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HELLENIC AGRICULTURAL
ORGANIZATION “DEMETER”
Fertilizing Olive Trees
Dr Georgios Psarras
Institute for Olive Tree & Subtropical Plants
Lab of Plant Mineral Nutrition & Physiology
Introduction
Law of Minimum(von Liebig)
Max yield
Potential
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Introduction
DEFICIENCY ADEQUACY TOXICITY
Nutrient concentration
In leaves
Pla
nt
Gro
wth
MacronutrientsNitrogen (Ν)
Phosphorus (Ρ)
Potassium (Κ)
Calcium (Ca)
Magnesium (Mg)
Sulphur (S)
Iron (Fe)
Manganese (Mn)
Zinc (Zn)
Boron (Β)
Copper (Cu)
Molybdenum (Μο)
Chloride (Cl)
Micronutrients
Plant Nutrient Requirements
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Sustainable fertilizing schedule
A sustainable fertilizing schedule has to: Retain nutrient concentration within adequacy
range Avoid deficiencies
Avoid toxicity
Retain nutrient balance
Replace nutrient removal from the orchard (removal from yield, pruning, etc.) Use of chemical fertilizers
Use of organic fertilizers or other organic material
Recycling of material removed from the tree (prunings, olive oil by-products, etc.)
Sustainable fertilizing schedule
Appropriate application scheduling:
Reduce fertilizer losses
Apply nutrients during the high nutrient demand season
Protection of the environment
Improve soil fertility
Increase of organic matter
Maintain pH within the appropriate limits for olive
Improve soil texture
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Defining nutrient requirements
Defining nutrient requirements is a key issue
for a sustainable fertilizing schedule
There are some basic estimates of nutrient
removal, mostly based on tree yield that will be
presented later on
However, these estimates may vary
considerably and data for local conditions
and/or cultivars should be available, since
olive tree is cultivated under significantly
variable orchard management schemes
“Natural” vs intensive management
Several of the traditional orchards are typically
adopting “low-input” management scheme,
resulting to a “low-output” (yield) too.
The potential for converting this “low-input”
system into a more productive but also more
intensive scheme, greatly depends on the
existing abilities to overcome current
restrictions.
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Olive tree growing systems
Growing system % world-wide Density (trees/ha)
Traditional in marginal
areas
20 Up to 100
Traditional – able to be
mechanized
50 Up to 100
Intensive 29 Up to 400
Hedgerow 1 1200 - 2000
Source: Tous et al., 2011
Empirical vs sustainable
In several cases, the existing pool of nutrients in the
soil is considerably higher than actual nutrient removal
and therefore, especially in traditional olive orchards,
the need for fertilizer use is limited for most of the
essential mineral nutrients
Since the actual nutrient requirements cannot easily
be calculated, even by agronomists, for a specific
orchard, it is obvious that empirical application of
fertilizers by farmers may lead to serious mistakes that
may increase the production cost and definitely reduce
the efficient use of resources
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Important knowledge and tools
Knowing the nutritional status of the tree:
Leaf analysis
Knowing key soil properties and indicative nutrient
availability:
Soil analysis
Olive tree fertilizing
The nutrients that are most commonly used for olive
tree fertilizing are N, P, K and B
In several cases and depending on local soil
properties, Ca and Mg might also be used, as well as
the rest of mineral elements in case of proven
deficiency
For every 50 kg of olive fruit produced, the amount of
nutrients that are removed are: 450 g N, 100 g P, 500
g K and 200 g Ca
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Olive tree nutrient removal by
yield and pruning
According to Fernandez-Escobar et al., 2015:
N
kg/Ha
P
kg/Ha
K
kg/Ha
Ca
kg/Ha
Amount 54.4 6.87 45.5 57.9
Main Source Yield and
Pruning
Yield Pruning
Introduction
Annual requirements for mineral elements vary considerably among different orchards depending upon: Tree age
Planting density
Cultivar
Pruning
Rainfall and availability of irrigation water
Soil characteristics: Soil texture
Soil carbonate content
Soil organic matter
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27%
73%
IRRIGATED
Low
Normal58%
42%
RAINFED
Low
Normal
Nitrogen
41%
59%
IRRIGATED
Low
Normal 65%
35%
RAINFED
Low
Normal
Potassium
Nitrogen
Typically, in fertilized orchards, N is added on an
annual basis
Typical Mediterranean soils are low in organic matter
and therefore:
Plants use almost exclusively the N added through fertilizers
It is important to replenish soil N resources
Olive tree responds to N fertilizing in various ways
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Nitrogen
Increased yield
Higher flowering quality
Longer shoot growth
Reduced biennial bearing fluctuations
Nitrogen cycle in the farm
Ν2
Atmospheric Ν
Mineral N
Fertilizing
Organic Ν
(Manure,
Compost, etc)
NH3
Ammonia
Soil
Organic N
ΝΗ4+
Αμμωνιακό Ν
Mineralization
ΝΟ2-
ΝΟ3-
Nitrate-N
Nitrification
Leaching
N fixation
Uptake by
Olive trees
N-fixing
plants
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Nitrogen
N losses depend upon climatic conditions (rainfall events), soil type and orchard topography (slope)
NO3-N leaching High rainfall
Coarse soil texure, Low organic matter
Atmospheric losses Hot and dry environment
High soil CaCO3 content (calcareous soil)
Flooded soil (anaerobic conditions)
Surface runoff losses Orchards on high slopes and increased soil erosion risk
High rainfall rates after application
Nitrogen
Long-term experiments in Crete showed that addition of 0,8 kg
N/tree can increase yield by 52-105% as compared to non-
fertilized control trees.
