Ammonium Nitrate

1
Ammonium Nitrates Disappearance and Record High
N Prices Implications for N Management Prepared
for Crop Pest Management School, 2006
by Clain Jones, Extension Soil Fertility
Specialistclainj_at_montana.edu 406 994-6076
2
Your profession

• Crop Advisers/Chemical Dealers?
• Extension Agents?
• Producers?
• Others?

3
Why Important?

• Of all the nutrients, N generally has the largest
  effect on yield and quality.
• Ammonium nitrate (34-0-0) has been discontinued
  by both Simplot and Agrium, affecting N source
  options for many growers.
• Many producers have historically used 34-0-0
  partially due to concerns with volatilization of
  alternatives, such as urea (46-0-0), and now will
  need information from you on these alternatives.

4
Presentation Outline

• N Fertilizer Manufacturing
• Volatilization
• - Mechanism
• - Amounts
• - Factors that affect it
• Management
• - N Source
• - Placement
• - Timing

5
Anhydrous Ammonia - The Base Material
Nitric Acid
Ammonium Nitrate (34-0-0)
Sulfuric Acid
Ammonium Sulfate (21-0-0-16)
NH3
Phosphoric Acid
Ammonium Phosphate (11-52-0, 18-46-0)
Carbon Dioxide
Urea (46-0-0)
Urea A.N. Water
Nitrogen Solution-UAN (28-0-0, 32-0-0)
6
N Source

• A pound of N is a pound of N-cost per unit of N
  and available equipment to apply N are likely 2
  most important factors in selecting N.

7
Ammonia Volatilization
READY FOR SOME CHEMISTRY??
8
Ammonia Volatilization

• Not an issue if fertilizer is incorporated at
  least 2 inches into soil-not an option with
  no-till or established forages
• Ammonia losses vary with environment and are
  difficult to predict. Most research done in
  southern U.S. where climate is more conducive to
  volatilization.

Looking at above equation, what is 1 factor that
increases volatilization?
High pH
9
N fertilizer can increase pH during hydrolysis
Urease enzyme
Ex Urea
CO(NH2)2 2H2O 2NH4 CO32-
CO32- H2O HCO3- OH- Effect on pH?
Increases temporarily. Why?
Good or bad?
Ammonium nitrate (AN) has little effect on soil
pH, therefore generally does not volatilize much.
Ammonium sulfate (AS) shouldnt raise pH much on
non-calcareous soils (but expensive per lb of N).
10
(No Transcript)
11
Why differences in volatilization?

• Urea and AS cause larger pH increases than AN.
• ½ of N in AN is nitrate which cant volatilize
• Note AS volatilizes more on calcareous soils
  than on non-calcareous soils

12
Factors Affecting Volatilization

• High soil pH
• High temperature, wind
• Low Cation Exchange Capacity (CEC)-why?
• Moist soil/humid conditions
• 0.1 in. of rain dissolves fertilizer, allows
  volatilization
• 0.5 in. of rain/irrigation pushes dissolved
  fertilizer about 2 in. into soil, minimizing
  volatilization if within about 2 days of
  fertilization
• Ground cover/vegetation/residue. WHY?
• Soluble and Exchangeable Ca (decreases)

Bottom line Large number of factors make
volatilization amounts VARIABLE and difficult to
predict.
13
Effect of Soil pH and Temperature on Relative
Amount of Ammonia
14
QUESTIONS?
15
Demonstration
Urea Treatment (300 lb N/ac) Ammonia odor Ammonia test (blue-very high green-high yellow-none)
Incorporated
Surface-Loam
Surface-Sand
Surface-Grass residue
Surface-Grass residue (100 lb N/ac)
16
N Management
-N Source -Placement-Timing
17
Granular N Sources Effect on Yield-Montana
Research Results
Note No journal-published data in Montana on
effect of N source on volatilization and only one
known published study on yield, though quite a
bit of unpublished research on sources
18
Economics?
19
Still, need to apply when cool, calm or some
ammonia will volatilize, especially from UR and
AS.
20
(No Transcript)
21
Summary Urea volatilization can happen, but in
Montana studies it generally did not have a
significant effect on yield compared to other
granular N fertilizers
How could UR produce similar yields as AN if UR
volatilizes more?

