impact of nitrogen rate on vegetative growth...fertilizer amounts have been adapted from other...
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Impact of Nitrogen Rate on Vegetative GrowthApril 18, 2013Dr. Mercy Olmstead, UF/IFAS, Horticultural Sciences Department
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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
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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
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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
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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?
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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
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N4 (240 lbs N/year)
N0 (0 lbs N/year)
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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
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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
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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
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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
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Bud Distribution
Vegetative – growing points for shoots
Floral – fruit production
Blind nodes – no bud
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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
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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
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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
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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
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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
%
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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?
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N0 = 0 lbs N/ac/yr
N3 = 160 lbs N/ac/yr