has two stable isotopes, 14N and 15N

14N = 99.6% of all N

Why might a researcher decide to

use N fertilizer spiked with 15N?

NITROGEN

N Reservoir

Biomass

Water

Atmosphere

Geosphere

Crust

Soils and Sediments

Mantle and Core

MegaTons

2.8 x 105

2.3 x 107

3.86 x 109

1.636 x 1011

0.13 - 1.4 x 1010

0.35 - 4.0 x 109

1.6 x 1011

% of Total

0.0002

0.014

2.3

97.7

0.78-8.4

0.21-2.4

95.6

Where is the N on planet earth ??

Most geosphere N is deep within the earth

and has little relevance to biological cycles.

Reservoir/Pool Type

Biomass

Water

Soil

Atmosphere

MegaTons

2.8 x 105

2.3 x 107

0.35 x 109

3.86 x 109

% of Total

0.0002

0.014

0.21

2.3

Biologically relevant N

% of BR N

<0.01

< 1%

~ 8 %

> 90 %

N2 ~ 78% of the earth’s atmosphere

Why is N2 so unreactive ???

N2 is chemically unreactive at the temperatures and pressures of the hydrosphere,

biosphere, and atmosphere because of its triple bond. This triple bond can only be

broken under extreme temperatures and or pressures or in the presence of select

enzymes.

Reactive

N

Reactive

N

Reactive

N Reactive

N

Lightning Pollution (primarily from engines)

Biological N

fixation in nature

Biological N

fixation in

agriculture

Industrial

N fixation

~ 5 MT

~ 20 MT

~ 30 MT

~ 85 MT

> 130 MT

~ 90% used for fertilizer

NH3 manufacturing plants

currently produce ~ as

much reactive N as all other

processes on planet earth

Human activities

are fertilizing the

entire planet with

reactive N

~ 20 MT

~ 30 MT > 130 MT

Nitrogen has many different oxidation states !

Species Name Oxidation State

NH3, NH4+ Ammonia, ammonium ion -3

N2H4 Hydrazine -2

NH2OH Hydroxylamine -1

N2 Nitrogen 0

N2O Nitrous oxide +1

NO Nitric oxide +2

HNO2, NO2- Nitrous acid, nitrite ion +3

NO2 Nitrogen dioxide +4

HNO3, NO3- Nitric acid, nitrate ion +5

Organic N

Well

aerated

soils

Plant

metabolism

Poorly

drained

soils

Most reduced

Most oxidized

C-NH2

more

electrons

less

electrons

Do any of you remember this view ???

April 19, 1995 - Alfred P. Murrah Federal Building

Nitrate is a

powerful

oxidizing

agent!

Ammonium

nitrate

+

diesel fuel

Why is this

combination

explosive ?

The on-going process of N shifting from one form

to another is collectively called the N cycle

Plant biomass

Soil

Microbial biomass

Can you

identify all the

different forms of N?

Can you

identify all the

N transformations

and/or translocations?

Why do plants

need N ?

Nitrogen is an integral component of

many essential plant compounds

Amino acids

Proteins

Nucleic acids

Chlorophyl

enzymes 2.5 - 4% of

plant dry matter

Old leaves first

Evidence of N

Deficiency

yellowing

(chlorosis) that

starts at the tip

and moves in

along the midrib

These symptoms

should not be used

to identify when N is

needed.

Major irreversible

yield loss has

already occurred

when these

symptoms are

present

Nitrogenase: the key to biological N fixation

Only way that N “fixation” can occur at

low temperatures and pressures

Substantial energy input is still required

~ 8 lbs of C per lb of N fixed

Major constraint on legume yields

Added N often has no impact on legume yields

Legume

nodules

come in

many shapes

and sizes

Legume inoculants

can be purchased in a variety of forms

Inoculation groups for commonly grown forage legumes.

Alfalfa Group

(Rhizobium meliloti)

Alfalfa

Black medic

Bur clover

Button clover

White sweetclover

Yellow sweetclover

Clover Group

(Rhizobium trifolii)

Alsike clover

Arrowleaf clover*

Ball clover

Berseem clover

Crimson clover

Hop clover

Persian clover

Red clover

Rose clover*

Subterranean clover*

White clover

Cowpea Group

(Bradyrhizobium japonicum spp.)

