Water productivity of irrigated corn in Nebraska

“This cornfield, and the sorghum patch behind the barn, were the only broken land in sight. Everywhere, as far the eye could reach, there was nothing but rough, shaggy, red grass”

Willa Cather (My Antonia, 1918), novelist from Red Cloud NE

Patricio GrassiniResearch Assistant ProfessorUniversity of Nebraska-Lincoln

Water roundtable meetingOct 9, 2013

Water and stability2000-2009 average yields and coefficient of variation by county for maize and soybean in Nebraska (USDA-NASS)

Assured water supply greatly increases yield and reduces year-to- year variation in yield. Irrigated agriculture attracted investment in livestock feeding

operations, biofuel refineries, and manufacturing of irrigation equipment.

Grassini, unpublished

Grassini et al., In Press

Water-food nexus•We need water to produce high and stable grain yields•Appropriate metrics that account for both crop production and water use are needed in the discussion about water & agriculture. •Water Productivity (WP, kg grain per inch of water supply) provides a good framework for the discussion

Developing a WP benchmark for corn in NE

• Yields were simulated over 20-y for 18 locations in western Corn Belt using Hybrid-Maize model.• Crops assumed to grow

under optimal conditions (no nutrient deficiencies and no incidence of pests, diseases, weeds).•Model inputs based on

actual sowing date, plant population, weather, and soil properties at each of the 18 locations.

Gra

in y

ield

(bu

ac-1

)

0

50

100

150

200

250

0 5 10 15 20 25 30 35 40 45 50Seasonal water supply* (in)

Water productivity (WP) boundary (11 bu ac-in-1)

Mean WP function (8 bu ac-in-1)

Gra

in y

ield

(bu

ac-1

)

0

50

100

150

200

250

0 5 10 15 20 25 30 35 40 45 50Seasonal water supply* (in)

Water productivity (WP) boundary (11 bu ac-in-1)

Mean WP function (8 bu ac-in-1)

RainfedIrrigated

Grassini et al. (2009)

*Available soil water (0-5 ft) at planting + planting-to-maturity rainfall + applied irrigation

Validation of Mean Water Productivity Function

Crops grown with adequate nutrient supply and without loss from diseases, insect pests, and weeds

Gra

in y

ield

(bu

ac-1

)

WP boundaryslope = 11 bu ac-in-1

Mean WP function slope = 8 bu ac-in-1

North Platte, NE, 1996-2006 (Payeroet al., 2006, 2008).

0

50

100

150

200

250

0 10 20 30 40 50Seasonal water supply (in)

n = 123Mead, NE, 2001-2006. High intensive management (Suyker and Verma, 2009)

Progressive farmer fields in Eastern Nebraska, 2007-2008 (Burgert, 2009)

North Platte, NE, 1983-1991 (Hergertet al., 1993). North Platte and Clay Center, NE, 2005-2006 (Irmak and Yang, unpublished data).

Farmer field winner of National Corn Grower yield contest. Manchester, IA, 2002 (Yang et al., 2004).

RainfedSprinkler irrigationSubsurface drip irrigation

Gra

in y

ield

(bu

ac-1

)

WP boundaryslope = 11 bu ac-in-1

Mean WP function slope = 8 bu ac-in-1

North Platte, NE, 1996-2006 (Payeroet al., 2006, 2008).

0

50

100

150

200

250

0 10 20 30 40 50Seasonal water supply (in)

n = 123Mead, NE, 2001-2006. High intensive management (Suyker and Verma, 2009)

Progressive farmer fields in Eastern Nebraska, 2007-2008 (Burgert, 2009)

North Platte, NE, 1983-1991 (Hergertet al., 1993). North Platte and Clay Center, NE, 2005-2006 (Irmak and Yang, unpublished data).

Farmer field winner of National Corn Grower yield contest. Manchester, IA, 2002 (Yang et al., 2004).

