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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
Grain Sorghum N Uptake
20%
40%
60%
80%
100%
V 6 Tassel MaturityStage Of Growth
% o
f Tot
al U
ptak
e
Potassium
Phosphorus
Nitrogen
Dry Matter
Corn Nutrient Uptake And Dry Matter Accumulation
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
Animal Manures
Soil OrganicMatter
Crop Residues
Plant Uptake NO3-
Nitrate
NH4+
Ammonium
Legume Fixation of
Atmospheric N2
Fertilizer Nitrogen
Nitrogen Fixation by Lightning
Ammonia Loss Through
Leaves
Immobilization
Immobilization (By Crop Residues)
Removed by Harvest
Removed by Denitrification (Gaseous Loss from Wet Soils
Removed by Leaching
(Ammonification)
(Nitr
ifica
tion)
Mineralization
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
Source of most soil N5% N, 1-3% released annually• 10-30 pounds N per year per 1% Organic MatterRate of release affected by:• Tillage • Temperature• Moisture• Past N inputs
Soil Organic Matter (SOM) AssumptionsWeight of Plow Layer (6-7”) of Soil equals 2,000,000 lb/acre1% SOM x 2,000,000 = 20,000 lbs SOM/a About 67% of residue carbon is lost as microbial CO2
About 1-3 % of SOM is decomposed each yearAssume soil organic matter is 5% N and 59% C
Soil Organic Matter N ContributionsFor soil with 1% SOM20,000 lb SOM x 5% N = 1,000 lbs N/A1, 000 x 2% Mineralized/yr = 20 lbs N/A/yr mineralized
25
30
35
40
45
50
55
60
65
1-Nov
8-Nov
15-N
ov
22-N
ov
29-N
ov
6-Dec
Date
Soil
Tem
p (F
)Clay Center Research Station,
Soil Temp @4 inches
Daily average Temp. 2001
15 year average
LEGUMES
• Alfalfa, clover, beans, etc.• Symbiotic relationship with
Rhizobium bacteria• Plant provides energy
(carbohydrate)• Bacteria synthesize N2 to
NH4
Symbiotic Fixation
Legume Crop N CreditsNitrogen 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)
12080400
6040200
Sweet Clover -Excellent StandGood Stand Poor Stand)
110600
553020
Red Clover -Excellent StandGood Stand Poor Stand)
80400
40200
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
100%
90%
50%
90%
65%
50%
40%
30%
20%
10%5%
Sweep Injected
Immediate Incorporation
1 Day 2 Days 3 Days 4 Days 5 Days 6 Days 7+ DaysKnife Injected
Sprinkler Irrigation
Time Between Broaccast Surface Application and Incorporation
Percent Of Inorganic N Available To Crops For Various Manure Management Systems
Estimated Organic N Available To Crops After Manure Application
Year 1 Year 2 Year 3- - - % Of Original Organic N Available - - -
Liquid Manure 30 12 6Solid Manure 25 12 6Compost 20 6 3
Manure TestResults From X = Plant Available Nutrients
Laboratory( Lb per ton ) ( Lb per ton )
Organic N X 25% Availabile In Year Of Application = Organic N
Ammonium N X Availability Factor From Fig. 1 = Ammonium N
Total N X = Ammonium + Organic N
Total P2O5 X 50% for V. Low - Low P Soil Tests = Available P2O5100% for Medium - V. High Soil Tests
Total K2O X 85% Potassium Efficiency Factor = Available K2O
Nutrient Availability Factor
Sum Of Organic & Ammonium N
Solid Manure Nutrient Crediting Worksheet
Manure TestResults From X = Plant Available Nutrients
Laboratory
( Lb per 1,000 gal ) ( Lb per 1,000 gal )
Organic N X 25% Availabile In Year Of Application = Organic N
Ammonium N X Availability Factor From Fig. 1 = Ammonium N
Total N X = Ammonium + Organic N
Total P2O5 X 50% for V. Low - Low P Soil Tests = Available P2O5
100% for Medium - V. High Soil Tests
Total K2O X 85% Potassium Efficiency Factor = Available K2O
Liquid Manure Nutrient Crediting Worksheet
Nutrient Availability Factor
Sum Of Organic & Ammonium N
Mineralization/Immobilization
Organic N(plant unavailable)
Inorganic N(plant available)
High C:N Ratios
Legume ResiduesManure
Soil Organic Matter
Low C:N Ratios
Corn StalksSorghum StubbleWheat Stubble
Soil Microbes Responsible For Both Conversions
Nitrogen Immobilization & Mineralization
C:N Ratio of Organic Material Affects Rate of Activity
ImmobilizationResidue with High C:N Ratio
Straw, Cornstalks, Sorghum stubble
Plant available nitrogen tied up
Mineralization
Residue with Low C:N Ratio Alfalfa, Soil Organic Matter, Manure
Plant available nitrogen rreleased
Inorganic N Organic NMineralization
C:N < ~ 25:1
C:N > ~ 25:1
Immobilization
Typical Carbon and Nitrogen Content of Organic Materials
Source
Alfalfa
Soybean Residue
Cornstalks
Small grain straw
Microorganisms
Soil O.M.