N fertilizing increases:
the number of perfect flowers
The length of annual shoot growth
The number of nods per shoot
The number of inflorescence
No effects on fruit drop percentage and total number of flowers
per inflorescence
Shoot growth starts earlier, an advantage for rainfed orchards.
Flowering and fruit set are also completed earlier.
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Nirogen
Low N content short length of annual growth and pale leaf color (chlorosis in whole leaf surface)
High N content long annual shoot growth, low yield, dark green leaf color
Long annual shoot growth no flower differentiation
Very short annual growth low yield potential for next year
Therefore, a balanced N fertilizing is required for achieving a good yield
Nitrogen deficiency
Source: Production Techniques in Olive Growing. IOC, 2007.
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Nitrogen
Typical annual requirements of olive trees range from
0.5-1.0 kg Ν per tree (not exceeding 150 kg/ha)
depending mostly on:
Tree size
Planting density
Water availability
If reduced water availability severely inhibits plant growth
and yield, then total N uptake (and fertilizing need) is also
significantly lower
In rainfed orchards, high N application rates may reduce
uptake of other nutrients, like K
Nitrogen and fruit/oil quality
Experiment: cv. ‘Picual’ in 2 areas with N applied either 100% from soil or 50-50 (soil-foliar appl.), after 3 years:
Total phenolic content was reduced as N content was increased reduced oil tolerance to oxidation and reduced bitterness.
Tocopherols were increased as N content was increased.
No effect on carotenoids, chlorophyll, and fatty acid composition.
Source: Fernández-Escobar et al., 2006
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Nitrogen and olive oil quality
Higher doses of N and P:
Decreased polyphenol content
Decreased peroxide value
Decreased MUFA C18:1
Increased PUFA C18:3
K dosage did not affect oil quality parameters
Source: Dag et al., 2009
Phosphorus
Under field conditions, olive tree yield is not affected
by P application in most cases.
However, low P content has been recorded in areas
cultivated for the first time (new orchards) and in acidic
soils in Crete.
Use of composite fertilizers usually leads to P surplus
in leaves and high levels of P in the soil.
Nonetheless, P is a quite important element for olive
tree, as in any other plant, and we have to be sure that
trees have adequate P levels.
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P and fruit yield
Source: Erel et al., 2008
Phosphorus and olive oil quality
Higher doses of N and P:
Decreased polyphenol content
Decreased peroxide value
Decreased MUFA C18:1
Increased PUFA C18:3
K dosage did not affect oil quality parameters
Source: Dag et al., 2009
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Phosphorus
Phosphorus in the soil
Phosphorus is strongly bound in the soil and only a
small part is available to the tree
P movement in the soil is very slow (in contrast to
N).
The highest risk for P losses is related to soil
erosion in sensitive areas
Phosphorus
Visual symptoms of P deficiency in the field is quite
rare.
Therefore, leaf analysis is usually the only way to
detect P deficiency
When P leaf content is marginal or low, winter
application of P usually solves the problem. Typical
rates for medium-sized trees are 0.4-0.6 kg P2O5/tree
However, the exact rate of application should be
defined taking into account various soil properties
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Potassium
Potassium deficiency is quite common in olive
orchards
K deficiency is more common in rainfed orchards,
where high K requirements coincide with the peak of
the dry season
Typical symptoms: chlorosis developing to necrosis of
leaf tip and/or leaf edges.
