Window of Opportunity

Peter ScharfUniversity of Missouri

Window of Opportunity?Window of Opportunity?

Sensors

Factors defining the window

Effect of N timing on yieldHow late can you go?

Effect of sensor timing on diagnostic accuracyHow early can you go?

0.0

0.2

0.4

0.6

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1.0

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0 4 8 12 16 20

growth stage of single N applic.

yiel

d r

elat

ive

to p

rep

lan

t N

missouri

nebraska

oklahoma

MO line

Effect of N timing on yield

tassel

How late can you apply?

Planned single application: as late as V11?Northern data needed

35 to 90 kg N/ha applied preplant

00.20.40.60.8

11.21.4

0 4 8 12 16 20

growth stage when balance of N applied

yie

ld r

ela

tiv

e t

o p

rep

lan

t N

Effect of N timing on yield

tassel

How late can you apply?

Planned single application: as late as V11?Northern data needed

With modest preplant N: later yet

How late can you apply?

Planned single application: as late as V11?Northern data needed

With modest preplant N: later yet

As a rescue application: at least silking

Factors defining the window

Effect of N timing on yieldEffect of sensor timing on

diagnostic accuracy

Effect of sensor timing on accuracy

Can work as early as V6

Effect of sensor timing on accuracy

Chlorophyll meter prediction of N rate V5 to V9, R2 = 0.53 V10 to R1, R2 = 0.66

Chlorophyll meter: equation changes as season progresses

Prime window: V6 to V11?

Discussion?

Effect of N timing on yield

Russelle et al. 1983 Evanylo 1991 Jokela and Randall 1989 Sripada et al. 2005 Miller et al. 1975 Hoeft Bausch

Effect of N timing on yield depends on placement…

Broadcast

Between-row

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2,000

4,000

6,000

8,000

10,000

0 30 60 90 120

Corn height (cm) when N was applied

Yie

ld (

kg h

a-1)

…and source (N burn)(average of 7 locations in Missouri, 2003-04)

TreatmentTreatment 1 foot1 foot 2 feet2 feet 3 feet3 feet 4 feet4 feet

Ammonium Ammonium nitratenitrate 11 88 2020 1818

28% N 28% N solutionsolution 99 1414 3333 6161

UreaUrea 00 00 XX 44

Yield loss (between-row minus broadcast) when 150 lb N applied broadcast at corn height:

Kansas producer 2006: 4000 Kansas producer 2006: 4000 acres of corn fertilized in six acres of corn fertilized in six days using sensorsdays using sensors

…and source (N burn)(average of 7 locations in Missouri, 2003-04)

TreatmentTreatment 1 foot1 foot 2 feet2 feet 3 feet3 feet 4 feet4 feet

Ammonium Ammonium nitratenitrate 11 88 2020 1818

28% N 28% N solutionsolution 99 1414 3333 6161

UreaUrea 00 00 XX 44

Yield loss (between-row minus broadcast) when 150 lb N applied broadcast at corn height:

Effect of N timing on yieldMissouri data, 28 expts. 1997-99

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 4 8 12 16 20

growth stage of single N application

yie

ld r

ela

tiv

e t

o p

rep

lan

t N

tassel

Scharf et al., 2002, Agron. J. 94:435-441

Nebraska data, 2 expts. 1993-1994

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0 4 8 12 16 20

growth stage of single N application

yie

ld r

ela

tiv

e t

o p

rep

lan

t N

Effect of N timing on yield

tassel

Binder et al., 2000, Agron. J. 92:1228-1236

Oklahoma data, 5 expts. 2005-06

0

0.2

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0.6

0.8

1

1.2

0 4 8 12 16 20

growth stage of single N application

yie

ld r

ela

tiv

e t

o p

rep

lan

t N

Effect of N timing on yield

tassel

Walsh, 2006, MS Thesis

35 to 90 kg N/ha applied preplant

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 4 8 12 16 20

growth stage when balance of N applied

yie

ld r

ela

tiv

e t

o p

rep

lan

t N

nebraska

oklahoma

missouri

Effect of N timing on yield

tassel

Effect of N timing on yield

Producer N rate, Producer N rate, preplant vs preplant vs sidedress (on sidedress (on average V9)average V9)

Field-length stripsField-length strips

Effect of N timing on yield

YearYear # # expts.expts.

Yield effect of Yield effect of sidedresssidedress

20042004 77 -5-5

20052005 55 -16-16

20062006 55 +4+4

Yield effect is very weather-dependent!

Yield response to late N: Only when corn hasOnly when corn has visible N stress visible N stress

Greenness of corn

Yield response to N applied when corn was shoulder-high

100% 0 91% 10 77% 37

Steve Watkins farm, Hayti, 2000; research by Gene Stevens

Window of Opportunity: Later for unplanned (rescue) applications

Application until at least silking can give a large yield response when N stress is substantial

35 to 50 bu/ac in three MO tests