This document discusses olive irrigation, including the physiological effects of water stress on olive trees and how irrigation can benefit olive production. Some key points: - Irrigation increases canopy growth, root development, and early onset of production in young olive trees. - Irrigation increases fruit production in adult trees by over 100% compared to unirrigated trees, with higher increases at lower planting densities. - Olive trees are drought resistant but need at least 600-700mm of water per year for regular growth and production. Deficit irrigation can be used to influence fruit and oil yield/quality. - The type of irrigation system used (furrow, drip, sprinkler) depends on soil type and other factors

1. Olive Irrigation

2. Learning Objectives
• Understanding the physiological response of olive trees to
water stress
• Determining how much water is needed for irrigation
• Managing deficit irrigation
• Determining what type of irrigation (furrow, drip irrigation)
is ideal
• Understanding water quality (salinity)

3. Transpiration: leaf cooling and water
uptake
Photosynthesis: sugar production
for vegetative and fruit growth
Photosynthesis-transpiration Compromise

4. Limitations in photosynthetic activity become clear
during water stress (time of the day when the traspiration
rate is very high). In such conditions, the tree needs to
close the stomata to avoid excessive water loss, but at
the same time the photosysnthetic rate decreases
severely.
Photosynthesis and transpiration rates are affected by
several factors: soil moisture, CO2, light radiation, air
temperature, humidity, wind speed, age of the leaf, etc.

5. W.U.E.
Water Use Efficiency = amount of assimilated C
per unit of transpired water
W.U.E. = A / T
Transpiration: leaf
cooling and water
uptake
Photosyntesis: sugar
production for vegetative
and fruit growth

6. Very drought resistant
The olive is able to survive with only 200mm per year of
rainfall (but needs at least 600-700mm per year to ensure
regular fruit and vegetative shoot growth)
Evergreen xerophitic species
(well-adapted to Mediterranean climate conditions)
Moving southward, olive cultivation and production
increases with rising average temperatures until drought
becomes the main limiting factor

7. Water stress resistance strategy
“Avoidant” species “Tolerant” species
Carob (Ceratonia siliqua L.)
Grape (Vitis vinifera L.)
Olive (Olea europaea L.)
Physiological and growing changes
that allow to optimize available
resources without further request.
Elimination of efficient transpirating
surfaces (or drying shoot in carob) if
optimum conditions are not
promptly restored.
Use all the available resources
without modifying physiological
mechanisms.
Elimination of old and unefficient
leaves only when water stress is
strong and prolongued.

8. Morpho-anatomical characteristics and physiological
strategies for drought stress resistance in the olive
1. Roots
Variable transmigration and depth depending on available water in the soil
Usually the root system is completely contained within 0.6-0.8m depth (newly
formed roots from the crown at 0.15-0.2m depth are possible in infrequent
rainfall conditions)
The olive is very sensitive to a lack of oxygen in the soil: root cortical
cells rapidly die because of excessive and irrecoverable membrane
deterioration with the outcome being more superficial roots in
asphyctical soils
High rehydration and restoration of hydraulic conductivity (root ability) after
strong drought stress

9. Morpho-anatomical characteristics and physiological
strategies for drought stress resistance in olive
2. Trunk
The single elements of olive xilem are tighter and longer than other
deciduous tree species (with porous-diffused xilem) typical of the
mediterranean area (Ceratonia siliqua L., Laurus nobilis L., Quercus ilex
L., Quercus pubescens Willd., Quercus suber L.)
Reduction of cavitation problems
Salleo and Nardini (1999) reports that in olive only the 5% of xilematic
vases stop trasport flux because of embolism in the lumen, when
LWP is near to – 3,5 MPa

10. Olive
Apricot
Kiwi
Grape
Stomaic conductivity (gs) plotted on leaf water potential (ψw) measured in potted and field olive, apricot, kiwi and vine
plants (modified from Cifre et al., 2005; Schultz, 2003 and from Gucci, 2003).
In olives, when LWP
decreases, stomatal
closure is less rapid than
in apricots, kiwis and
grapes.
LWP reduction is mainly
due to water loss in
tissues
Stoma are partially open
also when hydrical
potential is very low,
allowing an appreciable
leaf photosynthetic rate.
High Water Use
Efficiency
Olive: 315g water for 1g fruit dry matter
Citrus: 400g water for 1g fruit dry matter
Prunus: 560g water for 1g fruit dry matter

11. Drought Stress
• Delay onset of production in young olive trees
• Reduce total tree growth and vegetative shoot elongation
• Increase alternate bearing
• Reduce leaf photosynthetic rate
• Increase fruits drop
• Reduce final fruit number and dimension (pulp)
• Reduce final oil amount per fruit and per plant
• Anticipate fruit ripening
• Oil produced is more pungent and bitter

12. Visible Stress
(Fruit shrinkage)

13. Why should we irrigate olive trees?

14. (Xiloyannis and Palese, 2001)
Root and canopy growth in young olive trees (cv Coratina) vase-trained (6m x 3m), in
semi-arid environmental conditions, in irrigated and not irrigated conditions.
Unirrigated trees were irrigated only in the first year.
More: early onset of production
Years from planting
Considered parameter Irrigation
1 2 3 7
Yes 0.6 1.9 6.1 28.2
Leaf area (m
2
/ plant)
No - 1.2 3.8 14.9
Yes 0.5 2.9 8.6 16.8
Root exploration volume (m
3
/ plant)
No - 2.3 5.1 13.4
Yes 193 528 1263 3740
Root lenght (m / plant)
No - 511 806 2477
Yes 0.039 0.018 0.015 0.022
Root density (m root / m
3
soil)
No - 0.022 0.016 0.018
Yes 3.57 2.8 2.45 1.37
S/R ratio (mass)
No - 2.09 2.08 1.23
Yes 1.2 0.65 0.71 1.68
Leaf area / root exploration volume (m
2
/ m
3
)
No - 0.52 0.74 1.11
Irrigation of Young Trees
+ 33% canopy