Alyceclover

Cowpea

Kudzu

Peanut

Lespedeza

Joint vetch

Lupine Group

(Rhizobium lupini)

Blue lupine

White lupine

Pea and Vetch Group

(Rhizobium leguminosarum)

Bigflower vetch

Common vetch

Hairy vetch

Roughpea

Winter pea

Other**

Bird’s-foot trefoil (Rhizobium loti)

Cicer milk vetch

Crown vetch

Sainfoin (Rhizobium)

Soybean (Rhizobium japonicum)

Kura clover

Leucaena

Soybean has its own inoculation group

Typical amounts of N fixed

by forage legumes

Crop N fixed

(lb/A/year)

Alfalfa 150-300+

Red clover 75-200

White clover 75-150

Other annual forage

legumes 50-150

Not all legumes are efficient N fixers !

Efficient N fixers

forage legumes, soybeans

cowpeas, peanuts

Inefficient N fixers

snap beans

garden peas

lima beans

Often responsive to added N

Some non-legumes (e.g., alder trees)

fix N symbiotically with bacteria

other than rhizobia.

Some legumes (e.g., Styphnolobium affine)

are not able to fix N symbiotically.

Some N fixing bacteria (e.g., azotobacter)

are free-living - meaning that they do not

need host plants.

Styphnolobium

affine

Haber-Bosch process

http://4.bp.blogspot.com/_7RVwVtep2vE/SmrKGGhX4JI/AAAAAAAAAHI/iJUdqNU-ROg/s1600-h/haber2.gif

Where does

the hydrogen

come from??

CH4 Industrial N fixation invented over 100 yrs ago, refined but not replaced

~ 130 gallons of diesel fuel per ton of NH3

~ 185 GDF/ton NH3

~ 300 GDF/ton NH3

Industrial N fixation is very energy intensive!

Fig. 6.12 in Smil (2001)

Large

improvements

in energy

efficiency

were made

during the 20th

century.

> 700 GDF/ton NH3

GDF = gallon of diesel fuel

5.5 lbs N/GDF

8.9 lbs N/GDF

NH4+

Nitrification

Nitrification is actually a multi-step process

NO2- is a toxic intermediate product

Warm, aerated, near neutral conditions

promote rapid nitrification

NO3- NO2

-

Nitrification inhibitors like N-serve

disrupt the first step of this process

http://www.ipm.iastate.edu/ipm/icm/node/181/print

Nitrification is slower in cold soils

“If the industry is to

continue the practice of

fall N application, we

must police ourselves or

risk losing the option of

applying nitrogen in the

fall.”

“Being smart about the timing of anhydrous application can

pay large dividends!

WAIT UNTIL DAILY MAXIMUM SOIL TEMPERATURES AT

4-INCHES ARE BELOW 50 DEGREES FAHRENHEIT.

The rate of nitrification is significantly reduced when soil

temperature is below 50 degrees F, but microbial activity

continues until temperatures are below freezing.

In order to minimize risk, don’t apply nitrogen before the third

week of October in central Illinois, or the second week in

northern Illinois, even if air temperatures are getting cooler.

In addition, do not use nitrogen or nitrogen with a nitrification

inhibitor if you live south of Illinois Route 16 or if soils are

prone to leaching.”

http://www.isws.illinois.edu/warm/

Maximum soil temps

under bare soils at 4”

U of I anhydrous

application guidelines

are based on daily

maximum temp at 4”

Fall N application south of

IL HWY 16

is never recommended

by the U of I

DO NOT APPLY

WHEN YOUR

AREA IS RED!

Sample Date

Dec. 8 Apr. 2 May 3

Application N-serve % NH4-N Remaining

Nov. 7 (>50°F) No 39 19 3

Yes 63 28 17

Nov. 18 (<50°F) No 40 33 7

Yes 67 58 26

http://www.ipm.iastate.edu/ipm/icm/2001/10-22-2001/why50.html

Nitrification inhibitors are only cost-effective when

weather conditions occur that cause both significant

nitrification and loss of nitrate

It is normally more efficient to apply N in the spring

even if a nitrification inhibitor is used

Fall with N serve

Fall without N serve

Spring w/o N serve

http://soil.scijournals.org/cgi/content/full/68/2/545/FIG4

Soil pH

% N

itri

ficati

on

Impact of pH and N-serve on % nitrification

Inhibitor = N-Serve

w/o N serve

w/ N serve

Low ph inhibits nitrification as

much or more than N-serve High ph can override N-serve

Soil pH should be considered an important

factor affecting the risks and benefits

associated with fall applications of anhydrous

ammonia under climatic conditions found in the

Corn Belt.

Relatively rapid nitrification in higher-pH soils increases

the potential for leaching and denitrification of NO–3

before plants begin rapid growth and uptake of N.

N-Serve is probably a waste of money on low pH soils!

