IRRIGATION AND NUTRIENT MANAGEMENT IN TREE FRUIT PRODUCTION SYSTEMS

Neilsen, D1, Neilsen, G1, Forge T1

denise.neilsen@agr.gc.ca

1 Agriculture and Agri-Food Canada, Summerland, B.C. Canada KEYWORDS Irrigation and nutrient management are linked; micro-irrigation; irrigation scheduling; available soil moisture; automated irrigation systems; nutrient availability in the root zone; matching nutrient demand and supply.

ABSTRACT In irrigated production systems water management often controls nutrient availability. For apple, the change to dwarfing rootstocks and increasing tree density has provided the opportunity to focus water and nutrient inputs into the root zone, but this means that management needs to be more precise. As rootstock vigor decreases, the volume of soil accessed by the roots decreases Retention of nutrients in the root zone for as long as possible improves the chance of root uptake, increasing nutrient use efficiency and reducing fertilizer costs. This can be achieved by conservative water management and by applying fertilizer at the right time, rate and placement to meet plant requirements. Water management options include micro-irrigation systems which are well-engineered to meet peak demand and correctly designed for the crop/soil combination; mulches to reduce soil evaporation and irrigation scheduling. The amount of water required, depends on the stage of crop development, the amount of evapo-transpiration or precipitation that has occurred since the last irrigation and soil type. The lower the frequency of irrigation (sub-daily to several day intervals), the more important soil type becomes. Improving water management by scheduling irrigation to meet crop demand has the benefit of saving water (Figure 1) nutrients and potentially improving fruit quality.

Figure 1. Water and nitrogen retention in the root zone is determined by irrigation scheduling and timing of N applications. Losses are higher when irrigation is not scheduled to meet plant demands.

The most effective way to schedule irrigation is through fully automated monitoring systems based on estimates of evapo-transpiration and soil moisture measurements, which can then be used to control the irrigation system. The most effective way to match nutrient requirements to plant demand is through fertigation (applying nutrients through the irrigation system), which works best with drip and small radius micro-sprinkler. Nitrogen (N) is particularly suited for this as it is very mobile in soil and water, but because of that it is also difficult to control. In this case it is best to apply small amounts frequently (e.g. daily) and match the timing of application to plant demand. For apple and other tree fruits, it has been shown that there is little uptake from the soil until bloom as N which has been stored over-winter in the tree is used for early spring growth. Applying N during fruit cell division (approximately 6 weeks after bloom) promotes fruit and canopy development. Later N applications may have detrimental effects on fruit quality. If low, tree N status may be improved by postharvest foliar urea applications just before leaf senescence. Boron (B) is another mobile nutrient, like N, which can be fertigated. Phosphorus (P) is particularly important for tree root growth and early establishment. It can be applied pre-plant as a granular fertilizer and fertigated early in the season. A single large application is more effective than multiple small ones and should not be mixed with other fertilizers. Potassium (K) can become depleted under drip irrigation and fertigation or if ammonium N sources are used in other systems, particularly in coarse-textured (sandy) soils. Fruit removal of K can be double that of N, and if leaf K approaches deficiency, K applications do not negatively affect fruit storage quality.

Irrigation and nutrient management in tree fruit production systems

Denise Neilsen, Gerry Neilsen and Tom ForgePacific Agri-Food Research Centre,

Summerland, BC. Canada

WSU Fruit School, Wenatchee WA. Nov. 17, 2015

Irrigation requirements

• adequate supply

– prevent stress

– maximize yield

– improve fruit quality

• more challenging in high density plantings with restricted roots

0-1

6in

0-12in

M.9

Water Loss via Evapotranspiration (ET)

Transpiration from leaf stomates

Solar radiation Wind

Evaporation from the leaf surface and soil surface

water vapor

lost

CO2 for growth

assimilated

Open Closed

Dry soil

Water stress

Low growth

Plant water stress affects fruit size

• Even with optimum irrigation plants can sometimes experience stress

• In well watered trees sap flow (transpiration)was reduced when daily ET >0.28 in/day or Max T >95C

100% ET Irrigation< 100% ET Irrigation

• Conservative, well engineered systems

• Applying water to meet plant requirements

(irrigation scheduling)

Strategies for managing water well

• Reducing soil water evaporation

Well designed irrigation systems meet daily peak ET and total needs

• The weather information is available from WSU Ag weather net:

