Daniel C. BowmanDaniel C. Bowman

NCSUNCSU

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.

Why Is Nitrogen Harmful?

Nitrogen Enters Water

Algae Grow Rapidly

Algae Use Oxygen for Respiration

Oxygen Levels Drop

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

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.

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 NCSU’s fertilizer guidelines for turfgrass management.

Rain and Irrigation Moves Through a Porous Soil

Soil Cross-Section

Heavy Precipitation May Cause Runoff, Intermittent Flow

Water Moves Through Porous Soil at Top of Profile

AquatardAquatard

Aquatard Directs Subsurface Flow into a Stream

AquatardAquatard

Nitrate Moves with the Water

AquatardAquatard

NO3

NO3 NO3

NO3

NO3

NO3

NO3

NO3

Perched Water Table Continuous with Stream

AquatardAquatard

Compacted Layer Under Turf Also Direct Water to Stream

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?

Neuse Shoreline is Relatively Small Compared to the Shoreline of Tributaries

Neuse River

Buffers Remove Nitrate From Flowing Groundwater

Nit

rate

Con

cent

rati

on

Landscape Position

Uphill Buffer Stream

Subsurface Flow

Zone 220 feet

Zone 1, 30 feet20 feet limited harvest/10 ft undisturbed

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

Zone 220 feet

Zone 1, 30 feet20 feet limited harvest/10 ft undisturbed

Subsurface Flow

Nitrate Profile Through Buffer

Zone 220 feet

Zone 1, 30 feet20 feet limited harvest/10 ft undisturbed

Subsurface Flow

Rate of Runoff Through Buffer

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

Respiration vs. DenitrificationElectrons need to go somewhere, to be accepted

NO3- NO2

- NO N2O N2

e-

e-

O2 H2O

Normal respiration requires oxygen

Denitrification, an alternative when there is no oxygen

Requirements for Denitrification

• Waterlogged conditions

• Presence of nitrate

• Presence of organic matter

• Presence of specific denitrifying bacteria

NO3- NO2

- NO N2O N2

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

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.

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.