Irrigation and Root Health in HLB-affected Citrus

Davie Kadyampakeni

UF/IFAS CREC, Lake Alfred

Outline

Introduction on the current status of citrus production

Importance of water management on HLB management and root density

Effect of irrigation system (microsprinkler and drip) on root density

Root distribution pattern as a function of irrigation and non-irrigated zone

Summary

Acknowledgements

Current Status of HLB

• Citrus accounts for ~$10 billion in economic activity

• Current citrus production ~437,000 acres

• Significant reduction in production area due to HLB

• Declined tree performance, root loss and significant defoliation

• Roots influence water and nutrient uptake in citrus and other

crops

Irrigation strategies for managing HLB• Preventative measures: HLB negative (healthy trees)

• Frequent irrigation (daily or multiple times a day)• Regulated deficit irrigation or CUPS• Exclusion of Asian citrus psyllids (ACP).

• Curative management of HLB positive trees (asymptomatic trees)• Daily irrigation plus ACP control• Managing pH to optimum levels for nutrient availability (5.5 to 6.5)• Improved nutrition programs via fertigation and also controlled release

fertilizers

• Remediation/Management of HLB affected trees (symptomatic trees)• Daily irrigation plus Asian psyllid control• Managing pH to optimum levels for nutrient availability• Fertigation practices and controlled release fertilizers

Irrigation strategies for managing HLB (2)

Field studies on irrigation conducted in:• Irrigation studies at 3 sites: Ave Maria, Avon Park, Arcadia (2013-2014)

Comparison of Irrigation Schedules Daily, IFAS (irrigating every two days) and Intermediate (irrigating every 1.5 days) based on FAWN evapotranspiration

• Advanced Citrus Production Systems (ACPS) studies: Two Sites: Immokalee at UF/IFAS, SWFREC, and Lake Alfred (2008 to 2012)

Comparison of drip and modified microsprinkler irrigation with grower practices

• Greenhouse studies conducted at Immokalee, SWFREC (2014-2015)Comparison of HLB vs non-HLB affected citrus

IRRIGATION STRATEGIES FOR MANAGING HLB (3)

Avon Park

Vo

lum

etr

ic w

ate

r co

nte

nt

(m3 m

-3)

0.00

0.02

0.04

0.06

0.08

0.10

0.12 IFAS

Intermediate

Daily

Immokalee

Soil depth (cm)

0-15 15-30 30-45

Vo

lum

etr

ic w

ate

r co

nte

nt

(m3 m

-3)

0.00

0.02

0.04

0.06

0.08

0.10

0.12 IFAS

Intermediate

Daily

Arcadia

Vol

umet

ric

wat

er c

onte

nt (

m3 m

-3)

0.00

0.02

0.04

0.06

0.08

0.10

0.12IFAS

Intermediate

Daily

Arcadia

0.10 0.15 0.20 0.25

Sap

flow

(g

m-2

h-1

)

18

20

22

24

26

28

30

Syx = 0.2794

P = 0.02

r2 = 0.999***

Y = 13.62 + 57.4x

Avon Park

0.04 0.06 0.08 0.10

Sap

flow

(g

m-2

h-1

)

20

22

24

26

28

30

32

34

36

38

Syx = 0.5719

P = 0.0353

r2

= 0.999***

Y = 12.7 + 276.6x

Immokalee

Volumetric water content (m3 m

-3)

0.04 0.06 0.08 0.10 0.12 0.14

Sap

flo

w (

g h-

1 m

-2 h

-1)

5

10

15

20

25

30

35

40

45

Y = -27.5 + 534.3x

Syx = 1.523

P = 0.0488

r2= 0.994***

Moisture contents (left) and significant relationships with

sapflow (right)

Keeping water in the top 0-12 inches improved water use for HLB

affected trees. Greater moisture content beyond the root zone (at 45 cm) in Immokalee could be due to capillary rise since the soils have a high water table and in Avon Park could be due to deep percolation

because those soils are well drained.

More details: Hamido et al. 2017a. HortScience 52(6):916-921.

Irrigation strategies for managing HLB (4)

• Increasing total available water (TAW) with depth, greater uptake in the top 6 inches due to constant availability of water in the root zone.

• Greater TAW in top 6 inch than lower 6-18 inches for Daily than Intermediate and IFAS irrigation schedule.

• Increased root density in wetted zones

Irrigation strategies for managing HLB (5)

July 2010 Aug-Sept 2011

Julian day

188 192 196 200 204 208

Wate

r c

on

ten

t (%

)

0

5

10

15

20

25

30

CMP

MOHS

DOHS-C35

Julian day

234 236 238 240 242 244 246 248

Wat

er c

onte

nt (%

)

0

5

10

15

20

25

30

CMPMOHS DOHS-C35

CMP-Conventional microsprinkler irrigationMOHS-Microprinkleropen hydroponic system with daily irrigation and weekly fertigaton.DOHS-C35-Drip open hydroponic system with daily irrigation and fertigation

Soil moisture at 4-inch

depth was close to or

slightly above field

capacity in the range of

7 and 15%.Kadyampakeni et al. 2014a, b. Soil Science Society of America Journal 78:645–654; 78:1351–1361

IRRIGATION STRATEGIES FOR MANAGING HLB (5)Water monitoring at grove scale and soil moisture distribution at 6-, 12 and 24-inch soil depth

~217,238 gal/acre since Feb. 2018

EFFECT OF CONVENTIONAL MICROSPRINKLER

IRRIGATION SYSTEM ON ROOT DENSITYLateral root density distribution using

conventional microsprinkler irrigation

Cross-row (cm)

0 10 20 30 40

With

in r

ow (

cm)

0

5

10

15

20

25

30

0.07

0.08

0.09

0.10

0.11

MT

T=tree, M=microsprinkler

Roots uniformly distributed around the tree

Positions in the irrigated zones

of a conventional

microsprinkler showed

moderate root density

distribution. The root density

was about a third or quarter of

the density observed with drip

or linear microsprinkler

irrigating system.

