This is a PDF version of a power point presentation developed for my soil fertility class. Email if you would like to receive a copy of the powerpoint - j-gruver@wiu.edu

1. NITROGEN
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?

2. Where is the N on planet earth ??
N Reservoir MegaTons % of Total
Biomass 2.8 x 105 0.0002
Water 2.3 x 107 0.014
Atmosphere 3.86 x 109 2.3
Geosphere 1.636 x 1011 97.7
Crust 0.13 - 1.4 x 1010 0.78-8.4
Soils and Sediments 0.35 - 4.0 x 109 0.21-2.4
Mantle and Core 1.6 x 1011 95.6
Most geosphere N is deep within the earth
and has little relevance to biological cycles.

3. Biologically relevant N
Reservoir/Pool Type MegaTons BR N
% of Total
Biomass 2.8 x 105 <0.01
0.0002
Water 2.3 x 107 < 1%
0.014
Soil 0.35 x 109 ~8%
0.21
Atmosphere 3.86 x 109 2.3 %
> 90
N2
~ 78% of the earth’s atmosphere

4. 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.

5. Lightning Pollution
Reactive (primarily from engines)
N
Reactive Industrial Reactive
N fixation
N N
Biological N
fixation in
Reactive agriculture
Biological N
fixation in nature
N

6. ~ 5 MT NH3 manufacturing plants
currently produce ~ as
~ 20 MT much reactive N as all other
processes on planet earth
~ 30 MT
~ 85 MT
> 130 MT
~ 90% used for fertilizer

7. Human activities
~ 20 MT
are fertilizing the
entire planet with
reactive N
~ 30 MT
> 130 MT

8. Nitrogen has many different oxidation states !
Species Name Oxidation State
C-NH2 Organic N
Plant
NH3, NH4+ Ammonia, ammonium ion -3 Most reduced
metabolism
N2H4 Hydrazine -2 more
NH2OH Hydroxylamine -1 electrons
N2 Nitrogen 0
Poorly
drained N2O Nitrous oxide +1
soils NO Nitric oxide +2 less
HNO2, NO2- Nitrous acid, nitrite ion +3 electrons
Well NO2 Nitrogen dioxide +4
aerated
soils HNO3, NO3- Nitric acid, nitrate ion +5 Most oxidized

9. Do any of you remember this view ???
Why is this Ammonium Nitrate is a
powerful
combination nitrate oxidizing
explosive ?
+ agent!
diesel fuel
April 19, 1995 - Alfred P. Murrah Federal Building

10. The on-going process of N shifting from one form
to another is collectively called the N cycle
Soil
Microbial biomass
Plant biomass
Can you
Can you identify all the
identify all the N transformations
different forms of N? and/or translocations?

11. Why do plants
need N ?
Nitrogen is an integral component of
many essential plant compounds
Amino acids
2.5 - 4% of
Proteins enzymes
Nucleic acids
plant dry matter
Chlorophyl

12. Old leaves first
Evidence of N These symptoms
Deficiency should not be used
to identify when N is
needed.
yellowing
(chlorosis) that Major irreversible
starts at the tip yield loss has
and moves in already occurred
when these
along the midrib symptoms are
present

13. Nitrogenase: the key to biological N fixation

14. Added N often has no impact on legume yields
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

15. Legume
nodules
come in
many shapes
and sizes

16. Legume inoculants
can be purchased in a variety of forms

17. Inoculation groups for commonly grown forage legumes.
Alfalfa Group Alfalfa
(Rhizobium meliloti) Black medic
Bur clover
Button clover
White sweetclover
Yellow sweetclover
Clover Group Alsike clover
(Rhizobium trifolii) Arrowleaf clover*
Ball clover
Berseem clover
Crimson clover
Hop clover
Persian clover
Red clover
Rose clover*
Subterranean clover*
White clover
Cowpea Group Alyceclover
Soybean has its own inoculation group
(Bradyrhizobium japonicum spp.) Cowpea
Kudzu
Peanut

18. Typical amounts of N fixed
by forage legumes
N fixed
Crop
(lb/A/year)
Alfalfa 150-300+
Red clover 75-200
White clover 75-150
Other annual forage
50-150
legumes

19. 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

20. Some legumes (e.g., Styphnolobium affine)
are not able to fix N symbiotically.
Styphnolobium
affine
Some non-legumes (e.g., alder trees)
fix N symbiotically with bacteria
other than rhizobia.
Some N fixing bacteria (e.g., azotobacter)
are free-living - meaning that they do not
need host plants.

