Impact of Nitrogen Rate on Vegetative GrowthApril 18, 2013Dr. Mercy Olmstead, UF/IFAS, Horticultural Sciences Department

Peach Production in Florida

Nitrogen important in proteins, DNA, chlorophyll (photosynthesis)

Fertilizer amounts have been adapted from other regions

Climate differences Temperate vs. subtropical

Other crops Annual vs. perennial growth

Current recommended rate (UF/IFAS) = 100 lbs. N/ac annually

Disease – tree health link? Botryosphaeria Other pests

Nitrogen Effects

High nitrogen = increased tree vigor small fruit Problems with flower set

Too little nitrogen = deficiency

Overall yellowing in the tree Red spots on leaves, red in margins

LaRue and Johnson, 1989

Johnson, 2008

Nutrient Rates and Plant Growth

0

2

4

6

8

10

12

14

16

18

20

0 40 80 160 240 320

REL

ATI

VE

GR

OW

TH R

ATE

NITROGEN APPLIED ANNUALLY (LBS./ACRE)

OptimalLuxury Consumption

Deficient

Climate Effects on Plant Growth

Florida is classified as humid subtropical to tropical

High humidity Causes rapid growth rate

Annual peach shoot growth is 8-9 feet Summer pruning Winter pruning

Can we reduce to one pruning pass with N management?

How much N should we use to manage vigor and optimize fruit yield/size?

Materials and Methods

‘TropicBeauty’ x 9-4 (Greenleaf Flordaguard)

Planted in 2005

Previously fertilized with composted manure Chicken litter and plant material

5 nitrogen rates applied annually Broadcast 0 lbs. / ac 40 lbs./ac 80 lbs./ac 160 lbs./ac 240 lbs./ac

All receive 33 lbs. Phosphorus and 67 lbs. Potassium per UF/IFAS recommendations

N4 (240 lbs N/year)

N0 (0 lbs N/year)

Trunk Cross-Sectional Area (TCSA)

Measure of the trunk diameter = relative growth of tree

Use it in conjunction with yield to calculate yield efficiency

TCSA/Yield = Yield Efficiency Amount of fruit in relation to tree growth

TCSA in Mature Orchard

0

20

40

60

80

100

120

0 40 80 160 240

Trun

k Cr

oss-

Sect

iona

l Are

a (in

2)

Annual N applied per acre (lbs.)

2012 2013

2011 Pruning Weight

6.56 6.96 6.39 6.40 6.97

2.422.63

2.353.20

3.01

0 40 80 160 240

Lbs.

of S

hoot

s/W

ood

Amount of N Applied Annually (lbs.)

Summer 2011 Winter 2011

2012 Pruning Weight

10.10 10.2412.80

13.9811.99

2.95 2.60

4.013.38

3.40

0 40 80 160 240

Lbs.

Sho

ots/

Woo

d

Amount of N Applied Annually (lbs.)

Summer 2011 Winter 2011

Bud Distribution

Vegetative – growing points for shoots

Floral – fruit production

Blind nodes – no bud

Bud Distribution in Mature Orchard

1 year old growth 21.7

4.3 2.7 2.9 4 4.2

11.7

8.75.8 6.8 8.5 9.9

6.7

18.7 14.1 14.6 18.9 19.3

2011 0 40 80 160 240AMOUNT OF N APPLIED ANNUALLY (LBS.)

Vegetative Floral Blind 2012

Bud Distribution in Mature Orchard

20132.88 2.83

3.712.96 4.33

6.58 7.465.21 8.04

8.96

8.79 8.88 8 8.5 9

0 40 80 160 240AMOUNT OF N APPLIED ANNUALLY (LBS.)

Vegetative Floral Blind

Yield

*2012 = 80% reduction due to freeze events (Feb. 12/13)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0 40 80 160 240

Frui

t Yie

ld (l

bs.)

Amount of N Applied Annually (lbs.)

2011 2012

Yield Efficiency

Nitrogen Rate (lbs. N/ac) 2011 2012

0 0.07 0.04

40 0.08 0.05

80 0.11 0.03

160 0.09 0.03

240 0.12 0.04

Total Leaf N (%)

Optimal = 2.6 – 3.0%

0 40 80 160 2402011 4.3 4.5 4.6 4.6 4.82012 3.7 3.7 4 4.2 4.1

0

1

2

3

4

5

6

TOTA

L LE

AF

NIT

RO

GEN

%

Summary

Mature trees have a large buffering capacity High initial nitrogen % in leaves Separation between treatments (N0 vs. N4)?

Total leaf N (%) continues to be high

N rate does not appear to alter bud distribution in mature trees

Additional yield data in years without significant freeze damage important

Effect of varying N rates on tree establishment?

N0 = 0 lbs N/ac/yr

N3 = 160 lbs N/ac/yr