NO3- NO2

- NO N2O N2

Denitrification

Warm, anaerobic conditions + OM

promote rapid denitrification

N2O (nitrous oxide) is an ozone depleter and potent greenhouse gas

Why is nitrate such a slippery character ?

• Nitrate is an anion (i.e., negatively charged)

• Nitrate compounds are very soluble

• Nitrate is next in line as an electron acceptor

when O2 is not present

Denitrification

Immobilization

Net

min

era

lizati

on

N

et

imm

ob

iliz

ati

on

Jenkinson

Mineralized soil N

wheat pasture

Potential

N uptake by

SOM-N frequently does not become plant

available fast enough for maximum yield

Where does the N come from

that enters a corn crop ? Well-fertilized crops often obtain

more than half of their N from SOM

Why

more N

uptake?

Less

tie-up !

Magdoff and Weil (2003)

What happens to fertilizer N ?

http://agronomyday.cropsci.uiuc.edu/2001/tours/n-fate/index.html

Measured after harvest

Environmental

losses during

growing season

90

100

80

Which N

rate is

likely to

result in

the most

leaching

over the

winter?

So how were the scientists

able to track the fertilizer N?

They used fertilizer spiked with N15!

N rates applied to corn in the US

have been relatively stable for 3 decades

150 kg/ha = 134 lbs/ac

Corn yields have increased steadily since ~ 1940

160 bu/acre

2009 corn crop = 165 bu/ac (national average) 2010 corn crop = 153 bu/ac (national average)

What do you think it will be this year?

lb

s o

f g

rain

per

lb o

f N

As a result…

Yield per unit of N has increased over the last 30 years

Some IL farmers consistently harvest more than

75 lbs of grain (1.3 bu) for each lb of N applied

?

Should N rates for corn be based on expected yield?

Basing N rate on yield is logical - unfortunately optimal yield:N rate

relationships vary widely from site to site and season to season

Relationship between optimal N rate

and optimal corn yield in IL (72 site years)

Only 13 out of 72 site-years in IL required more than 1 lb of N per bushel

1 : 1 line

1.2 : 1 line

too high 96%

of the time

too high 82%

of the time

BOTTOM LINE

There is no line that fits

this data well

Yield is a poor predictor

of optimal N rate !!

www.extension.iastate.edu/Publications/PM2015.pdf

Can you

believe

prices were

this low just

5 years ago?

Current version of the N rate calculator

Maximum return to N

when price ratio is 0.05

PRICE RATIO

0.20

The N rate calculator uses regularly updated

data from regional N rate experiments and a

logical “Maximum Return to N” approach.

It is clearly more science based than yield

based methods of setting N rates but is

currently not used by many farmers.

So why do you think

the N rate calculator

is not more widely

used?

So how do IL

farmers manage

N for corn?

> 50 yrs vs. < 40 yrs

college vs. no college

> 1000 ac vs. < 1000 ac

Each of you needs to collect

answers to these questions

from 2 farmers that differ in

one of the following ways:

A few answers from last year

Why don’t most labs test for N ???

Total soil N is also a poor predictor of

in-season availability of N

Preseason mineral N is a poor predictor of

in season availability of N in humid regions

Soil

organic

matter

4000

160 80

200 200

Microbial

biomass

NO3- + NH4

+

From the

atmosphere

50

To the

atmosphere

10-50 ? Fertilizer Crop

uptake

Loss by

leaching

20-100 ?

Can we manage for the

variable amount of plant

available N supplied by

soil ?

PSNT = Pre-sidedress nitrate test

LSNT = Late spring nitrate test

Soil yield potential

Very high/high Medium/low

PSNT value Nitrogen credit

- - ppm N - - - - - lb N/a - - -

> 21

18-20 100 80

15-17 60 80

13-14 35 40

11-12 10 40

< 10 0 0

Nitrogen credits for the pre-sidedress soil nitrate test (PSNT)

http://ipcm.wisc.edu/WCMNews/tabid/53/EntryID/293/Default.aspx

Benefit from added N is unlikely

Researchers in many states

(other than IL) have evaluated

the PSNT and identified

modifications that work well for

specific crops and locations

Comparison of the ISNT and PY methods for predicting sites

where corn is nonresponsive to N fertilization.

No. of nonresponsive sites

Sites predicted by

Management

system

# of sites

studied total PY ISNT

Manured

within 1 year 21 19 6 17

Continuous

corn 27 16 0 14

Corn after

soybean 49 12 0 11

Corn after

alfalfa 6 5 0 5

Corn after

wheat 2 0 0 0

Total 105 52 6 47

The 84 sites identified by crop rotation had not received manure for at least three

years prior to the growing season studied.