• http://weather.wsu.edu/

0.16

0.18

0.2

0.22

0.24

0.26

0.28

1950 1960 1970 1980 1990 2000 2010 2020

Pe

ak E

T (i

n/d

ay)

Peak daily ET Summerland CS Weather station April-Oct

Average = 0.27in 0123456789

0 0.1 0.2 0.3 0.4

Pe

ak f

low

re

qu

ire

me

nt

(US

gpm

/acr

e)

Peak ET (in/day)

Design flow rates for peak ET(BCMA Sprinkler and Trickle Irrigation Manuals)

Micro-irrigation

Sprinkler irrigation

150

170

190

210

230

250

270

290

310

330

1950 1960 1970 1980 1990 2000 2010 2020

Gro

win

g se

aso

n E

T (i

n/y

ear

)

Growing season ET Summerland CS Weather station April-Oct

Well-designed irrigation systems take into account soil water availability

drainage

SATURATED SOIL

AVAILABLE WATER

BOUNDWATER

Dryin

g

• Important if soil is being used for water storage

– characteristic of sprinkler irrigation

– water is usually applied at intervals greater than 2-3 days

• For micro-irrigation, soil storage becomes less important if:

– water is applied at high frequency (<2 day intervals)

– in amounts to meet evaporative demand

– soil moisture is maintained at a high level

36

in

3.0in 1.2in 0.5in 4.6in 1.9in 0.73in 7.6in 3.0in 1.2in

Grape Apple Grape Apple Grape Apple

Sandy loam Silt loamSand

• Modified according to soil type, crop rooting depth, crop ability to extract water (allowable depletion)

• How frequently should it be replenished? - as often as possible

Water –what is really available

Improving water management with irrigation scheduling

• how long an irrigation system should run• matches water supply to demand• uses some measurement or estimate of demand (soil

moisture, climate)

0.4

0.8

1.2

1.6

2.4

2.0

2.8W

ate

r ap

plie

d (

in)

0

TDR manual –can be

automated

Electrical Resistance Block

Capacitance probes (fully automated

record)

Soil Moisture Monitoring

Tensiometermanual – can be automated

manual, semi-automated can be fully automated

Soil moisture range for micro-irrigation

systems

Soil Type Soil moisture tension

(cbars)

low (wet) high (dry)

Sand 10 15

Loamy sand 10 15

Sandy loam 15 20

loam 25 30

Estimating tree water use from potential evapotranspiration (ET0)

• Actual water use (mm or in) = K x ET0 (in)

• K is the crop coefficient and is related to canopy size

• K is the in water required per in of ET0 Cro

p c

oef

fici

en

t (K

c)

0

0.4

0.8

1.2

0 5 10 15 20 25 30Weeks after shoot leaf budburst

Apply 0.5 in/in ET0

Apply 1.2 in/in ET0

Automated sensor systems

Sensors

Electronic switch

Solenoid valve

Pressure transducer

Data-logger,

computer

Irrigator

Irrigation controller

Example of a multi-sensor system, communicating to various devices.There are others on the market

Schematic of a multi-sensor system, which controls the irrigation system

Targeting water in the root zone using automated sensing scheduling

• Water supply and demand can be matched very well with automated scheduling and micro-irrigation

0

4

8

12

16

20

120 160 200 240 280

Day of the year

Wat

er

(in

)

AdditionLossRainfallWater usePET

Microsprinkler

Low drainage & N loss

(Kc)

0

0.4

0.8

1.2

0 5 10 15 20 25 30Weeks after budburst

10

15

20

25

30

203 205 207 209 211

Day of the year

Soil

mo

istu

re (

%)

Drippers 15 cm from emitter

Microsprinklers 15 cm from emitter

Nutrient management in irrigated production

• In irrigated production systems water and nutrient management are closely linked and water management controls nutrient availability

• Compact root systems and micro-irrigation offer good opportunities for controlled application of nutrients

• Precision nutrition can reduce inputs and improve fruit quality

0-1

6in

0-12in

M.9

Nit

rate

-N (

pp

m)

140 160 180 200 220 240

Day of the year

0

20

40

60

80

100

BroadcastIrrigated weeklywith sprinkler10 day increased N availability

Fertigation can control N in the root zone over the growing season

• Soil N supply controlled with frequent small applications

Day of the year

110 130 150 170 190 210 2300

40

80

120

160

200(N1)

(N3)

Nit

rate

-N (

pp

m)

Fertigated dailywith drip

0

1

2

3

4

5

6

80 100 120 140 160 180 200 220

N (

g/t

ree

)

Day of the year

When should N be applied in spring?

