On-farm Evaluation of Optical Sensor Technology for Variable Rate N Application to Corn in Ontario and Quebec

Bao-Luo Ma, and Nicolas Tremblay

Eastern Cereal and Oilseed Research Centre, Ottawa, ON

613-759-1521, mab@agr.gc.ca

Canada

Introduction - Nitrogen

Fertilizer N represents the most costly input in grain cereal production, especially corn

Producers have to balance crop N needs while minimizing N losses via leaching, emission and runoff

NUE is low, about 50%

Soil physical, chemical and biological conditions tremendously affect NUE

N losses as NO3 to surface and ground water, as N2O and NH3 gases to the atmosphere

Annual Quantitative N Cycle for Corn/Soil/Atmosphere (kg N/ha)

Atmospheric N

Corn Crop N (Grain=123;Stover=61; Roots=22)

HN4-N+ NO3-N

-

Fertilizer N

Soil Organic N(6000)

14

120

83

10 2410

192

24

252

23150

14

Grain YieldGrain Yield

ChlorophyllChlorophyll NitrogenNitrogen

The basic relationshipThe basic relationship

Canopy reflectance x Nitrogen LevelCanopy reflectance x Nitrogen Level

Wavelength Wavelength (nm)(nm)

Refl

ecta

nce (

%)

Refl

ecta

nce (

%) High N

Low N

0

5

10

15

20

25

30

35

40

400 500 600 700 800 900

< N < chlorophyll= > reflectance< N < chlorophyll= > reflectance

> N > DW > LA= > reflectance> N > DW > LA= > reflectance

Critical levelsCritical levels

Figure 1 – Chlorophyll meter mesurements in four corn development stages(Argenta, 2001).

45,4

52,1

55,3

58,0

V3V3

Development stagesDevelopment stagesV6V6 V10V10

Sp

ad

Sp

ad

44

46

48

50

52

54

56

58

60

15 25 35 45 55 65 75

SilkingSilking

45,445,4

52,152,1

55,355,3

58,058,0Y = 33,928 + 0,654x - 0,004xY = 33,928 + 0,654x - 0,004x2 2 R R22= 0,98= 0,98

Suficiency index (SI):Suficiency index (SI):

SI =SI = NDVI in the high N reference stripNDVI in the high N reference strip

NDVI in the fieldNDVI in the field

Strip

Corn field

= 0.95= 0.95

ETAA Project Objectives

• To develop a crop-based indicator for corn N management that accounts for spatial variability;

• To determine if the new vehicle based optical sensing technology is sufficiently robust and practical for on-farm use;

• To determine if variable rate N application based on spectral reflectance can improve NUE and corn performance on a farm scale.

ETAA Variable Rate Nitrogen Study - 2005

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*

**

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**

*

***

**

*

*

*

**

*

***

***

5 3 2 1 6 9 4

7

9

7

8

o

30+60

o +o + +o +

8

3 4 5 6 1 2 6 5 1 7 3 4 2 2 9 5 4 6 39 1

7 9 7

10 8 10 10

16 26

33

34

2515

+o

+o +o

+o +o

+ooo

o

o

o o o

o

+ + + +

17 27 35

1 2 3 4 5 6 10 11 12 13 14 18 19 20 21 22 23 24 28 29 30 31 32 36 37 38 39 40

Rep 1 Rep 2 Rep 3 Rep 4North

30ft

960ft = 292.6 m

Nitrogen Rates

1) 0 kg N/ha preplant2) 30 kg N/ha preplant (26.7 lb/acre)3) 60 kg N/ha preplant (53.4 lb/acre)4) 90 kg N/ha preplant (80.1 lb/acre)5) 120 kg N/ha preplant (106.8 lb/acre)6) 150 kg N/ha preplant (133.5 lb/acre)7) 30 kg N/ha preplant + 30 kg N/ha sidedress at V68) 30 kg N/ha preplant + 60 kg N/ha sidedress at V69) 30 kg N/ha preplant + 90 kg N/ha sidedress at V6

10) 30 kg N/ha preplant + 120 kg N/ha sidedress at V6* 30 kg N/ha preplant + variable rate N at V6

Hybrid

Pioneer 39D 80 (2550 CHU)- (Roundup Ready + Poncho 250)

Nitrogen Type

1) Urea (46-0-0) broadcast preplant

2) Urea (46-0-0) sidedressed at V6

Dimensions12 rows per plot

30" rowsplot width = 30 ft

plot length = 80 m (for treatments 1-6),20 m (for treatments 7-10)

Total Area

2.34 ha = 5.8 acres

Revised June 29, 2005

30+60 30+120 30+120

    Applied N dose (kg N ha-1) Contrast analysis

   

0 30 60 90 120 150 Linear Quadratic Residual

NDVI_NS a 30DAS 0.35 0.40 0.43 0.43 0.43 0.41*

(41%) b

**(57%)

NS

                     

  NDVI_GS a

26DAS 0.35 0.37 0.40 0.38 0.40 0.37*

(18%)**

(58%)NS

33DAS 0.42 0.46 0.48 0.48 0.50 0.47*

(47%)*

(44%)NS

 

Responses of NDVI_GS  and NDVI_NS to fertilizer N rates

y = 0.0008x + 0.35

R2 = 0.74

0.30

0.35

0.40

0.45

0.50

0.55

0 30 60 90 120 150

Fertilizer N preplant (kg N ha-1)

Can

opy

refle

ctan

ce (N

DV

I)GreenSeeker measures canopy differences at pre-sidedress (2005)

Saturation index shows seasonal N needs (Qc data)

