GAINESVILLE, Fla. — As Florida citrus growers look to recover from the damages of Hurricane Irma and continue to cope with citrus greening, University of Florida scientists suggest using a complete and balanced nutrient program in their groves.

“Mineral nutrition plays a vital physiological role in the growth and development of a plant and as well as in plant-defense response,” said Tripti Vashisth, an assistant professor of horticultural sciences and a citrus Extension specialist with the UF Institute of Food and Agricultural Sciences. “UF/IFAS recommendations are developed after intensive scrutiny of each nutrient, its rate and its effect on citrus.”

The recommendations come after many researchers have worked together, amassing years of data, Vashisth said.

“Therefore, growers can be confident in using these recommendations,” she said.

Many micronutrients act as the catalyst in physiological reactions such as plant-hormone biosynthesis and regulation as well as in plant-defense mechanism, said Vashisth, a faculty member at the UF/IFAS Citrus Research and Education Center (CREC) in Lake Alfred, Florida.

Preliminary studies by UF/IFAS researchers suggest that increasing the supply of micronutrients can be beneficial.

Through funding from the state legislature-funded Citrus Initiative, Vashisth has found that leaves from greening-affected trees often show deficiencies in certain nutrients such as manganese, zinc, iron and more. This suggests that, because of greening, more of these are required and are critical for diseased plants’ survival.

Vashisth gives these recommendations:

• A constant supply of nutrients is important, and controlled release fertilizer (CRF) and fertigation are two methods to ensure that supply.
• Use CRF, also called “slow-release fertilizer.” In this, nutrients are coated with either clay or a polymer that causes the nutrients to be released in the soil and the roots over time, rather than all at once. The thickness of the coating determines the length of the release. Some growers combine CRF with traditional soluble dry fertilizer, and they are achieving good results.
• Some growers are applying liquid nutrients through their irrigation system or via drip-lines. The latter is known as fertigation. Fertigation allows to apply nutrients in small dose with irrigation and the nutrients become readily available to plant.

“Several growers are having very good success using this approach,” Vashisth said.

These recommendations are based on findings of an ongoing fertilizer field trial funded by Citrus Research and Development Foundation, she said. That trial has shown that by applying 20 percent to 50 percent more micronutrients through the soil, and by using controlled-release fertilizer, scientists can improve tree yield significantly.

Applying the nutrients in the nitrate form seems to be working very well, although some growers are applying nutrients in the oxide form, she said. Nitrates are most easily taken up and utilized by the trees.

Growers do not need to change the amounts of primary nutrients – nitrogen, phosphorus and potassium – that they are using, said Jude Grosser, a UF/IFAS professor of horticultural sciences, who’s also a CREC faculty member. For nitrogen, this means from 150 to 200 pounds per acre per year.

“However, in my opinion, the levels of secondary and micronutrients need to be increased,” Grosser said. “Then, the new formulations of nutrients must be spoon-fed to the trees, using one or more of the methods described.”

If you want to know more about UF/IFAS citrus nutrient research:

• Click here for the Citrus Production Guide.
• Click here for information about the nutrition of Florida citrus trees.

More information on nutrient recommendations will be shared at the 2018 Citrus Expo August 15-16 in Fort Myers, Florida.

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By: Brad Buck, 352-294-3303, bradbuck@ufl.edu

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

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