Nitrogen Sources and Turf Response
Laurie Trenholm
UF-IFAS Turf Specialist
Quick Release Nitrogen
•
•
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•
•
Soluble in water
Provide fairly rapid response in turf
Volatilize readily if not irrigated in
Useful for repair of injured turf- athletic fields
Provide for quicker turf establishment if
growing plugs or sprigs in
• Response seen for 30-45 days unless applied
at excessive rate
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Ammonium Sulfate
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•
•
•
21% N (NH4)2SO4
Highly soluble and leachable
Subject to volatilization
Very acidifying – useful in high
pH soils
• High salt index - 3.25 – must be
watered in
• Deep green and longer response
than many other soluble N
sources
Urea
• 46% N
• Soluble Synthetic
Organic
• Nonionic, highly
leachable
• Subject to volatilization
• Low acidity - 1.8/kg N
• Low salt index - 1.62
Urea
• Organic (but quick-release) N source
• Converted to ammonium-N form by enzyme
urease in the soil after short time in the soil
• This happens within about 24 hours
• After this conversion, much less likely to
leach if rainfall does occur
Ammonium Nitrate
• 33 – 34 % N
• Very soluble
• Subject to volatilization and
leaching
• Low acidity
– 1.8kg acid/kg
• High salt index -2.99
• Can be explosive
• Short term response
Slow or Controlled Release Nitrogen
• Use various mechanisms to release N
– Coating through which N diffuses
– Chemical reaction used to create chemical bonds that ties
the N up
• Release rates vary widely between products and
due to temperature and microbial activity
• More expensive than QRN
• Less likely to leach than QRN if applied to bare soil,
few differences in healthy turf that provides a
ground cover
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Sulfur Coated Urea
• 32-38% N
• Release depends upon
– thickness of sulfur coating
– microbial activity
– soil environment
• temperature
• pH
• Cool season response-erratic
• Coating fragile- some spreaders
may crack
• Response usually 60-90 days
Polymer Coated
• Variable N
• N release varies, influenced by
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–
–
–
coating thickness
soil temperature
not soil moisture
not influenced by soil moisture,
pH, microbial activity
• Week 1: Moisture comes in through
polymer coating, dissolves
encapsulated N inside
• After week 1: Soil temperature
causes N to diffuse through
membrane
Polymer-Sulfur Coated Urea
• N release influenced by
– coating thickness (vary by
product)
– diffusion rate
– Less influenced by soil
temperature and moisture
• Good for both warm and cool
season application
Urea Formaldehyde
• Insoluble organic
• 38% N ; 65-71% WIN
• Biological N release
– release by microbial activity
– soil temperature
• Less effective in cool seasons
• Reaction of urea and
formaldehyde gives chains of
alternating C and N
– Longer chains, slower release
• Nitroform, Blue Chip,
Nutralene
• Can also be in solution
Methylene Urea
• 40% N - 36% WIN
• Microbial N release
• More rapidly available than
UF
• Not as adversely influenced
by cool temperatures
• Reaction of urea and
formaldehyde gives chains
of alternating C and N
Triazones
• 30% N
• Ring structured Triazones may
contain methylene diurea
• N release by microbial action
• Response very similar to UF
solutions
IBDU - Isobutylidene Diurea
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•
•
•
31% N
90% slow release
N released by hydrolysis as urea
Release due to
– pH (lower better)
– Soil moisture
– Granule size
• Good cool season response
• Less effective during heavy rain
periods due to rapid release
Release Curves
% N release over time
• Urea Formaldehydes
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–
–
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1 mo: 20-40%
2 mo: 23-45%
4 mo: 31-53%
6 mo: 38-58%
• IBDU
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–
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1 mo: 21%
2 mo: 32%
4 mo: 50%
6 mo: 63%
• Polyon (Polymer Coated Urea)
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1 mo: 49%
2 mo: 75%
4 mo: 90%
6 mo: 94%
• Sulfur Coated Urea
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–
–
–
1 mo: 70%
2 mo: 84%
4 mo: 95%
6 mo: 99%
UF Materials Comparison
Nitroform
Nutralene
GUARANTEED ANALYSIS
GUARANTEED ANALYSIS
Total Nitrogen (N)........................................ 38%
Total Nitrogen (N)*.......................................40%
6% Urea Nitrogen
20% Slowly Available Water Soluble Nitrogen*
14% Water Insoluble Nitrogen
4.5% Urea Nitrogen
6.9% Slowly Available Water Soluble
Nitrogen*
26.6% Water Insoluble Nitrogen
Derived from: urea-formaldehyde
*6.9% slowly available Nitrogen from
methylenediurea and dimethylenetriurea.
Derived from: methylene urea
*20% slowly available Nitrogen from
methylenediurea and dimethylenetriurea.
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SRN Materials Label Comparison
Polyon
GUARANTEED ANALYSIS
Total Nitrogen (N)........................................ 30%
1.5% Ammoniacal Nitrogen
28.5% Urea Nitrogen*
8.0% Soluble Potash
0.955% Water Soluble Magnesium
0.2175% Water Soluble Iron
Derived from: Muriate of potash, polymer
coated urea, sulfate of ammonia, sulfate of
potash-magnesia, iron sucrate
*22.8% slow release Nitrogen from polymer
coated urea.
XCU (Polymer Sulfur
Coated Urea)
GUARANTEED ANALYSIS
Total Nitrogen (N)*....................................38-39%
Urea Nitrogen
Derived from: polymer coated sulfur
coated urea
*38-39% slowly available Nitrogen from polymer
sulfur coated urea.
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Palm Beach County Nitrogen Demo Plots
Treatments:
1.
2.
3.
4.
5.
6.
7.
Control
Urea (soluble) at 0.5 lb N 1,000 ft-2
Urea (soluble) at 1.0 lb N 1,000 ft-2
Polyon at 1 lb N 1,000 ft-2
Polyon at 2 lb N 1,000 ft-2
Milorganite at 1 lb N 1,000 ft-2
Methylene urea 1 lb N 1,000 ft-2
• Treatments applied Mar 12
• Irrigated in with ~ ¼” water
• Irrigated 3 x week to apply
0.08-0.3” each time
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Control
April 1
April 14
April 8
Soluble Urea @ 0.5 lb N/1,000
April 1
April 14
April 8
Soluble Urea @ 1.0 lb N/1,000
April 1
April 14
April 8
Polyon @ 1.0 lb N/1,000
April 1
April 14
April 8
Polyon @ 2.0 lb N/1,000
April 1
April 14
April 8
Milorganite @ 1.0 lb/1,000
April 1
April 8
April 14
Methylene Urea @ 1.0 lb N/1,000
April 1
April 14
April 8