Ammonium Nitrate has Gone Away: Implications for N Management

1
Ammonium Nitrate has Gone Away Implications for
N Management Eastern Extension Agent Training,
2005
by Clain Jones, Extension Soil Fertility
Specialistclainj_at_montana.edu 406 994-6076
2
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 ammonium
  nitrate partially due to concerns with
  volatilization of alternatives, such as urea
  (46-0-0), and now will need information from you
  on alternatives.

3
Presentation Outline

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

4
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)
5
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. Beware
  those who say differently.
• Exceptions to above rule N source can affect
• - volatilization if broadcast
• - volatilization and availability if coatings or
  inhibitors

6
Ammonia Volatilization

• Mechanism?
• Amounts?
• Factors affecting?

READY FOR SOME CHEMISTRY??
7
Ammonia Volatilization

• Not an issue if fertilizer is incorporated at
  least 1.5 inches into soil-not an option with
  established forages or no-till.
• Losses vary with environment and are
  difficult to predict. Most research done in
  Kansas and Texas where climate is more conducive
  to volatilization.

Looking at above equation, what is 1 factor that
increases volatilization?
High pH
8
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 its expensive).
9
(No Transcript)
10
Why differences in volatilization?

• Urea and AS cause larger pH increases than AN.
• ½ of N in AN is nitrate which cant volatilize
• Why does AS volatilize more on calcareous soils?

11
Factors Affecting Volatilization

• High soil pH
• 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
• High temperature, wind
• Ground cover/vegetation/residue. WHY?
• Soluble and Exchangeable Ca (decreases)

Bottom line Large number of factors make
volatilization amounts VARIABLE and difficult to
predict.
12
QUESTIONS?
13
N Management
-N Source -Placement-Timing
14
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
15
Economics?
16
Still, need to apply when cool, calm or some
ammonia will volatilize, especially from UR and
AS.
17
(No Transcript)
18
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?

• AN leaches more readily
• Takes less energy for plant to convert ammonium-N
  than nitrate-N to protein.

19
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

20
Urease Inhibitors

• Agrotain (NBPT) is main product. Delays
  hydrolysis by up to 14 days
• -advantage allows more chance for rain or
  irrigation to push N into ground
• -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 cost with
  urea cost, and consider potential for
  volatilization, including weather.

21
QUESTIONS?
22
Placement

• Granular
• - Surface broadcast. Best chance for
  volatilization. Established forage, essentially
  only option.
• - Seed-placed Dry grains-can dramatically
  decrease emergence. MSU recommends 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 (see next
  slide)

23
(No Transcript)
24
Placement (Contd)

• 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
25
Foliar Application

• Some N can be absorbed through leaves
• However, most foliar applied N ends up being
  washed off and 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 in same
  study (Rawluk et al., 2000).
• Risk of burn if gt 20 lb N/ac (crop dependent).
  Yield losses at higher rates (40-60 lb N/ac).

26
Timing

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

27
Timing, continued

• Fall vs Spring
• Generally better to apply near peak uptake to
  avoid losses (volatilization, denitrification,
  leaching, immobilization). 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
  delivered. Fall or Spring?

Spring
Fall
28
Conclusions

• Urea has become the primary N granular option, so
  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).

29
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 Nutrient Mgmt Modules http//landresources.mo
ntana.edu/nm MSU Soil Fertility webpage
http//landresources.montana.edu/soilfertility