applications between soil rootzone and foliar applications, such as two to the rootzone and two to the foliage. Rootzone applications “spoon-feed” the tree and foliar sprays act as “urgent care” for micronutrient deficiencies.
- Choose micronutrient sources that are from nitrates and sulfates, or those that are chelated, as they have better availability and uptake efficiency.
- Copper can be easily applied along with herbicides and pesticides.
This column is sponsored by Griffin Fertilizer Co., and the opinions expressed herein may not reflect those of CFAN or of its advertisers.
BIO: Mike Roberts is the Vice President of the Frostproof, Fla.-based Griffin Fertilizer Co. Roberts joined the company in November 2011. He has spent the majority of his career in the fertilizer/agchem industry. Roberts earned a Bachelor of Science degree in citrus production from Florida Southern College in Lakeland. For more information, visit griffinfertilizer.com.