applications of foliar nutrients for improved fruit set in

Applications of Foliar Nutrients for Improved Fruit Set in Blueberry:

Year 1

Lisa Wasko DeVetterAssistant Professor, Small Fruits

&Matthew Arrington

PhD Graduate Student

Dec. 3, 2015

Fruit Set in Washington Blueberry is Low

Blueberry can set 100% of flowers, but 80% considered a full crop Fruit set in Washington can be as

low as 50-60% (Strik, 2004)

Also, some cultivars exhibit premature fruit drop (e.g., ‘Draper’) Reduced fruit set and yield can be

due to: Poor pollination (being

addressed by SFH) Plant nutrition – specifically

boron and calcium

Why Boron (B)?

Boron is an essential micronutrient for plant growth and development Metalloid chemical element Primary role: Cell wall structure

(provides crosslinks for polysaccharides) Nucleic acid and protein synthesis Formation of sugar complexes Critically important in reproductive

processes, especially pollen functioning

Available forms: B(OH)3 and B(OH)4

Source: Stücke, 2006

Washington Blueberry May be Prone to Boron Deficiency

Most soils range from 1 to 467 mg/kg in concentration of total B Soils considered deficient if < 0.5 mg/kg

og B (Hart et al., 2006)

Symptoms of deficiency Tip dieback Aborted leaf and bud development Increased winter injury

Inadequate B may also reduce pollen viability, function, and subsequent fruit set

Source: Nasrallah, 2013

Sufficiency Levels for Blueberry

Leaf B Concentration (ppm) StatusBelow 20 Deficient

21-30 Below normal

31-80 Normal

81-150 Above normal

Above 150 Excess

Source: Hart et al., 2006

Determine from leaf samples collected mid-July to mid-Aug.

If deficient, apply B as a foliar spray before bloom and after harvest or before leaf drop

Use caution – fine line between deficiency and toxicity

Factors Influencing B Availability

Organic Matter – important reservoir for B Temperature extremes can slow decomposition and release

Soil Texture – course/sandy soils have low available B; clay soils have greater available B pH – availability is maximized between pH 5.0 – 7.5 Weather – Dry and cold weather can reduce root activity and B uptake

during times of demand Cool temperatures can also limit mobility in plants High rainfall can cause B leaching

Previous Research with Vaccinium spp.

Enhanced yield after B applied foliarlyon cranberry plants that displayed no symptoms of deficiency (DeMoranville and Deubert, 1987) Increased yield of lowbush blueberry

with fall applications of B at 400 and 600 ppm (Smagula, 1993) Increases in pollen germination and seed

number with B applications on lowbush blueberry (Chen et al., 1998)Mixed results with highbush blueberry Limited research with B in blueberry in

the PNW

Why Calcium (Ca)?

Calcium is an essential macronutrient Critical component in cell wall

structure Integral for proper membrane

functioning Other physiological roles (e.g.,

nutrient uptake, enzymatic and hormonal processes, and cell elongation)

Form used by plants: Ca2+Source: Zepper, 2007

Calcium in Blueberry

Deficiency seldom occurs in blueberry Leaf tissue ranges from 0.4-0.8% Distribution of Ca can be influenced

by fertility and vigor Calcium can improve blueberry fruit

quality (Conway et al., 2002; Hanson et al., 1993)

Foliar-applied calcium may reduce premature fruit drop in ‘Draper’ (Gerbrandt, personal communication)

… what about other cultivars?Gerbrandt, 2014

Factors Influencing Ca Availability

pH – availability is greater at higher soil pH If low soil pH is suspected for Ca deficiency, check

leaf Mn Leaf Mn >450 ppm indicates low pH and Ca

Cation Exchange Capacity Weather – high rainfall can cause Ca leaching Plant Factors – High vigor associated with low Ca Reduced transpiration limits Ca movement Distribution in plants across cultivars

Justification for Studying B and Ca

Reports that foliar B and Ca increases fruit set and yield Both nutrients often found in pre-bloom sprays Sufficiency levels may be different between

vegetative and reproductive (flowering/fruiting) tissue Nutrients may be deficient in times of crop demand Potential tools to increase fruit set of Washington

blueberry Limited research on blueberry in PNW

Project Objectives

Short term – Determine if foliar-applied B and Ca increases fruit set and yield in Washington highbush blueberry Long term – Contribute information

on approaches to enhance fruit set and how to achieve optimal nutrition in Washington blueberry

Methods: Experiment 1

Established ‘Duke’ plants at the WSU Mount Vernon Research and Extension Center Fall and summer soil and tissue

tests, respectively, in 2014 and 2015Experimental design – RCBD Three plant plots, replicated

three times, one plant buffer


Five treatments:1) Control2) Spring applied, low B (8

oz/A)3) Spring applied, high B (32

oz/A)4) Fall applied, low B (8 oz/A)5) Fall applied, high B (32 oz/A)

