Upload
jbgruver
View
1.664
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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 - [email protected]
Citation preview
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