RainfedSprinkler irrigationSubsurface drip irrigation

Grassini et al. (2011)

Framework to diagnose and identify options to improve water productivity in farmers’ fields

0

45

90

135

180

225

270

0 10 20 30 40 50

Seasonal water supply (in)

Gra

in y

ield

(bu

ac-1)

1) Higher yields, same water supply with better crop mgmt

2) Less water, same yield with improved irrigation mgmt

3) Higher yields with less irrigation water

Mean WP functionslope = 8 bu ac-in-1

WP boundaryslope =11 bu ac-in-1

160 bu/ac

225 bu/ac

33 in24 in

777 field-year observations from irrigated maize fields in central Nebraska (2005-2007)

Tri-Basin Natural Resources District

Each circle represents a producer field

Stars indicate weather stations ( ) or rain gauges ( )

CONTINUOUS

MAIZE (38%

)

SOYBEAN-

MAIZE (61%

)

CONTINUOUS

MAIZE (38%

)

SOYBEAN-

MAIZE (61%

)

STRIP

(10%)

NO-TILL(37%)

DISK(22%)RIDGE-

TILL(31%)

STRIP

(10%)

NO-TILL(37%)

DISK(22%)RIDGE-

TILL(31%)

Grassini et al. (2011)

Water productivity (WP) in the Tri-Basin NRD

Producer-reported yields in Tri-Basin NRD, 2005-2007. Each data point corresponds to an irrigated corn field.

Gra

in y

ield

(bu

ac-1)

0

40

80

120

160

200

240

280

0 5 10 15 20 25 30 35 40 45 50 55

Seasonal water supply (in)

WP boundary 11 bu ac-in-1

Mean-WP function slope = 8 bu ac-in-1

n = 777Maximum yields

~245 bu ac-1

Average farmer’s WP = 5.8 bu ac-in-1

Water requirement for maximum yield~ 36 in

120

160

200

240

280

15 25 35 45 55Seasonal water supply (in)

Gra

in y

ield

(bu

ac-1)

SURFACE

120

160

200

240

280

15 25 35 45 55

PIVOTn = 516

n = 261

WP = 6.0bu ac-in-1

WP = 5.3 bu ac-in-1

● Simulated yield under limited-irrigation management (75% of fully-irrigation except during the interval around silking when the crop was fully-irrigated)

■ Simulated yield under fully-irrigated conditions (irrigation based on ETO and phenology)

Opportunities to reduce applied irrigation water substantially without reducing productivity

Reported yield and actual water supply under pivot ( ) and gravity ( Δ ) irrigation systems.

128

160

192

224

256

288

16 24 32 40 48 56Seasonal water supply (in)

Gra

in y

ield

(bu

ac-1)

11 bu ac-in-18 bu ac-in-1

ActualPivot

ActualSurface

37,819 ac-ft yr-1

Optimalirrigation

20,639 ac-ft yr-1

Limitedirrigation

33,252 ac-ft yr-1

Total saving: 91,710 ac-ft y-1

(~32% of current water use in corn!)Energy saving equivalent to annualelectrical use of 4,300 houses in NE!

Large scope to save irrigation water, without hurting yield, through replacement of existing surface systems by pivots and fine tuning adjustment of irrigation schedule

Grassini et al. (2011)

Benchmarking yield and efficiency of corn & soybean cropping

systems in Nebraska

Patricio Grassini, Jessica A. Torrion, Kenneth G. Cassman, James E. Specht

Collaborators: Jenny Rees (UNL Extension Educator) & Daryl Andersen (Little Blue NRD)

Data on yield, N fertilizer rate, and irrigation water annually reported from 10,000+ fields since 2004

20 of 23 NRDs collaborating on this project

Nebraska Natural Resources Districts (NRD) data

On-farm data surveyData from 1030 dryland and irrigated fields in NE planted with corn and soybean in 2010, 2011, and 2012

Collected data include: field coordinates, yield, applied NPK fertilizer, lime and manure and time of application, irrigation, type of irrigation system, tillage system, crop rotation, planting date, crop

maturity, plant density, pesticide rates and time of application, incidence of diseases and insects.

Website:www.yieldgap.org

Thanks!

Questions?