Daniel C. Bowman

1
Buffers Fact and Fiction

• Daniel C. Bowman
• NCSU

2
What is a Riparian Buffer?

• Riparian refers to the land and/or ecosystem
  immediately adjacent to a river, stream or lake.
• Buffer refers to the biological and physical
  characteristics of the system which reduce the
  movement of unwanted materials from the land and
  into the waterway. Nitrogen and Phosphorus are
  of major concern.

3
Why Is Nitrogen Harmful?
Nitrogen Enters Water
Algae Grow Rapidly
Oxygen Levels Drop
Algae Use Oxygen for Respiration
4
The Neuse River Rules

• Designed to reduce N in the river by 30
• Designed to distribute responsibility among waste
  water treatment facilities, developers, farmers,
  and other fertilizer applicators (you)
• Substantially based on scientific principles, but
  also chock full of politics

5
Who Are Other Fertilizer Applicators?

• Anyone who applies fertilizer to 50 or more acres
  of, among other areas, turfgrass including golf
  courses, recreational areas, lawns, etc.

6
You Have Two Choices

• Complete a training course on nutrient
  management. You must sign up for the course
  during year one and complete the course within 5
  years
• Develop a written nutrient management plan for
  all fertilized areas. You may use NCSUs
  fertilizer guidelines for turfgrass management.

7
Rain and Irrigation Moves Through a Porous Soil
Soil Cross-Section
8
Heavy Precipitation May Cause Runoff,
Intermittent Flow
9
Water Moves Through Porous Soil at Top of Profile
Aquatard
Aquatard
10
Aquatard Directs Subsurface Flow into a Stream
Aquatard
Aquatard
11
Nitrate Moves with the Water
NO3
NO3
NO3
NO3
NO3
Aquatard
NO3
NO3
Aquatard
NO3
12
Perched Water Table Continuous with Stream
Aquatard
Aquatard
13
Compacted Layer Under Turf Also Direct Water to
Stream
14
What Defines a Stream?

• This has been a sticky issue. When is a ditch a
  stream, and when is it just a ditch?
• Size, width?
• Period of flow?
• Amount of flow?
• Presence of aquatic organisms?
• Characteristics of stream bed?

15
Neuse Shoreline is Relatively Small Compared to
the Shoreline of Tributaries
Neuse River
16
Buffers Remove Nitrate From Flowing Groundwater
Nitrate Concentration
Uphill Buffer Stream
Landscape Position
17
Subsurface Flow
Zone 2 20 feet
Zone 1, 30 feet
20 feet limited harvest/10 ft undisturbed
18
Why Two Zones?

• Zone One functions to remove NO3 through
  denitrification and also to reduce bank erosion.
  This can be crucial where livestock are present.
  
• Zone Two functions to reduce surface runoff, trap
  sediments, and increase infiltration. This zone
  is likely to cause the most problem for turfgrass
  managers because it is vague and has been poorly
  conceived from a scientific or practical
  viewpoint.
• my opinion

19
Subsurface Flow
Nitrate Profile Through Buffer
Zone 2 20 feet
Zone 1, 30 feet
20 feet limited harvest/10 ft undisturbed
20
Subsurface Flow
Rate of Runoff Through Buffer
Zone 2 20 feet
Zone 1, 30 feet
20 feet limited harvest/10 ft undisturbed
21
How Do Buffers Reduce Nitrate?

• Contrary to popular opinion, buffers do not
  absorb large amounts of nitrate
• Buffers do promote denitrification, which
  converts nitrate-N to gaseous forms of N which
  are lost to the atmosphere

22
Respiration vs. DenitrificationElectrons need to
go somewhere, to be accepted
e-
Normal respiration requires oxygen
O2 H2O
Denitrification, an alternative when there is no
oxygen
e-
NO3- NO2- NO N2O
N2
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Requirements for Denitrification

• Waterlogged conditions
• Presence of nitrate
• Presence of organic matter
• Presence of specific denitrifying bacteria

NO3- NO2- NO N2O
N2
24
Requirements for Denitrification

• Waterlogged conditions
• the perched water table provides this
• Presence of nitrate
• leaching from ag fertilizer (and natural sources)
• Presence of organic matter
• deep root systems secrete OM, also die
• Presence of specific denitrifying bacteria
• always present in most soils

25
Problems with Zone Two

• No plant material list. What qualifies?
• No fertilizers/pesticides allowed. This will
  lead to stand thinning, increased weediness,
  increased runoff, increased erosion, and
  increased non-compliance. Objections to this
  have been communicated by the scientific
  community, but it is unclear that anyone was
  listening.

26
Which Plants for Zone One?

• Native woody vegetation. Deep-rooted. Selective
  harvest?
• Selected ornamentals. Deep-rooted woody and
  herbaceous. NCSU Cooperative Extension may be
  asked for a list of appropriate plant materials.