21. CH4 Industrial Nprocess
Haber-Bosch fixation
invented over 100 yrs ago, refined but not replaced
Where does
the hydrogen
come from??
http://4.bp.blogspot.com/_7RVwVtep2vE/SmrKGGhX4JI/AAAAAAAAAHI/iJUdqNU-ROg/s1600-h/haber2.gif

22. Industrial N fixation is very energy intensive!
> 700 GDF/ton NH3
Large
improvements
in energy
efficiency
were made
during the 20th
century.
~ 300 GDF/ton NH3
5.5 lbs N/GDF
~ 185 GDF/ton NH3
~ 130 gallons of diesel fuel per ton of NH3 8.9 lbs N/GDF
GDF = gallon of diesel fuel
Fig. 6.12 in Smil (2001)

23. Nitrification inhibitors like N-serve
disrupt the first step of this process
Nitrification
NH4+ NO2- NO3-
Nitrification is actually a multi-step process
NO2- is a toxic intermediate product
Warm, aerated, near neutral conditions
promote rapid nitrification

24. Nitrification is slower in cold soils
http://www.ipm.iastate.edu/ipm/icm/node/181/print

25. “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.”

26. “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.”

27. Maximum soil temps
under bare soils at 4”
http://www.isws.illinois.edu/warm/
DOof I anhydrous
U NOT APPLY
application guidelines
are basedYOUR
WHEN on daily
maximumIS RED!
AREA temp at 4”
Fall N application south of
IL HWY 16
is never recommended
by the U of I

28. Nitrification inhibitors are only cost-effective when
weather conditions occur that cause both significant
nitrification and loss of nitrate
Sample Date
Dec. 8 Apr. 2 May 3
Application N-serve % NH4-N Remaining
No 39 19 3
Nov. 7 (>50°F)
Yes 63 28 17
No 40 33 7
Nov. 18 (<50°F)
Yes 67 58 26
http://www.ipm.iastate.edu/ipm/icm/2001/10-22-2001/why50.html

29. It is normally more efficient to apply N in the spring
even if a nitrification inhibitor is used
Spring w/o N serve
Fall with N serve
Fall without N serve

30. Impact of pH and N-serve on % nitrification
Inhibitor = N-Serve
w/o N serve
w/ N serve
% Nitrification
High ph inhibits nitrification as
Low ph can override N-serve
much or more than N-serve
Soil pH
http://soil.scijournals.org/cgi/content/full/68/2/545/FIG4

31. 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!

32. N2O (nitrous oxide) is an ozone depleter and potent greenhouse gas
Denitrification
NO3- NO2- NO N2O N2
Warm, anaerobic conditions + OM
promote rapid denitrification

33. 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

34. Immobilization

35. Net immobilization Net mineralization

36. SOM-N frequently does not become plant
available fast enough for maximum yield
Potential
N uptake by
wheat pasture
Mineralized soil N
Jenkinson

37. Well-fertilized the N often obtain
Where does crops come from
more than half of their Ncrop ?
that enters a corn from SOM
Why
Less
more N
tie-up !
uptake?
Magdoff and Weil (2003)

38. What happens to fertilizer N ?
100
So how were the scientists
90 able to track the fertilizer N? Environmental
losses during
80 They used fertilizer spiked with N15! growing season
Which N
rate is
likely to
result in
the most
Measured after harvest leaching
over the
http://agronomyday.cropsci.uiuc.edu/2001/tours/n-fate/index.html winter?

39. N rates applied to corn in the US
have been relatively stable for 3 decades
150 kg/ha = 134 lbs/ac

40. Corn yields have increased steadily since ~ 1940
160 bu/acre
2010 153
2009 corn crop = 165 bu/ac (national average)
What do you think it will be this year?

41. As a result…
Yield per unit of N has increased over the last 30 years
?
lbs of grain per lb of N
Some IL farmers consistently harvest more than
75 lbs of grain (1.3 bu) for each lb of N applied

42. 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

43. 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
too high 96%
of the time
1.2 : 1 line
1 : 1 line
BOTTOM LINE
There is no line that fits
too high 82% this data well
of the time
Yield is a poor predictor
of optimal N rate !!

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

45. Can you
believe
prices were
this low just
5 years ago?

46. Current version of the N rate calculator

48. Maximum return to N
0.20
when price ratio is 0.05
PRICE RATIO

49. So why do you think
The N rate calculator uses regularly updated
data from regional N rate experiments and a
the N rate calculator
logical “Maximum Return to N” approach.
is not more widely
It is clearly more science based than yield
based methods of setting N rates but is
used?
currently not used by many farmers.