In severe cases: leaf drop and shoot necrosis. In such
cases severe impact on yield.
Source: Production Techniques in Olive Growing. IOC, 2007.
K deficiency symptoms in leaves,
shoots and fruit
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Potassium
A typical dose for trees with a mean annual yield of 50 kg of olives is 0.5 kg K2O/ tree
This is the maintenance dose when soil and leaf content are within the adequacy range.
When there is a strong biennial bearing cycle, then K is preferably applied when the high yield is expected (“on” year).
In cases where soil K content is significantly low, then the application rate may be double or triple than actual tree requirements, depending on soil type, in order to restore K availability in the soil.
Calcium
Ca deficiency is not quite common, since olive is
traditionally cultivated in calcareous soils.
Typical symptom is leaf tip chlorosis
In table olives, Ca has been related (together with B)
to fruit abnormalities (soft nose)
Use of fertilizers than can lower soil pH may enhance
the Ca deficiency problems
Significant Ca deficiency problems have been
observed in soils with high Mg content
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Ca deficiency symptoms in
olive leaves
Calcium
Low Ca levels are typically linked to soils with
low CaCO3 content and low pH.
In such soils, soil liming is recommended
anyway, in order to improve soil pH. This
practice usually improves Ca uptake and
resolves the problem.
When soil pH is not a limiting factor (i.e. >6.5),
then fertilizers with readily availables forms of
Ca are applied (i.e. calcium nitrate)
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Magnesium
Typical symptoms of deficiency: chlorosis developing
from leaf edges and developing inwards. Symptoms
develop in older leaves.
Not a common deficiency in Greece, due to existing
soil types
However, it is an important macronutrient, which
should be monitored by leaf analysis and be included
in fertilization scheduling if levels in leaf and soil are
low
Magnesium
Source: F. Nigro, 2015
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Magnesium
Similarly to Ca, low soil availability is linked to low soil
pH.
When low Mg levels are detected in a low pH soil, then
liming with dolomite (containing both Ca and Mg)
should be applied.
When soil pH is not a limiting factor (i.e. >6.5), and leaf
analysis shows low Mg levels:
Soil or foliar application of MgSO4 can resolve the problem
(up to 2 kg/tree for soil application, repeated periodically)
Maintenance with Mg-containing fertilizers (e.g. K-Mg
sulphate)
Boron
The most common micro-nutrient deficiency for olive
trees.
Common to many different soil types, like coarse-
textured soils (B lost by leaching), fine-textured soils,
low or high soil pH (reduced B mobility in soils with
high clay, or carbonates or Al, Fe, Mn oxides)
Soil moisture greatly affects B availability
High organic matter in the soil can improve B release
to the nutrient solution
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Boron
Symptoms appear in both young and mature olive
trees, but deficiency develops faster in young trees
Step 1: Leaf tip chlorosis that develops to necrosis.
Leaves might have flattened tips and be smaller in
size
Step 2: Shoot growth is limited and lateral buds
develop instead of shoot-tip buds, resulting in “Witch’s
broom” symptom.
Step 3: Shoot necrosis and leaf drop
Boron
Brown necrotic spots may develop in thicker shoots
Under B deficiency, flowering is limited and fruit-set is
lower than normal.
Fruit drop and deformation of remaining (“monkey
face” symptom) are also typical
Despite the great variety of symptoms in several cases
it can be confused with other nutritional problems
Therefore, leaf analysis is again quite useful in early
detection of B deficiency, before developing severe
symptoms
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B deficiency in leaves
and fruit of cv.
“Throubolia”
Boron
Controlling B deficiency:
When B deficiency is diagnosed, typical treatment
is the application of 100-500 g of Borax per tree
(could be even higher for very large trees) during
winter.
Depending on soil type (especially in calcareous
soils) response to soil application may be delayed
or limited
Alternatively: foliar application of Borax (0,6-0,8 %)
before flowering
Quick response
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Boron
Soil application should be repeated every 3 years
Over-dosing in B application may lead to B toxicity
Use of composite fertilizers containing small
amounts of B could be effective for maintenance,
but may not be adequate for correcting a severe
deficiency
Other micro-nutrients
Deficiencies of zinc and copper are not as
common.