Grain Sorghum
Manure
Wood Chips
Glyphosate (Roundup)
% Carbon
40
---
40
40
50
52
40
--
40
-
% Nitrogen
3.0
---
0.7
0.5
6.2
5.0
0.5
--
0.1
-
C:N Ratio
13:1
15:1
60:1
80:1
8:1
10:1
80:1
<20:1
200:1
3:1
Ammonification (N mineralization) and Nitrification
Conversion of Nitrogen into plant-available forms through the microbial processes of ammonification and nitrification.
Soil Organic Matter
Manure
Rotting Plant Residues
+
Ammonification Nitrification
NH4+
Ammonium
NO2-
Nitrite
Oxygen
NO3-
NitrateNitrosomonas
BacteriaNitrobacter
Bacteria
Oxygen
H+
Acidity
Effect of Temperature on Nitrification Rate
100
80
60
40
20
Rate of Nitrate
Production (% of Max.)
Temperature - Degrees F at 4-inch Depth
032 41 50 68 7759
Effect of Time on Nitrification
100
80
60
40
20
% Nitrification
Time (Weeks)
032 3 96
75 Degrees F.52 Degrees F.
47 Degrees F.
42 Degrees F.
37 Degrees F.
Influence of Soil Temperature On NitrificationKansas Stae University
0
50
100
150
200
250
300
350
400
450
0 60 120 180 240 300
ppm
NH4
+-N
August October December February April June
August Application(warm soil)
November Application(cool soil)
Kansas State University
How Nitrogen Fertilizer Affects Soil Acidity
When the nitrification process converts the ammonium ion to nitrate, hydrogen ions are released:
NH4+ + 2O2 NO3
- + 2H+ + H2ONitrifying Bacteria
Ammonium Oxygen 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
None 6.5 6.7
Urea 6.2 5.9
UAN 6.2 5.8
Ammonium Sulfate 5.2 4.7
0-7” 0-1”
What Happens to Nitrate Nitrogen?
• Utilized by plants• Retained in soil as inorganic N• Immobilized to organic N
• Denitrification• Leaching
N Loss Through Denitrification
NO2-
NONO3
-
N2O
N2
Soil SurfaceEscapes As
Gases
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 non-sandy soil
Nitrogen Loss from Soil Saturated at Two Temperature Ranges (Univ. Neb.)
Period of Saturation Temperature (°F.) N Loss (%)
5
10
3
5
7
9
55-60
55-60
75-80
75-80
75-80
75-80
10
25
60
75
85
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
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-
NO3-
NO3-
NH4+
NH4+
NH4+
NH4+
NH4+
Nitrogen Leaching
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:
Unincorporated Surface applications• Manure• Urea containing materials under specific conditions
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.
(Urea Melt)
Anhydrous Ammonia Plant
CO2
(Carbon dioxide)NH3
Ammonia
82% N
Air
(N2,O2)N H Natural Gas
(CH4)
Urea Melt
N Solution Plant
Water
Ammonium Nitrate Melt
NH4NO3
Ammonium Nitrate
(34% N)
Ammonium Nitrate Plant
HNO3
(Nitric Acid)
Ammonium Nitrate
Melt
UAN
(Urea Ammonium Nitrate)
28-32% N
Prilling Tower
CO (NH2)2
(Urea) 46% N
Urea Plant
Granulator
Heat and Pressure +
Catalyst
Nitrogen
1 Part
Hydrogen
3 Parts
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . ..
......................
Nitric Acid Plant
Alternatives to Natural Gas for Ammonia Production
Coke» by-product of oil refinery
used to produce NH3 atCoffeyville, KS
Coal gasification
Anhydrous Ammonia - The Base Material
NH3
NitricAcid
SulfuricAcid
PhosphoricAcid
CarbonDioxide
Urea + A.N. +Water
Ammonium Nitrate
Ammonium Sulfate
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 SafelyRemember! 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
Ideal Moisture Correct Depth
Sealed at surface NH3
spreads about 4 inches
Some NH3lost at
surface
Slit does not seal, NH3does not penetrate
Ammonia moves too far
Some NH3reaches surface
Too Shallow Too Wet Too Dry or Sandy
Rate Too High For Soil
Recommended Knife Spacings
Crop
Corn, Sorghum
Winter Wheat
Spring Small Grain
Recommended Knife Spacing
(Inches)
30-40
12-18
9-15
Effect of Spacing of NH3 Knives On Corn Yield
Spacing & Locationof 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
0 7 14 0 7 14
60 96 100 35 60 90
100 100 100 80 100 100
100 100 100 100 100 100
200 lb N 400 lb NDepth of
Application
(Inches)
4
7
10
Temporary effects of NH3 : Freezing temperature, High pH, & high affinity for water.