PY = Proven Yield method of determining N rate for corn

Recommended N rate = Proven yield in bushels* 1.2 lbs of N/bushel

– manure or legume credits

Illinois Soil N test = Amino sugar test

The soil sample is treated with sodium hydroxide solution in a

Mason jar, then heated for five hours on a griddle at 48–50º C to

convert amino sugar-N to gaseous ammonia.

The ammonia is collected in boric acid-indicator solution and

determined by titration.

http://cropsci.uiuc.edu/classic/2002/Article9/figure1.cfm

Amino sugar N

No

response to

additional N

No relationship

between

ISNT and EONR

EONR =

economically

optimum N rate

University of Wisconsin-Madison Department of Soil Science 2006

Relationship between ISNT and

total SOM in Wisconsin

Strong correlation of ISNT values to soil organic matter (OM) shows

that the ISNT is probably measuring a constant fraction of soil

organic N rather than a special mineralizable N pool

Organic matter (%)

0 1 2 3 4 5

ISN

T (

mg

kg

-1)

0

100

200

300

400

y = 12.9715 + 62.5734x

r2 = 0.88

n = 80

Nitrogen (N) prices and environmental concerns have caused many corn

(Zea mays L.) producers and advisors to rethink their current N management

practices. These past 3 years, laboratory and field trials were conducted in

NY to evaluate the performance of the Illinois Soil N Test (ISNT) in identifying

whether or not additional N was needed. Initial test results showed the need

for temperature control in the laboratory and resulted in a modification of the

procedure to include enclosed boxes. Evaluation of the ability of the modified

ISNT procedure in detecting increases in organic N upon compost and

manure addition showed an increase in ISNT over time consistent with N

credits from manure currently employed for N management in New York.

However, to obtain an estimate of potential N release from readily available

organic N sources, sampling should not take place within 4-5 weeks after

manure (or fertilizers that contain ammonium) application or sod or cover

crop plowdown or chemical kill.

Research in NY

Results of the first 3 years of field trials showed that soil

samples taken to 20-cm (8 inch) depth and analyzed for

both ISNT and LOI-OM can be used to predict the need for

additional N for corn beyond starter fertilizer in New York

The ISNT has been discussed positively and

negatively in quite a few farm press articles

over the last 5 years.

http://www.usawaterquality.org/conferences/2009/PDF/Ag_BMPs-oral/Scharf09.pdf

GreenSeeker Technology

High N rate

strip needed

6. How has using GreenSeeker impacted your farming operations? Do you think

GreenSeeker saved you money either in cost savings or yield improvement?

We were a little conservative with GreenSeeker the first year. We used it on 4,000 acres and

reduced nitrogen application about 20 pounds an acre on average. We didn’t lose any yield. You

couldn’t tell any yield difference between fields with lower nitrogen applications and our regular

program, which averaged about 155 pounds. We saved at least 20 units across the board. The

total nitrogen savings was about $24,000. So I paid for the cost of GreenSeeker the first year.

7. What would you tell a fellow farmer who was considering GreenSeeker?

You have to trust what you are doing and have faith in the concept. Don’t go hog wild. Maybe only

do half your crop the first year. And then you will see whether it will pay for itself. There are a lot of

times when you are sidedressing (without GreenSeeker) and the crop doesn’t look like it needs it.

The GreenSeeker takes the guesswork out of it.

8. Any final thoughts on GreenSeeker.

The overall concept behind GreenSeeker will be even more important in the future. If you can save

yourself a little bit on each farm, it adds up.

Even though prices are good now, you still have to farm like your profit potential is poor. That is just

good business. The biggest way you can save money is with N.

If there is a penny to be saved, I am going to save it. Those pennies here and there are what got

you through when you were selling your corn for $2. The way nitrogen costs, we can’t afford to

waste it.

Some GreenSeeker results

from the IA Soybean Association On-Farm Network

What do you think this rig costs ?

