John L. Jifon

Foliar Potassium (K) Fertilization f M k lof Muskmelon:

Effects on Fruit Qualityy

John Jifon & Gene Lester

Lower Rio Grande Valley

The problem: I i t tInconsistent Fruit Quality

Taste – SweetnessFlavorAppearanceAppearanceTextureN t iti l d h lth b fitNutritional and health benefitsShelf life

The problem: pInconsistent Fruit Quality

Genetics alone (cultivars) not enoughNutrient imbalance KNutrient imbalance - K

Focus on Potassium FertilizationQuality nutrient: Numerous Functions in Plants

1 Ph t th i d ti1. Photosynthesis: sugar production2. Assimilate transport; phloem p ; p

loading/unloading 3 Enzyme activation3. Enzyme activation4. Regulation of water loss5. …many more….

Uptake limitationsMost K uptake is prior to fruiting Soil moisture, temperature, aeration …root activitySi k i i ( f i ) f b h dSink competition (roots vs fruits) for carbohydrates Competitive interactions with other ions - Ca and MgHigh pH (7 5+)High pH (7.5+)….many more..

Uptake limitationsMost K uptake is prior to fruiting Soil moisture, temperature, aeration …root activitySi k i i ( f i ) f b h dSink competition (roots vs fruits) for carbohydrates Competitive interactions with other ions - Ca and MgHigh pH (7 5+)High pH (7.5+)….many more..

Consequence:An apparent K deficiency during the critical fruit

development period because root uptake cannot keep up with fruit demandcannot keep up with fruit demand.

Soil characteristics

2005 2006 2007 CL

pH 8.1 ± 0.2 8.3 ± 0.2 8.4 ± 0.3 6.5

NO3-N 29 ± 4 23 ± 2 25 ± 2 -

P 55 ± 3 53 ± 3 51 ± 4 50

K 664 ± 26 612 ± 75 572 ± 13 175

Ca 7307 ± 247 7677 ± 574 8069 ± 827 180

Mg 442 ± 43 390 ± 31 430 ± 51 50Mg 442 ± 43 390 ± 31 430 ± 51 50

Na 188 ± 5 168 ± 9 162 ± 3 -

Glasshouse studies(Lester & Jifon, 2005, 2006)

• Supplementing soil derived K with foliar Kderived K with foliar K applications can overcome the apparent deficiency

• Improve fruit quality (soluble solids & firmness)

• Increase human health quality traitsquality traits

Objectives of the Current Study:• Determine extent to which this

approach is applicable under fieldapproach is applicable under field conditions

• Evaluate effects of different K sources on fruit quality.

Treatments:• Foliar K sources:

1. Control 0% K2O 2. KCl - potassium chloride 60% K2O 2

3. KNO3 - potassium nitrate 44% K2O 4. MKP - monopotassium phosphate (PeaK) 30% K2O 5. K2SO4 - potassium sulfate 50% K2O 2 4 p 2

6. KTS - potassium thiosulfate 25% K2O 7. K-Metalosate - glycine amino acid-complexed K, 24% K2O +surfactant (Silwet)(S )

• Timing & rates 4lbs K2O/A weekly (6 - 8am) from fruit set to maturationfrom fruit set to maturation

• Crop netted muskmelon ‘Cruiser’

Fruit harvests & processing• Soluble solids• Total Sugars• Total Sugars • Fruit firmness

