NITROGEN
Nitrogen
• Air
– 78% Nitrogen
– 35,000 Tons/Acre
– Unavailable Form
• Nitrogen Fertilization
– Required in largest quantities (2-6% in plants)
– Most frequently deficient nutrient
– Main environmental concern is leaching to groundwater
• Forms Used by plants as
– NO3 - Nitrate
– NH4+ Ammonium
Functions of N in Plants
• Constituent of
– Proteins (6.25 x %N for crops other than wheat)
(5.7x%N for wheat)
– Chlorophyll
– Enzymes and other compounds
• Necessary for respiration, growth and reproduction
• Increased grain and forage yield of nonlegumes
• Improved root growth and H2O use efficiency
Grain Sorghum N Uptake
Grain
Sorghum
Corn Nutrient Uptake And Dry
Matter Accumulation
100%
Potassium
% of Total Uptake
80%
Nitrogen
60%
Phosphorus
Dry Matter
40%
20%
V6
Tassel
Stage Of Growth
Maturity
Nutrient Deficiency Symptoms
• Pale green - yellow
coloration. Starts at
leaf tip & down midrib.
• Slow growth, stunted
plants
• Mobile - starts on
lower leaves
• Reduced tillering
• Low Protein
N Deficiency in Legumes
• Check roots
for active
nodules
Nitrogen Cycle
Soil Organic
Matter
Animal Manures
Mi
ne
(A
mm
on
if
Crop Residues
Im
Ammonia
Loss Through
Leaves
mo
bil
iz
ati
on
(
By
Cr
op
R
za
ti o
n
i ca
tio
n)
NH4+
Ammonium
Legume
Fixation of
Atmospheric N2
icatio
n)
Immobilization
ra
li
es
idu
es
)
Plant Uptake
(Nitri
f
Nitrogen Fixation
by Lightning
NO3Nitrate
Removed by
Harvest
Removed by Denitrification
(Gaseous Loss from Wet Soils
Removed by
Leaching
Fertilizer
Nitrogen
Nitrogen Cycle - Rainfall
• 3 to 10 lb N per Acre per year
• Unimportant over the short term,
but very important over hundreds
of thousands of years.
• Most deposited in summer with
thunderstorms, very little in snow
Mineralization
• Soil Organic Matter
¾ Source of most soil N
¾ 5% N, 1-3% released annually
• 10-30 pounds N per year per 1% Organic Matter
¾ Rate of release affected by:
•
•
•
•
Tillage
Temperature
Moisture
Past N inputs
Soil Organic Matter (SOM) Assumptions
9 Weight of Plow Layer (6-7”) of Soil equals 2,000,000 lb/acre
9 1% SOM x 2,000,000 = 20,000 lbs SOM/a
9
9 About 67% of residue carbon is lost as microbial CO2
9 About 1-3 % of SOM is decomposed each year
9 Assume soil organic matter is 5% N and 59% C
Soil Organic Matter N Contributions
9 For soil with 1% SOM
9 20,000 lb SOM x 5% N = 1,000 lbs N/A
9 1, 000 x 2% Mineralized/yr = 20 lbs N/A/yr mineralized
Clay Center Research Station,
Soil Temp @4 inches
65
Daily average Temp. 2001
55
50
45
40
15 year average
35
30
Date
ec
6D
29
-N
ov
ov
22
-N
ov
-N
15
ov
8N
ov
25
1N
Soil Temp (F)
60
LEGUMES
Symbiotic Fixation
• Alfalfa, clover, beans, etc.
• Symbiotic relationship with
Rhizobium bacteria
• Plant provides energy
(carbohydrate)
• Bacteria synthesize N2 to
NH4
Legume Crop N Credits
Nitrogen Credit (lb N/A)
Previous Crop
Warm Season
Cool Season**
Alfalfa Excellent Stand (5 or more plants/ft2)
Good Stand (2-4 plants/ft2)
Fair Stand (1-2 plants/ft2)
Poor Stand (less than 1 plants/ft2)
120
80
40
0
60
40
20
0
Sweet Clover Excellent Stand
Good Stand
Poor Stand)
110
60
0
55
30
20
Red Clover Excellent Stand
Good Stand
Poor Stand)
80
40
0
40
20
0
Soybeans
40
0
•N credits in no-till systems may be less.
