Improving Pomegranate Fertigation

and Water-Nitrogen Use Efficiency

with Drip Irrigation Systems

Contributing Research and Support StaffC.J. Phene, J.E. Ayars, S. Gao, A. Hendratna, R.C. Phene, R. Schoneman,

D. Wong, S. Zambrzuski, G. Banuelos, K.R. Day, and T.M. DeJong

UC-KARE Center and USDA-ARS-SJVASC Staffs

Supports/ContributorsCDFA/Fertilizer Research and Education Program

Paramount Farming CompanyLAKOS

TORO IrrigationNETAFIM

SDI+Verdegaal Brothers

2015 Research Objectives

To optimize water-nitrogen interactions to improve Water-and N-use efficiencies of Pomegranate and minimize

N-leaching losses

a. Determine the effect of three rates of N-fertigation of pomegranate with High Frequency Drip Irrigation and Subsurface Drip Irrigation on N leaching losses.

b. Determine the seasonal N requirement of DI- and SDI-fertigatedpomegranates which improves NUE without yield reduction.

c. Determine the seasonal water requirement of HF DI- and HF SDI-fertigated pomegranates which improves WUE without yield reduction.

IRRIGATION/FERTIGATION SYSTEMS

TORO Microirrigation, Drip In Classic with Rootguard,0.620 in. diameter, 0.53 gph, 0.045-in. wall thickness, 18-in emitter spacing, Installed 3.5 ft. on each side of thetree row.

SDI laterals are installed at 20-22-in. depth.

Irrigation scheduling Fully automated, based on hourlyETc from lysimeter to apply same water volume aslysimeter (2.64 gal/tree/SDI irrigation and 2.84 gal/tree/DIirrigation).

Fertigation, N-P-K injected with irrigation water at rates tomeet plant requirements, based on bi-weekly plant tissueanalyses.

C.J. Phene. R. Schoneman & R.C. PheneExperimental Layout

Randomized Complete Block

Design with Subsamples

Surface Drip (DI)

Subsurface Drip (SDI)

Irrigation Treatments

Nitrogen Treatments

50% N1

100% N2

150% N3

Five Replications

3.54 acres

16 x 12 ft. tree spacing

BASIC SDI SYSTEM DESIGN

Installation of Subsurface Drip Irrigation (SDI) line at 20-22 in. depth

N-pHURIC

K2TPhos

AcidAN-20

Sand Media Filter

Lysimeter

Solution

Refill Tank

pH & ECw

meters

N1

SDI DI

N2

SDI DI

N3

SDI DI

Electro-Magnetic Flow Meters

To Lysimeter Refill Tank

Weighing lysimeter (4 x 2 x 2 m) resolution of 0.05 mm of

evapotranspiration

SMP sensor 0.6 m

SMP sensor 0.91 m

SMP sensor 1.22 m

SMP sensor 1.52 m

Basic Soil & Irrigation Sciences

C.J. Phene

Desorption Curve For a Hanford Sandy Loam Soil

Late Irrig

ation

Co

ntro

l

Zo

ne

Early Irrig

ation

Co

ntro

l

Zo

ne

Crop Evapotranspiration, Etc , Reference

Evapotranspiration, ETo & Crop Coefficient, kc

R.C. Phene

POMEGRANATE WATER

BALANCE (in.)

Year ETo in.

Precip. in.

DI

Irrig. in.

SDI

Irrig. in.

ETc in.

Drainage in.

2010 49.73 17.34 1.0 1.0 2.1 N/A

2011 50.90 10.42 8.5 8.5 9.8 0

2012 54.60 8.97 18.6 17.7 19.7 0

2013 55.00 3.21 25.4 23.0 26.9 0

2014 57.80 8.62 33.4 30.7 35.9 0

2015** 49.61 3.52 34.76 31.46 34.8 0

2011 ETc values from 5/1 to 12/8 only. *Lysimeter ETc adjusted for orchard spacing **2015 Values are from January 1 to October 11th

Crop Evapotranspiration, ETc

Reference Evapotranspiration, ETo

Crop Coefficient, kc

ETc = ETo * kc

CIMIS, California Irrigation Management

Information System (www.cimis.water.ca.gov)

The crop coefficient, kc, is

developed to relate ETo to the

crop

Crop Evapotranspiration, ETc

Reference Evapotranspiration, ETo

Crop Coefficient, kc

The daily grass reference ET (CIMIS ETo)

and the orchard evapotranspiration (ETc)

measured hourly by the weighing lysimeter

were used to develop irrigation requirement

and crop coefficient for maturing

pomegranate.

Kc = -0.00x3 + 0.00x2 + 0.00x + 0.01R² = 0.87

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

3.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

5.50

6.00

6.50

7.00

7.50

8.00

8.50

1/2

1/10

1/18

1/26

2/3

2/11

2/19

2/27

3/6

3/14

3/22

3/30

4/7

4/15

4/23

5/1

5/9

5/17

5/25

6/2

6/10

6/18

6/26

7/4

7/12

7/20

7/28

8/5

8/13

8/21

8/29

9/6

9/14

9/22

9/30

Cro

p C

oeff

icie

nt,

Kc

Dail

y E

Tc

an

d E

To

, m

m

Time, date

2015 CIMIS ETo, Pomegranate ETc and KcEtc, mm Eto,mm OrchaKc

0.19

0.40

0.480.55

0.610.67

0.720.76

0.800.84

0.880.92

0.95

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct

Cro

p C

oef

fici

ent,

Kc

2014 Bi-monthly Pomegranate Kc

0.30

Soil Matric Potential & Hydraulic Gradient

C.J. Phene & R. Schoneman

-40

-38

-36

-34

-32

-30

-281 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

SMP(cbar)