In general, micronutrient deficiencies are
linked to alkaline soil pH
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Zinc
Despite the fact that olive is typically cultivated
in calcareous soils with high pH, where Zn
availability is low, in general, olive tree is not
as sensitive in developing Zn deficiency as
other tree crops (e.g. citrus)
However, in recent years several cases of Zn
deficiency have been detected
Recent work has linked Zn deficiency to high P
levels in soil and olive trees
Copper
Rarely found in low concentrations in leaves
Usually, application of Cu-containing
fungicides also covers (in surplus) the olive
tree requirements
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Iron
Iron deficiency symptoms have been detected in olive
trees grown in calcareous soils with high pH
Flooding conditions in the soil may enhance Fe
deficiency problems
Cultivar seems to be the most important factor in
developing Fe deficiency in calcareous soils
Symptoms: leaf yellowing with veins remaining green,
loss of vigor and reduced yield
Fruit are smaller and pale in color (disadvantage for
table olives)
Iron
Iron deficiency is not easily detected by leaf
analysis.
Therefore, it is the only nutrient deficiency that
is better detected by the visual symptoms in
the trees (linked to soil analysis)
Difficult to correct (high cost)
Therefore, avoid its development is better than
trying to resolve the problem
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Iron
Planting non-sensitive cultivars in calcareous
soils is essential
Using a tolerant cultivar as rootstock could be
another alternative
Reference Sensitive Less sensitive Tolerant
Pastor et al., 2002 Arbequina,
Manzanilla de
Sevilla
Cornicabra,
Hojiblanca,
Nevadillo negro
Alcantara et al.
2003
Leccino, Arbequina,
Lechin de Sevilla,
Galega
Cornezuelo de
Jaen
Nevadillo negro,
Pajarero,
Manzanilla de
Sevilla
Iron
Source: Production Techniques in Olive Growing. IOC, 2007.
Fe deficiency symptoms in
leaves and fruit
Source: Franco Nigro, 2015
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Toxicities
NaCl toxicity
B toxicity
Mn toxicity
In summary
N is typically applied on an annual basis
P is usually in surplus in soil and leaves when compound fertilizers have been used for several years
In highly productive trees, K is also used on an annual basis, due to significant removal by the produced fruit
B has to be periodically applied in most olive orchards
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Defining mineral nutrient requirements
For defining the nutrient requirements and
develop a fertilizing schedule, the agronomist
should have in hand the following information:
Informative material on key orchard characteristics:
Age, density, tree size, water availability, mean annual
yield, visual symptoms of deficiency, fertilizing during the
last 3 years, etc.
Soil analysis, at least for basic soil properties and
macro-nutrient content
Leaf analysis
Soil analysis
Soil analysis:
The knowledge of key soil characteristics is essential for
defining the details of a fertilizing schedule. Important
parameters are:
Soil pH and CaCO3 content
It is important to define the type of fertilizers to be used
In soils with pH>7 and adequate CaCO3 the use of ammonium
sulphate is preferable
In soils with lower pH and low CaCO3 the use of fertilizers that do
not contribute to soil acidification is preferable (e.g. calcium
ammonium nitrate)
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Soil pH effect on nutrient
availability
NK
Ca
P
Fe
Mg
S
Mn
MoZn
Cu
B
Soil analysis
Soil salinity:
Usually, when good quality water is used for irrigation soil
salinity levels are <1 dS/m
Increased salinity is usually linked to the use of saline
irrigation water
When soil salinity is high, the use of fertilizers containing
Cl (e.g. potassium chloride) is avoided since they may
enhance the problem
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Soil analysis
Soil texture
Coarse textured soils (sandy):
Higher losses of nutrient due to leaching
Measures like increase of organic matter, application of fertilizers
at the end of the raining season, splitting of N application in more
doses and fertigation should be considered
Fine-textured soils:
Elements like K are strongly bound and less available to plants.
Higher doses of K, Ca and Mg might be required in order to
correct deficiency problems
Measures to avoid flooding should be taken, since it results in
root damage, stunted growth and nutrient uptake, if it occurs
during spring
Soil analysis
Soil organic matter content
High organic matter % can provide significant amounts of
N, P and micronutrients and therefore, application of
chemical fertilizers should be adjusted accordingly
Increasing of soil organic matter is always favourable in
improving nutrient availability and reducing losses
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Soil analysis
Soil mineral element availability
Much more important for annual crops
However, it provides useful information concerning the
availability of some key macro-nutrients
The complexity of mechanisms involved in soil nutrient
availability and the antagonistic effects among different
nutrients make difficult the prediction of the actual
nutrient availability to the plant. Leaf analysis is far more
important in determining the existing nutritional
problems.
