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Regional Nitrogen Rate Guidelines. John Sawyer Department of Agronomy Iowa State University. Regional Effort - Participating States and University Personnel: John Sawyer, Iowa State University Emerson Nafziger, University of Illinois Gyles Randall, University of Minnesota - PowerPoint PPT Presentation
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Regional Nitrogen Rate Guidelines
John Sawyer
Department of Agronomy
Iowa State University
Regional Effort - Participating States and University Personnel: John Sawyer, Iowa State University Emerson Nafziger, University of Illinois Gyles Randall, University of Minnesota George Rehm, University of Minnesota Larry Bundy, University of Wisconsin Brad Joern, Purdue, University Robert Hoeft, University of Illinois Carrie Laboski, University of Wisconsin Robert Mullen, The Ohio State University Randy Killorn, Iowa State University Sylvie Brouder, Purdue University
Exploring a Regional Approach to N Rate Guidelines
Diverse N rate recommendation systems across states
Lack of optimum N rate relationship with corn yield
Concerns about N rates with corn yields at record levels
Historically high N fertilizer prices
Historic Nitrogen:Corn Price Ratios
U.S. Average Ammonia N Price - Iowa Corn Grain Price
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
1960 1970 1980 1990 2000
Year
Pri
ce R
atio
, $/l
b N
:$/b
u
N:Corn Price Ratio
Corn Yields and N Rates
0
50
100
150
200
250
0 100 200 300Optimum Yield, bu/acre
Op
tim
um
N R
ate,
lb
N/a
cre
Six State SC - 389 Trials
0.10 Price Ratio$0.22/lb N:$2.20/bu
0
50
100
150
200
250
0 100 200 300Optimum Yield, bu/acre
Op
tim
um
N R
ate,
lb
N/a
cre
Six State SC - 389 Trials
0.10 Price Ratio$0.22/lb N:$2.20/bu
Methods for Analyzing N Response Data43 Corn Following Soybean Sites in Iowa ($0.22/lb N:$2.20/bu)
43 Sites 35 Responsive Sites
Method N Rate
Net Return N Rate
Net Return
lb N/acre $/acre lb N/acre $/acre
Mean of EONRs 79 49 97 67
EONR - Mean Yield 104 53 108 69
Maximum RTN 105 51 113 68
Discrete Mar. Prod. 108 51 111 68
Site Optimum 79 60 97 73
Measured Yield† 174 40 177 58
Yield History† 140 47 140 65† 1.2 lb N/bu factor, 50 lb soybean rotation “credit”
Maximum Return To N (MRTN) Database Driven Approach
Previously described by Nafziger, Sawyer, and Hoeft (2004); and Sawyer and Nafziger (2005) Accumulate corn N response data from many
recent trials Determine economic response and most
profitable N rates directly from trials in N response database
Data → N Rate Guidelines
N Response Trial Database
3 to 4 replications 5 to 7 N rates – spring and sidedress Non-irrigated High and very high yield potential soils Experiment station or producer field Corn following Soybean (SC)
and Corn following Corn (CC) Grain yield measured for each N rate N Response curve fit to each trial
698 Trials> 95% since 1990> 60% since 2000
Calculation of MRTN 1st - Compile database from corn yield N
response trials for desired rotationExample of a Few Site N Response Trials with SC
50
100
150
200
250
0 50 100 150 200
N Rate, lb N/acre
Co
rn Y
ield
, b
u/a
cre
Clay 03
Boone-SN 02
Harrison 03
Johnson 03
Calculation of MRTN
2nd – For each trial in database calculate Return To N (RTN) using the a, b, c and plateau values from each response curve For every 1 lb N/acre from 0 through 240
lb N/acre calculate the yield increase over the yield obtained with zero lb N/acre
RTN = yield increase times price of corn minus the cost of N
Calculation of MRTNClay 2001 Site -- SC
40
60
80
100
120
140
160
180
200
0 40 80 120 160 200
Nitrogen Rate, lb N/acre
Co
rn Y
ield
, bu
/acr
e
Grain Yield
Response
EONR = 138 lb N/acre
Yield = 117.7 + 0.8219N - 0.00263N2
a b c
Yield Plateau
Clay 2001 Site -- SC
40
60
80
100
120
140
160
180
200
0 40 80 120 160 200
Nitrogen Rate, lb N/acre
Co
rn Y
ield
, bu
/acr
e
Grain Yield
Response
EONR = 138 lb N/acre
Yield = 117.7 + 0.8219N - 0.00263N2
a b c
Yield Plateau
Clay 2001 Site -- SC
