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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Grassini, unpublished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
(b
uac
-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
(b
uac
-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)
Rainfed
Irrigated
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
(b
uac
-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 50
Seasonal 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).
Rainfed
Sprinkler irrigationSubsurface drip irrigation
Gra
in y
ield
(b
uac
-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 50
Seasonal 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).
Rainfed
Sprinkler 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
(b
u a
c-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 ( )
CO
NTIN
UO
US
MA
IZE (38%
)
SO
YB
EA
N-
MA
IZE (61%
)
CO
NTIN
UO
US
MA
IZE (38%
)
SO
YB
EA
N-
MA
IZE (61%
)
STR
IP
(10%)
NO-TILL(37%)
DISK(22%)RIDGE-
TILL(31%)
STR
IP
(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
(b
u a
c-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 55
Seasonal water supply (in)
Gra
in y
ield
(b
u a
c-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 56
Seasonal water supply (in)
Gra
in y
ield
(b
u a
c-1)
11 bu ac-in-1
8 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 annual
electrical 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 survey
Data 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.
Thanks!
Questions?