Soil sampling
Timing
Not many restrictions
For practical reasons: when soil is wet and before the
application of fertilizers
Sampling
Ideal: use of auger for extracting a soil profile from 5-30
cm
In deep soil profiles a second sample beyond 30 cm
may be taken, although nutrient uptake is usually taking
place in the upper 30-40 cm
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Soil sampling
Sampling
For small orchards (up to 0.5 ha) and uniform soil, 1
composite sample per depth is collected
When an known or visible soil variability exists, 1
sample for each case is collected, independently from
field size
In large orchards, it is recommended to take more than
1 samples, independently from soil uniformity
Soil sampling
Sampling
Sampling point: under the tree canopy or in the area
where fertilizer is spread.
Tree canopy
Fertilizer
application
area
Right sampling
point
Wrong sampling
pointX
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Soil sampling
Sampling
In irrigated orchards it is better to sample along the drip
line
Drip line
Sampling points:
• At least 10
points per
sample
• After mixing
about 1 kg
is sent for
analysis
Soil sampling
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Soil analysis interpretation
Parameter Values
Soil pH 6.5 – 8.0
Soil texture Medium-textured
Total CaCO3 >2%
Organic matter content >2%
Electr. conductivity <4 dS/m
NO3-N 10-20 mg/kg
P 10-20 mg/kg
K (medium soil texture) ~150 mg/kg
Ca (medium soil texture) >1000 mg/kg
Mg (medium soil texture) ~100 mg/kg
Fe >3 mg/kg
Zn >0.8 mg/kg
Mn >1.4 mg/kg
Cu > 0,2 mg/kg
B >1 mg/kg
Defining mineral nutrient requirements
Leaf analysis
Defining the mineral nutrient content in leaf tissue is
the most important tool to detect nutritional
deficiencies, imbalances and toxicities in an olive
orchard
Using this information, and knowing key soil
properties and basic information about the orchard
we try to interpret the analysis and detect the
source of the problem
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Defining mineral nutrient requirements
Sample recording information (Ref.
No., Farmer, Location, Contact
Information, etc.)
Crop and cultivar
Tree age
Planting density
Tree size
Visual deficiency symptoms
Other important problems
Winter fertilizing schedule (last 3
years)
Foliar applications or fertigation
Irrigated or rainfed
Defining mineral nutrient requirements
Leaf analysis
Detecting the source of nutritional problems
Low nutrient availability in soil adding the missing
nutrient
Antagonism minimize application of another nutrient
Wrong application timing optimize timing rather than
increase amount
Wrong application method adjust (e.g. foliar application
instead of soil application)
Low uptake due to soil pH adjust (e.g. liming)
Disease Disease control
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Defining mineral nutrient requirements
Leaf analysis
Based on the above, we give information for
required modifications, additions or exclusions to
the existing fertilizing scheduling
Leaf analysis
Orchard information
Previous fertilizing schedule
Leaf analysis
Adjusting
Fertilizing
Soil analysisSelect fertilizer
type, frequency or
method
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Leaf analysis
Orchard information
Previous fertilizing schedule
Leaf analysis
Adjusting
Fertilizing
Soil analysisSelect fertilizer
type, frequency or
method
Ν P K Ca Mg Fe Zn Mn Cu
Ε
Φ
Ε
Φ
Ε
Φ
Ε
Φ
Ε
Φ
Ε
Φ
Ε
Φ
Δείγμα 1
Δείγμα 2
Δείγμα 3
Δείγμα 4
Δείγμα 5
Δείγμα 6
Δείγμα 7
Very Low
Low
Optimum
High
Excess
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Leaf analysis
Sampling time:
In all tree crops, leaf nutrient content is changing
over time depending on leaf age and plant growth
cycle.
Therefore, leaf analysis is performed during a
period where the content of different elements is
the most stable.
Moreover, the standards that have been developed
also refer to a certain period and not to the whole
growing season.
Leaf analysis
Two possible periods:
Summer: Second half of July
Winter: Late October - November
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Leaf analysis
Period of sampling
Summer sampling:
+ The leaf content is not affected by the fruit load
+ Fertilizing can be adjusted according to the
known expected fruit load
- Rainfed trees might already be stressed and
therefore nutrient content be affected by water
stress and not by nutrient availability
- Not enough ways to correct nutrient deficiencies
at that period of time in most of the orchards
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Period of sampling
Winter sampling:
+ The tree water status is adequate
+ The degree of exhaustion is known and
measures can be taken in order to avoid key
nutrient deficiencies early in the following season
- Nutrient content might have been affected more
by fruit yield than by nutrient availability in the soil
Leaf sampling
Leaf age:
Leaves from current growth
3-5 months old
Sample size:
About 200 leaves
At least 10-20 trees. Trees should be
representative of the typical situation for the
orchard.
