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Nitrogen Fertilizer Rate in Corn:Factors to Consider
Jason [email protected]
South Dakota State University
Economic optimal N rates (EONR): How variable are they?
How variable is EONR across the U.S. Midwest over a 3-year period.
7 N rate studies in 2018
N fertilizer treatments created two N response curves
Nitrogen Treatments
Single Nitrogen Application
Split Nitrogen Application
––––––lbs.-N ac-1––––––
0 0
40 40+0
80 40+40
120 40+80
160 40+120
200 40+160
240 40+200
280 40+240
0
50
100
150
200
250
0 100 200 300 400
Gra
in Y
ield
(b
u. a
c-1)
Nitrogen Rate (lbs./acre)
Single N Single N Split N Split N
Split EONR=141
Single EONR=157
EONR varied from 0-280 lbs./ac
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay1
6
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
There was a wide range of EONRs within states among years
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay1
6
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
North Dakota Nebraska
Minnesota Iowa
What do I need to consider when deciding on my nitrogen fertilizer rate?
Nitrogen response data over 3-years at a total of 49 sites
Weather
Precipitation and temperature
Soil SamplingSoil characterization• Texture• Bulk density• Organic matter• Carbon• Total nitrogen• pH• CECSoil nitrate• Pre-plant (PPNT), 0-90 cm• V5 (PSNT), 0-60 cm
Mean annual temperature increases from 35 to 65oF
Precipitation increases from 14 to 52 in.
Soil textures varied across the 49 site-years
What do soil measurements tell me about N fertilizer rate?
Soil Texture’s influence on EONR
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay16
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
Tiled Irrigated
Coarse Medium Fine
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay16
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
\
Tiled Irrigated
0 - 2% 2 - 3.5% 3.5+ %
Soil Organic Matter’s influence on EONR
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay16
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
Crop rotation’s influence on EONRTiled Irrigated
Corn Sunflower Soybean
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd
15
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd1
6
Bo
on
e15
Am
enia
14
New
Ric
hla
nd
14
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay1
6
Was
eca1
6
Loes
s16
Bec
ker1
6
Bay
14
Urb
ana1
5
Tro
th16
Dar
lingt
on
15
Tro
th15
Bra
nd
es14
Bro
wn
sto
wn
14
Lon
eTre
e15
Bra
nd
es15
Eco
no
mic
Op
tim
al N
itro
gen
Rat
e (l
bs.
-N/a
c)
Site-years
Tillage’s influence on EONRTiled Irrigated
No-till Conventional tillage
Decomposition of Organic Materials Nitrogen Fertilizers
Organic-nitrogen
Inorganic-nitrogenNO3
- and NH4+
Inorganic-nitrogen
0
50
100
150
200
250
Du
rbin
14
Bec
ker1
6
Lon
eTre
e15
Tro
th15
Du
rbin
15
Bro
wn
sto
wn
14
Urb
ana1
4
Bo
on
e15
Am
enia
15
Loam
15
Mas
on
Cit
y14
Bro
wn
sto
wn
15
Bra
nd
es15
Bay
14
StC
har
les1
4
Am
enia
14
San
d15
Lew
is1
5
New
Ric
hla
nd
14
Bra
dfo
rd1
6
Tro
th16
Loam
16
Urb
ana1
6
Urb
ana1
5
Was
eca1
6
Tro
th14
Shu
mw
ay16
Loam
14
Cra
wfo
rd16
Sto
ry1
6
Am
es1
4
San
d14
Steu
ben
14
Bra
nd
es14
Loes
s16
Wau
zeka
14
Du
rbin
16
Dar
lingt
on
15
New
Ric
hla
nd
15
Lore
nzo
16
StC
har
les1
5
San
d16
Kye
s16
Am
enia
16
Bel
mo
nt1
5
Pla
no
16
SCA
L14
SCA
L16
SCA
L15
Gra
in Y
ield
, 0-N
(b
u/a
c)
Site-years
Grain yield with NO nitrogen applied
19 – 100% of N required by corn crop
CO2 evolution increases
NO3-
CO2
Time
Nit
roge
n A
vaila
bili
ty
Available N increases through N Mineralization
Available soil N decreases/immobilized
Decomposition of soil organic matter by microorganisms
Length of Times Varies by Residue
0
20
40
60
80
C:N
Rat
io
Time
Net Mineralization
Net Immobilization
Soybean C:N 33:1
Alfalfa C:N 13-25:1
Greater C:N increases time until net mineralization
Corn C:N- 57:1
Wheat C:N- 80:1
0
20
40
60
80
C:N
Rat
io
Time
Net Mineralization
Net Immobilization
Annual RyegrassC:N 21:1
Crimson CloverC:N 21:1
Greater C:N increases time until net mineralization
Rye C:N-82:1 Straw37:1 Anthesis26:1 Veg.