50. So how do IL
farmers manage
N for corn?
Each of you needs to collect
answers to these questions
from 2 farmers that differ in
one of the following ways:
> 50 yrs vs. < 40 yrs
college vs. no college
> 1000 ac vs. < 1000 ac

51. A few answers from last year

52. Why don’t most labs test for N ???
From the To the
atmosphere atmosphere Crop
50 10-50 ? Fertilizer uptake
200 200
Soil
organic
matter
4000 160 80
NO3- + NH4+
Microbial
biomass
Loss by
leaching
Preseason mineral N a poor predictor of of
Total soil N is also is a poor predictor 20-100 ?
in season availability of N in humid regions
in-season availability of N

53. Can we manage for the
variable amount of plant
available N supplied by
soil ?

54. PSNT = Pre-sidedress nitrate test
LSNT = Late spring nitrate test

56. Nitrogen credits for the pre-sidedress soil nitrate test (PSNT)
Soil yield potential
Very high/high Medium/low
PSNT value Nitrogen credit
- - ppm N - - - - - lb N/a - - -
> 21 Benefit from added N is unlikely
18-20 100 80
15-17 60 80
13-14 35 40
11-12 10 40
< 10 0 0
http://ipcm.wisc.edu/WCMNews/tabid/53/EntryID/293/Default.aspx

57. Researchers in many states
(other than IL) have evaluated
the PSNT and identified
modifications that work well for
specific crops and locations

59. Comparison of the ISNT and PY methods for predicting sites
where corn is nonresponsive to N fertilization.
PY = Proven Yield method of determining N ratesites
No. of nonresponsive for corn
Sites predicted by
Management # N rate = Proven yield in bushels* 1.2 lbs of N/bushel
Recommended of sites
total PY ISNT
system studied – manure or legume credits
Manured
21 19 6 17
within 1 year
Continuous
27 16 0 14
corn
Corn after
49 12 0 11
soybean
Corn after
6 5 0 5
alfalfa
Corn after
2 0 0 0
wheat
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.

60. 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.

61. Amino sugar N
No
response to
additional N
http://cropsci.uiuc.edu/classic/2002/Article9/figure1.cfm

62. No relationship
between
ISNT and EONR
EONR =
economically
optimum N rate

63. 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
400
y = 12.9715 + 62.5734x
2
r = 0.88
n = 80
300
ISNT (mg kg-1)
200
100
0
0 1 2 3 4 5
Organic matter (%)
University of Wisconsin-Madison Department of Soil Science 2006

65. Research in NY
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.
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

66. The ISNT has been discussed positively and
negatively in quite a few farm press articles
over the last 5 years.

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

68. GreenSeeker Technology

69. High N rate
strip needed

72. 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.

73. Some GreenSeeker results
from the IA Soybean Association On-Farm Network

74. What do you think this rig costs ?

76. How much N is
taken up after
tasseling? A lot!!!

77. http://www.beckshybrids.com/research/2010/pg168.pdf

78. Most widely used N fertilizers

79. Ammonium phosphates
Very high phosphorus
Monoammonium 52% P2O5, 11% N, 100%
analysis. Excellent material
phosphate (MAP) water soluble
for use in starter fertilizer
Most common phosphorus
Diammonium phosphate 46% P2O5, 18% N, 100% fertilizer. Used extensively
(DAP) water soluble as the basis for blended
fertilizers
Solid: 55% P2O5, 11% N Liquid form is very common
Ammonium polyphosphate
Liquid: 34% P2O5, 10% N N and P fluid fertilizer

80. N fertilizer materials purchased in IL
All #s are tons
Material fall06 spring07
MAP 11-52-0 6,955 4,017 10.5%
DAP 18-46-0 56,653 42,147
10-34-0* 766 1,567
28-0-0 19,173 127,447
UAN 22.5%
32-0-0 12,616 75,737
Urea 46-0-0 10,136 23,480 3.2%
AA 82-0-0 293,375 277,952
55 %
82.5-0-0 17,906 4830
98.8 % of material grade 1,043,307
94.6% of total N
* (10-30-0, 10-32-0, 10-34-0, 11-33-0, 11-37-0)

81. Shift toward greater use of urea and UAN in the Midwest

82. 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

83. Ammonia Hazards
• 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 Anhyd-06

84. 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.

85. The Equaply system is only one of a number of good options for
uniform anhydrous application on the market today!

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

87. Urea (46-0-0)
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.

88. 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 !

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

93. • Effective
• Efficient
• Environmentally Smart Nitrogen
http://www.agrium.com/5228.jsp

94. 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

95. Recommended adjustments in N rates for legumes or manure

96. 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.

97. So how well did you do ?
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.

98. Cornstalk nitrate testing
700-2000 ppm = optimum
http://www.extension.iastate.edu/Publications/PM1584.pdf