In-Season Nitrogen Fertilization Based on Sensor-Estimated Potential Yield
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In-Season Nitrogen Fertilization Based on Sensor-Estimated
Potential Yield
In-Season Nitrogen Fertilization Based on Sensor-Estimated
Potential Yield
E.V. Lukina, K.W. Freeman,K.J. Wynn, W.E. Thomason, G.V. Johnson,
M.L. Stone, J.B. Solie, W.R. Raun
E.V. Lukina, K.W. Freeman,K.J. Wynn, W.E. Thomason, G.V. Johnson,
M.L. Stone, J.B. Solie, W.R. Raun
Oklahoma State UniversityOklahoma State UniversityDepartment of Plant and Soil SciencesDepartment of Plant and Soil Sciences
Introduction Introduction
Low nitrogen use efficiency for cereal production (33%) In-season reflectance readings from wheat at high
resolutions (1m2) have been shown to be highly correlated with biomass
Our present focus has been to apply N rates to each 1m2 area based on predicted potential yield Potential grain yield: yield predicted for a given year and
site, based on the assumption that the level of growth factors responsible for early stages of development of the crop will be maintained (limitations that existed at early stages of growth will continue to similarly influence development to maturity, e.g., N deficiency)
Low nitrogen use efficiency for cereal production (33%) In-season reflectance readings from wheat at high
resolutions (1m2) have been shown to be highly correlated with biomass
Our present focus has been to apply N rates to each 1m2 area based on predicted potential yield Potential grain yield: yield predicted for a given year and
site, based on the assumption that the level of growth factors responsible for early stages of development of the crop will be maintained (limitations that existed at early stages of growth will continue to similarly influence development to maturity, e.g., N deficiency)
ObjectiveObjective
To investigate the potential for N fertilization using in-season estimates of potential yield for every 1m2 based on plant reflectance readings
To investigate the potential for N fertilization using in-season estimates of potential yield for every 1m2 based on plant reflectance readings
Materials and MethodsMaterials and Methods
Winter wheat Coker, Custer, and 7853 Experimental design
Randomized complete block Four replications 4m x 7m plots 1m2 subplots for variable rate treatments
Spectral reflectance readings at 671nm (red) and 780nm (near infrared) taken at Feekes physiological growth stages 4 and 5
Winter wheat Coker, Custer, and 7853 Experimental design
Randomized complete block Four replications 4m x 7m plots 1m2 subplots for variable rate treatments
Spectral reflectance readings at 671nm (red) and 780nm (near infrared) taken at Feekes physiological growth stages 4 and 5
Optical sensor developed by OSUOptical sensor developed by OSU
Materials and MethodsMaterials and Methods
NDVI (Normalized Difference Vegetation Index) calculated for each subplot (1m2) by the equation (NIR-Red)/(NIR+Red)
For two of the treatments, N rates were determined based on tissue N need at F4 and F5, respectively
For the yield potential treatment, N rates were determined based on EY (estimated yield) index:
EY=(NDVIF4+NDVIF5)/GDDGDD=(Tmin+Tmax)/2- 4.4 °C
NDVI (Normalized Difference Vegetation Index) calculated for each subplot (1m2) by the equation (NIR-Red)/(NIR+Red)
For two of the treatments, N rates were determined based on tissue N need at F4 and F5, respectively
For the yield potential treatment, N rates were determined based on EY (estimated yield) index:
EY=(NDVIF4+NDVIF5)/GDDGDD=(Tmin+Tmax)/2- 4.4 °C
Materials and MethodsMaterials and Methods
Ammonium nitrate applied after sensing in early March (March 6-13)
Plots harvested by treatment (4m x 7m) in mid June
Grain weight and percent moisture automatically recorded
Total N in grain samples analyzed by dry combustion (Schepers et al., 1989)
Ammonium nitrate applied after sensing in early March (March 6-13)
Plots harvested by treatment (4m x 7m) in mid June
Grain weight and percent moisture automatically recorded
Total N in grain samples analyzed by dry combustion (Schepers et al., 1989)
Spatial variabilitySpatial variability
0.24
0.28
0.32
0.36
0.40
0.44
0.48
0.52
0.56
0.60
0.64
0.68
0.72
0.76
0.80Covington Feekes5 NDVI Contour MapCovington Feekes5 NDVI Contour Map
ResultsResults
Due to weed problems and high soil test N, one field experiment in 1998-99 did not respond to N fertilizer
Grain yield and N fertilizer requirement were highly correlated with yield potential-based N fertilization for both years at both locations.
Grain yield, N uptake and NUE were increased using EY compared to fixed rates in 1999, while the next year results were not consistent with the first year of study.