•Cool season crops include winter small grains which grow in cool months of the year.
•Warm season crops include corn, sorghums, sunflowers and others which grow in
summer
Manure
• Highly variable nutrient content
• Year of application nutrient credit
– N = 25-90%
– P = 50-100%
– K > 85%
• NH3 volatilization if unincorporated or
applied through pivot
Percent Of Inorganic N Available To Crops For Various
Manure Management Systems
100%
90%
90%
65%
50%
50%
40%
30%
20%
10%
5%
Sweep
Injected
Knife
Injected
Sprinkler
Irrigation
Immediate 1 Day
Incorporation
2 Days
3 Days
4 Days
5 Days
6 Days
7+ Days
Time Between Broaccast Surface Application and Incorporation
Estimated Organic N Available To Crops After Manure Application
Year 1
Year 2
Year 3
- - - % Of Original Organic N Available - - -
Liquid Manure
Solid Manure
Compost
30
25
20
12
12
6
6
6
3
Solid Manure Nutrient Crediting Worksheet
Manure Test
Results From X
Laboratory
Nutrient Availability Factor
( Lb per ton )
=
Plant Available Nutrients
( Lb per ton )
Organic N
X
Ammonium N
25%
Availabile In Year Of Application
=
Organic N
X
Availability Factor From Fig. 1
=
Ammonium N
Total N
X
Sum Of Organic & Ammonium N
=
Ammonium + Organic N
Total P2O5
X
50% for V. Low - Low P Soil Tests
100% for Medium - V. High Soil Tests
=
Available P2O5
Total K2O
X
Potassium Efficiency Factor
=
Available K2O
85%
Liquid Manure Nutrient Crediting Worksheet
Manure Test
Results From X
Laboratory
Nutrient Availability Factor
( Lb per 1,000 gal )
=
Plant Available Nutrients
( Lb per 1,000 gal )
Organic N
X
Ammonium N
25%
Availabile In Year Of Application
=
Organic N
X
Availability Factor From Fig. 1
=
Ammonium N
Total N
X
Sum Of Organic & Ammonium N
=
Ammonium + Organic N
Total P2O5
X
50% for V. Low - Low P Soil Tests
100% for Medium - V. High Soil Tests
=
Available P2O5
Total K2O
X
Potassium Efficiency Factor
=
Available K2O
85%
Mineralization/Immobilization
Legume Residues
Manure
Soil Organic Matter
Organic N
Low C:N Ratios
Inorganic N
(plant available)
(plant unavailable)
High C:N Ratios
Corn Stalks
Sorghum Stubble
Wheat Stubble
Soil Microbes Responsible For Both Conversions
Nitrogen Immobilization & Mineralization
C:N > ~ 25:1
Immobilization
Inorganic N
Mineralization
Organic N
C:N < ~ 25:1
C:N Ratio of Organic Material Affects Rate of Activity
Immobilization
Residue with High C:N Ratio
Mineralization
Residue with Low C:N Ratio
Straw, Cornstalks, Sorghum stubble
Alfalfa, Soil Organic Matter, Manure
Plant available nitrogen tied up
Plant available nitrogen rreleased
Typical Carbon and Nitrogen
Content of Organic Materials
Source
% Carbon
% Nitrogen
C:N Ratio
Alfalfa
40
3.0
13:1
Soybean Residue
---
---
15:1
Cornstalks
40
0.7
60:1
Small grain straw
40
0.5
80:1
Microorganisms
50
6.2
8:1
Soil O.M.