Stand (% of Normal)
Ammonia Effect on Bacteria Population*
Days After Injection Point 1-inch Away 2-inch Away
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
Bacteria/Gram Dry Soil
pH in injection zone
Earthworm Population After Ammonia ApplicationDeibert and Uttier, North Dakota State University
EarthwormsCocoonsTotal
0 N9862160
Sept. 15
50 N9871
169
Nov. 1
50 N29298
390
Anhydrous Ammonia Application
- - - Earthworms per square yard - - -
Doesn’t Anhydrous make the Soil Hard?
Nitrogen SourceSoil pH
Soil OM Bray P-1 NO3
--N NH4+-N Density
(%) - - - - - ppm - - - - (lb/cu ft)
Check (No N) 6.2 2.0 38 4 5 100Anhydrous Ammonia 5.2 1.8 27 27 9 99
Ammonium Nitrate 5.2 2.3 26 21 11 99Urea 5.1 2.3 24 31 12 99
UAN Solution 5.2 2.0 28 20 8 100
Effect Of 20 Years Of N Fertilizers On Soils (Kansas State University)
78 bu/A for Ammonia. Ammonium Nitrate, Urea, UAN over last 4 years37 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 5%• Oxygen 60%• Nitrogen 35%• Bulk Density 48 to 58 lb/cu ft• Critical Relative Humidity 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
Potential volatilization lossDo not place in direct seed contact
Urea Production
Ammonia + Carbon Dioxide
Urea + Water
Energy (production)
Urea (CO(NH2)2) 46-0-0
• Hydrogen 6.6%• Oxygen 26.7%• Carbon 20%• Nitrogen 46.7%• Bulk Density 45 to 48 lb/cu ft• Critical Relative Humidity 75.2%
Ammonia Volatilization
Ammonia + Carbon Dioxide
Urea + Water
Enzyme (biological)
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
Warm, Moist Drying Soils- Not Hot, Dry Conditions
Residue- Urease, Moist Soil Surface
Immobilization Effects
D. Kissel - McInnes, et. al Kansas State University
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)
Properties of 28% and 32% UAN Solutions
Nitrogen, %
Composition by Weight,
% Ammonium Nitrate
Urea
Water
Salt Out Temperature degrees F.
Density, lb/gal. @ 60 degrees F.
pH*
28.0
38.8
31.0
30
0
10.6
5.5-7.2
32.0
44.3
35.4
20
32
11.06
5.5-7.2
UAN is approximately 75% ammonium or ammonium forming and 25% nitrate
* 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 29,968 1817.5 21,127 156
15.0 15,246 14530.0 7,550 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 ApplicationsIn-Season ApplicationSpring ApplicationN-Serve
“Best” Practical N Management Options
Avoiding High N Loss Risk SituationsIncorporation of Urea and UANNo Fall Applications On SandsDelay Fall Applications Until Soils Cooled ??Managing Surface Application With ResiduesUnderstand The N Cycle and Manage AccordinglyOthers ??
Total N Fall E. Spr Later 2003 2004 Average0 --- --- --- 49 42 46
40 0 40 0 69 75 7240 40 0 0 68 71 7040 20 20 0 69 73 71
80 0 80 0 95 88 9280 80 0 0 92 88 9080 40 40 0 94 89 92
120 0 120 0 96 89 93120 120 0 0 91 88 90120 60 60 0 95 87 91
80 0 40 40/F6 68 73 7180 0 40 40/F8 70 70 70
80 0 0 80/F6 67 70 6980 0 0 80/F8 51 58 55
N Rate and Application Timing Effect On Wheat YieldB. Gordon, KSU, Belleville
NITROGEN
N Source and Method For Conventional Till Grain SorghumLamo nd, 2004, KSU
50
70
90
110
130
0 30 60 90 120N Rate (lb N/a)
Yiel
d (b
u/a)
No-TillConventional
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. True b. False
Th b hi h l t il bl i it f t d b
. 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. Ammonium nitrate.b. Ammonium sulfate.c. Urea.d. 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. Legume fixation b. Denitrification.c. Nitrate leaching into drainage tile and surface water runoff from land.d. 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. Leaching of nitrate b. Denitrification of nitratec. Volatilization of ammonia d. Surface runoff of urea and nitrate
3. A nitrification inhibitor blocks conversion of:
a. NH4+ to NO2
-. (ammonium to nitrite) b. NO2-. to NO3
-.(nitrite to nitrate)c. 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. Fall application of anhydrous ammoniab F ll li ti f UAN