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250N Rate, lb N/acre
$/ac
re
Yield Return to NNet Return to NFertilizer Cost
Calculation of MRTN
3rd - Find the N rate with the greatest average return to N, this is the MRTN and N rate at the MRTN
Return to N at various N rates (lb/acre)Site
71.05
107.01
77.09
85.78
106.56
140
72.0372.4472.9872.5972.0069.24Average
79.2981.3182.3782.3781.3179.203
87.9889.3282.9476.5670.1863.802
108.76110.96113.16115.10115.43113.961
107.25
130
104.96
$/acre
110
102.43
100
106.5798.9894.6092
1209080
Return to N at various N rates (lb/acre)Site
71.05
107.01
77.09
85.78
106.56
140
72.0372.4472.9872.5972.0069.24Average
79.2981.3182.3782.3781.3179.203
87.9889.3282.9476.5670.1863.802
108.76110.96113.16115.10115.43113.961
107.25
130
104.96
$/acre
110
102.43
100
106.5798.9894.6092
1209080
MRTN
Calculation of MRTN
4th - Find the N rates with returns to N within $1.00/acre of MRTN This provides a range of most profitable N rates
Return to N at various N rates (lb/acre)Site
71.05
107.01
77.09
85.78
106.56
140
72.0372.4472.9872.5972.0069.24Average
79.2981.3182.3782.3781.3179.203
87.9889.3282.9476.5670.1863.802
108.76110.96113.16115.10115.43113.961
107.25
130
104.96
$/acre
110
102.43
100
106.5798.9894.6092
1209080
Return to N at various N rates (lb/acre)Site
71.05
107.01
77.09
85.78
106.56
140
72.0372.4472.9872.5972.0069.24Average
79.2981.3182.3782.3781.3179.203
87.9889.3282.9476.5670.1863.802
108.76110.96113.16115.10115.43113.961
107.25
130
104.96
$/acre
110
102.43
100
106.5798.9894.6092
1209080
MRTN
LOW HIGH
Can Examine Different Fertilizer N and Corn Prices
Corn held at $2.20/bu Fertilizer N prices at $0.11, $0.22,
$0.33, and $0.44/lb N Gives N price:corn price ratios of
0.05, 0.10, 0.15, and 0.20
Effect of Price Ratio on Net ReturnIowa - SC
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250
N Rate, lb N/acre
Ret
urn
to
N,
$/ac
re
0.050.100.150.20 HIGH
MRTNLOW
$2.20/bu
$0.11/lb N
$0.22
$0.33
$0.44
Effect of Price Ratio on Net ReturnIowa - CC
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250
N Rate, lb N/acre
Ret
urn
to
N,
$/ac
re
0.050.100.150.20
Example N Rate Guidelines Based On MRTN Approach - Iowa
Previous Crop
Price Ratio
Soybean Corn
LOW† MRTN HIGH† LOW† MRTN HIGH†
$/lb:$/bu - - - - - - - - - - - - - lb N/acre - - - - - - - - - - - - -
0.05 125 145 170 180 200 230
0.10 105 125 145 155 175 195
0.15 90 110 125 140 155 170
0.20 80 95 110 125 140 155
† LOW and HIGH rates approximate the most profitable range for $1.00/acre below and above the MRTN for each price ratio.
Effect of Price Ratio on Expected Corn Yield
Iowa - CC
0
20
40
60
80
100
0 50 100 150 200 250
N Rate, lb N/acre
Per
cen
t o
f M
axim
um
Yie
ld 0.050.100.150.20
IA - SC
0
20
40
60
80
100
0 50 100 150 200 250
N Rate, lb N/acre
Per
cen
t o
f M
axim
um
Yie
ld 0.050.100.150.20
Iowa SC Dataset, 0.10 Price Ratio
-100
-80
-60
-40
-20
0
20
40
60
80
100
0 50 100 150 200 250
N Rate, lb N/acre
$/ac
re o
r %
Fre
qu
ency
Site Frequency of EONR's > N Rate
Net Loss for Sites with EONR's > N Rate
Site Frequency of EONR's < N Rate
Net Loss for Sites with EONR's < N Rate
Advantages of MRTN Approach Can use a variety of N response trials Uses yield response rather than yield Specific responses of each site considered Easy to add new trial data Not excessively influenced by non-
responsive sites Straightforward calculations and uses
economic outcome Can create dataset sub-groups Can evaluate risk assessment Can include environmental costs
Corn Nitrogen Rate Calculatorhttp://extension.agron.iastate.edu/soilfertility/nrate.aspx
Resources for Regional Approach
Regional publication
Web based MRTN calculation tool
Concepts and Rationale for Regional Nitrogen
Rate Guidelines for Corn
Economic Return at N Rates Above and Below Each Site Optimum
N Cost: 0.33 $/lb N Ratio: 0.15Corn Price: 2.20 $/bu
121 Iowa - SC Sites
-40
-30
-20
-10
0
10
20
-50 -40 -30 -20 -10 0 10 20 30 40 50
lb N/acre Above or Below Each Site-Year Optimum
$/ac
re Yield
Fertilizer
Net