52
5.0
10:1
Grain Sorghum
40
0.5
80:1
Manure
--
--
<20:1
Wood Chips
40
0.1
200:1
Glyphosate
(Roundup)
-
-
3:1
Ammonification (N mineralization) and Nitrification
Conversion of Nitrogen into plant-available forms through the microbial processes of
ammonification and nitrification.
Ammonification
Soil
Organic
Matter
Manure
Rotting
Plant
Residues
Nitrification
Oxygen
Oxygen
NH4+
H+
Ammonium
Acidity
Nitrosomonas
Bacteria
+
NO2-
NO3-
Nitrite
Nitrate
Nitrobacter
Bacteria
Effect of Temperature on Nitrification Rate
100
80
Rate of
Nitrate
Production 60
(% of Max.)
40
20
0
32
41
50
59
68
Temperature - Degrees F at 4-inch Depth
77
Effect of Time on Nitrification
75 Degrees F.
100
52 Degrees F.
80
%
Nitrification
60
47 Degrees F.
40
42 Degrees F.
20
37 Degrees F.
0
32
3
6
Time (Weeks)
9
Influence of Soil Temperature On Nitrification
Kansas
Stae University
Kansas State
University
450
400
November Application
(cool soil)
350
ppm NH4+-N
300
250
200
150
August Application
(warm soil)
100
50
0
0
August
60
October
120
December
180
February
240
April
300
June
How Nitrogen Fertilizer Affects
Soil Acidity
When the nitrification process converts the ammonium
ion to nitrate, hydrogen ions are released:
NH4+ + 2O2
Ammonium
Nitrifying Bacteria
Oxygen
NO3- + 2H+ + H2O
Nitrate
Hydrogen
Water
Effect of N Sources on Soil pH After 5 Years
of Applying 180 lb N/A to a No-till Field
N Source
Soil Sample Depth
0-7”
0-1”
None
6.5
6.7
Urea
6.2
5.9
UAN
6.2
5.8
Ammonium Sulfate
5.2
4.7
What Happens to Nitrate Nitrogen?
• Utilized by plants
• Retained in soil as inorganic N
• Immobilized to organic N
• Denitrification
• Leaching
N Loss Through Denitrification
Escapes As
Gases
Soil Surface
N2
NO
NO3-
NO2-
N2O
Caused by soil organisms that flourish in the absence of soil oxygen.
Obtain oxygen (O) by from NO3- .
Occurs in warm, saturated. Losses can be severe
Denitrification Losses in Waterlogged Soil
- how much can be lost?
• Depends on:
– temperature
– duration of anerobic
condition
– Can be more
significant than
leaching loss on nonsandy soil
Nitrogen Loss from Soil Saturated at Two
Temperature Ranges (Univ. Neb.)
Period of Saturation
Temperature (°F.)
N Loss (%)
5
55-60
10
10
55-60
25
3
75-80
60
5
75-80
75
7
75-80
85
9
75-80
95
What Can You Do To Manage
Denitrification N Loss ?
•
Improve soil drainage
•
Delay N application on wet soils
•
Nitrification Inhibitor
• Ammonium Containing/Forming N Sources
Nitrogen Leaching
Ammonium and Nitrate Ion Mobility
•
Ammonium (NH4+) Ions
– Positively charged
– Attracted to negatively
charged soil colloids
– Relatively immobile in soil
•
Nitrate (NO3-) Ions
– Negatively charged
– Repelled by negatively
charged soil colloids
– Move through the soil in
all directions
NO3+
NO3- NH4
NH4+
NH4+
NO3NH4+
NH4+
NO3-
Factors Affecting
Nitrogen Leaching
– Sandy soils
–
– Vertical channels (cracks, wormholes)
– N rate exceeds crop needs
– Improper application timing
– Nitrate N forms
Excessive Irrigation or Precipitation
Groundwater nitrate is a major environmental issue affecting
N fertilizer management
Environmental and Health Concerns
of NO3- in Water
• Blue baby (methemoglobinemia)
– 10 ppm N03- N standard
• Effect on aquatic life
–
–
–
–
increased algae growth
oxygen deficiency
Contributes to hypoxia (dead zone) in Gulf of Mexico
Nitrate sources include leaching (tile lines) and N runoff
Volatilization
• Loss of gaseous NH3 to atmosphere
can occur from:
¾ Unincorporated Surface applications
• Manure
• Urea containing materials under specific
conditions
¾ Anhydrous ammonia
• Poor sealing
• Too shallow
™ Will discuss in detail in urea section
N Volatilization From Leaves
• NH3 or N oxides
• 30-70 lbs/acre, much is reabsorbed in canopy
• % N recovery by plant may be higher than is
often reported (66% to 85%)
• Implication: Crops are more efficient at
recovering N than previously thought; thus less
is potentially available in soil for leaching.