Product: NUE Boron 10% 10% boric acid Discussed product with

growers

Additional Experiment: Experiment 2

Observed blueberry shock virus in many plots at WSU-NWREC in 2015Expanded project and added an

additional experiment Four sites 2 in Whatcom county (‘Draper’) 2 in Skagit County (‘Bluecrop’,

organic)

Pscheidt, 2004

Pscheidt, 2007


Experimental design is RCBD Treatments applied to 5-plant plots,replicated four times:

1) HIGH boron using Solubor® at 6 lbs/acre- 20.5% as disodium octaborate tetrahydrate

2) LOW boron using Solubor® at 3 lbs/acre 3) HIGH calcium using Phyta-Cal QCTM at 4 qt/acre

- 8% Ca as calcium chloride (CaCl2) 4 qt/acre4) LOW calcium Phyta-Cal QCTM at 2 qt/acre5) HIGH B + Ca using Phyta-Set QCTM at 4 qt/acre

- 6% Ca as CaCl2- 1% B as sodium tetraborate

6) LOW B + Ca using Phyta-Set QCTM at 2 qt/acre7) Untreated control

Applied at early pink bud stage and re-applied every 7-10 days (6 total applications)Image: http://www.homedepot.com/

Data Collected

Soil, foliar, and fruit nutrient content Fruit set and estimated yieldBerry size Fruit firmnessSeed numberPremature fruit dropPollen viability

Progress Report: Experiment 1

Interpret data cautiously…unusual year and lots of shock No significant differences in fruit set, estimated yield,

nor fruit firmness Soil tests ranged from 0.32 to 0.44 mg B/kg Deficiency if < 0.5 mg B/kg

Tissue concentrations of B ranged from 42 to 63 ppm 31-80 ppm is recommended and deficient is < 20 ppm (Hart

et al., 2006) Plants treated in fall had higher [B] than those treated in

spring (61 vs. 55 ppm, respectively)

Experiment 1: Fruit Set andEstimated Yield in ‘Duke’, 2015

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Control Spring, low [B] Spring, high[B]

Fall, low [B] Fall, high [B]

Perc

ent f

ruit

set (

%)

Treatment

0

1

2

3

4

5

6

7

Control Spring, low [B] Spring, high [B] Fall, low [B] Fall, high [B]

Estim

ated

yie

ld (l

bs/p

lant

)

Treatment

No significant differences Note high fruit set in

2015 Estimated yield low due

to BIShV

Progress Report: Experiment 2

Again, interpret data in context of an unusual year No statistical differences in fruit set, estimated

yield, nor firmnessNo premature fruit dropStatistically insignificant trend of increasing fruit

set with Ca + B treatment Little uptake of Ca in leaves and fruitsCultivars responded differently

Experiment 2: Fruit Set in ‘Duke and ‘Draper’, 2015

0%

20%

40%

60%

80%

100%

120%

1 2 3 4 5 6 7

Perc

ent f

ruit

set (

%)

Treatment codes

Bluecrop site 1

Bluecrop site 2

Draper site 1

Draper site 2

Treatment codes correspond to the following: 1) untreated control; 2) Solubor® at 3lbs/acre (low B); 3) Solubor® at 6 lbs/acre (high B); 4) Phyta-Ca QCTM at 2 qt/acre (low Ca); 5) Phyta-Ca QCTM at 4 qt/acre (high Ca); 6) Phyta-Set QCTM at 2 qt/acre (low B+Ca); and 7) Phyta-Set QCTM at 4 qt/acre (high B+Ca).

Con. Low B

High B

Low Ca

High Ca

Low B+Ca

High B+Ca

Experiment 2: Fruit and foliar concentrationsof B in ‘Bluecrop’ and ‘Draper’ treated with foliar

applications of B and Ca, 2015


No statistical differencesUp to 60% more B

in high B treatments

‘Bluecrop’ seemed more sensitive to B applications

Experiment 2: Fruit and foliar concentrations of Ca in ‘Bluecrop’ and ‘Draper’ treated with foliar

applications of B and Ca, 2015


No statistical differencesModest increases

(average of 7%; up to 22% in fruit Ca)

‘Draper’ had more Ca in fruit and leaves

Conclusions and Plans for 2016

Little conclusive data from 2015Results influenced by

unusual weather and naturally high fruit setContinue with treatment

applications, data collection, and analyses for Experiments 1 and 2

Project Assistance Grower cooperators Sean Watkinson Lee Kalcsits Whatcom Farmers Co-op/CNS

AcknowledgementsFunding Washington Blueberry

Commission

Thank you! Questions?

applications of foliar nutrients for improved fruit set in

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