Hairy Vetch C:N- 11:1
Oilseed RadishC:N 20:1
Soybean residue decomposes and mineralizes N faster than corn residue
(Adapted from Li et al., 2013)Incubation time (days)
40
30
20
10Min
era
l N (
ug
N g
-1so
il)
0
10 20 30 40 50 60
Soybean Residue
Corn Residue
More N is mineralized after soybean than corn
(Gentry et al., 2001)1998 1999
Cu
mu
lati
ve m
iner
aliz
atio
n (
kg N
ha
-1)
Soybean Residue
Corn Residue
Oct Dec Feb Apr Jun Aug Oct
120
100
80
60
40
20
0
Tillage and crop rotation influences N fertilizer needs
Labor and fuel costs
Weed Control
Compaction
Soil temperature, moisture, and structure
Residue Incorporation
Nitrogen availability
Tillage affects soil characteristics and erosion
Fall
Spring
In-crop
Control
0 lbs. N/ac
50 lbs. N/ac
100 lbs. N/ac
200 lbs. N/ac
Herbicide Timing
Nitrogen Rate
FallConv
Sp.Conv
FallStrip
Sp.Strip
No-till
Tillage type and timing
Study designed to compare tillage, herbicide, and nitrogen treatments
Results
Fall and Spring Strip-till + Control and No-till + Control
No additional nitrogen was needed when herbicides were used to control alfalfa
0
5
10
15
20
25
30
35
0 50 100 150 200
Sila
ge Y
ield
(to
ns/
ac)
Nitrogen Rate (lbs. ac-1)
FCT-FSCT-FFST-FSST-FNT-FFCT-SPSCT-SPFST-SPSST-SPNT-SPFCT-ICSCT-ICFST-ICSST-ICNT-ICFCT-CSCT-CFST-CSST-CNT-C
Decomposition of Organic Materials Nitrogen Fertilizers
Organic-nitrogen
Inorganic-nitrogenNO3
- and NH4+
Inorganic-nitrogen
Can we estimate nitrogen mineralization to adjust N fertilizer guidelines?
Anaerobic Potentially Mineralizable Nitrogen Test(PMNan)
What’s the best PMNan protocol to predict EONR?• Soil sampling timing: Pre-plant and V5 (5 horizontal leaves)• Nitrogen Rate: 0 and 180 kg ha-1 (V5 sampling time)• Incubation length: 7, 14, 28 days
Sampling timing and N fertilizer addition altered PMNan in some sites.
50
23 27
63
31
6
0
20
40
60
80
100P
P =
V5
PP
> V
5
PP
< V
5
0-N
= 1
80
-N
0-N
> 1
80
-N
0-N
< 1
80
-N
Perc
en
t o
f Si
tes
Statistical Groups
PP vs. V5 0-N vs. 180-N
Questions• Q-1) Will changes in PMNan due to sampling
timing, N rate, and incubation length improve predictability of EONR?
• Q-2) Can using PMNan values in conjunction with other soil-N tests improve corn response predictions?
PMNanSI: 0-171SP: 0-147
SI: 80-165SP: 95-169
SI: 126-213SP: 104-253
SI: 0-238SP: 0-155
SI: 183-273SP: 110-134
SI: 146-315SP: 158-315
SI: 96-198SP: 106-171
SI: 23-315SP: 24-182
EONR
=
52-240
65-125
101-230
172-226
58-143
97-143
72-92
76-197
?
y = -1.15x + 189.51R² = 0.07
0
50
100
150
200
250
300
0 10 20 30 40 50 60 70 80 90
EON
R (
lbs.
-N/a
c)
Pre-Plant PMNan (ppm)
Pre-plant N mineralization does not predict EONR well
y = -0.05x + 149.98R² = < 0.01
0
50
100
150
200
250
300
0 20 40 60 80 100 120
EON
R (
lbs.
-N/a
c)
V5 PMNan @ 0-N (ppm)
V5 N mineralization WITHOUT Ndoes not predict EONR well
y = -0.33x + 182.33R² = 0.01
0
50
100
150
200
250
300
0 50 100 150 200 250
EON
R (
lbs.
-N/a
c)
V5 PMNan @ 160-N (ppm)
V5 N mineralization WITH Ndoes not predict EONR well
Delayed sampling and increased incubation length do not improve predictability of EONR
0.07 0.050.08
< 0.01 < 0.01
0.07
0.01 0.01 < 0.010
0.1
0.2
0.3
0.4
0.5
7-d 14-d 28-d 7-d 14-d 28-d 7-d 14-d 28-d
Pre-Plant V5-0N V5-180N
R-s
qu
are
Soil Sampling and Incubation Length
V5-160N
Soil inorganic N + Mineralization
Predicting grain yield at 0-N, grain yield at EONR, and EONR with:
• Soil nitrate (PPNT and PSNT)
• Soil nitrate + mineralizable N (PMNan)
• Soil nitrate + PMNan + initial NH4+
Q-2) Can using PMNan values in conjunctionwith other soil-N tests improve cornresponse predictions?
