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 – HPWDMarch 22, 2016

Acknowledgements:

High Plains Water DistrictOgallala Aquifer Program

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.

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.

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: Grain Yield/Seasonal Crop Water Use

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

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

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 ftof drip line

Flow meter on the first drop to each zone

80 mesh filter

LDN package with pressure regulator

Dragon-Line Flex H

ose

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)

Plot Plan

PMDI and LEPA located at the inner circle (red) and in span 5 (red)

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

MethodsShort Season Corn P9697 (CRM 96 days) planted on June 23, 2015 after previous corn crop was hailed out on June 14

RESULTS

Average of Daily Values of Weather Parameters for 2015 at Bushland, Texas

Month Rainfall(in.)

Air Temperature

(°F)

RH(%)

Wind Speed(mph)

June* 2.9 75.2 68.5 9.2July 8.9 76.6 70.0 8.5Aug 2.6 75.7 66.3 8.3Sept 0.8 73.4 60.9 9.8

Weather Data

*June 14, 2015 hail storm stripped and buggy-whipped corn below its growth point

Soil Water Content & Fraction of Depletion in top 5’

-0.2

0

0.2

0.4

0.6

0.8

1201 218 230 236 243 254 264 317

% D

eple

tion

DOY

PMDILEPALESA

July 20 Nov 13

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4

Dep

th (f

eet)

Soil Water Content (ft3 ft-3)

201230218236243254264317

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)

Kernelsper 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

SummaryYield and WUE of PMDI was similar to LESA and LEPA

Design ConsiderationsMust be customized to crop statureMaintain dripline in furrow

AdvantagesWheel tracks near PMDI were drier than LESARunoff was observed to be less than LEPA in furrowsMay offer flexibility for pre-season irrigation; sustain irrigated crop production

DisadvantagesMaintenance- filtration, additional partsUpfront cost

Future: Revise the design of the upper and lower portions of the PMDI system; repeat study in summer of 2016

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.