Fertilizing the Hass Avocado for Maximum Productivity

UNIVERSITY OF CALIFORNIA, RIVERSIDE
Department of
Botany
and
Plant Sciences
www.ucr.edu
$Fertilizing the ‘Hass’
$
Avocado for Maximum
Profitability
Carol Lovatt
$
$
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Professor of Plant Physiology
University of California-Riverside
$
carol.lovatt@ucr.edu
www.plantbiology.ucr.edu
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Fertilizing
the ‘Hass’ Avocado
1) An overview of fertilization.
$
2) Fertilizer best management
practices
make
dollars
and
$sense.
$
$
$we fertilize our way out of
3) Can
alternate bearing?
$
Fertilizing the ‘Hass’ avocado
• Optimizing fertilization of the ‘Hass’
avocado is a cost-effective strategy
for increasing yield and profitability.
• In California, despite four decades of
research, only a limited number of
experiments have been conducted to
determine optimal rates of soilapplied fertilizers - N, P, K, Fe, and Zn.
Problems
• All other fertilizer recommendations are
based on leaf analyses using optimum
ranges borrowed from citrus and,
though modified over the years, are not
related to any avocado yield parameter.
• Avocado leaf analyses do not detect
differences in tree nutrient status or
fertilization rates related to yield.
Problems
• Leaves for nutrient analysis are
collected in August-September, which
is too late to correct deficiencies that
negatively impact the current crop.
• Avocado leaf analyses were developed
to guide replacement fertilization for the
next year’s crop; careful management is
required to prevent under-fertilization of
ON-crop trees and over-fertilization of
OFF-crop trees!
Fertilizer Best Management
Practices (BMPs)
A demand-driven fertilization strategy
• matches fertilizer rates and application
times to meet the nutrient demand of
the different stages of avocado tree
phenology,
• increases fertilizer-use efficiency
• is cost-effective and environmentally
friendly.
Our Approach
• Identify the role essential nutrients play
in the physiology of the crop,
• Apply the nutrient as a foliar or soil
fertilizer at a key stage in the phenology
of the tree when nutrient demand is high
to stimulate a specific metabolic process
that results in increased yield, fruit size
or quality and a net grower profit.
An overview of fertilization
of ‘Hass’ avocado trees
An overview of fertilization
of ‘Hass’ avocado trees
An overview of fertilization
of ‘Hass’ avocado trees
X
X
An overview of fertilization
of ‘Hass’ avocado trees
An overview of fertilization
of ‘Hass’ avocado trees
2x N in April or November – significantly
increased total yield, yield of commercially
valuable fruit and reduced alternate bearing
An overview of fertilization
of ‘Hass’ avocado trees
XX
X
XX
X
2x N in January, February or June – had no effect
on yield, fruit size or alternate bearing, thus there
is no need to add extra N at these times
An overview of fertilization
of ‘Hass’ avocado trees
1x N or N-P-K in July and August – significantly
increased total yield and yield of commercially
valuable fruit compared trees that did not receive
N or N-P-K in both July and August
An overview of fertilization
of ‘Hass’ avocado trees
X
X
1x N-P-K applied four times (April, July, August,
November) or 2x N-P-K in April or November –
reduced total yield and yield of commercially
valuable fruit
100
90
Fruit Dry Wt (g/fruit)
80
70
Total
Flesh
Peel
Seed
60
50
40
30
20
10
0
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Nitrogen content of ‘Hass’ avocado fruit.
Fruit N content (mg/fruit)
2000
1500
1000
500
0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Each point is the mean between 5 and 12 fruit, with standard error bars.
Potassium content of ‘Hass’ avocado fruit.
2000
Fruit K content (mg/fruit)
B.
1500
1000
500
0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Each point is the mean between 5 and 12 fruit, with standard error bars.
Fruit Ca content (mg/fruit)
Calcium content of ‘Hass’ avocado fruit.
80
C.
60
40
20
0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Each point is the mean between 5 and 12 fruit, with standard error bars.
Mineral balance (g per tree) of 20-year-old ‘Hass’
avocado in California.
Leaves
& twigs
N
P
K
Ca
Mg
S
Al
B
Fe
Mn
Na
Zn
559
118
373
575
183
101
1.1
1.8
3.4
3.0
9.8
2.1
Branches Trunk
Roots
Fruit
Total
Proportion
removed
by fruit (%)
657
129
610
1093
471
120
4.4
3.6
6.4
3.6
23.9
3.9
293
85
251
317
61
65
32.7
1.7
22.0
1.3
85.8
7.6
191
53
377
6
16
45
0.0
1.4
0.3
0.1
1.8
0.5
1734
399
1665
2086
742
345
39
9
33
8
131
15
11.0
13.3
22.6
0.3
2.2
13.2
0.1
15.9
1.1
1.1
1.4
3.3
34
13
56
95
12
14
0.7
0.4
0.9
0.3
9.2
0.8
Fertilizer BMPs make
dollar$ and sense
Shoot K
Fruit Ca + K
Root N, K, Ca, Fe + Zn
Fruit K
Fertilizer BMPs make
dollar$ and sense
Matching fertilizer rates and application
times to meet the nutrient demand of
different stages of avocado tree
phenology makes sense based on
• tree physiology
• fertilizer-use efficiency
• cost to benefit
• protection of the environment.
Can we fertilize our way our
of alternate?
• Our understanding of best management
practices in an alternate bearing ‘Hass’
avocado orchard would definitely
benefit from additional research.
• There are fertilizer practices with known
benefits that should be considered.
Boron @ 1.3 lbs B/acre (6.3 lbs Solubor/acre;
20.5% B)
Urea-N @ 23 lbs N/acre (50 lbs urea/acre;
46% N, 0.25% biuret)
Boron increased yield 12,125 lbs/acre/3 yrs
Urea increased yield 10,913 lbs/acre/3 yrs
Can we fertilize our way out of
alternate bearing?
Can we fertilize our way out of
alternate bearing?
Periods of N uptake by ‘Hass’ avocado trees
Can we fertilize our way out of
alternate bearing?
Can we fertilizer our way out
of alternate bearing?
Since fruit number drives the uptake of many
essential nutrients, matching fertilizer rates and
application times
• to periods of high nutrient demand by the fruit
• to periods of strong canopy growth (floral and
vegetative)
is a solid approach to maximizing yield with the
potential to mitigate alternate bearing.
Maximize ‘Hass’ Tree Physiology
1. Maintain healthy roots (uptake of water and
nutrients) and leaves (energy production).
2. Maintain balance between leaf number and
fruit number for large size fruit.
3. Maintain balance between shoot number and
fruit number to reduce alternate bearing
(prune early in the on-crop year).
4. Fertilize the current crop load, includes both
setting and maturing fruit; do not fertilize
to replace what the previous crop used.
5. If possible, harvest earlier rather than later.