PPNT is not well related to grain yield at 0-N.
y = 0.48x + 4.84R² = 0.18
0
2
4
6
8
10
12
14
16
0 5 10 15 20
Gra
in Y
ield
at
0-N
(M
g h
a-1)
PPNT (mg kg-1)
PSNT improves relationship with grain yield at 0-N.
y = 0.41x + 4.24R² = 0.39
0
2
4
6
8
10
12
14
16
0 5 10 15 20 25 30
Gra
in Y
ield
at
0-N
(M
g h
a-1)
PSNT (mg kg-1)
PPNT: R2 = 0.18
Including soil NO3-, PMNan, and NH4
+
improves predictability of grain yield at 0-N.
0.18
0.39
0.15
0.37
0.22
0.44
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
PPNT PSNT
R-s
qu
are
Soil N Sampling Timing
Soil-N Soil-N+PMNan Soil-N+PMNan+NH4+
Soil textures varied across the 49 site-years
Coarse
Medium
Fine
Mean annual temperature increases from 35 to 65oF
LOW
High
Texture or temperature categories improved predictability of grain yield at 0-N
00.10.20.30.40.50.60.70.80.9
1
Coarse Medium Fine High Low
Texture Temperature
R-s
qu
are
Texture and Temperature Categories
'PSNT+PP0N+NH4 'PSNT+V50N+NH4 'PSNT+V5160N+NH4
Adding N lowers the ability to predict grain yield.
< 0.01 0.010.09 0.13
0.20.25
00.10.20.30.40.50.60.70.80.9
1
PPNT PSNT
R-s
qu
are
Soil N Sampling Timing
Grain Yield at EONR
Soil-N Soil-N+PMNan Soil-N+PMNan+NH4
0.22
0.44
00.10.20.30.40.50.60.70.80.9
1
Coarse Medium Fine High Low
Texture Temperature
R-s
qu
are
Texture and Temperature Categories
Grain Yield at EONR
'PSNT+PP0N+NH4 'PSNT+V50N+NH4 'PSNT+V5160N+NH4
Texture or temperature categories improvedpredictability of grain yield at EONR
PPNT and PSNT alone best predicts EONR
0.140.18
0.1 0.120.1 0.12
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
PPNT PSNT
R-s
qu
are
Soil N Sampling Timing
Soil-N Soil-N+PMNan Soil-N+PMNan+NH4
0.22
0.44
Texture or temperature categories improved predictability of EONR
00.10.20.30.40.50.60.70.80.9
1
Coarse Medium Fine High Low
Texture Temperature
R-s
qu
are
Texture and Temperature Categories
'PSNT 'PSNT+PP0N 'PSNT+PP0N+NH4
'PSNT+V50N+NH4 'PSNT+V5180N+NH4
No increase in the predictability of EONR by:• Increasing incubation length• Delaying soil sampling• N fertilizer addition
Conclusions
Predictability of Grain yield and EONR increases:
• Delaying soil-N sampling from PPNT to PSNT
• Separating by soil texture and temperature• Including PMNan and initial NH4
+
• PMNan used varies by texture or temperature categories
What do I need to consider when deciding on my nitrogen fertilizer rate?
• Crop rotation
• Soil organic matter
• Soil texture
• Nitrogen carryover
• Tillage practices
• Cover crop use
• Temperature
• Precipitation
• Topography
0
50
100
150
200
250
300
Bel
mo
nt1
5
Am
enia
16
Du
rbin
16
SCA
L15
SCA
L16
Lore
nzo
16
Cra
wfo
rd16
SCA
L14
New
Ric
hla
nd1
5
Du
rbin
15
Steu
ben
14
Pla
no
16
Loam
15
Lew
is1
5
San
d16
Wau
zeka
14
Bro
wn
sto
wn
15
StC
har
les1
4
Loam
14
Mas
on
Cit
y14
Am
es1
4
Loam
16
Bra
dfo
rd16
Bo
on
e15
Am
enia
14
New
Ric
hla
nd1
4
Du
rbin
14
Kye
s16
Sto
ry1
6
San
d14
Am
enia
15
StC
har
les1
5
Urb
ana1
6
San
d15
Tro
th14
Urb
ana1
4
Shu
mw
ay16
Was
eca1
6
Loes
s16
Bec
ker1
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Bra
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Site-years
South Dakota State University310 Berg Agricultural Hall (SAG), Box 2207ABrookings, SD 57007
605-688-4395
iGrow.org
Jason Clark
