ESSENTIAL ELEMENTS

farm management

Essential Elements

Basics of Nutrient Sources for Blueberry Fertilization in Florida

photo by HUNTER VICKERS

THERE ARE 17 NUTRIENT ELEMENTS essential for blueberry production. These essential nutrient elements include nine macronutrients: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) and eight micronutrients: iron (Fe), boron (B), copper (Cu), manganese (Mn), molybdenum (Mo), zinc (Zn), chlorine (Cl), and nickel (Ni), which was added to the list of essential elements in 2004 (https://edis.ifas.ufl.edu/ Nitrogen

Nitrogen has many important roles in plant nutrition and nitrogen fertilizer is needed annually to support vegetative and reproductive growth. Blueberry crops prefer nitrogen fertilizers with ammoniacal nitrogen (Table 1). Thus, the following nitrogen fertilizers are preferably used. Growers need to carefully minimize using fertilizers containing nitrate such as calcium nitrate, potassium nitrate, or sodium nitrate. Ammonium nitrate can be used in blended fertilizers where the nitrate is only a small portion of the nitrogen and the soil pH is below 5.3. Acidforming ammonium sulfate is an excellent N source and is often used to help maintain soil pH in the proper range.

Table 1. Composition of Some Water-soluble Fertilizer Nitrogen Sources N source Nutrient Content (%) N P2O5 S Physical State Ammonium sulfate 21 0 24 Solid Urea 45-46 0 0 Solid UAN-32 (50% urea and 50% ammonium nitrate) 32 0 0 Liquid UAN-28 (50% urea and 50% ammonium nitrate) 28 0 0 Liquid Monoammonium Phosphate 11 48-55 0 Solid Diammonium Phosphate 18-21 46-54 0 Solid Superior Nitrogen & Potash 15 0 15 Liquid

For organic blueberry production, blood meal and fish meal (Table 2) can provide nitrogen.

Table 2. Composition of Some Organic Fertilizer Nitrogen Sources N source Nutrient Content (%) N P2O5 K2O Physical State Blood Meal 12-14 1 0.5-0.6 Solid

Fish Meal 4-8 6-12 0 Solid

Bat Guano

7 3 1 Solid Organic Fish Fertilizer 8 6 0 Solid Organic Gardening Fish Fertilizer 3 3 0.3 Liquid

Phosphorus

Phosphorus (P) is essential for cellular energy transfer through formation of high-energy bonds and is also important for root growth and development. Virgin, acidic, sandy soils may be initially low in P. However, P can accumulate in many soils over time. Soil tests can be used to determine preplant P fertilizer needs for new plantings and periodic soil and leaf tissue testing can be used to assess the need for additional P fertilization. Excessively high soil P levels can inhibit iron and zinc uptake and may result in iron and zinc deficiency.

Table 3. Composition of Common Phosphorus Fertilizer Sources P source Nutrient Content (%) Physical StateN P2O5 K2O Ca S Single Superphosphate 0 16-22 0 21 11 Solid Phosphoric Acid 0 48-53 0 0 0 Liquid Triple Superphosphate 0 44-53 0 13-15 0 Solid Monopotassium Phosphate 0 51 35 0 0 Solid Monoammonium Phosphate 11 48-55 0 0 0 Solid Diammonium Phosphate 18-21 46-54 0 0 0 Solid

Blueberry plants thrive under acidic growth conditions, phosphoric acid can provide a great opportunity for growers to control or acidify soil pH as well as supply P nutrient (Table 3).

For organic blueberry production, the following fertilizer P sources (Table 4) can be used.

Table 4. Composition of Some Organic Phosphorus Fertilizer Sources P source Nutrient Content (%) N P2O5 K2O Physical State Seabird Guano 0 11 0 Solid

Organic Bone Meal Bio-Live 3 15 0 Solid 5 4 2 Solid

Fish Bone Meal Bio-Fish 3-4 12-18 0 Solid 7 7 2 Liquid

Blueberry plants thrive under acidic growth conditions, phosphoric acid can provide a great opportunity for growers to control or acidify soil pH as well as supply P nutrient (Table 3).