• Before petal fall leaf growth (spur leaves) supported by remobilized N

• Root uptake occurs mainly after bloom to support shoot and fruit growth

• N inflow into fruit occurs mainly after cell division

Root uptake into shoot leaves and fruit

Shoots

Spur leaves

Fruit

Tree stored N moves into spur, shoot leaves and

fruit

Budbreak

Full bloom

Petal fall

End of cell division

Apply fertilizer after bloom

1oz. = 28.4g

When should we apply Fall foliar urea?

0

5

10

15

20

25

30

35

40

45

50

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Pe

rce

nta

ge

of

tota

l s

tore

d N

(%

)

Leaf N content (g m-2)

N from leaf

N from spray

• In trees with low

leaf N, fall urea

applications may

increase N

storage for

growth next year

• In high N trees

foliar urea is not

necessary

Re-drawn from Cheng et al., 2002 J. Hort. Sci &Biotech 77

oz/tree lb/ac*Golden Delicious/M.9 first year 0.10 8.1

Gala/M.9 third year 0.23 19.7

Elstar/M.9 fourth year 0.34 31.0

Gala/M.9 sixth year 0.43 37.2

• assumes a tree density of 1350 trees/ac

How much N? - removal in fruit and senescent leaves of apple trees

Water and N drainage reduced by irrigation scheduling in Gala/M.9

• water losses high under unscheduled irrigation during periods of low ET

• water and N losses related during fertigation period

• irrigation scheduling keeps N in the root zone

Wat

er lo

ss (

gal/

tree

)

aa

a

0

25

50

0

6

9

12

N lo

ss (

lb/a

cre)

a

fertigation period

3

May June July Aug. Sept. Oct-May May

Scheduled to meet ETUnscheduled (fixed rate)

b

b

bb

15

130 160 190 220

Day of the year

200

0

150

100

50Soil

P (

pp

m)

Year 1Year 2Year 3

Single application

Soil P availability - Fertigated phosphorus in apple (drip irrigation)

Single large fertigatedapplication can keep P available 2-3 months

Phosphorus effects on fruit production - 5 apple cvs/M.9

• Phosphorus additions are effective when targeted to the roots through fertigation

• (20g actual P/tree) as Ammonium Polyphosphate

21

Cu

mu

lati

ve Y

ield

(lb

/tre

e)

Cumulative Yield (2000-04)

0

-P

+P20

40

60

80

100 *

0

4

8

12

2001 2002 2003

Fru

it P

(mg

/10

0g

F.W

.)

Fruit P concentration

** ** **

0g K/acre/year45lb K/acre/year

Averaged for four apple cultivars (Gala, Fuji, Spartan, Fiesta)

Effect of fertigated K on leaf K concentration

Yr 1 Yr 2 Yr 3 Yr 4 Yr 50

1

2

Leaf

K (

% d

w)

b

aa

a

a a

b bb

b

1.3%

Treatment – applied at 90lb K/acre2002

0.5

0.0

1.0

1.5

2.0

Check KCl KMag K2SO4 KTS

1.3% Kc

aba

aba

ab

c

aab

a

2000

Effects of K fertilizer forms on leaf K concentration in Braeburn/M.9

3.0

6.0

9.0

12.0

15.0

Check KCl KMag K2SO4 KTS

Treatment

Bitter pit incidence averaged over 3 years

K applications in a low K orchard did not increase bitter

pit

Summary: slender spindle apple nutrition

Nutrient Form Application duration Application rate (g/tree)

N 15.5-0-0; Can 17;

Urea

Daily 6 weeks after bloom 60lb N/ac

If using 10-34-0

then 30 lb/ac

P 0-65-0 (P-acid)

10-34-0

One day after bloom 45lb P/ac

45lb P + 30lb N/ac

K 0-0-60 (KCl)

K2SO4; Kmag; KTS;

KNO3

Daily for 6 weeks starting

4 weeks after bloom

60lb K/ac

B Solubor (20.3% B) Daily for 6 weeks starting

4 weeks after bloom

0.51lb B/ac

Assumes 1333 trees/acre

Thank you