How much N is

taken up after

tasseling? A lot!!!

htt

p:/

/ww

w.b

ecksh

yb

rid

s.c

om

/researc

h/2

01

0/p

g1

68.p

df

Most widely used N fertilizers

Monoammonium phosphate (MAP)

52% P2O5, 11% N, 100% water soluble

Very high phosphorus analysis. Excellent material for use in starter fertilizer

Diammonium phosphate (DAP)

46% P2O5, 18% N, 100% water soluble

Most common phosphorus fertilizer. Used extensively as the basis for blended fertilizers

Ammonium polyphosphate Solid: 55% P2O5, 11% N Liquid: 34% P2O5, 10% N

Liquid form is very common N and P fluid fertilizer

Ammonium phosphates

Material fall06 spring07 11-52-0 6,955 4,017 18-46-0 56,653 42,147

10-34-0* 766 1,567 28-0-0 19,173 127,447 32-0-0 12,616 75,737 46-0-0 10,136 23,480 82-0-0 293,375 277,952

82.5-0-0 17,906 4830 98.8 % of material grade

94.6% of total N

N fertilizer materials purchased in IL

* (10-30-0, 10-32-0, 10-34-0, 11-33-0, 11-37-0)

1,043,307

55 %

22.5%

10.5%

AA

Urea

UAN

DAP

3.2%

MAP

All #s are tons

Shift toward greater use of urea and UAN in the Midwest

Reasons for the decline in use of NH3

Concerns about human safety and impacts on soil

Rail companies are raising rates and limiting transport of NH3

When application window is short, UAN is favored over NH3

Weather/soil conditions limit NH3 application window

UAN application is faster and more flexible

1-2 thousand acre/day for UAN vs. a few hundred acres for NH3

UAN can be applied with other crop inputs

Ammonia Hazards

Anhyd-06

• Caustic (alkali) burns

• Freezing burns

• Inhalation danger to

lining of mouth, throat

and lungs

• Does not support

respiration – suffocation

danger

• Especially dangerous to

eyes

Agrochemicals and Security: Security and Anhydrous Ammonia

Many anhydrous ammonia applicators give

uneven applications, particularly applicators

with older manifolds.

Manifold outlets across from the intake usually

put out higher rates than outlets near the intake.

When an older manifold is used, the most

important management practice is to randomize

the hoses. This means that a row getting a low

rate is more likely to be next to a row getting a

high rate, which will minimize yield loss.

The Equaply system is only one of a number of good options for

uniform anhydrous application on the market today!

Nitrogen components of phosphorus (P)

fertilizers can also be safely credited if they

are spring-applied. Crediting half the N is safer

if the P was applied in the fall before growth of

a summer crop. Nitrogen components of

starter fertilizers and nitrogen applied with

herbicides should be included as part of the

total intended N rate.

Don’t ignore the N in DAP, MAP and starter fertilizer

Urea should not be broadcast and left on the surface

for extended periods.

Missouri research has shown a 14 bu/acre yield penalty in

corn (average of 38 experiments, mostly no-till) and a 5

bu/acre yield penalty in wheat (average of 9 experiments)

when urea is broadcast and not incorporated.

Recommended methods of applying urea:

• Treatment with Agrotain volatilization inhibitor before

broadcasting.

• Incorporation with tillage (within 3 or 4 days of

application).

• Incorporation with irrigation (within 3 or 4 days).

• Knife injection.

Urea (46-0-0)

UAN (urea-ammonium nitrate) solution (28%–32% N)

should not be broadcast on high-residue surfaces.

Missouri research has shown a 25 bu/acre yield

penalty when solution is broadcast in no-till corn

(average of 20 experiments, mostly corn-soybean

rotation). In tillage systems with less residue, less

yield loss would be expected.

Dribbling solution reduces contact

between nitrogen and residue, and

injection is best !

http://frec.cropsci.uiuc.edu/2007/report9/

• Effective

• Efficient

• Environmentally Smart Nitrogen

http://www.agrium.com/5228.jsp

How many IL farmers actually use

slow release N sources???

All of them! > 50% of the N taken up by corn

is normally from OM

Recommended adjustments in N rates for legumes or manure

Less N is needed when corn is planted late

Research at the Northern Illinois Research Center has shown that less nitrogen fertilizer is required for most profitable yield when planting date is delayed. Based upon that research, U of I agronomists suggest that for each week of delay in planting after the optimal date for an area, the nitrogen rate can be reduced 20 pounds per acre - down to 80 to 90 pounds per acre as the minimum for very late planting in a corn–soybean cropping system. Suggested reference dates are April 10 to 15 in southern Illinois, April 20 to May 1 in central Illinois, and May 1 to 10 in northern Illinois.

The cornstalk nitrate test developed by Iowa State

University (Iowa State Extension publication PM-

1584, Cornstalk Testing to Evaluate Nitrogen

Management) is a reliable way to evaluate your N

program at or near harvest. It cannot be used to

guide N application rate, but can be used to tell

whether the N rate in a particular area was too low,

optimal or excessive. Feedback gained from this test

can help producers improve rate decisions in

following years.

So how well did you do ?

Cornstalk nitrate testing

700-2000 ppm = optimum

http://www.extension.iastate.edu/Publications/PM1584.pdf