Nitrogen Sources and Turf Response

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Nitrogen Sources and Turf Response
Laurie Trenholm UF-IFAS Turf Specialist
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Quick Release Nitrogen

• 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

• 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

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Urea

• 46 N
• Soluble Synthetic Organic
• Nonionic, highly leachable
• Subject to volatilization
• Low acidity - 1.8/kg N
• Low salt index - 1.62

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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

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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

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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

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Polymer Coated

• Variable N
• N release varies, influenced by
• 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

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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

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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

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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

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Triazones

• 30 N
• Ring structured Triazones may contain methylene
  diurea
• N release by microbial action
• Response very similar to UF solutions

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IBDU - Isobutylidene Diurea

• 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

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Release Curves N release over time

• Urea Formaldehydes
• 1 mo 20-40
• 2 mo 23-45
• 4 mo 31-53
• 6 mo 38-58
• IBDU
• 1 mo 21
• 2 mo 32
• 4 mo 50
• 6 mo 63

• Polyon (Polymer Coated Urea)
• 1 mo 49
• 2 mo 75
• 4 mo 90
• 6 mo 94
• Sulfur Coated Urea
• 1 mo 70
• 2 mo 84
• 4 mo 95
• 6 mo 99

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UF Materials Comparison

• Nitroform
• GUARANTEED ANALYSIS
• Total Nitrogen (N)................................
  ........ 38
• 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.

• Nutralene
• GUARANTEED ANALYSIS
• Total Nitrogen (N)...............................
  ........40
• 6 Urea Nitrogen
• 20 Slowly Available Water Soluble Nitrogen
• 14 Water Insoluble Nitrogen
• 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
• 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 8
April 14
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Soluble Urea _at_ 0.5 lb N/1,000
April 1
April 8
April 14
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Soluble Urea _at_ 1.0 lb N/1,000
April 1
April 8
April 14
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Polyon _at_ 1.0 lb N/1,000
April 1
April 8
April 14
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Polyon _at_ 2.0 lb N/1,000
April 1
April 8
April 14
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Milorganite _at_ 1.0 lb/1,000
April 1
April 8
April 14
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Methylene Urea _at_ 1.0 lb N/1,000
April 1
April 8
April 14