Center Pivot Irrigation for Corn:

Water Management and System

Design Considerations

Steve Hines

Extension Educator

University of Idaho

Jerome County

December 12, 2013

This talk summarizes UI Bulletin BUL 881

Center Pivot Irrigation for Corn: Water Management and System Design Considerations in Southern IdahoBy S. Hines and H. Neibling

http://www.cals.uidaho.edu/edComm/pdf/BUL/BUL0881.pdf

Or

Google: University of Idaho Bulletin 881

Factors Affecting Corn YieldDr Fred Below, University of Illinois

Factor

• Weather (Irrigation)

• Nitrogen

• Hybrid

• Previous Crop

• Plant Population

• Tillage

• Growth Regulators

Weight on Yield (%)

27%

26

19

10

8

6

4

100%

Outline

• Impact of stress on yield depends on crop stage

• Water stress may occur because insufficient water is applied to match ET

– Irrigation scheduling problem

– Irrigation design problem

• Water stress may occur because part of applied water is lost to surface runoff.

PollinationV6 V7-V12

Critical growth stages

Drought Stressed Ears

Outline

• Impact of stress on yield depends on crop stage

• Water stress may occur because insufficient water is applied to match ET

– Irrigation scheduling problem

– Irrigation design problem

• Water stress may occur because part of applied water is lost to surface runoff.

Date

Winter Grain

Spring Grain

Dry Beans

Potatoes

Field Corn

Sugar Beets

Alfalfa

Tillering

Tillering

Boot - flower

Boot - flower

Flowering

Tuber set

PollinationGermination, Emergence

& Early Growth

Early growth New fall seedings

V-6

Timing of Crop ET and Critical Crop Stages

for Magic Valley Conditions

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Ag

rim

et E

stim

ated

Cro

p E

T, in

/dAverage 30-Year ET for Corn in the Magic Valley

7.5 gpm/a

6.5 gpm/a

Critical pollination and

ear development stage

0

5

10

15

20

25

30

35

5/1 5/31 6/30 7/30 8/29 9/28 10/28

ET

an

d I

rrig

ati

on

, in

ch

es

Date

Bliss Corn Silage 2005

AGRIMET ET

Max irrigation

Actual irrig

7/20

7 gpm/acre

Scheduling deficiency

Outline

• Impact of stress on yield depends on crop stage

• Water stress may occur because insufficient water is applied to match ET

– Irrigation scheduling problem

– Irrigation design problem

• Water stress may occur because part of applied water is lost to surface runoff.

7.5 gpm/a

6.5 gpm/a

7.5 gpm/a

6.5 gpm/a

You may not be able to supply enough water at mid-season, so how much

usable water can you bank in your soil?

Maximum Storable Water

• Sandy Loam (1.7 in/ft * 0.5 = 0.85 in/ft)–1 ft: 0.8 in

–2 ft: 1.7 in

–3 ft: 2.6 in

• Silt loam (2.4 in/ft * 0.5 = 1.2 in/ft)–1 ft: 1.2 in

–2 ft: 2.4 in

–3 ft: 3.6 in

50% MADOnly 40% during pollination

Outline

• Impact of stress on yield depends on crop stage

• Water stress may occur because insufficient water is applied to match ET

– Irrigation scheduling problem

– Irrigation design problem

• Water stress may occur because part of applied water is lost to surface runoff.

Spread the water stream over a wider area to match infiltration rate of your soil

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 2 4 6 8 10 12

Spri

nkl

er

& In

filt

rati

on

rat

e, i

n/h

Time after irrigation is started, hours

Portneuf silt loamKimberly, ID

first pivot span

infiltration

20' dia.

45' dia.

100' dia.

Fore and Aft Booms Spread the Application Pattern &

Reduce Runoff

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

0 5 10 15 20 25 30 35 40 45 50

Spri

nkl

er

& In

filt

rati

on

rat

e, i

n/h

Time after irrigation is started, minutes

Portneuf silt loamKimberly, ID

last pivot span

infiltration

20' dia.

45' dia.

45' + booms (75)

100' dia.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

0 5 10 15 20 25 30 35 40 45 50

Spri

nkl

er

& In

filt

rati

on

rat

e, i

n/h

Time after irrigation is started, minutes

Portneuf silt loamKimberly, ID

last pivot span

infiltration

20' dia.

45' dia.

45' + booms (75)

100' dia.

infiltration + 0.5 insurface storage

Reservoir Tillage

• Increases surface storage to minimize runoff

• More effective on flat fields than sloping ones

• Storage capacity

– 0-2% slopes, 0.75 inch storage

– 2-5% slopes, 0.5 inch storage

– >5% slopes, 0.25 inch storage

• “Mini ponds” tend to break down as the season progresses

0

20

40

60

80

100

120

0

1

2

3

4

5

6

7

0 200 400 600 800 1000 1200 1400

Fie

ld a

rea,

%

Ap

plic

atio

n o

r In

filt

rati

on

Rat

e, i

n/h

Distance From Pivot Point, feet

20 ft

45 ft

100 ft

sandy loam

field area

1320 ft pivot

Reduce Pivot & linear Runoff Losses By:

• Choose proper application pack

• Use fore & aft booms to spread application pattern

• Limit application per revolution

• Use reservoir tillage (dammer-diker)

Final Irrigation Considerations

Growth Stage Plant

Moisture %

Days to

maturity

Water use to

maturity

(inches)

Blister (R2) 45 10.5

Dough (R4) 80 34 7.5

Full Dent (R5) 75 24 5.0

¼ Milk Line 70 19 3.75

½ Milk Line 66 13 2.25

¾ Milk Line 63 7 1.0

Physiological

Maturity

59 0 0.0

Summary - Pivots and Linears

• Avoid excessive early and late-season irrigation but….

• Fill the soil profile early

• Pay attention to critical ET timing of corn for maximum yield

• Use faster rotation speeds or dammer-diking to reduce runoff

• You can grow good corn on 80% water with good management

• Refer to your Proceedings or UI Bulletin 881

Questions?