Selected shoots also representative.
Avoid leaves or trees with disease damage or
any other distinct symptom and trees at the
borders of the orchard
Sample taken at human height (middle
section of the canopy)
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Leaf sampling
Number of samples:
1 sample for each uniform block of soil
Different samples if trees of different age, cultivar, management
system, etc. are present
Sample treatment:
Ideally: place in a cool box and transfer to the lab
If leaves are not to be transferred soon to the lab, they have to be
stored in the refrigerator for short period (1-2 days).
Soil and leaf analysis time-frame
1. A soil analysis detects key soil properties and
nutrient availability
2. Leaf analysis detects nutritional problems.
3. Leaf analysis is repeated for 1 or 2 years to
finalize adjustments.
4. After that, leaf analysis is repeated every 2-3
years
5. Soil analysis is repeated every 5 years
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Proposed values for leaf analysis interpretation (October-November sampling / leaves
5-6 months old).
ElementDeficiency Low High Excess
Nitrogen (%) <1.2 1.2-1.6 1.8-2.2 >2.2
Phosphorus (%) <0.07 0.07-0.10 0.13-0.15 >0.15
Potassium (%) <0.5 0.5-0.8 1.1-1.3 >1.3
Calcium (%) <0.5 0.5-1.0 >2.5
Magnesium (%) <0.07 0.07-0.10 >0.30
Boron (ppm) <15 15-20 50-150 >150
Iron (ppm) 20-50 150-500
Zinc (ppm) 5-10 >30
Manganese (ppm) <10 10-20 60-150 >150
Copper (ppm) <5 >20
Source: Androulakis I.
Proposed values for leaf analysis interpretation (July sampling / leaves 3-5 months old).
ElementDeficient Toxic
Nitrogen (%) 1.4 --
Phosphorus (%) 0.05 --
Potassium (%) 0.4 --
Calcium (%) 0.3
Magnesium (%) 0.08
Boron (ppm) 14 185
Iron (ppm)
Zinc (ppm)
Manganese (ppm)
Copper (ppm)
Source: Fernandez-Escobar 2004
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Fertilizing olive trees
As soon as the nutritional status of the tree and the soil properties
are known, a fertilizing scheduling is issued, determining:
The timing of application
The type of fertilizer to be used
The quantity of fertilizers (depending upon the nutrient contant of the
selected type)
Additional corrective measures to be taken to improve soil fertility, or
other properties
The optimal application method to be used depending on available
means and soil properties
Alternative methods to be used
Soil application (winter or spring)
Fertigation
Foliar application
Injection
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Soil application - Timing
Optimal timing depends upon the climatic conditions of the area
Water is a crucial factor (amount and distribution of precipitation)
Κ, Ρ, Β: Up to the end of December (Cretan example)
Ν fertilizers (Cretan example):
Ammonium sulphate: Second half of January
Calcium ammonium nitrate: mid-February
Ammonium nitrate: Before the last rainfalls
Application of ammonium-containing fertilizers should not be followed by extended periods of hot and dry weather
Soil application – Type of fertilizer
In general, it is better to select single-element fertilizers, as compared to compound fertilizers Timing of N vs P or K application is different and therefore
optimal timing cannot be achieved by the use of a composite fertilizer
Depending on soil pH, different fertilizers have to be used: Alkaline pH and high CaCO3 Ammonium sulfate
Acid pH and low CaCO3 Calcium ammonium nitrate
Salinity and soil texture issues should be considered: Avoid Cl containing fertilizers in soils with high salinity (e.g.