Due to weed problems and high soil test N, one field experiment in 1998-99 did not respond to N fertilizer
Grain yield and N fertilizer requirement were highly correlated with yield potential-based N fertilization for both years at both locations.
Grain yield, N uptake and NUE were increased using EY compared to fixed rates in 1999, while the next year results were not consistent with the first year of study.
ResultsResults
The highest grain yield and N uptake during the second year of experiment was obtained on the plots with fixed N rate of 90 kg N per ha.
The highest NUE’s were observed on the yield potential-based N fertilization plots at Morrison location, and 45 kg of N per ha (fixed rate) at Covington.
The highest grain yield and N uptake during the second year of experiment was obtained on the plots with fixed N rate of 90 kg N per ha.
The highest NUE’s were observed on the yield potential-based N fertilization plots at Morrison location, and 45 kg of N per ha (fixed rate) at Covington.
Grain yield response to N rates,Covington, 1999
Grain yield response to N rates,Covington, 1999
Yield response to fixed N rates
y = 0.1074x2 - 1.5561x + 1122.6
R2 = 0.2773
0
1000
2000
3000
0 20 40 60 80 100
N Rate (kg/ha)
Gra
in Y
ield
(kg
/ha
)
Yield response to fixed N rates
y = 0.1074x2 - 1.5561x + 1122.6
R2 = 0.2773
0
1000
2000
3000
0 20 40 60 80 100
N Rate (kg/ha)
Gra
in Y
ield
(kg
/ha
)
Yield response to YP-based N rates
y = -1.7659x2 + 343.3x - 13177
R2 = 0.9576
0
1000
2000
3000
4000
50 60 70 80 90 100 110
N Rate (kg/ha)G
rain
Yie
ld (
kg
/ha
)
Yield response to YP-based N rates
y = -1.7659x2 + 343.3x - 13177
R2 = 0.9576
0
1000
2000
3000
4000
50 60 70 80 90 100 110
N Rate (kg/ha)G
rain
Yie
ld (
kg
/ha
)
Grain yield response to N rates,Covington, 2000
Grain yield response to N rates,Covington, 2000
Yield response to fixed N rates
y = -0.2082x2 + 33.03x + 1406.5R2 = 0.851
1000
2000
3000
4000
5000
0 20 40 60 80 100
N Rate (kg/ha)
Gra
in Y
ield
(kg
/ha
)
Yield response to YP-based N rates
y = 2.5076x2 - 154.99x + 3837.8
R2 = 0.9996
1000
2000
3000
4000
5000
30 40 50 60
N Rates (kg/ha)G
rain
Yile
d (k
g/ha
)
Grain yield response to N rates,Morrison, 2000
Grain yield response to N rates,Morrison, 2000
Yield response to fixed N rates
y = -0.0354x2 + 14.323x + 2926.9R2 = 0.5245
1000
2000
3000
4000
5000
0 20 40 60 80 100
N Rate (kg/ha)
Gra
in Y
ield
(kg
/ha
)
Yield response to YP-based N rates
y = 40.824x2 - 1928.1x + 26061R2 = 0.7514
1000
2000
3000
4000
5000
20 22 24 26 28 30
N Rate (kg/ha)
Gra
in Y
ield
(kg
/ha
)
N fertilizer requirement as influenced by N rates, Covington, 1999
N fertilizer requirement as influenced by N rates, Covington, 1999
N requirement vs YP-based N rates
y = 0.0277x2 - 4.878x + 239.07
R2 = 0.8416
0
10
20
30
40
50
50 60 70 80 90 100 110N Rate (kg/ha)
kg
of N
/ to
n o
f w
he
at
N requirement vs YP-based N rates
y = 0.0277x2 - 4.878x + 239.07
R2 = 0.8416
0
10
20
30
40
50
50 60 70 80 90 100 110N Rate (kg/ha)
kg
of N
/ to
n o
f w
he
at
N requirement vs fixed N rates
y = -0.0043x2 + 0.9904x - 1E-13
R2 = 0.8009
0
20
40
60
80
100
0 50 100
N Rate (kg/ha)
kg
of N
/ to
n o
f w
he
at
N requirement vs fixed N rates
y = -0.0043x2 + 0.9904x - 1E-13
R2 = 0.8009
0
20
40
60
80
100
0 50 100
N Rate (kg/ha)
kg
of N
/ to
n o
f w
he
at
N fertilizer requirement as influenced by N rates, Covington, 2000