1. AN leaches more readily
2. Takes less energy for plant to convert ammonium-N
   than nitrate-N to protein.
3. Relatively little UR volatilized

22
Liquid Fertilizers

• Advantages
• -can more easily top-dress if have equipment
• -some N can be absorbed through leaves?
• Disadvantage
• - mainly cost
• - volatilization can be higher than granular

23
Urease Inhibitors

• Agrotain (NBPT) is main product. Delays
  hydrolysis by up to 14 days
• -advantage allows more chance for rain or
  irrigation
• -disadvantage will delay time to become
  available, volatilization can still occur, and
  cost (adds 50/t-urea).
• Research Results Few published studies. One
  showed NBPT significantly reduced ammonia
  volatilization (Watson, C.J. et al., 1994) on
  grassland and one showed Kentucky bluegrass yield
  increased 15 (Joo et al., 1991).
• Use? Would need to compare Agrotain with urea
  costs, and consider volatilization potential,
  including weather.

24
QUESTIONS?
25
Placement

• Granular
• - Surface broadcast. Best chance for
  volatilization. Established forage, essentially
  only option.
• - Seed-placed Dry grains-can dramatically
  decrease emergence. MSU Fertilizer Guidelines
  recommend less than 10-20 lb N/ac be applied
  directly with seed depending on crop, with 0-10
  lb N/ac for urea.
• Increasing spreader width can help

26
Maximum Fertilizer N K2O Recommended with Seed
Crop General Guideline (lb NK2O/ac) Urea with 6-7 in. spacing(lb NK2O/ac)
Wheat 20 10
Barley 30 15
Oat 25 25

• Higher amounts dont necessarily cause problems.
  Rates shown are designed to protect grower under
  worst-case conditions (dry and warm)
• When using wider row spacing, urea is not
  recommended. Wider openers, however, allow more
  fertilizer than shown.

27
(No Transcript)
28

• Liquid (UAN 32-0-0 or 28-0-0) Surface broadcast
  (including fertigation), surface band, or knifed.
• Method Forage Yield
• Surface Broadcast 2.9 t/ac
• Surface Band 3.4 t/ac
• WHY?

N. Central Regional Extension Pub 326, KSU
Hypothesized to be due to limited urease
concentration, slowing hydrolysis
29
Foliar Application

• Some N can be absorbed through leaves
• However, most foliar applied N ends up being
  taken up by roots
• -Only 8-11 of foliar applied liquid urea was
  taken up by leaves, whereas 37-67 of
  soil-applied N was taken up by plant (Rawluk et
  al., 2000).
• Risk of burn if gt 20-40 lb N/ac (crop dependent).
  Yield losses at higher rates (40-60 lb N/ac).

30
Timing

• Because UR may take days to weeks to become
  available, UR should be applied earlier than AN
  historically was for fast green-up on grass hay
  fields.
• Yield and quality are affected by timing

31
What makes yield?
Heads/area x Kernels/heads
x Weight/kernel
32
When are yield components set?
Weight/kernel set
Heads/acre set
Kernels/head set
33
Impacts of nitrogen
Nitrogen late Kernel Weight Higher grain protein
Nitrogen early Number of tillers and
kernels/head Grain protein from remobilized N
34
(No Transcript)
35
Timing, continued

• Fall vs Spring
• Generally better to apply near peak uptake to
  avoid losses. However, weather conditions (temp.,
  precip.) in first few days after application
  combined with soil texture may be more important.
  
• 1. Ex Shallow, coarse soil. Fall or Spring?
• 2. Ex Cool Fall temps with ability to irrigate,
  or warmer spring temps before irrigation water
  turned on. Fall or Spring?

Spring
Fall
36
Conclusions

• Urea has become the primary N granular option, so
  crop advisers and Extension agents will likely be
  getting more questions on its use.
• Urea volatilization can happen but doesnt appear
  to have large effects on crop yield in Montana.
  Effects can be reduced with well thought out
  placement and timing.
• Urea should be applied during cool, calm periods
  prior to irrigation or rain event (gt0.5).

37
QUESTIONS?
For more information on urea volatilization and
management, see http//www.oznet.ksu.edu/library/
crpsl2/NCR326.pdf For more information on N
cycling, fertilizer sources, placement and timing
see http//landresources.montana.edu/nm MSU
Soil Fertility webpage http//landresources.monta
na.edu/soilfertility