For organic blueberry production, the following fertilizer P sources (Table 4) can be used. Potassium

Potassium is involved in many important plant processes such as photosynthesis, osmoregulation, water relations, and activation of key enzymes to name just a few. Potassium is usually applied annually to blueberry plantings. Potassium deficiency may present as marginal leaf burn, leaf cupping and/or interveinal chlorosis. Leaf tissue analyses can be used to monitor plant potassium levels. Muriate of potash (MOP, KCl) is inexpensive but is not recommended because blueberry plants are sensitive to soils with high chloride content.

Table 5. Composition of Some Potash Fertilizer Sources K source Nutrient Content (%) Physical StateP2O5 K2O Mg S Potassium sulfate 0 50-52 0 17 Solid Potassium magnesium sulfate 0 22 11 22 Solid Monopotassium phosphate 52 34 0 0 Solid Potassium thiosulfate 0 0 25 17 Solid Polysulphate 0 13.5 3.3 18.8 Solid

Table 5 lists all suitable potash fertilizers for conventional blueberry production. For organic blueberry production, the following fertilizer K sources (Table 6) can be used.

Table 6. Composition of Some Organic Potash Fertilizer Sources

K source Organic Langbeinite Ocean Kelp Extract 0 Nutrient Content (%) Physical N P2O5 K2O Ca Mg S State 0 0 22 0 10.8 22 Solid

10 0 8 1.8 0 3 Solid

Pro K

0 0 20 0 0 0 Liquid Calcium and Magnesium

In Florida, 90% of the irrigation water source is from the Floridan Aquifer. This water source is high in calcium. Usually, calcium is not deficient in Florida blueberries. Magnesium deficiency, however, is fairly common where high-Ca irrigation water is used. Calcium (Ca) and magnesium (Mg) compete for plant uptake and high Ca in irrigation water may lead to Mg deficiency in blueberry fields. Magnesium deficiency may appear as yellowing or reddening of leaf tissue between major lateral veins with the middle of the leaf around the midvein and major lateral veins remaining green. Plant Ca and Mg status can be monitored with leaf tissue testing. Table 7 has suitable calcium and magnesium fertilizer sources.

Table 7. Composition of Common Calcium and Magnesium Fertilizer Sources Ca or Mg source N P2 Nutrient Content (%) O5 K2O Ca Mg S Physical State Single Superphosphate 0 16-22 0 21 0 11 Solid

Gypsum

0 0 0 23.3 0 18.5 Solid Super - Cal 0 0 0 10 0 0 Liquid Liquid Calcium 0 0 0 5 0 0 Liquid Epsom Salts 0 0 0 0 9.8 12.9 Solid

(magnesium sulfate heptahydrate) Opulent Magnesium Botanicare Cal-Mag Plus Organic Cal-Mag 0 0 0 0 6.1 0 Liquid

2 0 0 3.2 1.2 0 Liquid

0 0 0 4.5 1.1 0 Liquid

Sul-Po-Mag 0 0 21.5 0 11 22 Solid

Micronutrients

Micronutrients are required in smaller amounts than macronutrients but are just as essential. Iron and other micronutrients are subject to being oxidized and then become not bioavailable to blueberry plants. Thus, chelate iron and other chelate micronutrients should be used. For chelate iron or other chelate micronutrients, this EDIS article has more at https:// edis.ifas.ufl.edu/publication/HS1208. Table 8 listed the right iron and other micronutrient sources.

Table 8. Composition of Micronutrient Fertilizer Sources

P source Opulent Iron Nutrient Content (%) Physical Fe (II) Mn Cu Zn B State 7.3 0 0 0 0 Liquid

Almighty Iron 12 0 0 0 0 Liquid

Liquid Iron

5 0 0 0 0 Liquid Zinc Sulfate Granular 0 0 0 31 0 Solid Opulent Manganese 0 12 0 0 0 Liquid Opulent Boron 0 0 0 0 4.5 Liquid Opulent Copper 0 0 12 0 0 Liquid Minor Element 2.75 1 0.25 0 0 Liquid Jackpot Liquid Fertilizer 0.3 0.5 0.3 0.9 0.1 Liquid

