Managing Irrigation water:

Lyndon KelleyMSU Extension / Purdue University

Irrigation Management Agent

WWW.msue.msu.edu - find St. Joseph Co. - then hit the Irrigation button

Size , Scale and Make-up

County Irrigated Acres

%

St Joseph 104,000 23.0

Montcalm 47,000 10.4

Branch 39,300 8.7

Kalamazoo 29,600 6.6

Cass 25,400 5.6

Van Buren 23,900 5.3

Berrien 19,200 4.2

Allegan 15,300 3.4

Ottawa 13,500 3.0

Calhoun 10,400 2.3

Tuscola 5,800 1.3

Sum

mar

ized

fro

m 2

002

Agr

icul

tura

l Ce

nsus

Michigan – 452,000 acres Indiana 313,000 acres

County Irrigated Acres

%

LaPorte 32,400 10.4

Knox 24,600 7.8

Elkhart 23,500 7.5

LaGrange 21,700 6.9

Jasper 20,600 6.6

St. Joseph 19,500 6.2

Pulaski 19,200 6.1

Kosciusko 19,100 6.1

Fulton 16,200 5.2

Starke 11,100 3.5

Bartholomew 9,100 2.9

11 Counties = 69.2 % of total11 Counties = 73.8 % of total

0

1

2

3

4

5

6

7

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

Inch

es o

f W

ater

Corn Water UseNormal Rainfall

Crop need15.6” total

Normal rainfall34.6

Needed Irrigation5.5”

Scientific Investigations Report 2005–5284U.S. Department of the InteriorU.S. Geological Survey

Estimated rainfall recharge

Water Quantity Needed

• Irrigation water replaces the plant water use (removed from soil)

• Water use is directly correlated to light interception• 50% light interception results in about 50% of the

maximum water use• Maximum water use mid-July early August, full light

interception, highest temperatures brightest and longest days.

Evapotranspiration (ET) = fn (net radiation) +fn (temperature) +fn (wind speed) +fn (air humidity)

Weighing Lysimeter

Rain and Irrigation increase weightEvapotransporation decrease weight

Crop Water use curve

0

0.05

0.1

0.15

0.2

0.25

0.3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Weeks after emergence

Wa

ter

us

e (

inc

he

s)

Series1

Series2

Series3

Series4

Series5

Field beans Soys

Corn

Alfalfa

Field beans

Corn

Soys

Potato

Alfalfa

From Minnesota Extension bulletin “Irrigation Scheduling”, assuming temperature 80-89

1. Irrigation Runoff

(comparing irrigation application rate to soil infiltration rate) 0 -30 % loss

3. Evaporative loss to the air•Minimal loss in our humid area•0 – 6%•Estimated 4-6% loss in Nebraska

Catch Can Volume (ml)

0

20

40

60

80

100

120

140

160

180

0 200 400 600 800 1000 1200 1400 1600

Distance from Pivot (ft)

Can

Volu

me (

ml)

Catch Can Volume (ml)

Sprinkler overlap with end gun

2. Lack of system uniformity• 5-35% loss in effectivenessThree factor

reducing effective water application

Necessary application rate to achieve effective evapo-transportation rates at various application efficiencies

Average application efficiency

Desired Inches of effective application 70% 75% 80% 85% 90% 95%

0.16 0.21 0.20 0.19 0.18 0.18 0.17

0.18 0.23 0.23 0.22 0.21 0.20 0.19

0.20 0.26 0.25 0.24 0.23 0.22 0.21

0.22 0.29 0.28 0.26 0.25 0.24 0.23

0.24 0.31 0.30 0.29 0.28 0.26 0.25

0.26 0.34 0.33 0.31 0.30 0.29 0.27

0.28 0.36 0.35 0.34 0.32 0.31 0.29

0.30 0.39 0.38 0.36 0.35 0.33 0.32

0.32 0.42 0.40 0.38 0.37 0.35 0.34

Quantity Needed

• Maximum water use for most crops is .27 - .32 in./day

• 3 gal/minute/acre pump capacity = 1”/week

• 5 gal/minute/acre pump capacity = .25 in./day

• 7 gal/minute/acre pump capacity =.33 in./day, 1”every 3 days

• 500 gal/minute pump can provide 1” every 4 days on 100 acres

Think of your soil as a bank

Intake rate:Water applied faster than the soil intake rate is lost.

Deletion:Plants can pull out only 30 - 60% of the water

Water holding capacity:The soil (bank) can hold only a given volume of water before it allow it to pass lower down.