N fertilizer requirement as influenced by N rates, Covington, 2000
N requirem ent vs fixed N rates
y = -0.0008x2 + 0.4429x - 6E-14R2 = 0.9807
0
10
20
30
40
50
0 20 40 60 80 100
N Rate (kg/ha)
kg o
f N /
ton
of w
heat
N requirem ent vs YP-based N rates
y = -0.0257x2 + 2.0346x - 16.27R2 = 0.9993
20
21
22
23
24
25
30 35 40 45 50 55N Rate (kg/ha)
kg o
f N/ t
on o
f whe
at
N fertilizer requirement as influenced by N rates, Morrison, 2000
N fertilizer requirement as influenced by N rates, Morrison, 2000
N requirement vs fixed N rates
y = -0.0008x2 + 0.3252x - 5E-14R2 = 0.9894
0
5
10
15
20
25
30
0 20 40 60 80 100
N Rate (kg/ha)
kg o
f N /
ton
of w
he
at
N requirement vs YP-based N rates
y = -0.0688x2 + 3.4837x - 36.652R2 = 0.2325
0
2
4
6
8
10
20 22.5 25 27.5 30
N Rate (kg/ha)
kg o
f N /
ton
of w
he
at
Grain yield response to TreatmentGrain yield response to Treatment
Grain Yield & N Rate vs TreatmentCovington, 1999
0500
10001500200025003000
45 90 YP F4 F5
Treatment
Gra
in Y
ield
(k
g/h
a)
0
20
40
60
80
100
N r
ate
ap
plie
d
(kg
/ha
)
Grain Yield
N Rate
Grain yield response to TreatmentGrain yield response to Treatment
Grain Yield & N Rate vs TreatmentCovington, 2000
0
1000
2000
3000
4000
5000
0 45 90 YP1 YP2 F5
Treatment
Gra
in Y
ield
(k
g/ha
)
0
20
40
60
80
100
N ra
te a
pplie
d (k
g/ha
)
Grain Yield
N Rate
Grain Yield & N Rate vs TreatmentMorrison, 2000
0
1000
2000
3000
4000
5000
0 45 90 YP1 YP2 F5
TreatmentG
rain
Yie
ld
(kg/
ha)
0
20
40
60
80
100
N r
ate
appl
ied
(kg/
ha)
Grain Yield
N Rate
YP1 (based on 98, 99, 00 forage N uptake data)YP2 (based on 00 N uptake data only)YP1 (based on 98, 99, 00 forage N uptake data)YP2 (based on 00 N uptake data only)
N uptake response to TreatmentN uptake response to Treatment
N uptake & N Rate vs TreatmentCovington, 1999
0
10
20
30
40
50
60
45 90 YP F4 F5
Treatment
Tot
al N
upt
ake
by
grai
n (k
g/ha
)
0
20
40
60
80
100
N r
ate
appl
ied
(kg/
ha)
N uptake
N Rate
N uptake response to TreatmentN uptake response to Treatment
N uptake & N Rate vs TreatmentCovington, 2000
0
10
20
30
40
50
0 45 90 YP1 YP2 F5
Treatment
To
tal N
up
tak
e
by
gra
in (
kg
/ha
)
0
20
40
60
80
100
N r
ate
ap
plie
d
(kg
/ha
)
N uptake
N Rate
N uptake & N Rate vs TreatmentMorrison, 2000
0
20
40
60
80
100
0 45 90 YP1 YP2 F5
TreatmentT
ota
l N u
pta
ke
b
y g
rain
(k
g/h
a)
0
20
40
60
80
100
N r
ate
ap
plie
d
(kg
/ha
)
N uptake
N Rate
NUE response to TreatmentNUE response to Treatment
NUE & N Rate vs TreatmentCovington, 1999
0
10
20
30
40
50
45 90 YP F4 F5
Treatment
NU
E
0
20
40
60
80
100
N r
ate
ap
plie
d
(kg
/ha
)
NUE
N Rate
NUE response to TreatmentNUE response to Treatment
NUE & N Rate vs TreatmentCovington, 2000
0
10
20
30
40
45 90 YP1 YP2 F5
Treatment
NU
E
0
20
40
60
80
100
N r
ate
ap
pli
ed
(kg
/ha
)
NUE
N Rate
NUE & N Rate vs TreatmentMorrison, 2000
0
20
4060
80
100
120
45 90 YP1 YP2 F5
Treatment
NU
E
0
20
40
60
80
100
N r
ate
ap
pli
ed
(kg
/ha
)
NUE
N Rate
ConclusionConclusion
EY may be used as a predictor of potential yield and for adjustment of in-season N fertilization rates
Yield potential-based in-season N fertilization may increase grain yield, N uptake and NUE
EY may be used as a predictor of potential yield and for adjustment of in-season N fertilization rates
Yield potential-based in-season N fertilization may increase grain yield, N uptake and NUE
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