Soil pH may change in response to fertilizer applications and these changes are related to the type of fertilizer applied. Basically, the application of cation nutrients such as ammonium nitrogen (NH+ 4), potassium (K+), calcium (Ca2 +), etc. will decrease soil pH while anion nutrients such as nitrate nitrogen (NO-3) increase soil pH. Blueberry crops prefer acidic soil growth conditions. When fertilizing blueberry crops, growers select the right fertilizers with cation nutrients which can help blueberry plants keep soil in the right acidic condition. This intentional selection of fertilizers to properly manage soil pH is important for blueberry production. For more information on blueberry nutrition and fertilization, see “Nutrition and Fertilization Practices for Southern Highbush Blueberry in Florida” UF-EDIS publication #HS1356 (https://edis.ifas.ufl.edu/publication/HS1356).

______ CREDIT by GUODONG LIU & JEFF WILLIAMSON, Horticultural Sciences Dept., IFAS, University of Florida

president's letter, cont. from page 6

until late May. With the extra chill hours, we had a heavy crop on our Farthing. We did the best we could, babying the plants and fruit through the stress of 95 degree days until we picked our last berry May 27. We were fortunate to be able to pick most of our late fruit by machine and at night. It was not easy, but I guess farming never has been.

Like you, we are hustling to get ready for harvest 2022. We’ve hedged our farm and are entrenched in our annual battle with Chilli Thrips, Spider Mites, Citrus root weevils and Rust. Plus we’re evolving the farm by supplanting some of our problem varieties with more reliably productive and healthy University of Florida introductions targeted at our prime Florida market window.

Our industry can have a bright future, but we are all going to have to figure out how to deal with a new era of higher costs from many corners. From Ag chems to energy, labor, and government compliance, we have to find solutions to mitigate their impact to our financial health. All this is coming against a backdrop of surging competition from south of the border. Nevertheless, I believe the members of the Florida Blueberry Growers Association can adapt to these challenges and look forward to the 2022 harvest season with great anticipation… with of course the usual dose of trepidation that comes along with farming.

photo by HUNTER VICKERS

growers' thoughts, cont. from page 15

The following are some specifics from Sentinel trial site evaluations. Detailed information on all UF blueberry cultivars can be found in the UF/IFAS Blueberry Growers Guide app and at https://www.blueberrybreeding.com/ varieties. • Cultivar name: Sentinel (selection code FL11-155) • Region best adapted to: north-central and central Florida • Production system: performs well in deciduous system in both north-central & central FL; additional data to be gathered for evergreen system • Hydrogen cyanamide: not required • Machine Harvestability: no data yet; trials to be conducted in 2021 • Per plant yields: – North-Central FL (2018-2020): 8.8 – 21.0 lbs/plant, average 16.4 lbs/plant – Central FL (2018-2020): 5.6 – 10.9 lbs/ plant, average 8.2 lbs/plant • Known disease susceptibility: none observed to date • Known insect damage susceptibility: moderate level of susceptibility to chilli thrips observed, similar to other cultivars • Fruit quality data: – Fruit firmness: 197 – 217 g/mm, average 207, a little higher than Emerald – Berry Weight: 2.0 – 2.9 grams, average 2.4 grams, similar to Emerald – Berry Diameter: 15.4 – 19.4 mm, average 17.6 mm, similar to Emerald – Brix: 10.0 – 12.5, average 11.5, similar to Emerald – Brix/Acid Ratio: 27.2 – 83, average 49.7, better than Emerald – Fruit scar: normal (small, dry), similar to

Emerald – Wax/bloom: medium, similar to Emerald – Fruit defects: none – Flavor: high flavor score from taste panels (27.5). Higher than Emerald (19.9), very close to Kestrel (29.0). – Aroma: low • Cultivars with similar flowering time: – North-Central FL – Optimus, Patrecia, Vireo, Magnus – Central FL – Optimus, Arcadia, Avanti, and Chickadee • Other information: High vigor, with large yield in the early part of the season. Good performance with no observed disease issues.