R2 = 0.750

2

4

6

8

10

75 80 85 90 95 100 105

Saturation index (%)

Yie

ld d

iffe

renc

e du

e to

N (

t/ha

)

Grain yield

0 30 60 90 120 150 30+30 30+60 30+90 30+120 Variable

Fertilizer rate (kg N/ha)

0

2

4

6

8

10

12

14

16

Gra

in y

ield

(Mg/

ha)

** *

y = -0.0002x2 + 0.077x + 7.3

R2 = 0.979

y = -0.0002x2 + 0.066x + 7.3

R 2 = 0.995

6789

101112131415

0 30 60 90 120 150

Fertilizer (kg N ha-1)

Gra

in y

ield

(M

g h

a-1)

Preplant 30+sidedress

ETAA Variable Rate Nitrogen Study - 2006 Revised: May 10, 2006

600 ft

9 N

49

71000 ft

48 76 2 5 12 11 1 4 3 1 38

o10 3 8 6 5 12 11 1 2 1 4+o 37 600 ft

47

o 936

8 +o+ + +o 10 + +o +

52 51 50 46 45 44 43 42 41 40 39 35 34 33 32 31 30 29 28 27

Rep 4 Rep 350 ft

-30 ft- Rep 1 Rep 21 2 3 4 5 6 7 8 9 13 14 15 19 20 21 22 23 24 25 26

+o + + 10 + + +o+o 8

10

5 3 1 11 12 1 6 4 8 2 o600 ft o 16

11

9 101000 ft

12 +o7 6 17 3 4 12 11 1 1 2 5

7

18

9

Nitrogen Rates1) 0 kg N/ha preplant2) 30 kg N/ha preplant (26.7 lb/acre)3) 60 kg N/ha preplant (53.4 lb/acre) Hybrid4) 90 kg N/ha preplant (80.1 lb/acre) Pioneer 39D80 (2550 CHU)5) 120 kg N/ha preplant (106.8 lb/acre) - (Roundup Ready + Poncho 1250)6) 150 kg N/ha preplant (133.5 lb/acre)7) 30 kg N/ha preplant + 30 kg N/ha sidedress at V6 Nitrogen Type8) 30 kg N/ha preplant + 60 kg N/ha sidedress at V6 1) Urea (46-0-0) broadcast preplant9) 30 kg N/ha preplant + 90 kg N/ha sidedress at V6 2) UAN (28-0-0) sidedressed at V610) 30 kg N/ha preplant + 120 kg N/ha sidedress at V611) Variable rate - 30 kg N/ha preplant + variable rate N at V6 Note: the variable rate plots are surounded on either side by a 0 N plot and 180 kg N/h plot12) 180 kg N/ha preplant

Adjustable Sensor Mounting

Ottawa Equipment

• Ford 7610 tractor with modified hydraulic returns• Yetter 2995 Bubble Fertilizer Coulters with rear Knife• 250 liter tank with filter• John Blue positive displacement piston pump with flow divider• Rawson Accurate Controller• Dickey John Radar• Raven GPS• GreenSeeker RT200

GreenSeeker MappingJune 26, 2006

REP AVG MAX MIN

1 .57 .78 .32

2 .51 .76 .25

3 .58 .83 .26

4 .66 .85 .32

Corn 32” to 36” high on Application Day, Ottawa

Ottawa Application

• Non-irrigated spring wheat with modified inputs gave a very reasonable application curve

• On application day the curve could not be manipulated to suite our rates because of high NDVI values.

• Only choice we had was to use the 16 point stepped (not interpolated) graph

• In StJean, the non-irrigated spring wheat was manipulated to give a very reasonable curve

Ottawa Rate

NDVI US gal/ac

.2 0

.25 0

.3 0

.35 0

.4 0

.45 0

.5 0

.55 9.2

.6 35.9

.65 35.0

.7 33.1

.75 32.1

.8 28.5

.85 21.2

.9 11.0

.95 9.2

Accurate controller settings:9.2 to 36.8 gal /ac was the preset range(30 kg N/ha to 120 kg N/ha)Controller works on percentage change from a mid point.23 gal/ac as the mid point with 4 % increment giving .92 galThere are 32 increments.

Summary (2005)

• Very high grain yield in 2005; yield did not plateau;

• Yield was more responsive to sidedress (77 kg/kg N) than preplant (66 kg/kg N) fertilizer N;

• Canopy reflectance (NDVI) differentiate low from high soil N

• NDVI ranges are narrow, sensitive with crop growth stage

• Better economic return with sidedressed fertilizer N. But, further research is needed for variable N rate application.

Summary (2006)• First year of variable rate N application based on NDVI saturation

index (SI)• Canopy NDVI values change rapidly from V6 to V8 (plants 2.5-3

feet tall) and can be quickly saturated (NDVI >0.82).• The rainfed spring wheat algorithm provided by the RT-200

GreenSeeker was used in Quebec where NDVIref <0.7• In Ottawa site, differences in canopy reflectance among preplant

broadcast fertilizer N rates was confounded with poor seedling growth under high N rates due to low soil pH coupled with cool spring.

• Although such confounding effect was minimal around or after sidedress, it made difficult interpret the NDVI data.

• The maximum NDVI value was used to derive SI, and Nmin and Nmax were set at 9.2 and 36.8 gal/ac; variable N rate application was made using the 16 points algorithm.

• It is expected that a better NDVI-N requirement algorithm will be available or developed at site for use next year.

Acknowledgements

Ontario Soil and Crop Improvement Association

Lynne Evenson, Doug Balchin,

Vivianne Deslauriers