Crop Water Demand, Use and Importance of Water Management in Forage Crops

Irriga&on  Management  Workshop      

Western  Alfalfa  and  Forage  Symposium,  “Producing  Forages  in  a  Water-­‐Challenged  

World”      

Reno,  NV,    December  2,  2015    

Dr.  Howard  Neibling,  P.E.    Water  Management  Engineer  

University  of  Idaho  

What do we want the irrigation system to do??

•  Supply water to meet crop needs (minimal stress) for best crop yield and quality – The right amount of water at the right time – Keep up (a system design issue)

•  Match wetted depth to root extraction pattern (minimize deep percolation losses, but enhance development of a deep root zone)

Right amount of water at right time and be able to “keep up”

•  Therefore, we need good information about daily crop water use – Seasonal crop water use pattern – Peak use – Variability form year to year

3/30

4/13

4/27

5/11

5/25 6/8 6/2

2 7/6 7/20 8/3 8/1

78/3

19/1

49/2

810

/1210

/26

Date

Winter Grain

Spring Grain

Dry Beans

Potatoes

Field CornSugar Beets

Alfalfa

Tillering

Tillering

Boot - flower

Boot - flower

Flowering

Tuber set

PollinationGermination, Emergence

& Early Growth

Early growth New fall seedings

Timing of Crop ET and Critical Crop Stages for Magic Valley Conditions

How do you get crop water use (ET) information?

•  Lysimeter data (measured using water balance)

•  Remote Sensing (Metric, EC) •  Estimated use based on daily weather data

(historical data for planning and current year data for scheduling) – CIMIS – AgriMet – …

0.00  

0.05  

0.10  

0.15  

0.20  

0.25  

0.30  

0.35  

0.40  

0.45  

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

Actual  ET,in/d  

Alfalfa  Lysimeter  Trial,  2014    Davis,  CA  

Actual  ET"   CIMIS  PM  ETo  

0.00  

0.05  

0.10  

0.15  

0.20  

0.25  

0.30  

0.35  

0.40  

3/1   3/31   4/30   5/30   6/29   7/29   8/28   9/27   10/27  

Actual  ET,  in/d  

Alfalfa  Lysimeter  Trial,  2015    Davis,  CA  

Actual  ET   CIMIS  PM  ETo  

Average 30-Year Alfalfa ET With Cutting, Kimberly

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

3/31 4/14 4/28 5/12 5/26 6/9 6/23 7/7 7/21 8/4 8/18 9/1 9/15 9/29 10/13 10/27

Kim

ber

ly P

enm

an E

stim

ated

ET

, in

/d Max. Pivot Capacity @ 6.5 gpm/ac & 80% AE

Max. Pivot Capacity @8 gpm/ac & 80% AE

What is the relationship between crop water use and alfalfa

production?

What is the relationship between crop water use and alfalfa production?

•  Linear increase in yield with increasing water use to estimated peak ET, then drops off

•  Slope of line changes with location •  At Kimberly, what is an inch of water

worth? – Early season: about 510 lb – Remaining season: 400 lb

Adequate Early-season Water Is Important for Alfalfa Production!

What is an inch of water worth? – Early season: about 510 lb – Remaining season: 400 lb

Alfalfa •  Yield proportional to water added (5 inches per ton of

hay) •  Irrigate young stands frequently to develop adequate root

depth •  Roots will develop to 4 ft + if soil and irrigation

management allow •  Irrigate right after harvest to enhance re-growth •  Better to stretch water over more acres than to fully

irrigate limited acres

Pivot design should accommodate some uncertainty in peak ET

Yearly water use patterns are quite variable, so irrigating

according to “average” values may not give the best results

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0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

5/1 5/29 6/26 7/24 8/21 9/18

AG

RIM

ET E

T, in

/d

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Picabo 1992-2007

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0.05

0.1

0.15

0.2

0.25

0.3

0.35

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4/1 5/1 5/31 6/30 7/30 8/29 9/28

Agr

iMet

Est

imat

e E

T, in

/day

Rexburg Alfalfa

92-07 average (29 in) 2007 (38 in) 1992 (25 in)

6 gpm/ac

Moderate Elevation Sites

High Elevation Sites

Mean Alfalfa ET - Kimberly

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

1/0 1/14

1/28

2/11

2/25

3/10

3/24 4/7 4/2

1 5/5 5/19 6/2 6/1

66/3

07/1

47/2

88/1

18/2

5 9/8 9/22

10/6

10/20

AGRI

MRT

ET,

Inch

es/d

ay

200391-02 avg

Max. center pivot rate at 6.9 gpm/ac

Max. Set-Move rate at 9 gpm/ac

The End -- Questions ??

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0.25

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0.35

0.4

4/9 5/7 6/4 7/2 7/30 8/27 9/24 10/22

AG

RIM

ET E

T,In

/d

Picabo, 2000

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0.05

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0.25

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0.35

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0.45

4/9 5/7 6/4 7/2 7/30 8/27 9/24 10/22

AG

RIM

ET E

T,In

/d

Picabo, 2003

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

4/9 5/7 6/4 7/2 7/30 8/27 9/24 10/22

AG

RIM

ET E

T,In

/d

Picabo, 2007

Alfalfa Irrigation Considerations •  Alfalfa is deep rooted with nearly uniform water extraction

with depth •  Pivots need to be run as slow as possible without runoff to

encourage deeper roots •  Set-move systems

–  Need to return fast enough so that crops are not stressed between sets

–  Need to apply only water to re-fill root zone •  Seasonally high water table

–  Limits root depth –  therefore each irrigation must be smaller and irrigations should

occur more often to avoid leaching & stress

Pivot design should accommodate some uncertainty in peak ET

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0.05

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0.25

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0.35

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5/4 5/24 6/13 7/3 7/23 8/12 9/1 9/21

2004

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

5/4 5/24 6/13 7/3 7/23 8/12 9/1 9/21

2007

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

5/4 5/24 6/13 7/3 7/23 8/12 9/1 9/21

2008

0

0.05

0.1

0.15

0.2

0.25

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0.35

0.4

0.45

5/4 5/24 6/13 7/3 7/23 8/12 9/1 9/21

2009