EFFECT OF IRRIGATION SYSTEM

(MICROSPRINKLER AND DRIP) ON ROOT DENSITY

Lateral root density distribution using

drip irrigation.

Cross-row (cm)

0 10 20 30 40W

ithin

ro

w (

cm)

0

5

10

15

20

25

30

0.15

0.20

0.25

0.30 T

D

D

T=tree, D=dripper, Roots concentrated

below the drippers

Positions in the irrigated

zones of drip irrigation

systems showed higher

root density (2 to 3x

greater) than non-irrigated

zones.

Positions in the

irrigated zones of

linear

microsprinkler

showed higher root

density than non-

irrigated zones

Cross-row (cm)

0 10 20 30 40

With

in r

ow

(cm

)

0

5

10

15

20

25

30

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

MT

EFFECT OF LINEAR MICROSPRINKLER IRRIGATION

SYSTEM ON ROOT DENSITY

Lateral root length density (cm cm-3) distribution

using modified microsprinkler irrigation

M = microsprinkler

T = tree

SOIL MOISTURE AVAILABILITY AMONG HLB

AFFECTED AND NON-AFFECTED TREES

75% ET for HLB positive citrus trees

Month

Mar. Apr. May June July Aug. Sept Oct.

So

il m

ois

ture

co

nte

nt

(cm

3 c

m-3

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

100% ET for HLB positive citrus trees

Month

April May June July Aug. Sept. Oct.

So

il m

ois

ture

co

nte

nt

(cm

3 c

m-3

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30100% ET for healthy citrus trees

Month

March April May June July Aug. Sep. Oct.

Soil

mois

ture

conte

nt (c

m3 c

m-3

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

100% ET on sand only 100% ET on sand and 5% compost100% ET on sand and 3% biochar

75% ET for healthy citrus trees

Month

Mar. Apr. May June July Aug. Sept Oct.

Soil

mois

ture

conte

nt (c

m3 c

m-3

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

75% ET on sand only 75% ET on sand and 5% compost75% ET with sand and 3% biochar

Temporal soil moisture distribution as a function of citrus greening disease and irrigation rate under greenhouse conditions.

Soil moisture in the soil without any amendment showed 40 to 52% greater soil moisture than those HLB-affected trees grown on sand amended with compost and biochar at 100% ET irrigation signaling greater water uptake for the latter.

Frequent irrigation at 100% evapotranspiration (ET) was recommended for HLB affected trees due to limited growth at 75% ET.

WATER USE OF HLB AFFECTED TREES IN SOUTHWEST FLORIDA UNDER GREENHOUSE CONDITIONS

• 22 to 35% greater water use for Non-HLB affected trees

• Inter-season and annual variability in water use

• Comparable water use between varieties

Month -year ETo(mm d-1)

ETc (mm d-1) ETc diff. (%)

‡

Hamlin-Non HLB Hamlin-HLB

Jan-Jun-14 3.57 2.97 2.23 23.73

Jul-Dec-14 4.42 4.16 2.63 34.82

Jan-Jun-2015 3.38 4.08 2.83 29.82

Jun-Oct-15 3.73 4.94 3.18 35.20

Overall Average 3.79 4.00a** 2.69b** 30.75

Valencia-Non HLB Valencia-HLB

Jan-Jun-14 3.57 2.83 2.22 22.28

Jul-Dec-14 4.42 3.97 2.83 28.85

Jan-Jun-2015 3.38 3.85 2.69 30.98

Jun-Oct-15 3.73 4.79 3.56 26.42

Overall Average 3.79 3.82a** 2.80b** 26.99**

Effect of irrigation practices on canopy size

Canopy volume as a function of

irrigation practice at the Lake Alfred site

Advanced citrus production

system (ACPS) fertigation had

greater tree size than

conventional practice

Date

11/1/09 1/1/10 3/1/10 5/1/10 7/1/10

Can

opy

volu

me

(m3 )

0.0

0.5

1.0

1.5

2.0

2.5

DOHS-Swingle

CMP

MOHS

DOHS-C35

Treatments: DOHS is the drip open hydroponic system on Swingle or C-35 rootstockCMP is the conventional microsprinklerpracticeMOHS is a microsprinkler hydroponic system applying water linearly in the tree row.

Summary

Daily, frequent irrigation critical for improved tree performance, soil moisture distribution and water use

HLB affected trees use 22 to 35% less water than the non-affected trees, thus irrigation amount could be reduced without affecting yield. This needs to be validated at field scale since this was a greenhouse study.

Intensive irrigation practices could be adapted to grower practices for vigorous tree growth, water use, greater root density and nutrient accumulation.

Acknowledgements

• Dr. Morgan, Dr. Ebel, Dr. Hamido, Dr. Strauss - UF/IFAS SWFREC

• Dr. Schumann, UF/IFAS, CREC• My lab team: Dr. Bandaranayake, William Pihilla,

Samuel Kwakye, Alex Hernandez• Grove Space:

• UF/IFAS SWFREC, Immokalee, FL• Gapway Groves, Auburndale, FL • Pacific Inc., Ave Maria, FL• Orange Co., Arcadia, FL• Ben Hill Griffin, Avon Park, FL

• Funding: Southwest FL WMD, FDACS, UF/IFAS

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