Irrigation strategies for

apple production.

Denise Neilsen and Gerry Neilsen

Agriculture and Agri-Food Canada

Summerland, B.C. Canada

International Apple Symposium

Cuauhtémoc, Mexico

November 12th, 2008

Okanagan region of British Columbia,

Canada

April/04

Okanagan Basin

◼ Semi-arid climate

◼ Dependent on winter snow for water supply

◼ Increasing competition for water

183

259

258

168

760

689

732

826

Mean

Precipitation

Okanagan Basin Climate April - October

Growing season

water deficits

◼ 430 to 658mm

◼ Irrigation

required

Mean

Evapotranspiration

Irrigated agriculture in the Okanagan

Basin◼ high value horticultural crops

◼ high density apple production

◼ sweet cherries, peaches

◼ wine grapes

Range of water management practices

Irrigated agriculture

◼ Highly productive

Approximately 40% of the world’s food

comes from the 17% of the land that is

irrigated (Postel, 2000).

Water managed for

• flood control

• power generation

• in stream requirements

• fish

• other ecological needs

• water supply

• agriculture 70-80% of

diverted water

• municipal

• recreation

• urban development

Agricultural vulnerability:

competition for water and land

Widespread North American drought in

2003 (September map)

Drought has moderated in the last 2-3

years (Sept 2008 map)

Precipitation

in interior BC

& Washington

below normal

Precipitation

in

Chihuahua

nearer

normal in

last 2 years

Standardized precipitation index for

semi-arid regions of Chihuahua

Above

normal

rainfall

Below normal

rainfall

Drought is recurring

SP

I

◼ Much of western N. America has

unreliable water supply for irrigation

◼ Conservative irrigation practices are

required to reduce the risk from drought

Presentation structure

◼ Plant water requirements

◼ Water management of tree fruits

Strategies for managing water well

◼ Increasing planting density

◼ Conservative systems

◼ Irrigation scheduling

◼ Amendments

◼ Deficit irrigation

Plant water requirements

Water in plants ◼ Plant constituent (e.g. apple fruit ~ 80%

water)

◼ Transports nutrients

◼ Chemical reactant

◼ Maintains cell turgidity - important for growth

◼ Modifies micro-climate (cools through evaporation, increases humidity)

Plant water requirements

◼ adequate supply for crops

prevent stress

maximise yield

improve fruit quality

Plant water movement

Root

Stem

Leaf

Transpiration

AbsorptionSoil

Water

◼ Water moves from soil to the air through the plant

◼ increases with high temperature and wind

◼ decreases with low soil water content

Soil Water Content

Rapidly drained

Water Available Water

Bound

Water

Sandy Loam Soil

Clay Soil

Sandy or Gravelly Soil

Gravitational

Water Available Water

Bound

Water

Courtesy Curt Rom

Saturation

Rapid drainage stops

Time

So

il m

ois

ture

co

nte

nt

Plant stress

begins

Water applied

Completely dry

Readily

Available

Water

Plant dies

Changes in soil water content over time

Water movement through the plant –

stomates

(100k – 350K/sq in)

Mainly on undersides of

leaves

Water movement through the plant –

stomates

Open

light

water vapour

lost

Carbon dioxide for

growth from the

air

X

Closed

Low light

Dry soil

water stress

No carbon dioxide

for growth

Need to avoid detrimental stress

(Gala/M.9)

0

50

100

150

200

full irrigation

¼ irrigation

*

**

**

****

0

50

100

150

200

full irrigation

¼ irrigation

*

**

**

****

Stress started

Stress finished

June July August Sept

Fru

it W

eig

ht

(g)

Water Management

Increasing plant density - more water

management options

• Conservative, well

engineered systems

• Applying water to meet plant

requirements

(irrigation scheduling)

Strategies for managing water well

• Reducing soil water

evaporation

Conservative water management

options

Small radius (1.5-2ft)

micro sprinkler

Drip (pressure

compensating)

Irrigation systems that position water in the

root zone

Drip ( PC) -in line for

surface or sub-

surface installation

Irrigation scheduling

◼ how long an irrigation system should run

◼ matches water supply to demand

◼ uses some measurement or estimate of demand

Improving water management with

irrigation scheduling

Irrigation scheduling techniques

1. Soil Moisture Monitoring

2. Climate Monitoring

TDRTensiometer

Electrical Resistance Block

Watermark

Capacitance

probes (fully

automated)

Soil moisture monitoring

0

10

20

30

40

50

60

70

80

0 5 10 15

Soil moisture tension (bars)

So

il w

ate

r co

nte

nt

(%)

Clay

Sandy loam

PWP

Loamy sand

Soil moisture tension is also called soil suction or soil matric

potential

SATURATIONSoil moisture tension

Tensiometers measure soil moisture tension

between 0 and 1 bar (0 and 100 centibars)

• for saturated soils tension = 0

• for dry soils tension = 100

0

20

10

40

30

50

70

60

90

100

80

Tensiometer

Works best

in coarse

soils (sands-

sandy

loams)