Rooting depth:The plant can only get water to the depth of it’s roots.

Soil type :Heavier soil can hold more water / foot of depth than light soils

Water lost from the bottom of the profile can wash out (leach) water soluble nutrients and pesticides.

Soil Name

Depth

Inches

Available water holding capacity

Average Available water holding capacity

Ave. Available water holding capacity

( 24 in.)

Ave. Available water holding capacity

( 36 in.)

Oshtemo 0 - 14

14 – 35

35 - 60

0.10 – 0.15

0.12 – 0.19

0.06 – 0.10

0.125

0.155

0.08

14” x 0.125=1.75

10” x 0.155=1.55

-----------------------

= 3.3

14” x 0.125= 1.75

21” x 0.155= 3.26

1” x 0.08 = 0.08

-----------------------

= 5.09

Spinks 0 – 10

10 – 26

26 - 60

0.08 – 0.10

0.08 – 0.10

0.04 – 0.08

0.09

0.09

0.06

10” x 0.09= 0.9

14” x 0.09= 1.26

-----------------------

= 2.16

10” x 0.09= 0.9

16” x 0.09= 1.26

8” x 0.06= 0.48

-----------------------

= 2.64

Calculating Water Holding Capacity

Calculating drought capacity• Crop ET. was 0.30 in./day

• Available water capacity of 03.0 in. (AWCI

• Irrigation system can apply 0.20 in./day.

• Started irrigating when the AWC was 1.0 in. down

• 3.0 in. (AWC) - 1.0 in. = 2.0 in. available capacity

• 2.0 in. available capacity / 0.10 daily deficit = 20 days

• 20 days of drought capacity- Not Considering down time

Limited water supply Irrigation Management

• Diversify the crops sharing the water supply between high and low water use.

• Stager planting date to stager peak water need times.

• Plant part of irrigated area to a sacrifice crop to neglect during extended drought.

• Start irrigating early to bank water ahead.• Stager forage crop cutting dates to avoid

simultaneous peak use.

1109’

1320’

Field #10

20 acres

20 acres

30 acres

30 acres

Jun 21Jun 22Jun 23Jun 24Jun 25Jun 26

757585857575

.15

.15

.18

.18

.15

.15

501.5

3.0

-0--0--0--0--0--0-

2.001.851.701.521.341.941.79

0.75

corn 6-1-08SW 1/4

36”

Available

Date- July 1Stage/

ET.Estimate

July 2Stage/

ET.Estimate

July 3Stage/

ET.Estimate

July 4Stage/

ET.Estimate

July 5Stage/

ET.Estimate

July 6Stage/

ET.Estimate

Corn

Emerged

May 1

.19

1st. Tassel

.20 .20 .20 .20

full tassel

.22

Corn

Emerged

May 7

.17

10 leaf

.17 .19 .19 .19

1st. Tassel

.20

Corn

Emerged

May 14

.15

8 leaf

.15 .15 .16

.16

10 leaf

.17

Soybean

Emerged

May 7

6th. Trifolliate

.18

.18 .18 .20 .20

First flower

.21

Soybean

Emerged

May 14

4th. Trifolliate

.15

.16 .16 .16 .18

6th. Trifolliate

.18

Grass -reference

crop

4” standard

.17

4” standard .20

4” standard .17

4” standard

.20

4” standard .20

4” standard

.20

Mendon Estimated Evapotranspiration (ET) for July 4, 2008Irrigation scheduling links:•Historical E.T. for this site•MSU Scheduler IS 4•MichIana Irrigation Scheduler•MSU Scheduler Excel•MSU Paper check book system

Explanation of estimated E.T..Corn – 105 day maturity emerging on the listed date in 30” rows.Soybean – for grow 3.0 emerging on the listed date.E.T. have been estimate for two days in the future based on future weather forecast.

www.agry.purdue.edu/irrigation/IrrDown.htm

MichIana Irrigation Scheduler: Purdue Agronomy web site –Est. From High / Low temp. & date

MichIana Irrigation Scheduler – out put

Irrigation Scheduling Checkbook Challenges

Errors will accumulate over time -Weekly ground truthing needed

Rainfall variability is more than often considered

Only "effective” rainfall and irrigation should be considered - Only water entering root zone uniformly is "effective”

Corn crop mature in program by calendar, not heat

?? Soil Moisture ??

