Corn Fertility

Peter Scharf

University of Missouri

2018 Regional Corn Meeting

Sikeston, December 12

What’s the most important nutrient for corn?

•Nitrogen!• Worldwide, half of crop yield from N fertilizer

(except legumes like soybean, dry bean, alfalfa…)

• Half of the nitrogen in YOUR BODY came from fertilizer

• Where does fertilizer N come from?

• What if we didn’t have N fertilizer?

• Does anyone here grow organic crops?

North Korea: an inadvertent experiment

Figure 1. DPRK Fertilizer use and Grain Production

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North Korea: an inadvertent experiment

Figure 1. DPRK Fertilizer use and Grain Production

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10% died

What happens to corn that doesn’t have enough N?

•Leaves are light-colored (low chlorophyll)

•Bouncing light back to space instead of catching it and turning it into grain

•All other functions are scaled back

Why would corn not have enough N?

•Lots of rain

•Lost between application and when the crop needs it

Iowa July 2018lots of rain = N deficiency

When does corn need nitrogen?

•All the way through

•Most crucial: Thigh high to blister

How necessary is preplant N?

• Ken Ferrie (Farm Journal): “Never let corn have a bad day”

• Ken Ferrie: “N deficiency V5 to V8 might cut 18 rows to 14 or 16”

Does N stress cut back on row number?

• 11 years continuous corn with zero N

• Zero N treatment in 2017• 135 bushels behind best treatment• 0.3 rows behind best treatment

• It takes massive N deficiency to reduce row number

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2006 2008 2010 2012 2014 2016 2018

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best preplant best sidedress

Sidedress beats preplant

Sidedress-only ties split

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best preplant best sidedress

sidedress 0 pre sidedress 50 pre

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time of single 200 lb N application

Corn N timing, Mississippi County

irr. '97

non-irr. '97

irr. '98

non-irr. '98

pre Knee-high Chest-high

Don’t worry about preplant N

(or early deficiency)

Injecting UAN paid off; June paid off

3-year average, 140 lb N/ac, single shot

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Ammonium nitrate in June won(all 3 years)

3-year average, 140 lb N/ac, single shot

3-year average, 140 lb N/ac, single shot

020406080

100120140160180

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UAN-injected urea urea + Agrotain

Urea as good as UAN, July as good as June

Spring N• I like dry with a cart on corn that’s 1-2 feet tall

•Fast

•Good yield

•Low risk of loss (NBPT on urea)

•Need high clearance or air backup

N catch 2016 production field

Yield was low where N catch was low

If you lose N, does it pay to replace it?

Rescue N—100’ with, 100’ without

+30 bu

0 bu If you can see it, it’s money

How can you see it?• 88 of these babies went up in February 2017

• 6 images of this convention building Dec 1-10

• Planet.com

Corn, rye, and nitrogen: early N stress often seen

Data acknowledgements:Peter Scharf (13)Kelly Nelson (13)John Lory (10)Tim Reinbott (3)Bruce Burdick (3)Bill Wiebold (3)

Thanks for sharing!

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effect of rye cover on corn yield

average 12 bushel yield penalty45 Missouri experiments99.97% probability that yield penalty is real

I could not overcome this yield penalty with:

• In-furrow N

• Extra sidedress

• Color-based N rate diagnosis

Effect of rye cover on corn yield

N, P, K: What are they like?

Nitrogen

Phosphorus, Potassium

You’re not going to get in trouble quickly on P & K

Most of my on-farm tests for P & K showed no yield boost

Future of PK management: automated on-farm trials to put P & K where they’re profitable

Questions?Comments?

Photo courtesy of Fred Blackmer

Yield loss to N burn(average of 7 locations in Missouri, 2003-04)

Treatment 1 foot 2 feet 3 feet 4 feet

Ammonium

nitrate1 8 20 18

28% N solution 9 14 33 61

Urea 0 0 4

150 lb N applied broadcast at corn height:

But it can look bad enough to make a producer uncomfortable

Foliar N for N stress?

Product Rate (lb N/ac)Yield response of

N-stressed corn

CoRoN 15* 31

CoRoN 50 47

Urea solution 50 61

Urea +

Agrotain (dry)50 64

*2 applications of label rate (3 gal/ac)

Field maps of variability in N need

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B. deep loess 2000

4322350

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C. Mississippi delta 2000

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EONR, kg N/ha

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D. claypan 2001

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A. claypan 2000

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optimal N rates, lb/acre

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80 to 120

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Field maps of variability in N need

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Deep Loess2001

MississippiDelta 2001

Deep Loess2002

MississippiDelta 2002

optimal N rates, lb/acre

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80 to 120

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How can you find the places that need more? And less?

Crop color

More accurate than:• Yield

• Soil tests

• Soil conductivity

• Computer models?

How?• Aerial photos/satellite images

• Applicator-mounted sensors

• Hand-held meters

Overview•N for corn

• When?

• What? Where?

• How much?

y = 209.48x - 197.59

R2 = 0.70

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Crop Circle Yellow/Near-Infrared Relative

to High N Plots

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2008: Our first cotton demo

2006-07: Calibration research, looks great2008 demo: Saved 45 lb N/acre, looks great!!

Sensor-based strips defoliated better

sensor producer

October 3October 4

Sensor strip width

Cotton sensor demo outcomes

•14 on-farm field-scale demonstrations

•On average:• 19 lb/acre more lint• 6 lb/acre less N

Wheat: topdress N timing

Columbia

20050

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N timing

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Wheat: topdress N timing

2006

When should I apply my spring N?

•Answer: March!• 20 bushels more than January (2 tests)• 5 bushels more than February (10 tests)• 8 bushels more than February when yield is

above 70 (4 tests)

•But I can’t get it all done in March

LSD (p=0.05) =

If you must topdress early, use ESN!

Columbia 2005, 2006

Anytime you topdress urea,

use Agrotain!

When should I apply my spring N?

•Answer: March!

• Exception: Thin stand in February

•When the stand is thin, tillering has probably been limited by N availability

• February N will stimulate new tillers

February N will stimulate new tillers

Should I split my spring N?

1 bushel

advantage

Average of 7 Missouri experiments

Take-home• Pre-plant N for corn:

• Fails if it rains a lot

• Isn’t needed for full yield

• Late N applications are effective if the corn needs it

• Injecting UAN pays off (compared to dribbling)

• Ammonium nitrate is a great N source

• N over the top is fast (but bad patterns cost yield)

• The most profitable N rate varies widely in fields

• Crop color is the best diagnostic (aerial, sensor)

Take-home• Leaf color works to diagnose N rate for cotton too

• Profitable in on-farm tests (both corn and cotton)

• Just before jointing is the best time for N on wheat

• But if thinly tillered, greenup N is needed

• Coated urea (ESN) good if topdressing early

• NBPT/Agrotain needed on urea at any temperature

• I have not seen benefits to splitting spring N