15. Irrigation of Adult and Productive Trees
Fruit production increase > 100% compared to unirrigated olive orchards
(Goldhamer et al., 1994; Pastor et al., 1998; Patumi et al., 1999)
In Andalucia: increase included between 50% and 100% with respect to
planting density (lower increase for 300pt / ha and higher for 100pt / ha)
In south Italy, oil production increase higher than 40% in three cultivars
(Dettori and Russo, 1993)
In Greece: 30% and 36% increase, respectively, in olive and oil production in
irrigated trees compared to unirrigated in cultivar Koroneiki (Michelakis,
2002)
In central Italy (Tuscany), production increase of about 20% in 2001, but no
effects in 2002 characterized by aboundant rainfall (Gucci, 2002)
The more arid the climatic conditions are, the more positive are the
effects of irrigation!

16. Furrow
A deep, narrow furrow on a sandy soil
A wide, shallow furrow on a clay soil
Zig zag

17. Wet zone
sand loam clay

18. To obtain a uniform water distribution along the furrow
length, it is very important to have a uniform slope and a
large enough stream size so that water advances rapidly
down the furrow
Ideal Wetting Pattern

19. Sprinkler irrigation
Sub-irrigation

20. Drip irrigation (localized on the ground)
Drip irrigation (suspended on trees

21. Drip irrigation (localized
ring around trunk)
Drip irrigation localized ring
around trunk (sub-irrigation)

24. Use of Salty Irrigation Water
Olive grove in high salty growing conditions
Salts surfacing Reduced tree size and leaf drop
Symptoms of desiccation of
the shoot’s terminal portion
due to high salt
concentration in the soil

25. Sand Clay
Wetting patterns for sand and clay soils with high and low
discharge rates

26. Salinity index Unit Conversion
coefficient
CE electric
conductivity
dS m; mmho cm-1 1
NaCl
concentration
mM; meq L-1 10-12
mg L-1 580-700
Total soluble salts % 0.064
ppm 640
Osmotic pressure MPa 0.036

27. Avoid new plantation when oil production decrease 10%
compared to trees without salt stress
Olive is a Medium Salt-resistant Species
(FAO, Ayers and Westcot, 1985)
The estimated need for
1 ton of olive fruit is
400 tons of water

28. When to Irrigate
• Winter (rest phase)
• Vegetative growth
• Flowering (key process of fruit set)
• Fruit development (double sigmoid)
• Ripening (fruit quality)
• Post harvest (before the rest)

29. When to Irrigate
(Tentative Guideline)
• Winter (rest phase)
– Plant survival (2.5 months 10% )
• Vegetative growth
– Bud break, flower formation, new vegetative cycle (2 months
30%)
• Flowering (bloom and fruit set 2 weeks 7%)
• Fruit development (double sigmoid)
– 1 stage 6 weeks 20%
– 2 stage 2 weeks 3%
– 3 phase 2 months 20%
• Ripening (fruit quality) 1 month 7%
• Post harvest (flower induction and storage) 2 months 6%
(Taher and Davide, 2012)

30. Ten years average climat conditions (Tulkarm)
0
20
40
60
80
100
120
140
160
180
200
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mm
0
5
10
15
20
25
30
C
Rainfall
Temperature

31. Ten years average climat conditions (Nablus)
0
20
40
60
80
100
120
140
160
180
200
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mm
0
5
10
15
20
25
30
C
Rainfall
Temperature

32. Irrigation Systems
Full Irrigation
Complementary Irrigation
(Supply water when trees undergo severe stress and according to the
phenological stage)
Regulated Deficit Irrigation (RDI)
(Use irrigation to effect the growth of fruit and its tissues, and oil yield and
quality)

33. Settimane DPF
4 8 12 16 20
Volume
del
frutto
(ml)
0
1
2
FI
DI
SI
Irrigation affected fruit growth…
Weeks AFB
Fruit
volume
(ml)

34. 21 settimane DPF
Valore integrato giornaliero PIFN (MPa)
-4 -3 -2 -1 0
Olio
nel
mesocarpo
(%
s.s.)
0
20
40
60
FI
DI
SI
… and oil accumulation in the pulp
21 weeks AFB
PLWP daily integrated value (MPa)
Oil
in
the
pulp
(%d.m.)

35. 21 settimane DPF
Carico di frutti (kg p.f. frutti dm
-2
ASTT)
0 5 10 15 20 25
Olio
per
pianta
(kg)
0
1
2
3 FI
DI
SI
R2 = 0,10
R2 = 0,12
R2 = 0,12
…higher oil
production
per plant!
Crop load (kg fruit f.w. dm-2 TCSA)
Oil
content
per
plant
(Kg)
21 weeks AFB

36. Carico di frutti (kg p.f. frutti dm
-2
ASTT)
0 5 10 15 20 25
Indice
di
maturazione
2
3
4
5
21 settimane DPF
SI
DI
FI
Crop load (kg fruit f.w. dm-2 TCSA)
Maturation
index 21 weeks AFB
…irrigation delays fruit ripening!

37. Fruit and Oil Quality
Free fatty acidity Not affected
Total polyphenols
(bitter-spicy)
Decreasing content
Volatile compounds
(erbaceous aroma)
Pulp firmness
Increasing content
Parameter Increasing Irrigation Volume
Decreasing values