Anhydrous Ammonia Plant
Air
N
Natural Gas
H
(N2,O2)
(CH4)
Nitrogen
Hydrogen
1 Part
3 Parts
Heat and
Pressure +
Catalyst
CO2
Nitric Acid Plant
HNO3
(Nitric Acid)
NH3
(Carbon dioxide)
Ammonia
Urea Plant
82% N
Urea Melt
Granulator
Ammonium Nitrate Plant
CO (NH2)2
Ammonium Nitrate Melt
(Urea) 46% N
Prilling Tower
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . ..
......................
(Urea Melt)
Ammonium Nitrate
Melt
Water
N Solution Plant
NH4NO3
UAN
Ammonium Nitrate
(Urea Ammonium Nitrate)
(34% N)
28-32% N
Alternatives to Natural Gas for
Ammonia Production
z
Coke
» by-product of oil refinery
used to produce NH3 at
Coffeyville, KS
z
Coal gasification
Anhydrous Ammonia
- The Base Material
NH3
Nitric
Acid
Ammonium Nitrate
Sulfuric
Acid
Ammonium Sulfate
Phosphoric
Acid
Carbon
Dioxide
Urea + A.N.
+Water
Ammonium Phosphate
Urea
Nitrogen Solution
Properties of Ammonia - NH3
N Content
82%
H Content
18%
Weight (lb/Gal)
5.7 at - 28 Degrees F.
5.3 at 32 Degrees F.
5.1 at 60 Degrees F.
4.9 at 100 Degrees F.
Expansion Rate
1 Gal. Liquid = 850 Gal. Vapor
Flammable Limits
16 to 25% by Volume in Air at 1500 ° F.
Specific Gravity [lb/gl]
0.588
Solubility
Extremely Water Soluble
Vaporization Point (Boiling Point)
-28 Degrees F.
Vapor Pressure at 0 Degrees F.
15.7 psi.
70 Degrees F.
114.1 psi.
100 Degrees F.
197.2 psi.
Handling Anhydrous Ammonia Safely
Remember! NH3 is hazardous because of tremendous affinity for water!
•NH3 Injury
• Dehydrates eyes, lungs and skin tissue
• Treat with water, water, more water!
• Have a shower or water tank at plant and 5 Gal water
container for tanks
• Don’t use salves for 24 hours
• Protect Lungs with a water soaked towel
•AVOID ACCIDENTS
• Work up-wind
• Maintain equipment
• Goggles, gloves, boots, and other equipment
• Instruct farmer users
Proper Sealing of NH3
• How much N loss?
Proper Placement of Ammonia
Too Shallow
Too Wet
Too Dry or
Sandy
Rate Too High
For Soil
Ammonia
moves too far
Some NH3
reaches
surface
Ideal Moisture
Correct Depth
Sealed at
surface NH3
spreads
about 4
inches
Some NH3
lost at
surface
Slit does not
seal, NH3
does not
penetrate
Recommended Knife Spacings
Crop
Recommended
Knife Spacing
(Inches)
Corn, Sorghum
30-40
Winter Wheat
12-18
Spring Small Grain
9-15
Effect of Spacing of NH3 Knives
On Corn Yield
Spacing & Location
of NH3 knife
Corn Yield
.
