Use of By-Plot CV’s for Use of By-Plot CV’s for Refining Mid-Season Fertilizer Refining Mid-Season Fertilizer

N RatesN Rates

Daryl Brian ArnallDaryl Brian ArnallPlant and Soil Sciences DepartmentPlant and Soil Sciences Department

Oklahoma State UniversityOklahoma State University

IntroductionIntroductionScrutiny of Nitrogen Application Scrutiny of Nitrogen Application

Rise in Nitrogen costRise in Nitrogen cost

Environmental impactEnvironmental impact

Precision Nitrogen ApplicationPrecision Nitrogen ApplicationGreat PotentialGreat Potential

Reduce Application LevelsReduce Application Levels

Use of Statistical Analysis for ImprovingUse of Statistical Analysis for Improving

Application Not Completely Examined Application Not Completely Examined

ObjectiveObjective

Determine the relationship between Determine the relationship between the CV measured using spectral radiance the CV measured using spectral radiance measurements, and plant population at measurements, and plant population at early growth stages. early growth stages.

Sensing direction in relation to the Sensing direction in relation to the crop row direction impact on NDVI.crop row direction impact on NDVI.

MethodMethod

25 plots at 3 locations:25 plots at 3 locations:

Plots measured 1.48m by 4.88mPlots measured 1.48m by 4.88m

3 nitrogen treatments implemented with 3 nitrogen treatments implemented with each plot.each plot.

0 N, 120kg/ha Fall App., 80 kg/ha Top-0 N, 120kg/ha Fall App., 80 kg/ha Top-dressdress

Plot PlanPlot Plan

Check

0 N

N-Rich120 kg/ha N Fall App.

Farmer Practice

80 kg/ha NTopdress

Method cont.Method cont.

At Feekes 1 (At Feekes 1 (EmergenceEmergence))::

Plots were established.Plots were established.

Fall nitrogen applied.Fall nitrogen applied.

Plant counts taken on 4 randomly selected Plant counts taken on 4 randomly selected rows.rows.

At Feekes 6 (At Feekes 6 (Stem ElongationStem Elongation))::

Topdress nitrogen appliedTopdress nitrogen applied

Method cont.Method cont.Sensing Sensing

Began in January.Began in January.Concluded at physiological maturity.Concluded at physiological maturity.

Sensor held 75cm to 100 cm over the crop Sensor held 75cm to 100 cm over the crop canopy.canopy.

3 seconds allowed for each reading.3 seconds allowed for each reading.

Sensing PlanSensing Plan

1 2 3 4 5 6 7 8

1

2

3

4

Row

5

1 2 3 4 5 6 7 8

1

2

3

4

Row

5

5 Readings per trt: 2 with row, 2 across row, 5 Readings per trt: 2 with row, 2 across row, and 1 at a 45 degree to the seed row.and 1 at a 45 degree to the seed row.

Sensing PlanSensing Plan

Method cont.Method cont.At Physiological Maturity:At Physiological Maturity:

A 1mA 1m22 area hand harvested from each area hand harvested from each plot.plot.

Thrashed with a mechanical thrasher.Thrashed with a mechanical thrasher.

Grain weighed for yield.Grain weighed for yield.Processed and analyzed for N content.Processed and analyzed for N content.

2004 harvest2004 harvest

ResultsResults

CV and PopulationCV and Population

Feekes 5

0

100

200

300

400

500

600

0 10 20 30 40 50CV, %

Pla

nts

/m2

Perkins

Efaw

LCB

LCB03

Perkins03

Henn03

EFAW03

y = -12.94x + 321Intercept; CV = 20 Population = 52

Feekes 5

0

100

200

300

400

500

600

0 10 20 30 40 50CV, %

Pla

nts

/m2

Perkins

Efaw

LCB

LCB03

Perkins03

Henn03

EFAW03

Feekes 5

0

100

200

300

400

500

600

0 10 20 30 40 50CV, %

Pla

nts

/m2

Perkins

Efaw

LCB

LCB03

Perkins03

Henn03

EFAW03

y = -12.94x + 321Intercept; CV = 20 Population = 52

CV over TimeCV over Time

0

5

10

15

20

25

30

5-Jan 19-Jan 2-Feb 16-Feb 1-Mar 15-Mar 29-Mar 12-Apr

CV

Check

120 Fall App.

80 Top-dress

Top-dress N applied

F3 F9F7F5

Top-dress N appliedTop-dress N applied

F3 F9F7F5

0

5

10

15

20

25

30

5-Jan 19-Jan 2-Feb 16-Feb 1-Mar 15-Mar 29-Mar 12-Apr

CV

Check

120 Fall App.

80 Top-dress

Top-dress N applied

F10.5F3 F7F5

Top-dress N appliedTop-dress N applied

F10.5F3 F7F5

RI HybridRI HybridRI = Response Index

RIharvest = Yield of N-rich plot / Yield of the check

RIndvi = NDVI of N-rich plot / NDVI of check plot

y = 0.52x + 0.73

R2 = 0.17

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.5 1.0 1.5 2.0 2.5RIndvi

RIh

arve

st

RIhybrid = NDVI of N-rich /

(NDVI of check plot /

SqRt of the check plot CV)

y = 1.9x + 0.70

R2 = 0.36

0.0

0.5

1.0

1.5

2.0

2.5

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7RIhybrid

RIh

arve

st

Sensor DirectionSensor Direction

0.00

0.20

0.40

0.60

0.80

0.00 0.20 0.40 0.60 0.80

With Row NDVI

Acr

oss

Row

ND

VI

PERKINS04

EFAW04

LCB04

EFAW03

LCB03

Perk03

Henn03

n = 3660y = 0.98x + 0.01R2 = 0.97

0.00

0.20

0.40

0.60

0.80

0.00 0.20 0.40 0.60 0.80

With row NDVI

45 D

egre

e N

DV

I

PERKINS

EFAW

LCBn = 2325y = 1.01x + 0.00R2 = 0.97

Directional CVDirectional CV

R2 = 0.71

R2 = 0.72

R2 = 0.78

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 20 40 60 80 100 120 140 160

GDD>0

CV

With Row

Across Row

45 Degree

ConclusionConclusionHigh CV’s from sensor NDVI readings can High CV’s from sensor NDVI readings can

be used as an indicator of poor plant be used as an indicator of poor plant stands.stands.

CV can be used to improve determination of CV can be used to improve determination of RI.RI.

Seed row direction had no effect on NDVI Seed row direction had no effect on NDVI Readings.Readings.

Questions?Questions?