Improving NUE in Corn With Crop Sensing: Reflections, Concerns,

and Needed Research

Rain fed Southern Corn Belt

Improving NUE in Corn With Crop Sensing: Reflections, Concerns,

and Needed Research

Rain fed Southern Corn Belt

Predominant N Management Issues

• Soil variability (some fields and soil types will be much better suited for sensor-driven N applications) alluvial >> loess > claypan

• Balance between meeting early N corn needs and not adding too much early such that the plant poorly predicts what the soil will provide

• If weather cooperates, N will be fall applied setting up a scenario of potential N loss

Predominant N Management Issues

• Excessive spring and early summer rainfall setting up the need for a rescue

• Opportunity of application (can be especially narrow for poorly drained soils like the claypan soils)

• Hard to match side-dress UAN with preplant AA performance (source & placement issues)

• Hot & Dry weather (if only all growing seasons were like 2004)

• Shift of C-S to C-C with feed-to-fuel market shifts

• Scenarios that best fit sensor-driven N fertilizer applications:– Fields following wet spring and early summer

(loss of fall applied N)– Fields that have received recent manure

applications and uncertainty exists for how much N is available

– Fields receiving uneven N fertilization (fertilizer or manure)

– Fields coming out of pasture, hay, or CRP– Fields with extreme variability in soil type– Fields of corn-after-corn when drought occurred

the first year (i.e. non-uniform carry over)

Other Thoughts and Reflections

What will the impact of public What will the impact of public funding be on the future of VR funding be on the future of VR N management?N management?

• Can a small nitrogen-rich reference area serve a large, variable field?• Will we eventually get by without a reference area within each field?

0

25

50

75

100

-250 -200 -150 -100 -50 0 50 100 150 200

Difference from EONR, kg ha-1

Yie

ld E

ffic

ien

cy

, k

g g

rain

(k

g N

)-1 B04

CI04

CII04

D04

H04

P04

S04

W04

Yield efficiency (or NUE) not the same at EONR

corn price ($/bu)cost of N ($/lb) $1.60 $1.80 $2.00 $2.20 $2.40 $2.60 $2.80 $3.00 $3.20

$0.15 10.7 12.0 13.3 14.7 16.0 17.3 18.7 20.0 21.3$0.20 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0$0.25 6.4 7.2 8.0 8.8 9.6 10.4 11.2 12.0 12.8$0.30 5.3 6.0 6.7 7.3 8.0 8.7 9.3 10.0 10.7$0.35 4.6 5.1 5.7 6.3 6.9 7.4 8.0 8.6 9.1$0.40 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0$0.45 3.6 4.0 4.4 4.9 5.3 5.8 6.2 6.7 7.1$0.50 3.2 3.6 4.0 4.4 4.8 5.2 5.6 6.0 6.4$0.55 2.9 3.3 3.6 4.0 4.4 4.7 5.1 5.5 5.8$0.60 2.7 3.0 3.3 3.7 4.0 4.3 4.7 5.0 5.3

Issues of a changing EONR and reporting results

0

25

50

75

100

-250 -200 -150 -100 -50 0 50 100 150 200

Difference from EONR, kg ha-1

Yie

ld E

ffic

ien

cy

, k

g g

rain

(k

g N

)-1 B04

CI04

CII04

D04

H04

P04

S04

W04

Yield efficiency related to EONR for 2004 fields

3.6 12.8

0

50

100

150

200

-250 -200 -150 -100 -50 0 50 100 150

Difference from EONR, kg ha-1

Pro

file

Ino

rga

nic

N, k

g h

a-1 D04

P04

S04

Profile inorganic N related to EONR for 2004 fields

3.6 12.8

When it comes to sensor indices….

• Some indices stretch out differences better than others: CHL index ~ simple ratio > NDVI

• Nice to have sensors output either Vis or NIR for purposes of indice performance testing

• NDVI and the simple ratio are mathematically related

Vissimple ratio = ---------------

NIR

NIR- VISNDVI = --------------------

NIR +VIS

(1 – simple ratio)NDVI = -------------------------

(1 + simple ratio)

(1 – NDVI)simple ratio = -------------------------

(1 + NDVI)

If n is our friend,

why is that N is our nemesis?

If n is our friend,

why is that N is our nemesis?