(bu/A)
30”, beneath corn row
144
30”, between rows
148
60”, beneath row
149
60”, between rows
145
60”, beneath adjacent rows
139
Effect of Application Depth and Time of Planting on
the Effect of Ammonia Toxicity on Corn Stands
Days Delay in Planting after NH3 Application
Depth of
Application
0
7
14
0
200 lb N
(Inches)
7
14
400 lb N
Stand (% of Normal)
4
60
96
100
35
60
90
7
100
100
100
80
100
100
10
100
100
100
100
100
100
Temporary effects of NH3 : Freezing temperature, High pH, & high affinity for water.
Ammonia Effect on Bacteria Population*
Days After
Injection Point 1-inch Away
2-inch Away
Bacteria/Gram Dry Soil
0
260,000
4,600,000
2,300,000
3
7,200,000
6,400,000
3,000,000
10
8,400,000
5,400,000
2,000,000
*Original Count 2,250,000 bacteria/gm of soil
pH in
injection
zone
Earthworm Population After Ammonia Application
Deibert and Uttier, North Dakota State University
Anhydrous Ammonia Application
Sept. 15
Nov. 1
-
Earthworms
Cocoons
Total
-
-
Earthworms per square yard
-
-
-
0 N
50 N
50 N
98
62
160
98
71
169
292
98
390
Doesn’t Anhydrous make
the Soil Hard?
Effect Of 20 Years Of N Fertilizers On Soils
(Kansas State University)
Nitrogen Source
Soil
pH
Soil
OM
(%)
NO3--N
Bray P-1
-
-
-
-
- ppm -
NH4+-N
-
-
-
Density
(lb/cu ft)
Check (No N)
6.2
2.0
38
4
5
100
Anhydrous Ammonia
5.2
1.8
27
27
9
99
Ammonium Nitrate
5.2
2.3
26
21
11
99
Urea
5.1
2.3
24
31
12
99
UAN Solution
5.2
2.0
28
20
8
100
78 bu/A for Ammonia. Ammonium Nitrate, Urea, UAN over last 4 years
37 bu/A for Check (No N) treatment over last 4 years
Sources of Knife to Knife Variability in
Output with NH3 Applicators
• Manifolds
– type and setup
– Hose barbs
Sources of Knife to Knife Variability
in Output with NH3 Applicators
• Hose length and size
• Knife styles, plugging
and wear
Sources of Knife to Knife Variability in
Output with NH3 Applicators
• Manifolds
– type and setup
• Hose length and size
• Knife styles, plugging
and wear
Ammonium Nitrate (NH4NO3, 34-0-0)
•
•
•
•
•
Hydrogen
Oxygen
Nitrogen
Bulk Density
Critical Relative Humidity
5%
60%
35%
48 to 58 lb/cu ft
59.4%
Ammonium Nitrate
• Advantages
– Not subject to volatilization losses
– Contains readily available, mobile nitrate
• Disadvantages
– Availability declining in market
– Can not ship internationally
– Nitrate portion is subject to leaching
– Cost of production is higher
– More corrosive to metal and concrete
– HydroscopicProduction continues to decline
Urea
•
•
•
•
•
Highest analysis dry fertilizer, 46-0-0
Dominates international marketplace
Good physical and handling characteristics
Fewer environmental production problems
Lower cost per pound of N
9 Potential volatilization loss
9 Do not place in direct seed contact
Urea Production
Ammonia
+
Carbon Dioxide
Energy (production)
Urea
+
Water
Urea (CO(NH2)2) 46-0-0
•
•
•
•
•
•
Hydrogen
Oxygen
Carbon
Nitrogen
Bulk Density
Critical Relative Humidity
6.6%
26.7%
20%
46.7%
45 to 48 lb/cu ft
75.2%
Ammonia Volatilization
Urea
+
Water
Enzyme (biological)
Ammonia
+
Carbon Dioxide
Factors Affecting Volatilization of
Surface Applied Urea
• Unincorporated surface applications
• Warm, moist, drying soil conditions
• Residues associated with enzyme
•
•
• Sandy soils and high soil pH increase potential
• No-till grain sorghum probably is most
susceptible (residues, warmer soils)
Understanding and Managing
Urea Containing Fertilizers
D. Kissel - McInnes, et. al
Kansas State University
D. Kissel - McInnes, et. al
Kansas State University
Warm, Moist Drying Soils
- Not Hot, Dry Conditions
