Oklahoma State University

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Optical Sensor Based Nitrogen Recommendations for
Corn and Wheat
Oklahoma State University
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NUE in Cereals

• Author Crop Method Year Location NUE (grain)
• Varvel Corn 15N 1990 NE 43-53
• Russelle Corn Diff. 1981 NE 46
• Raun Corn Diff. 1989 NE 30-40
• Olson Wheat 15N 1984 KS 27-33
• Bronson Wheat 15N 1991 CO 53
• Raun Wheat 15N 1999 OK 21-32
• Lees Wheat 15N 2000 OK 38-41
• Westerman Sorghum 15N 1972 IL 51
• Varvel Sorghum 15N 1991 NE 48
• DeDatta Rice 15N 1988 Asia 37-47

IN USA, generally less than 50
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Problem

• Cereal NUE (corn, wheat, rice) averages 33 world
  wide
• Profitability of the System
• Environmental Sensitivity of Corn and Wheat
  Production Systems

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SCIENCE Magazine

• Excess nitrogen flowing down the Mississippi each
  year is estimated to be worth 750,000,000
  (Science, Malakoff, 1998)
• NUE in cereal production must be improved

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Review

• Yield Goals average of last 3-5 years 30
• Nebraska study showed that farmers overestimated
  yield by 2 Mg ha-1 (32 bu ac-1), resulting in an
  excess of 35 kg N ha-1 (Schepers et al., 1986)
• Over-optimistic yield goals were the largest
  contributor to excess N applications with average
  yield goals exceeding actual yields by over 15,
  only about 30 of the fields were within 5 of
  the yield goal (Daberkow et al., 2001)

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Solutions
Technological Requirement

• Nitrogen Rich Strip
• N Rich Strips, Ramped N
• Sensor Based N Rate Calculator
• Variable N Rate Applicators

NONE
NONE
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Questions. Answers

• Do N Rates Vary from one year to the next in the
  same Field?
• If they do, why?
• Can N Rates be Adjusted based on Predicted Yield?
• Can the Responsiveness to N be Predicted?
• How does the new system work (based on predicted
  yield and RI)?

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Optimum N Rate (Grain N Uptake Max Yield Grain
N Uptake Check)/0.50
Are your yields the same every year? Should N
supply be based on demand? Is demand controlled
by weather?
Long-Term Winter Wheat ExperimentLahoma, OK
After the FACT N Rate required for MAX Yields
Ranged from 0 to 140 lbs N/ac
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Optimum N Rate (Grain N Uptake Max Yield Grain
N Uptake Check)/0.50
Long-Term Corn ExperimentR.A. Olson, UNL
After the FACT N Rate required for MAX Yields
Ranged from 25 to 165 lbs N/ac
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Nitrogen Rich Strip
Must be put out preplant or soon after
planting Corn 200 to 300 lbs N/ac (want N
non-limiting for the entire season)remaining
portion of each field should use a preplant rate
from 50 to 80 lbs N/ac Wheat
100 to 150 lbs N/ac (want N non-limiting for the
entire season) Rate depends on whether it is a
forage, or grain production systemRemaining
portion of each field should use a preplant rate
from 30 to 60 lbs N/ac.
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Nitrogen Rich Strip
Mid-Season Evaluation of N Rich Strip (Ciudad
Obregon, MX)Average Wheat Yields 150 bu/ac
(irrigated spring wheat)
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Response Index NDVI, N Rich Strip NDVI,
Farmer Practice
Residual NLegume creditsMineralizationManureNi
trate in rainfall and/or irrigation water
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Calibration Stamp2002-2004
Ramped N Rich Strip2005
Agron. J. 2005 97 338-342
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Ramped N Rich StripVisual InterpretationOptical
Sensing
NDVI
RI 1.5
RI 1.5
Ramped N Rich StripsAre an Advancement over the
Calibration StampPower Response Index or RI
Distance
0 50 100 150
N Rate
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Response Indexvariable from year to year in the
same field
2004
1995
Long term N-P-K Experiments(1969-2004) Dr. Billy
Tucker
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2006
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1. Can Yield Potential (similar to yield goals)
be Predicted MID-SEASON?
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Growth Stage V8 V10
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Predicting Yield Potential in Corn
ANSWER YES!Look at the Dashed Line which is
30 plus the yield predictionNOTE The
objective is to predict yield potential not
yield.
NDVI, V8 to V10

INSEY
Days from planting to sensing
CORN
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NDVI at F5
ANSWER YES!Look at the Dashed Line which is
30 plus the yield predictionNOTE The
objective is to predict yield potential not
yield.

INSEY
Days from planting to sensing, GDDgt0
Winter Wheat
Units biomass, kg/ha/day, where GDDgt0
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Yield Potential
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Mid-Season Yield Potential
Biomass produced per day growth rate yield
potentialNOTE Yield potential prediction
equations are very similar for the different
crops (Irrigated Corn being the highest)
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2. Can the Response Index (RI) be predicted from
MID-Season NDVI readings?
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Response Index
Robert Mullen
Gordon JohnsonKyle FreemanPaul Hodgen
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Can RI Be Predicted in Corn?
MullenAgronomy Journal 95347-351 (2003)Winter
Wheat
ANSWER YES!In both Wheat and Corn
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3. How can MID-Season Yield Potential and RI be
used to predict the ideal topdress N rate?
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N Fertilization Algorithm
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Yield Prediction Response Index (N Rich Strip
Compared to the Farmer Practice) Yield
obtainable with added N (YPN RI
YP0) Fertilizer Rate (GNUPYPN-GNUPYP0)/0.6
2
1
3
4
2
4
The efficiency factor of 0.6 can change depending
on the crop and production circumstances
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RI-NFOAYPNYP0 RI
YP0
YPN
YPN
YPMAX
RI1.5
RI2.0
Grain yield
INSEY (NDVI/days from planting to sensing)
Nf (YP0RI) YP0))/Ef

