High-Efficiency Fertilizers for Growers

At the Citrus & Specialty Crop Expo, Davie Kadyampakeni recommended what he termed “high-efficiency fertilizers” to improve canopy, fruit yield and juice quality, especially in HLB-affected trees. Kadyampakeni is an assistant professor specializing in citrus water and nutrient management the University of Florida Institute of Food and Agricultural Sciences.

FOUR TYPES
Kadyampakeni described four categories of high-efficiency fertilizers:

1. Slow-release fertilizer (SRF) and controlled-release fertilizer (CRF), each including some macronutrients and micronutrients. He suggested that 6- to 9-month SRF and CRF be applied three times per year, and that 12-month CRF be applied twice per year.
2. Improved blends for granular application containing micronutrients can be applied four times per year. It is ideal to apply dry soluble at the following times: 20% in February, 30% in April, 30% in June and 20% in October.
3. Liquid fertilizer applied via fertigation. Kadyampakeni suggested applying this 12 times per year if fertigating monthly or 20 times per year if fertigating biweekly. Fertigation should be done mainly between February and October, avoiding the cold weather months of November to January. He suggested avoiding fertigation in the summer months; consider using CRF/SRF from June to August to prevent leaching.
4. Foliar fertilizers can be applied three to four times per year. Apply micronutrients foliarly as a remedy for correcting deficiency. Selected micronutrients such as calcium and potassium can also be sprayed in small amounts to improve fruit retention and quality as needed in addition to soil fertilization.

ORGANIC OPTIONS
Organic fertilizer sources that can substitute for inorganic fertilizer include animal manure, agricultural waste, agricultural industrial waste and plant residue. Kadyampakeni suggested placing animal manure/waste, agricultural waste and agricultural industrial waste in the tree row to reach the root zone and ensure efficacy of uptake. Those products should be disked in or applied on the surface if runoff isn’t a problem. Apply the manure or waste one or two times a year, he suggested.

Kadyampakeni said the benefits of animal, agricultural waste or plant residue include:

• Increased organic matter and soil carbon and soil health parameters
• Improved water and nutrient retention
• Long-term improved soil fertility
• Increased microbial activity in the soil and nutrient cycling and transformation
• Moderation of soil quality; for example, soil pH and salinity are optimized
• The products are easy to find in areas close to ranches and agricultural industrial sites.
• Their use can offset high costs associated with inorganic fertilizers.

Challenges include:

• Slow nutrient release, so they’re not ideal for short-term needs.
• It is very important to know the nutrient ratios to avoid oversupply of nutrients.

Key takeaways of Kadyampakeni’s presentation were:

• Addition/application of livestock manure increases nitrogen, phosphorus, potassium and other nutrients and can be used to offset the absence or scarcity of inorganic fertilizers.
• Regular compost applications in Florida’s sandy soils improve nutrient retention and water-holding capacity and can increase long-term tree productivity of nutrient-depleted groves.
• Fertilization should be based on soil, leaf and/or manure/agricultural waste lab tests to determine correct citrus tree nutrition needs.

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