Residue
- Urease, Moist Soil Surface
Immobilization Effects
Laboratory
Study
Urea Volatilization Loss Summary
• Potential for volatilization loss greatly
exaggerated
• Amount of loss is also greatly
exaggerated
• Need to recognize when volatilization
loss may potentially occur
Urea Volatility
• Only possible with unincorporated surface
applications
• Losses vary with environment, are difficult to
predict and often exaggerated
• Need to manage urea to minimize potential,
ammonium nitrate is not the universal solution
Managing Potential Urea Volatilization
• Small grains and pasture
– Summer applications are of a concern
– Late fall through early spring performs well
• Row Crops
– Incorporation or subsurface banding
– Apply early in spring
– Surface Band
• No-till or Minimum till
– Inject or surface band to improve efficiency
– Apply early in spring
Urea-Ammonium Nitrate Solution (UAN)
UAN is approximately 75% ammonium or ammonium forming and 25% nitrate
Properties of 28% and 32% UAN Solutions
28.0
32.0
% Ammonium Nitrate
38.8
44.3
Urea
31.0
35.4
Water
30
20
Salt Out Temperature degrees F.
0
32
Density, lb/gal. @ 60 degrees F.
10.6
11.06
5.5-7.2
5.5-7.2
Nitrogen, %
Composition by Weight,
pH*
* Varies with corrosion inhibitor used
Urea-Ammonium Nitrate Solution (UAN)
Made by mixing urea liquor and
ammonium nitrate liquor and diluting
with a little water
Very difficult to make from solid urea
and solid ammonium nitrate locally.
UAN Solution
• Advantages
– Flexibility
–
–
–
–
–
No high pressure equipment needed
Less power required for application
Compatible pesticides
Suited to application with irrigation water
Suited to topdressing crops
• Disadvantages
– Higher purchase price
– Volatilization potential
How About UAN Leaf Burn ?
• Leaf burn on emerged crops
– Burning is temporary
– Least under cool temperatures and
low humidity
– Dilute with water 50:50 ?
– Winter wheat is very tolerant
– Corn and grain sorghum are
tolerant but most herbicide
combinations are not labeled post
Effect Of Urea Placed With Corn Seed
(Minnesota)
N Applied
with Seed
Emerged
Population
Grain Yield
lbs/acre
plants/acre
bu./acre
0
7.5
15.0
30.0
29,968
21,127
15,246
7,550
181
156
145
96
Selection of N Source/Method of
Application
•
•
•
•
•
•
•
•
•
•
Method of Application
Time of Application
Tillage System
Equipment Availability
Labor Availability
Personal Preference/Comfort
Flexibility Required
Cost
N Management Options
“Best” Agronomic N Management Options
Subsurface Applications
In-Season Application
Spring Application
N-Serve
“Best” Practical N Management Options
Avoiding High N Loss Risk Situations
Incorporation of Urea and UAN
No Fall Applications On Sands
Delay Fall Applications Until Soils Cooled ??
Managing Surface Application With Residues
Understand The N Cycle and Manage Accordingly
Others ??
N Rate and Application Timing Effect On Wheat Yield
B. Gordon, KSU, Belleville
Total N
Fall
E. Spr
Later
2003
2004
Average
0
---
---
---
49
42
46
40
0
40
0
69
75
72
40
40
40
20
0
20
0
0
68
69
71
73
70
71
80
0
80
0
95
88
92
80
80
0
0
92
88
90
80
40
40
0
94
89
92
120
0
120
0
96
89
93
120
120
0
0
91
88
90
120
60
60
0
95
87
91
80
0
40
40/F6
68
73
71
80
0
40
40/F8
70
70
70
80
0
0
80/F6
67
70
69
80
0
0
80/F8
51
58
55
NITROGEN
N Source and Method For Conventional Till Grain Sorghum
La m o nd, 2 0 0 4 , KS U
130
No-Till
Yield (bu/a)
Conventional
110
90
70
50
0
30
60
N Rate (lb N/a)
90
120
Review Exercises
. Nitrogen is an essential part of ___________________.
