AZdrip: Long-term Evaluation of SDI

Tom ThompsonDept. of Soil, Water, and Environmental Science

Presented at Drip Irrigation Field DayMaricopa Agricultural Center, 7 July, 2005

AZdrip “AZdrip”—long-term subsurface drip

irrigation demonstration and research project located at the Maricopa Agricultural Center

Features: Large plots (70’ x 400’) 3 acres total Two drip tubing configurations:

- 3 lines per permanent 80” bed- 1 line per 40” bed (or 2 lines per 80” bed)- Furrow-irrigated plot included for comparison

High and low irrigation frequencies Long-term monitoring of crop yield and

quality, economic returns, nutrient and chemical use, soil properties, salt build-up, and nutrient depletion in root zone.

Field Plan

Roa

d w

ay

Drip PlotLow Frequency20 beds @ 40"

Furrow Plot Drip PlotLow Frequency10 beds @ 80"

Drip Plot High Frequency20 beds @ 40"

Drip PlotHigh Frequency10 beds @ 80"

Field Demensions380' EW x 411' NS

Study Area360' EW x 394'NS

Plot Area66.7' EW x 394 NS

Inner Plot borders6.7'

flush manifolds

irrigation facility12 x 36'

N

S

EW

Canal

Road way, Tractor Access

Road w

ay66.

11 '

test

row

s2

@ 4

0''

2 @

80'

'

30 '

Final PlotPlan9/4/02

9”19”

80”

9”19”

80”

Permanent 80” beds with three drip lines:

40”

9”

40”

9”

40” beds with one drip line per bed:

Bed Configurations

High frequency irrigation scheduling:Between 8 am and 8pm: Five 12” tensiometers in

each of the high-frequency plots are read and averaged automatically every hour.

If average reading is >10 cbar, irrigation is turned on for 30 min (0.07”).

Cycle is repeated every hour.

Irrigation Management (1)

With “high-frequency”irrigation, automated tensiometers achieve real-time irrigation control

Irrigation Management (2)

Low frequency irrigation scheduling: When the average of

5 manual tensiometers in each low-frequency plot reaches 25-30 cbar, 0.5 to 1.0” of water are applied.

Frequency is every 3-7 days.

With “low-frequency”irrigation, standard tensiometers are used toschedule 0.5-1.0” irrigations

AZdrip Installation Costs

“Scaled up” to a 100 acre installation, broken up into six 16 acre blocks: 3 lines per permanent 80” bed, $

2050/achigh frequency irrigation

1 line per 40” bed, high frequency $ 1833/acirrigation

3 lines per permanent 80” bed, $ 1947/aclow frequency irrigation

1 line per 40” bed, low frequency $ 1730/acirrigation

AZdrip Water Quality

pH 8.0 EC (dS/m) 1.6

NO3-N (ppm) 6.0 HCO3- (ppm) 171

Na (ppm) 240 SAR 7.1

Water Treatment/Chemigation

Irrigation water quality is monitored weekly. Irrigation water is continuously acidified to pH 6.0 with sulfuric acid.

Nitrogen is applied as UAN-32 solution.

Phosphorus is applied as 0-52-0 solution.

2002-2003

0

200

400

600

800

1000

80" beds, HighFreq.

80" beds, LowFreq.

40" beds, HighFreq.

40" beds, LowFreq.

Furrow

Yie

ld (c

arto

ns/a

cre)

† Plots were harvested commercially once, and yields wereestimated by hand in small plots.

0

100

200

300

400

80" beds, HighFreq.

80" beds, LowFreq.

40" beds, HighFreq.

40" beds, LowFreq.

Furrow

Yield

(cart

ons/acre)

†Plots were harvested commercially once.

2003-2004

0

10

20

30

40

50

60

Drip 3lines High

Drip 2lines High

Drip 3lines Low

Drip 2lines Low

Furrow

Yie

ld (l

b/ac

x 1

000)

SeedlessPollinator

Broccoli

Broccoli Watermelon2003

0

50100

150

200250

300350400450500

80" beds,HF

40" beds,HF

80" beds, LF 40" beds, LF Furrow

Yie

ld (c

arto

ns/a

c)

BunchesCrowns

Commercial harvest 1/28 to 2/2/05

Broccoli2004-05

Watermelon Commercial Harvest Yield July 2, 2005

0

10

20

30

40

50

60

Drip 3 linesHigh

Drip 2 linesHigh

Drip 3 linesLow

Drip 2 linesLow

Furrow

Yie

ld (l

b/ac

x 1

000)

0

5

10

15

20

25

-5 15 35 55 75 95 115 135

Days After Planting

Wat

er A

ppli

ed (i

n.)

Drip 80" HighDrip 40" HighDrip 80" LowDrip 40" LowFurrow

0

10

20

30

40

-10 10 30 50 70 90 110

Days After Planting

Wat

er A

pplie

d (i

n.)

Drip 3 lines HighDrip 2 lines HighDrip 3 lines LowDrip 2 lines LowFurrow

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Days after planting

Water

app

lied

(in.)

80" HF40" HF80" LF40"LFFurrow

02468

101214161820

0 20 40 60 80 100 120 140

Days After Planting

Wat

er A

pplie

d (i

n.)

Drip 80" High

Drip 40" High

Drip 80" Low

Drip 40" Low

Furrow (actual)

Broccoli 2002-03

Broccoli 2003-04 Broccoli 2004-05

Watermelon 2003

Water Use

Water Use Efficiency

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Wate

r Use

Efficie

ncy (

lb yie

ld/ac-i

n/ac)

80" beds,High Freq.

40" beds,High Freq

80" beds,Low Freq

40" beds,Low Freq.

Furrow

Benefits of SDI Ease of harvest, field operations Lower water use Better crop uniformity Reduces soil tillage—improved soil

tilth More flexible management options

—frequency of irrigation/fertigation Higher yields

Limitations of SDI

Initial cost Salt management, especially with

small-seeded vegetable crops Time/cost for repair of drip tubing

damage High level of management

expertise and maintenance is necessary

Summary of AZdrip Results, 2002-2005

Generally higher yields with SDI. Generally higher yields with high-

frequency SDI compared to low-frequency SDI.

Higher water use efficiency with SDI—even under conditions favoring high water use efficiency with surface irrigation.

After 5 seasons, the SDI system continues to perform well.

Acknowledgements

Colleagues participating on this project: Ed Martin, Russ Tronstad, Mary Olsen,

Jim Walworth, Pat Clay, Kai Umeda Funding by the University of

Arizona Technology and Research Initiative Fund (TRIF), Water Sustainability Program

Questions/Comments?

Visit our web site at http://ag.arizona.edu/azdrip

Contact Tom Thompson:520-621-3670 or thompson@ag.arizona.edu