Methods to Estimate Soil Moisture

• Feel an Appearance

• Electrical resistance – electrodes on blocks in soil

• Tensiometers – measures soil moisture tension

                                                                                                                     

DEVICENP TDR GS AP AQ TM GB WB

INITIAL COST 3 1 8 2 7 8 8 8

FIELD SITE SETUP REQUIREMENTS

7 3 10 3 10 7 6 6

OBTAINING A ROUTINE READING

8 8 1 8 4 10 8 8

INTERPRETATION OF READINGS

10 10 10 10 3 5 3 5

ACCURACY 10 10 10 8 2 7 2 3

MAINTENANCE 9 9 8 9 7 3 9 9

SPECIAL CONSIDERATIONS 2 8 5 8 9 7 5 8

COMPOSITE RATING 49 49 52 48 42 47 41 47

NP - Neutron ProbeTDR -Time Domain ReflectometryGS - Gravimetric SamplingAP - Troxler Sentry 200-AP

AQ - Aquaterr ProbeTM - TensiometerGB - Gypsum BlockWB - Watermark Block

Qualitative evaluation of soil water monitoring devices.

 

A score of 1 is least favorable while a score of 10 is most favorable.

Gravimetric Sampling

• Wet weight – Dry weight of a know volume of soil.

• Often refered to as a “can test”

Have you seen yield map patterns that match the irrigation system

configuration?

Catch Can Volume (ml)

0

20

40

60

80

100

120

140

160

180

0 200 400 600 800 1000 1200 1400 1600

Distance from Pivot (ft)

Can

Volu

me (

ml)

Catch Can Volume (ml)Tower

1Tower

3Tower

5Tower

7 Tower 8

Sprinkler overlap with end gun

WWW.msue.msu.edu/St Joe /Irrigation

Greatest improvement needed

• End gun stop adjustment

• Water supply over or under design

• End gun orifice, too little or too much

• Wrong sprinkler or tip

• Leaks, plugs and no turn sprinklers

Water supply over or under designsupply over design yield tail up, supply under design yield tail down

Example of Water supply under volume for sprinkler design

165’

825’

1320’1155’

8 acres

6 acres330’

495’

660’

990’

2 acres

18 acres31 acres

49 acres

71 acres

96 acres126acres

10 acres

13 acres

18 acres

22 acres

25 acres

30 acres

Total Acres

Feet from center

4145’3109’

2072’

5181’6217’

7253’8290’

circumference

Over and under

application issue affect the majority

of the application

area

Most system apply within 85% of the expected application

Application is 4 %

under expectation

Measure flow at desired pressure prior to ordering sprinkler package

Poor performance:

Ask dealer to measure flow at peak water use season and compare to design parameters.

Assure the best plant stand

possible

• Irrigate, if necessary, to make sure to get maximum germination and uniform emergence.

• Wet down 2.5” within five days of planting, ½” in most irrigated soil

• Maintain a moist surface,0.10” to 0.20” applications, till spike.

• Are you ready to irrigate the day you plant?

Using irrigation to get the most from pesticides and nutrients

Timely application of irrigation water:• Improves incorporation of herbicides. • Improves activation of herbicides. • Improves activation/reactivation of

insecticides.

• Reduces nitrogen volatilization.• Maximizes yield to utilize the resources.

• Do not apply this product through any type of irrigation system.

• If available, sprinkler irrigate within 2 days after application. Apply ½” -1” of water. Use lower water volumes (½” ) on coarse-textured soils, higher volumes heavier soils (1”) on fine-textured soils.

Are appropriate backflow prevention devices in place and properly maintained if fertigation or chemigation is used?

2.9 Irrigation Management Practices

Backflow prevention safety devices are used and properly maintained if fertigation or chemigation are used.

Are appropriate backflow prevention devices in place and properly maintained if fertigation or chemigation is used?

2.11 Irrigation Management Practices

Distance requirements between well and contamination, and agricultural chemical/fertilizer storage and preparation areas are at least 150 feet from the well.

Irrigation management to Protect Groundwater

• Backflow protection with Air gap and vacuum relief

-required for chemigation and fertigation- good idea for all systems.-Interlocks between nitrogen pump and

irrigation pump.-Backflow protection between injection point

and supply tank.

Chemigation / Fertigation Systems - Safety Interlock

Are split applications of nitrogen fertilizer

used when nitrogen is used in irrigated field?

2.8 Irrigation Management Practices

Split applications of nitrogen fertilizer are used when nitrogen is used in an irrigated field. N application does not exceed MSU recommendation.

Chemigation – Application of pesticide via irrigation water.

Fertigation – Application of fertilizer via irrigation water.