Time,Hour

HourlySMPandResponsesto1.0mmSDIIrriga onSMP-1upper SMP-2 SMP-3 SMP-4lowest SMP-5upper SMP-6 SMP-7 SMP-8lowest

1.0 mm irrigation

2015 NITROGEN

0

25

50

75

100

125

150

175

200

225

250

275

300

325

3/29 4/13 4/28 5/13 5/28 6/12 6/27 7/12 7/27 8/11 8/26 9/10 9/25 10/10

Inje

cte

d N

itro

gen

Fert

iliz

er,

lb

/ac

Time, date

N1 lb N/ac N2, lb N/ac N3, lb N/ac

Leafing out Flowering Fruiting Maturing Harvest

US-10 + AN-20

US-10

2015 NITROGEN CONCENTRATION

0

25

50

75

100

125

150

175

200

225

250

275

300

325

3/29 4/13 4/28 5/13 5/28 6/12 6/27 7/12 7/27 8/11 8/26 9/10 9/25

Nit

rog

en

Co

ncen

trati

on

, p

pm

Time, Date

N-1 Conc. ppm N-2 Conc ppm N-3 Conc. ppm

Leafing out Flowering Fruiting Maturing Harvest

Total Nitrogen in Leaf Tissue (2015)

%N

1.20

1.40

1.60

1.80

2.00

2.20

2.40

2.60

2.80

17

-Mar

16

-Ap

r

16

-May

15

-Ju

n

15

-Ju

l

14

-Au

g

13

-Se

p

N1 DI N2 DI N3 DI

1.20

1.40

1.60

1.80

2.00

2.20

2.40

2.60

2.80

17

-Mar

16

-Ap

r

16

-May

15

-Ju

n

15

-Ju

l

14

-Au

g

13

-Se

p

N1 SDI N2 SDI N3 SDI

%N

Total Nitrogen & Carbon in Leaf Tissue (2015)

1.5

1.7

1.9

2.1

2.3

2.5

4/1

8

5/1

8

6/1

7

7/1

7

8/1

6

9/1

5

% Nitrogen

40

42

44

46

48

50

52

54

4/1

8

5/1

8

6/1

7

7/1

7

8/1

6

9/1

5

% Carbon

N1

N2

N3

0.72 0.73

0.970.91 0.92 0.92

N1 DI N1 SDI N2 DI N2 SDI N3 DI N3 SDI

%N in Pomegranate Peels

Total Nitrogen in Fruit Parts (2014 harvest)

0.73

0.94 0.920.87 0.86

N1 N2 N3 DI SDI

aa

b

AA

1.03

1.27

1.11 1.12 1.14

N1 N2 N3 DI SDI

a

bab AA

Total Carbon in Fruit:No significant difference

among treatments.

TC in peels 45% & arils

42.5%.

Total Nitrogen in Fruit Parts (2014 harvest)

1.00 1.051.17

1.40

1.171.04

N1 DI N1 SDI N2 DI N2 SDI N3 DI N3 SDI

%N in Pomegranate Arils

Soil Nitrate Profile (2014)

0

10

20

30

40

50

60

0 20 40 60 80 100 120 140 160

Soil

de

pth

(in

)NO3-N (mg/L)

March

0

10

20

30

40

50

60

0 20 40 60 80 100 120 140 160

Soil

de

pth

(in

)

N1 DI N1 SDI

N2 DI N2 SDI

N3 DI N3 SDI

July

0

10

20

30

40

50

60

0 20 40 60 80 100 120So

il d

epth

(in

)

March

DI SDI

0

10

20

30

40

50

60

0 20 40 60 80 100 120

Soil

de

pth

(in

)

July

DI SDI

Soil Nitrate Profile (2014)

NO3-N (mg/L)

Yields, WUE, NUE

2014 Yields Marketable TotalIrrigation Methods Yield, lb/ac Yield, lb/ac

Surface Drip (DI) 28,909a 37,119a

Subsurface Drip (SDI) 33,442a 42,591a

Prob > "F" value (5%) NS NS

Nitrogen Levels (N)

(N-1) 35 lb N/ac 28,245a 40,344a

(N-2) 199 lb N/ac 30,532a 35,871a

(N-3) 305 lb N/ac 34,7494a 43,352a

Prob > "F" value (5%) NS NS

Effects of irrigation and nitrogen treatments on

WUE and NUE of pomegranate in 2014

IRRIGATION WUE- WUE NUE-N1 NUE-N2 NUE-N3

TREATMENTS PRIME JUICE

lb Fruit/ac-in lb Fruit/lb N/ac

DI 865.5a 226.7a 1060.6a 186.5a 121.7a

SDI 1089.3b 285.3a 1216.9a 214.0b 139.6a

Prob > F value 0.0086 NS NS 0.0043 NS

Effects of Irrigation and Fertigation

Treatments on Residual Weed Biomass

Following six years of intensive pomegranate irrigation and fertigation

research with high frequency surface drip irrigation (DI) and subsurface

drip irrigation (SDI), results have demonstrated that the high frequency

SDI system has the potential to provide:

1. Higher and more durable system performance.

2. Minimize nitrate leaching by controlling the gravitational gradient.

3. More efficient water use efficiency (WUE) than DI.

4. Minimum potential for nitrate-nitrogen (N) leaching than DI.

5. Lower weed population and mass than DI.

5. Improved orchard cultural practices, development and production.

6. No significant differences in pomegranate fruit and juice quality.

Conclusions

2014-2015