0

20

10

4030

50

7060

90

100

80

Scheduling micro-irrigation systems

◼ Operate on 1-3 day

cycle

◼ Maintain desired

moisture level by

adjusting run time or

increasing frequency

Climate based methods for potential ET

Evap. pan

Weather station

Web service

Fully automated

atmometer scheduling

Provide

estimates

of

potential

ET

Transpiration from leaf stomates

Evaporation from the leaf surface

Evaporation from the soil surface

Water Loss via Evapotranspiration (ET)

Solar radiation Wind

Estimating tree water use

◼ Actual water use (mm) = K x ETo (mm )

◼ K is the crop coefficient and is related to

canopy size

◼ K is the mm water required per mm of ETo

Cro

p c

oeff

icie

nt

(Kc)

mm

wate

r u

se/m

m

evap

ora

tio

n

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20 25 30

Weeks after shoot leaf budburst

Apply 0.5 mm/mmET0

Apply 1.2 mm/mmET0

Change in the crop coefficient (Kc) over

the growing season

Data logger or

computer

programmed

with crop

coefficients etc.

Irrigation

controller

Electronically measure

evaporation daily using an

ATMOMETER

Estimate amount of

water used

Replace water

used next day

Automating scheduling using an

electronic atmometer

10

15

20

25

30

203 205 207 209 211

Day of the year

So

il m

ois

ture

(%

)

Drippers 15 cm from emitter

Microsprinklers 15 cm from emitter

How well can we do?

Soil moisture under scheduled micro-

irrigation

Wate

r lo

ss (

L/t

ree)

May June July Aug. Sept. Oct.-May May

Scheduled to meet evaporative demand

Unscheduled (fixed rate)

1998 1999

*

*

**

0

100

200

Water added

(L/tree/season)

Scheduled 646

Unscheduled 1304

Water use and loss of water beneath the

root zone with irrigation scheduling

Other conservation methods - to be

covered in the later talk

Geotextile mulchesOrganic mulches

Paper mulches

0

500

1000

1500

2000

2500

3000

0 20 40 60

Mulch

No mulch

L H

2O

used

(3/0

5 t

o 2

7/0

9)

Trunk Diameter (mm)

Water use of apple trees under mulch

Water use

under mulch

~ 50%

Preparing for and managing drought -

deficit irrigation

◼ High density planting: 3333 trees/ha

◼ Conservative irrigation system: pressure compensating drip

◼ Scheduled irrigation:100%; 50%; 33% (ET)

◼ Managed crop load: 3; 6; 10 fruit/cm2 TCSA

◼ 100% irrigation applied to herbicide strip = 480 mm/ha in 2008

Ambrosia/M.9

Deficit irrigation

Ambrosia/M.9

0

10

20

30

40

50

60

70

80

Low Standard High

Yie

ld (

T/h

a)

100% I50% I (both sides)50% I (one side)33% I (2day accumulation)

IxCL *Standard crop loads

Yield maintained at 50% irrigation

Low crop loads

Yield maintained at 33% irrigation

Deficit irrigation

Ambrosia/M.9

Irrigation effect

0

1

2

3

4

5

6

7

Sta

rch

In

de

x

b b b

a

100%

both

sides

50%

both

sides

50%

one

side

33%

alternate days

Crop load effect

0

1

2

3

4

5

6

7S

tarc

h Index

b ab a

Low Standard High

Irrigation effect

Water stressed fruit mature earlier

Crop load effect

Fruit mature earlier at higher crop loads

Deficit irrigation Irrigation effect

0

50

100

150

200

250

Fru

it s

ize

(g

)

100%

both

sides

50%

both

sides

50%

one

side

33%

alternate days

b

aaa

Crop load effect

0

50

100

150

200

250

300F

ruit s

ize (

g)

Low Standard High

c

b

a

Ambrosia/M.9

Irrigation effect

Fruit size maintained at 50% irrigation

- 200g at 50% irrigation

Crop load effects

Fruit size decreased as crop

load increased

Increase

planting

density

Design

conservative

irrigation

systems

Apply

irrigation

scheduling

Make use of

soil

amendments

Improving water management

Deficit

irrigation

◼ International Dwarf Fruit Tree Association

◼ Washington Tree Fruit Research Commission

◼ Okanagan Kootenay Cherry Fruit Growers Association

◼ Agriculture and Agri-food Canada Matching Investment Initiative MII

Financial support

Thank you

Water supply is unreliable – winter

snow

May 15th Snowpack

0

100

200

300

400

500

600

1960 1970 1980 1990 2000 2010

Sn

ow

wa

ter

eq

uiv

ale

nt

(mm

)

Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P.,

2005, Declining mountain snowpack in western North

America, BAMS, 86 (1): 39-49

Trends in Snow pack – W. North America

Many areas:

◼ Higher winter and springtime temperatures

◼ Reduction in precipitation that falls as snow

◼ Earlier snow melt and runoff

◼ Recharge to aquifers reduced