KCl)
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Fertilizer labeling example
18-6-12
18% N
6% P2O5
12% K2O
Content of additional
nutrients is also
mentioned
Terminology:
Fertilizing Unit
Examples of single-nutrient
fertilizers
Nitrogen
Ammonium sulfate (21-0-0)
Calcium ammonium nitrate (26-0-0)
Ammonium nitrate (34-0-0)
Urea (46-0-0)
Potassium
Potassium sulfate (0-0-50)
Potassium chloride (0-0-60)
K-Mg sulphate (0-0-30)
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Soil application
Mechanical
Soil application
Manual
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Soil application
Incorporation to the soil is in general
suggested at least for K and P fertilizers
However, especially in sloppy areas, the
disadvantages of any kind of soil cultivation
are more than the advantages of fertilizer
incorporation
Soil application during spring
In areas where there are significant rainfall
events during spring, application of N fertilizers
could be split in 2 (winter + spring application)
Advantages:
Lower risk of losses through leaching
Nitrogen demand during spring is high
Ammonium nitrate is the typical fertilizer used
Not applicable in areas where spring is
typically “dry”
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Fertigation and foliar application
Apart from application of fertilizers to the soil,
foliar application and fertigation are also
practiced in olive orchards
Both methods have the advantage of targeted
application timing that coincides with high
demand periods for certain nutrients
However, cost of application and lack of
means of application lead to limited use in
most traditional olive orchards
JAN FEB MAR APR MAY JUN AUGJUL OCT NOV DECSEP
Dormancy Active shoot
growth
Limited shoot
growth
Active shoot
growth
Dormancy
Flower. bud
differentiation
Fruit
growth
Increase of
Oil contentFruit-
set
Pit
hardening
Flower bud
formation
Flowering
Fruit color
change
Maturation
Harvesting Harvesting
Annual growth cycle – Mineral nutrient requirements
High demand on nutrient requirements
B N K
Determination of yield potential
JAN FEB MAR APR MAY JUN AUGJUL OCT NOV DECSEP
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49
Fertigation
Advantages:
Fertilizer is applied in the root zone under favorable soil moisture
conditions and therefore nutrient uptake ratio is higher as compared
to soil application during winter
The nutrient use efficiency is increased
Nutrient losses are limited
Application can be adjusted according to expected fruit load
Disadvantages:
Only applicable in irrigated orchards
Only applicable under certain irrigation methods
Not adequate experimental data exist for most areas and cultivars
In problematic soils it may increase soil salinity problems
Costs involved
Problems in scheduling in areas where water availability is limited
Fertigation
It can be applied as an exclusive method for
nutrient application, or additionally to winter
application
Data from a summer foliar analysis program
could be used in an optimal way at fertigated
olive orchards
At a higher cost, the application of water and
nutrients could be fully automated
Application of water and nutrients at high rates
could reduce olive oil quality
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50
Fertigation
Nitrogen: If fertigation is exclusively used for fertilizing the
orchard, applications should start early in spring, even if there is
no need for irrigation
Potassium: Higher demands after June
Fertigation
Not all fertilizers are equally appropriate to be
used for fertigation
FertilizerN – P2O5 – K2O
content
Solubility
(g/l) at 20 C
Ammonium nitrate
Ammonium sulphate
Urea
Monoammonium phosphate
Diammonium phosphate
Potassium chloride
Potassium nitrate
Potassium sulphate
Monopotassium phosphate
Phosphoric acid
34-0-0
21-0-0
46-0-0
12-61-0
18-46-0
0-0-60
13-0-44
0-0-50
0-52-34
0-52-0
1830
760
1100
282
575
347
316
110
230
457
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51
Foliar application
Advantages: When soil properties do not favor the uptake of certain
nutrients, foliar application can be the most effective way to correct deficiencies
Tree response is faster, as compared to soil application
An alternative for rainfed orchards in cases of long dry periods that do not favor soil application
Foliar application
Disadvantages: Application rates are low and therefore macronutrient
requirements (N or K) cannot be covered by a single foliar application. Usually applied as a supplementary method
Cost may be high to cover macronutrient requirements
Not effective for long. It usually covers the annual requirements of micronutrients but should be repeated on an annual basis
Rainfall after application may affect the effectiveness
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Foliar application
Efficiency of foliar application is affected by
several environmental factors:
Light, Temperature, Humidity
Effects of environmental factors could be:
Direct effects on spray solution prior to absorption
Indirect effects on leaf development processes
Indirect effects on photosynthesis, stomatal
opening and sink activity, affecting energy and
metabolite availability involved in the uptake
process
Foliar application
Nutrient uptake is higher in young olive leaves as compared to older leaves
Not well hydrated leaves (water stressed) uptake less nutrients than fully hydrated leaves.
