Developing Sidedress N Recommendations for Corn in Central PA

using a Crop Circle ACS-210

John Schmidt Adam DellingerDoug Beegle

ARS and Penn State

Background

Improving N recommendations for corn

Sidedressing N is common in PA

Many fields with a manure history

Spatial variability in relief, aspect, soil water content

Field selection – 2005

State College area, four fields

Previous crop

Corn, Soybean, Soybean with manure history, Alfalfa

Soil pH: 5.5 – 6.2

Soil P (M3): 17 – 101 mg kg-1

Soil K (M3): 93 – 160 mg kg-1

Treatment design

Whole plot, 30 x 105 ft

Control

50 lb acre-1 N as NH4NO3

Manure, 115 – 165 lb acre-1 total N

Split-plot, 30 x 15 ft

Control

250 lb acre-1 N as NH4NO3 at planting

20, 40, 80, 120, and 160 lb acre-1 N as NH4NO3 at sidedress

Four Blocks

Sensor

Crop Circle ACS-210 Plant Canopy Reflectance

Emission Bands: 590 and 880 nm

Two detectors: 400 – 680 nm, 800 – 1100 nm

Data collection

8 samples per second

Simultaneously georeferenced

Trimble Pro XRS GPS and TSCe Field Device

24 – 32 inch sensor height

Weekly, June 8 – July 12

Data collection

Grain yield

PSNT from the control

SPAD readings at sidedress

Leaf tissue at silking

Stalk nitrate test, selected trts

Grain yield response – Corn after corn

0

20

4060

80

100

120140

160

180

0 50 100 150 200 250

N rate (lb / acre)

Gra

in y

ield

(b

u /

acre

) .

Control

50 lb N / acre

Manure

$0.30 / lb N$2 / bu corn

EONR = 94

EONR = 73 EONR = 124

0

2040

60

80100

120

140160

180

0 50 100 150 200 250

N rate (lb / acre)

Gra

in y

ield

(b

u /

acre

) .

Control

50 lb N / acre

Manure

Grain yield response – Corn after soybean

EONR = 43

EONR = 0EONR = 54

20

4060

80100

120140

160180

200

0 50 100 150 200 250

N rate (lb / acre)

Gra

in y

ield

(b

u /

acre

) .

Control

50 lb N / acre

Manure

Grain yield response – Corn after alfalfa

020

4060

80100

120140

160180

0 50 100 150 200 250

N rate (lb / acre)

Gra

in y

ield

(b

u /

acre

) .

Control

50 lb N / acre

Manure

Grain yield response – Corn after soybean (manure history)

EONR (Economic Optimum N Rate)

Previous cropPrevious crop Whole plot trtWhole plot trt EONR (lb N / acre)EONR (lb N / acre)

CornCorn ControlControl 9494

50 lb N / acre50 lb N / acre 7373

ManureManure 124124

SoybeanSoybean ControlControl 4343

50 lb N / acre50 lb N / acre 00

ManureManure 5454

AlfalfaAlfalfa 00

Soybean (manure history)Soybean (manure history) 00

0.2

0.3

0.4

0.5

0.6

0.7

0 50 100 150 200 250N rate (lb / acre)

ND

VI

7-Jun 15-Jun 21-Jun 30-Jun 11-Jul

NDVI, Corn after corn, Control (whole plot)

June 24N applied

NDVI, Corn after corn, Control (whole plot)

0.2

0.3

0.4

0.5

0.6

0.7

2-Jun 12-Jun 22-Jun 2-Jul 12-JulCalendar date

ND

VI

.

Control 250 lb N / acre

NDVI, NDVIratio and SPADratio

VISNIR

VISNIRNDVI

0

250

NDVI

NDVINDVIratio

0

250

SPAD

SPADSPAD ratio

EONR as a function of NDVI ratio

y = 289x - 269

r2 = 0.73

y = 358x - 322

r2 = 0.72

0

20

40

60

80

100

120

140

0.8 0.9 1 1.1 1.2 1.3NDVIratio

EO

NR

(lb

/ ac

re)

.

21-Jun11-Jul

y = -4.2x2 + 10.0x - 4.7

r2 = 0.79

0.8

0.9

1.0

1.1

1.2

0.8 0.9 1.0 1.1 1.2

SPAD ratio

ND

VI r

ati

o

.NDVIratio compared to SPAD ratio, June 21

y = 358x - 322

r2 = 0.72

y = 368x - 337

r2 = 0.40

0

20

40

60

80

100

120

140

160

0.8 0.9 1 1.1 1.2Ratio Value

EO

NR

(lb

N /

acre

) .

SPAD ratioNDVI ratio

EONR as a function of NDVIratio or SPAD ratio

June 21

Summary

First year of results in PA

Sensor was effective at those sites requiring N fertilizer

NDVI ratio was correlated to SPAD ratio

NDVI ratio was better correlated to EONR than SPAD ratio