Dr. Susan O'Shaughnessy, with USDA-ARS in Bushland, TX, discusses findings from a study comparing different irrigation methods.

1. A COMPARISON OF PRECISION
MOBILE DRIP IRRIGATION,
LESA, AND LEPA
S.A. O’Shaughnessy1 and P.D.Colaizzi1
1United States Department of Agriculture, Agricultural Research Service,
Bushland,Texas, USA
WATTS Conference – HPWD
March 22, 2016

2. Acknowledgements:
High PlainsWater District
Ogallala Aquifer Program

3. Background
Early forms of precision mobile drip irrigation (PMDI) are reported
in the literature as traveling trickle systems, Rawlins et al. (1974)
and in Phene et al. (1985).
Olson and Rogers (2008) compared PMDI with low elevation spray
application (LESA) for corn in northwest Kansas, and reported no
yield differences.
Concerns noted in their study were emitter clogging and the drip
lines climbed up onto the crop.

4. Objectives
• Investigate corn yields and water use efficiency between
PMDI, Low Elevation Spray Application (LESA) and Low
Energy Precision Application (LEPA) methods in the High
Plains Region.
• Observe and quantify advantages and disadvantages of
the PMDI system.
• Modify PMDI design where needed.

5. Surface
(45-75%)
Sprinkler
(70-95%)
MicroIrrigation
(80-95%)
Potential
Application
Efficiencies
of Irrigation
Systems
Application Efficiency: ratio of average depth of irrigation water
contributing to target depth of irrigation water applied during a defined
time interval (Burt et al., 1997; ASCE 123(6): 423-442.)
 Inefficiencies can be due to wind and evaporative losses at canopy and soil
level, runoff, and deep percolation
Crop water use efficiency: GrainYield/Seasonal Crop Water Use

6. Materials and Methods
PMDI was installed on 24 drops of a six-span center pivot that
included variable rate irrigation (VRI)
12 drops were in the First Span, in Sprinkler Zones 1 & 2, which were
within 78 - 128 ft. of the pivot point
12 drops were in the Fifth Span, in Sprinkler Zone 19 (660-690 ft.
from the pivot point). Additional drop tubes at 30 inch spacing
reduced the length of the PMDI line

7. PMDI
UV PVC sleeves over drop tubes
Continuous UV PVC drop
Bracing System-
horizontal 16 gauge wire anchored at
wheel tower and between truss rods
at the opposite end
Guide wires tied 6 ft. above ground to
the truss rods
Maintain spray option for
germination and chemigation;
pigtails maintains axis of the
spray in a horizontal position

8. Dripline Tube
Specifications:
Dragon-line emitter tube
is 0.570” OD; wall
thickness 45 mil;
pressure compensated
emitters are spaced
every 6”; requires
filtration
Flow rate: 1 GPH per ft
of drip line
Flow meter on the
first drop to each
zone
80 mesh filter
LDN package with
pressure regulator
Dragon-LineFlexHose

9. Farming practices: plant in circles,
crop row spacing is 30 in.; sprinkler
spacing¹ is 60 in.; hose drop in every
other furrow; furrows were diked
LESA:
nozzle height: 12-18” above ground;
potential application efficiency ~ 85-90%
LEPA:
bubblers or socks-
socks are 24 in. long, open on both ends;
potential application efficiency ~
90-96%
Low Elevation Spray Application (LESA)
Low Elevation Precision Application
(LEPA)

10. Plot Plan
PMDI and LEPA
located at the inner
circle (red) and in
span 5 (red)

11. Soil water measurements with neutron probe
taken weekly
Irrigations were from July 20 – September 22,
2015
Plant measurements were made every two
weeks
Harvest hand samples were taken on
November 4, 2015
Methods
Short Season Corn P9697 (CRM 96 days)
planted on June 23, 2015 after previous corn
crop was hailed out on June 14

12. RESULTS

13. Average of DailyValues ofWeather Parameters for 2015 at Bushland,
Texas
Month Rainfall
(in.)
Air
Temperature
(°F)
RH
(%)
Wind Speed
(mph)
June* 2.9 75.2 68.5 9.2
July 8.9 76.6 70.0 8.5
Aug 2.6 75.7 66.3 8.3
Sept 0.8 73.4 60.9 9.8
Weather Data
*June 14, 2015 hail storm stripped and buggy-whipped corn below its growth
point

14. Soil Water Content & Fraction of Depletion in top 5’
-0.2
0
0.2
0.4
0.6
0.8
1
201 218 230 236 243 254 264 317
%Depletion
DOY
PMDI
LEPA
LESA
July 20 Nov 13
0
1
2
3
4
5
6
7
8
0 0.1 0.2 0.3 0.4
Depth(feet)
SoilWater Content (ft3 ft-3)
201
230
218
236
243
254
264
317

15. Irrigation
Method
Water
Applied
(in.)
Adjusted
Yield *
(bu ac-1)
Seasonal
Crop
Water Use
(in.)
Water Use
Efficiency
(bu ac-1 in-1)
Kernel
Weight
(mg)
Kernels
per ear
HI
LESA 11.4 182a 20.4a 8.9a 265a 453a 0.54a
PMDI 12.4 177a 21.6a 8.3ab 261a 451a 0.55a
LEPA 12.3 171a 21.8a 7.8b 258a 448a 0.55a
*Adjusted to 15.5% moisture
Irrigation Amounts and Crop Response

16. Summary
Yield andWUE of PMDI was similar to LESA and LEPA
Design Considerations
Must be customized to crop stature
Maintain dripline in furrow
Advantages
Wheel tracks near PMDI were drier than LESA
Runoff was observed to be less than LEPA in furrows
May offer flexibility for pre-season irrigation; sustain irrigated crop production
Disadvantages
Maintenance- filtration, additional parts
Upfront cost
Future: Revise the design of the upper and lower portions of the PMDI system; repeat
study in summer of 2016

17. Thank you for your Attention!
Questions?
References for PMDI:
Olson, B.L.S. and Rogers D.H. (2008). Comparing drag hoses verses sprinklers on corn
irrigated by a center pivot. Appl. Engr. ASABE. 24(1): 41-45.
Phene, C.J., Howell, T.A., and Sikorski, M.D. (1985). A traveling trickle irrigation system. Ed.
Hillel, D. (Ed.), Advances in irrigation (pp. 1-47). London: Academic Press.
Rawlins, S.L., Hoffman. G.W. and Merrill, S.D. (1974). Traveling trickle system. Proc. Int. Drip
Irrig. Congr., 2nd, San Diego, pp.184-187.