Therefore, spring (preferably) and autumn (if rain occurs) sprays are more effective than summer sprays
Avoidance of hot days and application during the cooler part of the day increases absorption
Surfactants are used to increase absorption
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53
Foliar application
Foliar application has been effectively used as a supplementary method for applying N or K in olive trees
In cases of severe K deficiency trees may respond faster as compared to soil application
There are reports suggesting that late spring application of K gave better results than late summer application in olive trees
Not effective for Fe application
Spring application of Boron may enhance fruit set as compared to untreated olive trees
Common compounds used
Macronutrient Common element
compounds
References
N Urea, ammonium sulphate,
ammonium nitrate
Zhang et al. (2009); Fageria et
al. (2009)
P H3PO4, KH2PO4, NH4H2PO4,
Ca(H2PO4)2, phosphites
Noack et al. (2011); Schreiner
(2010); Hossain and Ryu (2009)
K K2SO4, KCl, KNO3, K2CO3,
KH2PO4
Lester et al. (2010), Restrepo-
Dνaz et al. (2008)
Mg MgSO4, MgCl2, Mg(NO3)2 Dordas (2009a), Allen (1960)
Ca CaCl2, Ca-propionate, Ca-
acetate
Val and Fernαndez (2011);
Wojcik et al. (2010); Kraemer et
al. (2009a,b)
Source: V. Fernandez, T. Sotiropoulos. P. Brown, 2013
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54
Common compounds used
Micronutrient Common element
compounds
References
B Boric acid (B(OH)3), Borax
(Na2B4O7), Na-octoborate
(Na2B8O13), B-polyols
Will et al. (2011); Sarkar et al.
(2007), Nyomora et al. (1999)
Fe FeSO4, Fe(III)-chelates, Fe-
complexes (lignosulphonates,
glucoheptonates, etc.)
Rodriguez-Lucena et al.
(2010a, 2000b); Fernαndez et
al. (2008b); Fernαndez and
Ebert (2005); Moran (2004)
Mn MnSO4, Mn(II)-chelates Moosavi and Ronaghi (2010),
Dordas (2009a), Papadakis et
al. (2007), Moran (2004)
Zn ZnSO4, Zn(II)-chelates, ZnO,
Zn-organic ‘complexes’
Amiri et al. (2008); Haslett et al.
(2001), Moran (2004); Zhang
and Brown (1999).
Source: V. Fernandez, T. Sotiropoulos. P. Brown, 2013
Οκτ-96 Νοε-96 Δεκ-96 Ιαν-97 Φεβ-97 Μαρ-97
25
27
29
31
33
35
37
39
41
43
Ξη
ρό
βά
ρο
ς σ
ε g
r /1
00
κα
ρπ
ούς
Ημερομηνία δειγματοληψίαςΟυρία 2%
Μάρτυρας
Θειικό Κάλι 2%
Fru
it d
ry w
eig
ht
(g/1
00 f
ruit
)
DateUrea 2%
Control
K2SO4 2%
Oct Nov Dec Jan Feb Mar
Effect of autumn N and K foliar application on fruit dry weight
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55
Effect of autumn N and K foliar application on flesh/stone dw ratio
1,10
1,30
1,50
1,70
1,90
2,10
Οκτ-96 Νοε-96 Δεκ-96 Ιαν-97 Φεβ-97 Μαρ-97
Ημερομηνία δειγματοληψίας
Λό
γο
ς ξ
.β.σ
άρ
κα
ς / ξ
.β.π
υρ
ήν
α
Ουρία 2%
Μάρτυρας
Θειικό Καλι 2%
Ure
a 2
%C
on
tro
l K2S
O4
2%
Date
Oct Nov Dec Jan Feb Mar
Fle
sh
d.w
./sto
ne
d.w
. ra
tio
50
51
52
53
54
55
56
57
58
59
60
61
62
1/10/1996 1/11/1996 1/12/1996 1/1/1997 1/2/1997 1/3/1997
Ημερομηνία δειγ ματοληψ ίας
Ελα
ιοπ
εριε
κτι
κότη
τα %
ξ.ο
.τη
ε σ
άρ
κας
Μάρτυρες
K2SO4 2%
Ουρία 2%
Effect of autumn N and K foliar application on fruit oil percentage (dw)
Ure
a 2
%
Contr
ol
K2S
O4
2%
Date
Oct Nov Dec Jan Feb Mar
Oil
% (
d.w
.)
24/10/2016
56
Thank you for your attention
HELLENIC AGRICULTURAL
ORGANIZATION “DEMETER”
Institute of Olive Tree,
Subtropical Crops and Viticulture
Laboratory of Plant
Mineral Nutrition & Physiology
e-mail: [email protected]
www.nagref-cha.gr