.
Protein
.
Plant enzymes.
.
Chlorophyll.
.
All of the above.
.
None of the above.
. Which of the following is generally not a nitrogen deficiency symptom in plants?
.
Slow growth rate.
.
Pale green or yellow color.
. Nitrogen may be lost from the nitrogen cycle through _________________.
.
Nitrogen fixation by lightning.
.
Animal manure.
.
Nitrate leaching.
.
Legume fixation.
.
All the above.
None of the above.
.
. About 10% of total soil nitrogen is found in the soil organic matter.
a.
Th
True
b.
b
False
hi h l t
il bl
i
it
f
t db
. A soil pH range of _____________ is optimum for nitrification.
4.5 to 5.5.
.
b. 5.5 to 6.0.
c. 6.0 to 8.5.
d. 8.6 to 10.0.
. The installation of tile drainage in a field that frequently becomes waterlogged would
most likely ____________________ denitrification.
a. Increase
b.
Decrease
c. have no effect on
0. ____ions have the highest potential for leaching significant quantities of N from the soil.
a.
Ammonium b. Nitrate
c. Nitrite
d. Ammonia
1. Most nitrogen fertilizer comes from the synthetic fixation of atmospheric nitrogen using
UAN as a base product.
3. Proper application depth is the single most important way to avoid seedling toxicity
from anhydrous ammonia.
a. True.
b.
False.
4. In comparing ammonium nitrate fertilizer to urea, ammonium nitrate is__________
than urea.
.
Higher in nitrogen content.
.
Less subject to volatilization losses.
.
Less expensive to produce.
.
Less corrosive.
5. Volatilization loss from surface-applied urea is of most concern under which TWO of
the following conditions?
17. Which nitrogen fertilizer, when applied at equal rates of N, will create the greatest
soil acidity?
a.
b.
c.
d.
Ammonium nitrate.
Ammonium sulfate.
Urea.
UAN solutions.
8. All nitrogen fertilizer sources can be good choices from an economic standpoint if
properly applied.
a.
True.
b.
False.
19. Symbiotic nitrogen fixation refers to:
.
Tie up of nitrogen by soil bacteria
.
Production of available nitrogen in the soil by soil bacteria
.
Production of available nitrogen by bacteria in legume nodules
21. The major source of nitrate nitrogen that enters rivers and lakes is generally:
a.
c.
d.
Legume fixation b. Denitrification.
Nitrate leaching into drainage tile and surface water runoff from land.
N in rainfall
22. Which mechanism of nitrogen loss is most likely to occur in the month following application
under the following conditions? Urea-ammonium nitrate solution (UAN) is applied to grass pasture in
late winter. The soil is a silt loam with a slope of 3-5%. There is no frost in the ground. Air
temperatures are in the 30-45 degree range. There is 6 inches of precipitation in the form of rain or
snow in the next 30 days.
a.
c.
Leaching of nitrate
Volatilization of ammonia
b.
d.
Denitrification of nitrate
Surface runoff of urea and nitrate
3. A nitrification inhibitor blocks conversion of:
a.
c.
NH4+ to NO2-. (ammonium to nitrite)
b. NO2-. to NO3-.(nitrite to nitrate)
Organic N to NH4+ (organic N to ammonium) d. NO3-. to N2. (nitrate to elemental N)
4. The greatest potential for increasing nitrate pollution of ground water occurs with which of the
following applications of nitrogen for row crops such as corn or sorghum:
a.
b
Fall application of anhydrous ammonia
F ll
li ti
f UAN