Mike Roberts

Don’t Overlook the Basics

With so much focus on the new treatments for greening, it can be easy to forget the importance of the essential basics.

UF/IFAS associate professor of citrus water and nutrient management Davie Kadyampakeni reminds Florida citrus growers that “it is important to make sure citrus trees always receive adequate nutrient supplies,” even with the new therapies coming out, like oxytetracycline trunk-injections and plant growth regulators like gibberellic acid. 

Fertilizers are an absolute necessity for optimal tree growth, fruit yields and juice quality, and they should not be neglected to focus on new therapies

Citrus Nutrients

Primary macronutrients—nitrogen (N), phosphorus (P) and potassium (K)—need to be applied in the correct ratio to optimize fruit yield. N and K should be applied at rates as close to a 1:1 ratio as possible, with P being less due to its abundance in Florida soils; Kadyampakeni advises conducting soil and leaf analyses to calculate your grove’s phosphorus (P) needs.

Secondary macronutrients like Calcium (Ca), magnesium (Mg) and sulfur (S) should be applied following current UF/IFAS recommendations to boost root health and immunity. Ca and S should also be used to achieve optimal soil ph.

Lastly, micronutrients like boron, zinc, iron, manganese, copper, and more should be applied to the root zone by fertigation or fertilizer spreaders, and additional supplemental foliar sprays are advised three to four times a year based on leaf test results.

Additional Fertilizer Program Tips

Your citrus fertilizer program can also benefit through the following actions:

  • Routinely testing soil pH to keep the soil pH between 5.8 and 6.5. 
  • Use leaf tissue tests to ensure each nutrient is in the optimal or high range based on UF/IFAS recommendations. 
  • Compare soil tests and leaf tissue to each other as leaf tissue tests will show what is available to the plant, not just what is in the soil.
  • Omit nutrients for four to six months that are in the excessive nutrient concentration in leaf test results to allow them to revert to optimal ranges.
  • Split your applications of fertilizers. Fertigation should be split into a minimum of 12 to 30 applications per year, dry soluble fertilizer should be divided into four split applications, and controlled or slow-release fertilizer should be split into two to three applications per year.
  • Slow-release, controlled-release. or conventional granular fertilizers blends should have both macronutrients and micronutrients included for optimal tree health and production.

As always, it’s important to bear in mind the 4 Rs of nutrient stewardship.

  • Right source, at the 
  • Right rate, at the
  • Right time, in the 
  • Right place

Following these principles can help increase production, boost farmer profitability, enhance environmental protection, and improve sustainability. To learn more, go to nutrientstewardship.org.

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.

This column is sponsored by Griffin Fertilizer Co., and the opinions expressed herein may not reflect those of CFAN or of its advertisers.

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