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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
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 [email protected]