Internal color• Internal color• Tissue K content• Vitamin C • β-carotene

• Yield

Soil characteristics

2005 2006 2007 CL

pH 8.1 ± 0.2 8.3 ± 0.2 8.4 ± 0.3 6.5

NO3-N 29 ± 4 23 ± 2 25 ± 2 -

P 55 ± 3 53 ± 3 51 ± 4 50

K 664 ± 26 612 ± 75 572 ± 13 175

Ca 7307 ± 247 7677 ± 574 8069 ± 827 180

Mg 442 ± 43 390 ± 31 430 ± 51 50Mg 442 ± 43 390 ± 31 430 ± 51 50

Na 188 ± 5 168 ± 9 162 ± 3 -

40

50

g/gd

wt

30

40

Leaf

[K],

mg

20

10

K Source

0KNO3KCl K2SO4 K-

MetalosateControlPre-

fruit set

200514

162005

6

8

10

12

14

t

0

2

4

2006

tion,

mg/

gdw

t

14

1618

um c

once

ntra

t

4

6

810

12

14

Leaf

pot

assi

u

02

4

2007

14161820

2468

1012

K Source

02

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

Petiole [K]5060

Stem [K]2005

20

30

40

50

wt

2005

20

30

40

50

60

wt

0

10

2006

trat

ion,

mg/

gdw

50

60

700

10

20

2006

ntra

tion,

mg/

gdw

50

60

70

tass

ium

con

cent

0

10

20

30

40

80otas

sium

con

cen

0

10

20

30

40

100

Stem

pot 0

2007

40

60

80

Petio

le p

o 02007

40

60

80

100

K Source

0

20

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

K Source

0

20

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

K SourceK Source

Fruit [K]2005

20

30

0

10

2006

mg.

gdw

t-1)

30

soca

rp [K

], (m

10

20

30

Frui

t mes

02007

30

0

10

20

K Source

0KNO3KCl KTSK2SO4KH2PO4

PeaKK-

MetalosateControl

Soluble solids

2005

8

10

12

14

0

2

4

6

200614

2006

Brix

(%)

6

8

10

12

B

0

2

4

200710

12

4

6

8

K Source

0

2

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

Fruit sugars20052005

30

40

50

60

0

10

20

2006

(mg.

gdw

t-1)

70

80

ar c

onte

nts

(

30

40

50

60

70

ruit

tota

l sug

0

10

20

200750

F

10

20

30

40

K Source

0

10

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

Fruit Texture200518

202005

68

1012141618

0246

2006

S (N

ewto

ns)

12

14

ruit

FIR

MN

ES

S

4

6

8

10

12

Inte

rnal

fr

0

2

2007

8

10

12

0

2

4

6

8

K Source

0KNO3KCl KTSK2SO4KH2PO4

PeaKK-

MetalosateControl

Fruit color 2005

75

65

70

2006e an

gle,

o )

2006

eara

nce

(hue

70

75ui

t fle

sh a

ppe

652007

75

Fru

70

K Source

65KNO3KCl KTSK2SO4KH2PO4

PeaKK-

MetalosateControl

Ascorbic acidβ-carotene2005

10

15

20

)

2005

10

15

20

)

0

5

2006

tent

s (µ

g/gF

W)

20

25

0

5

2006

tent

s (µ

g/gF

W)

20

25

a ca

rote

ne c

on

0

5

10

15

20

a ca

rote

ne c

on

0

5

10

15

20

Frui

t bet

a 02007

6

8

10

12

14

Frui

t bet

a 02007

6

8

10

12

14

0

2

4

6

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control0

2

4

6

KNO3KCl KTSK2SO4KH2PO4PeaK

K-Metalosate

Control

K Source K Source

Fruit yield, x1000 lbs/acre

25

30 2005 2006 2007**

lbs/

ac

20

25

∗

d, x

1000

15

Yiel

5

10

0

5

KNO3KCl K-K2SO4KH2PO4 K-Control

K Source

3Thiosulfate

2 42 4PeaK Metalosate

Leaf mineralsnitrogen **nitrogen **

15

20

25

30

phosphorus2 5 phosphorus

0.5

1.0

1.5

2.0

2.5

potassium **14ns, m

g/gd

wt

8

10

12

magnesium

con

cent

ratio

n

910

Leaf

min

eral

6789

calcium

110

120

90

100

110

sulfur

6

7

K Source

4

5

6

KNO3KCl K2SO4 K-Metalosate

Control

Weather ConditionsA50 A

PF, m

ol.m

-2.d

ay-1

10

20

30

40

50

PP

0

10

Bm

p., o C

15202530

Air T

em

0

510

15

C

, %

100

Air R

el. H

umid

ity

40

60

80

D

emp.

, o C

20

25

30

2005

Day of Year

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

Soi

l Te

10

1520062007

Summary: weekly foliar K applied to field grown melonsweekly foliar K applied to field-grown melons

–↑ fruit firmness–↑ soluble solids↑–↑ fruit sweetness↑ total sugar content–↑ total sugar content

Differences between sources?? ↓KNO3

V t bl d F it I t C tSpecial Thanks

• Vegetable and Fruit Improvement Center –Texas A&M University; “Designing Foods for Health” Program,Health Program,

• Fluid Fertilizer Foundation,• International Plant Nutrition Institute,,• Tessenderlo Kerley Inc., • Albion Laboratories,,• Rotem BKG LLC, • Nutra-Flo,• Western Laboratories

THANK YOU