What New Equipment Is Available to Improve N-Use Efficiency?

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The Mystery of the Nitrogen Treasure and the
Capricious Wheat
by C. S. Lewis a.k.a Booner SU
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N Treasure Mysteries

• N was applied in known amounts but only 33 was
  recovered in the grain
• N Rates seem to vary from one year to the next in
  the same Field. Why?
• Can N Rates be Adjusted based on Predicted Yield?
• Can the Responsiveness to N be Predicted?
• Is there a better method to unlock the mystery of
  the N treasure?

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Plant Uptake
pH gt7.0gt50F
gt50FMoisture Stress
Volatilization
Plant Loss
gt50Fanaerobic
N Treasure
Immobilization
Denitrification
lt50F
Leaching
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Thief 1 Ammonia Volatilization
Influenced by Soil pHTemperatureUrease
ActivityApplication MethodCEC
Denitrification LeachingLeaching VolatilizationN
itrification Nitrification Leaching Leaching
50F
If pH and temperature can be kept low, little
risk exists for the loss of N as ammonia (urea or
anhydrous N sources)
pH 7.0
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Thief 2 Nitrate Leaching

• Usually takes place in the winter
• Excess N applied in-season that is not used
• Temperatures below 50F (microbial pools not
  active)

Denitrification LeachingLeaching VolatilizationN
itrification Nitrification Leaching Leaching
50F
pH 7.0
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Thief 3, Denitrification
Burford and Bremner, 1975
Denitrification LeachingLeaching VolatilizationN
itrification Nitrification Leaching Leaching
50F
pH 7.0
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Thief 3, Denitrification
Aulakh, Rennie and Paul, 1984
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406
0.1
0.9
0.09
0.8
0.08
0.7
Total Soil N,
0.07
Organic Carbon,
0.6
0.06
TSN
SED TSN 0.002
0.5
0.05
SED OC 0.03
OC
0.04
0.4
0
40
80
120
160
200
N Rate, kg/ha
Raun, W.R., G.V. Johnson, S.B. Phillips and R.L.
Westerman. 1998. Effect of long-term nitrogen
fertilization on soil organic C and total N in
continuous wheat under conventional tillage in
Oklahoma. Soil Tillage Res. 47323-330.
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Thief 4, Plant N Loss
photosynthesis
carbohydrates
respiration
carbon skeletons
reducing power
NADH or NADPH
amino
NH
NO
NO
3
acids
2
3
nitrite
nitrate
reductase
reductase
ferredoxin
siroheme
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Thief 4, Plant N Loss
Total N uptake in winter wheat with time and
estimated loss following flowering.
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Lees, H.L., W.R. Raun and G.V. Johnson. 2000.
Increased plant N loss with increasing nitrogen
applied in winter wheat observed with 15N. J.
Plant Nutr. 23219-230.
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REPRODUCTIVE
VEGETATIVE
R-NH2
R-NH2 NO3 NH4
Total N
moistureheat
Total N
NH3
amino
NH
NO
NO
3
acids
2
3
nitrate reductase
nitrite reductase
NO3- 2e (nitrate reductase) NO2- 6e (nitrite
reductase) NH4
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100
Time of N Applied
Fall
90
Split
Forage ProductionSystems AvoidPlant N Loss
Spring
80
N use efficiency,
70
60
50
50
75
100
150
200
N Rate, lb/acre
Estimated fertilizer N use efficiency as affected
by N rate and time of application, Burneyville,
OK, 1979-1992 (Altom et al., 1996)
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Nitrogen TreasureWhere did all the Nitrogen
Go? Magruder Plots 1892 4.0 organic matter
0.35 1.8 OCOC 2.03TN 0.16Pb 1.623
(0-12") lb N/ac Pb ppm N 2.7194 1.623
1600 2.7194 7061 10 lbs N/year in the
rainfall 1050 (105 10) 8111 1997OC
0.62TN 0.0694 lb N/ac 1.623694
2.71943063 Difference 8111 - 3063 5048 lbs
N  
N
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Grain N removal14.6 bu/ac 60 lb/bu 876
lbs876 lbs 105 years 91980 lbs grain91980
lbs 0.022086 N 2031 lbs N Plant N loss10.7
lb/ac/yr (Kanampiu et al., 1995, avg. of 2
experiments)105 10.7 1130 lbs
N  Denitrification 2.85 lb/ac/yr (Aulakh et al.
1984)105 2.85 300 lbs N  Balance 1537 lbs
N Year 1 denitrification, ammonificationDenitrifi
cation, ug/g 50.0 OC 6.2 (Burford and
Bremner, 1975, p. 391) 50.0 2.03 6.2
107.7 ug/g 107.7 1.623 2.7194 475.34
lb/ac (0-12") New Balance 1062 lb N/ac (10.11
lb N/ac/yr unaccounted)
Leaching and Volatilization
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Mystery Resolutions for the
Magruder Plots Denitrification
losses the first year were likely much higher
since increased NO3-N would have been
present as a result of mineralized N from a very
large total N pool. Leaching losses in the
first 10 years were likely quite large in light
of how much N was mineralized from organic N
pools via the result of the first year of
oxidation When adequate inorganic N is present,
the incorporation of straw in conventional till
or the application of straw on the surface of
zero till doubles the accumulative gaseous N
losses (increased supply of energy to
denitrifying organisms). Aulakh et al.
(1984) Late N application can be efficiently
taken up by plants, and does not decrease soil N
uptake. To achieve acceptable grain protein
levels for bread wheat in this irrigated cropping
system, N should be supplied late in the season
to improve N uptake during grain fill (Wuest and
Cassman, 1992)
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Optimum N Rate (Grain N Uptake Max Yield Grain
N Uptake Check)/0.50
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100 27 63
76 56 20
126 40 Difference 86 lbs N/ac
50 NUE
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How to Keep the Leaching, Volatilization, Plant N
Loss, and Denitrification Thieves Away from our
Nitrogen Treasure?
N

• N Rich Strip
• Apply lower rates at Planting
• Base Topdress Rates off predicted yield potential
  and N Responsiveness

Only way to know how big the treasure is
how far we have to dig to find it
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Size of the Treasure
Wet, warm Winter40 lb N in rain
MineralizedGood Stand45 bu/ac Yld Potential65
bu/ac Yld Potential with NTopdress N 40 lb
N/ac
Dry, Cool Winter0-N MineralizedGood Stand30
bu/ac Yld Potential60 bu/ac Yld Potential with
NTopdress N 60 lb N/ac
N
N
Dry, Cool Winter0-N MineralizedPoor Stand20
bu/ac Yld Potential40 bu/ac Yld Potential with
NTopdress N 40 lb N/ac
Wet, warm Winter40 lb N in rain
MineralizedPoor Stand35 bu/ac Yld Potential45
bu/ac Yld Potential with NTopdress N 20 lb
N/ac
N
N
What Unlocks the Mystery of the Nitrogen
Treasure?
N Rich Strip and Yld Potential
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nue.okstate.edu
Winter Wheat
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Oklahoma Treasure

• 5,000,000 acres of wheat
• 10.00 savings per acre on N fertilizer
• 30 adoption
• 15,000,000/year

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Predicting Yield Potential in Corn
NDVI, V8 to V10

INSEY
Days from planting to sensing
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NDVI at F5

INSEY
Days from planting to sensing, GDDgt0
Winter Wheat
Units biomass, kg/ha/day where GDDgt0
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Calibration Stamp2002-2004
Ramped N Rich Strip2005-2006
Agron. J. 2005 97 338-342
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Ramped N Rich Strip