• The mechanics of how N rates are computed are
  really very simple
• Yield potential is predicted without N
• The yield achievable with added N is 1 times the
  RI
• Grain N uptake for 2 minus 1 Predicted
  Additional N Need
• Fertilizer Rate 3/ efficiency factor (usually
  0.5 to 0.7)

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8.9
6.3 Mg 80.0 kg N
1975 2.5
11.3
1978 7.4
3.8 Mg 48.6 kg N
Difference in Grain N Uptake of 31.4 kg NAt an
application efficiency of 50, 1.25 Grain NN
Fertilizer Requirement Differed by 62.8 kg N
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Can I Enter my NDVI data over the web and get the
right topdress N rate?ANSWER YES!
http//www.soiltesting.okstate.edu/SBNRC/SBNRC.php
http//www.nue.okstate.edu
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nue.okstate.edu
Rainfed and Irrigated Corn
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4. What are the benefits of using this Technology?
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• Wheat grain yield response to fertilizer N
  applied using variable N rate strategies and
  fixed preplant rates, Chickasha, OK, 2004.
• Trt Preplant Topdress Total Method Grain NUE Gros
  s
• N Rate N Rate N Rate Yield Revenue
• kg/ha kg/ha kg/ha kg/ha /ha
• 1 0 0 0 - 1510 - 194
• 2 135 0 135 All N pre 2631 20 264
• 3 0 27 27 Var. NFOA 2152 57 262
• 4 50 12 62 Var. NFOA 2377 32 271
• 5 0 29 29 Flat NFOA 1855 28 222
• 50 13 63 Flat NFOA 2647 42 305 20/ac
• 7 0 100 100 Flat Topdress 1781 6 174
• Sensor CV at F5 12 (NDVI 0.3)
• __________________________________________________
  _________
• NFOA nitrogen fertilization optimization
  algorithm
• Flat rate fertilizer applied uniformly to the
  entire treatmentGross Revenue using 52 USD /ton
  of wheat and 0.62 per kg N.

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Wheat grain yield response to fertilizer N
applied using variable N rate strategies and
fixed preplant rates, Efaw, OK,
2004. Trt Preplant Topdress Total
Method Grain NUE Gross N Rate N Rate N
Rate Yield Revenue kg/ha kg/ha kg/ha kg/ha
/ha 1 0 0 0 - 2105 - 270 2 135 0 135 All N
pre 2712 11 274 3 0 25 25 Var. NFOA 2724 60 337
27/ac 4 50 9 59 Var. NFOA 2693 23 313 5 0 34 34
Flat NFOA 2587 34 314 6 50 16 66 Flat
NFOA 2724 22 314Sensor CV at F5 16 (NDVI
0.4) _____________________________________________
_______ NFOA nitrogen fertilization
optimization algorithm Flat rate fertilizer
applied uniformly to the entire treatment Gross
Revenue using 52 USD per ton of wheat and 0.62
per kg N.
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Wheat grain yield response to fertilizer N
applied using variable N rate strategies and
fixed preplant rates, Lake Carl Blackwell, OK,
2004. Trt Preplant Topdress Total
Method Grain NUE Gross N Rate N Rate N
Rate Yield Revenue kg/ha kg/ha kg/ha kg/ha
/ha 1 0 0 0 - 3297 - 424 2 135 0 135 All N
pre 4065 13 448 3 0 14 14 Var. NFOA 3650 57 461 4
50 11 61 Var. NFOA 4155 33 500 5 0 22 22 Flat
NFOA 3519 26 440 6 50 14 64 Flat NFOA 4215 33 506
26/ac 7 50 34 84 Flat pre/top 4099 16 481Sen
sor CV at F5 22 (NDVI 0.5) ___________________
_______________________________________ NFOA
nitrogen fertilization optimization algorithm
Flat rate fertilizer applied uniformly to the
entire treatment Gross Revenue using 52 USD per
ton of wheat and 0.62 per kg N. obtained from
long-term trial 601 at LCB.
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10 Field Trials GreenSeekerTM Field Sprayer (OSU
Wheat)
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5. What is being done using Variable N?
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Wheat?Commercially available via NTech

• Sense and treat every 0.4m2
• Application rates of 0-100 lb N/ac in 10 lb
  increments

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Corn and Wheat?The use of CVs look promising
for adjusting N rates in both these crops
CORN, YPCV Applicator
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RICV-NFOA
RI2.0
YP0
YPN
YPMAX
CVlim 65 (corn)CVlim 40 (wheat)
CV
Grain yield
CV
INSEY (NDVI/days from planting to sensing)
YPN YP0RI CrCV (((-0.0003)POP)36.315) YPCV
YPN((65-CV)/(65-CrCV)) NRate
((YPCV-YP0)0.0125/0.6)
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Corn and Wheat?The use of CVs look promising
for adjusting N rates in both these crops (in
addition to NDVI)
Variable N Application in Wheat(0.4m2 resolution)
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CanadaArgentinaMexico
Optical Sensing Nitrogen Management Group
2005 International Corn Trials 2006 International
Corn Trials Planned
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Summary

• Use of N Rich Strip and the OSU-SBNRC can lead to
  increased profits gt 10/ac in winter wheatgt
  20/ac in corn
• Ramped N Reference Strips 2005 offer improved
  refinements in mid-season N recommendations
• Some US University and International programs are
  now using this approach