______ CREDIT by DR. PATRICIO MUNOZ, UF Assistant Professor, Blueberry Breeding and Genomics & DOUG PHILLIPS, UF Blueberry Extension Coordinator

Identifying Leaders in the Field

Among the most important things I’ll do as head of the Institute of Food and Agricultural Sciences is identify leaders who make a great impact on Florida agriculture. When I got to hire my first department chair, I discovered two leaders. One was the guy who got the job, Chris Gunter. The second was Brittany Lee.

As my first major hire, the Horticultural Sciences search was important not just for whom we hired but for how we did it—with Brittany’s participation on the stakeholder committee. I relied heavily upon stakeholder insights and their understanding of the industry’s research needs to inform my decision.

The stakeholder committee delivered the most persuasive six words about Gunter among the dozens of messages I received: “We recommend highly and without reservation.”

Perhaps the first thing you need to know about Gunter is that he’s Patricio Muñoz’s supervisor. The new chair has a huge task ahead of him. How does he improve a horticulture team that already has a top10-in-the-world ranking?

Gunter inherits a department (well led by Jackie Burns on an interim basis while we searched for a permanent chair) that is somehow still on the rise. Just this year we broke ground on a new blueberry lab, built a new on-campus greenhouse for our horticulturalists and cut the ribbon on 15 new growth chambers they will share with several other departments.

Horticultural Sciences is among the departments cooperating to launch a plant breeding Ph.D. program in the fall. Patricio is among those who will have one of the seven students in our inaugural cohort.

I’m not done with Brittany and other blueberry industry representatives. I’m counting on them to keep Chris and me abreast of the FBGA’s research agenda. I met Leonard Park during a recent visit to the Pasco County Extension office and will likely tap him for continuing feedback as well.

We’ll want to know what Brittany and Leonard think as Gunter seeks to build teams of horticulturalists and engineers to capitalize on the artificial intelligence (AI) initiative at UF. Their input will also help our team of plant breeders identify the most important traits in new varieties of fruits and vegetables.

Please invite Gunter—and me—to your farm. I am just finishing my first year and look forward to meeting many more of you. You can reach out directly to me or to Gunter at cc.gunter@ufl.edu.

Chris Gunter

J. Scott Angle

jangle@ufl.edu @IFAS_VP

J. Scott Angle is the University of Florida’s Vice President for Agriculture and Natural Resources and leader of the UF Institute of Food and Agricultural Sciences (UF/IFAS).

for the crop,cont. from page 32

modes of action, maintain an appropriate fungicide rotation program, avoid the exclusive use of a single fungicide or active ingredient, and implement an integrated disease management program. The Fungicide Resistance Action Committee also recommends following fungicide label directions, using products at the indicated dose rate, limiting the number of applications, and performing chemical sprays only when absolutely necessary.

______ CREDIT by DR. PHIL HARMON, Professor, Plant Pathology, University of Florida & DOUG PHILLIPS, UF Blueberry Extension Coordinator, University of Florida

Table 1. Seasonal leaf disease calendar for deciduous Florida blueberry production. Green shaded months indicate when the listed diseases are most likely to occur during a season, and when fungicides may be most effective.

SUGGESTED FUNGICIDE SPRAY SCHEDULE

JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC

BLOOM (1)

HARVEST (2)

POST-HARVEST (3)

PHOMOPSIS Pristine, Switch, Abound, Quash, Quilt Xcel SEPTORIA Orbit, Indar, Quash, Quilt Xcel, Proline, Luna Tranquility, Abound, Switch, Pristine, Bravo RUST Orbit, Indar, Quash, Proline, Pristine, Bravo ANTHRACNOSE Indar, Orbit, Quash, Quilt Xcel, Proline, Luna Tranquility, Abound (tank mixed with captan), Pristine, Switch, captan, Bravo TARGET SPOT Indar, Orbit, Quash, Quilt Xcel, Proline, Luna Tranquility, Abound, Pristine, Switch, cpatan, Bravo PHYLLOSTICTA Orbit, Quash, Tilr, Pristine (1) February through March for Nroth-Central, January through March for Central and South-Central in most years. check the preharvest interval of all products. (2) April through May for North-Central, March through May for Central and South-Central in most years. Check the preharvest interval of all products. (3) June through December for all regaions in most years.