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Water Buffers
Within Fields
Grassed waterway:
a natural or constructed vegetated channel that is shaped and graded
to carry surface water at a nonerosive velocity to a stable outlet.
Because of concentrated flow that normally occurs in waterways,
trapping of sediment and water infiltration can be minimal. Waterways
are most effective in trapping sediment and dissolved chemicals
when designed to spread concentrated water flow over a vegetated
filter adjacent to streams.
Contour buffer
strips:
strips of perennial vegetation alternated with wider cultivated
strips that are farmed on the contour. Buffers are most effective
in trapping pesticides when runoff enters uniformly as sheet flow.
Contour buffer strips are one of the most effective buffers in trapping
pesticides because there is less chance for concentrated flow and
smaller areas of cultivated field deliver runoff directly, within
a relatively short distance, to each strip, compared to some edge-of-field
buffers.
Vegetative barriers:
narrow, permanent strips of stiff stemmed, erect, tall, dense perennial
vegetation established in parallel rows and perpendicular to the
dominant slope of the field. These barriers function in a similar
manner to contour buffer strips and may be especially effective
in dispersing concentrated flow, thus increasing sediment trapping
and water infiltration.
Terrace tile
inlet buffer:
setbacks surrounding inlets to tile-outlet terrace systems. Some
herbicide labels describe leaving untreated setbacks around these
inlets when tiles draining terraces outlet directly into streams.
Because water ponds over these areas during runoff events, reductions
in herbicide runoff have occurred only proportion to reductions
in total area treated.
Edge-of-Field
Field borders: a band or strip of perennial vegetation
established on the edge of a cropland field. This type of buffer
reduces pesticide runoff only when runoff flows over the strip.
Even when no water flow occurs over the strip, some water quality
benefit may be gained due to physical separation of spraying operations
from adjacent areas, reducing drift and direct application to riparian
areas.
Filter
strips:
areas of grass or other permanent vegetation used to reduce sediment,
organics, nutrients, pesticides, and other contaminants from runoff
and to maintain or improve water quality. Filter strips are located
between crop fields and waterbodies. Efficiency in removing pesticides
can be improved by encouraging as much sheet flow as possible across
the strip. This may be accomplished by combining filter strips with
practices such as vegetative barriers, level spreaders, or water
bars.
Set backs: untreated areas where surface
runoff enters streams. Some herbicide labels describe leaving these
areas untreated. Seeding these areas to perennial grass improves
herbicide trapping, compared to trapping with untreated row crop.
Riparian forest
buffer:
an area of trees and shrubs located adjacent to streams, lakes,
ponds, and wetlands. Forest buffers are often combined with perennial
grass buffers. Woody vegetation provides food and cover for wildlife,
helps lower water temperatures by shading the waterbody, protects
stream banks, and slows out-of-bank flood flows. Deep roots of trees
may intercept nitrate entering streams in shallow subsurface flow
and provide soil carbon for microbial energy. Microbes can degrade
pesticides and denitrify nitrate.
Constructed
Wetlands
Most nitrate is
carried to streams by subsurface flow. Subsurface flow may also
carry low concentrations of pesticides. While riparian buffers can
intercept shallow subsurface flow and either cause uptake of nitrate
and utilization by plants or encourage denitrification, drainage
tiles bypass buffers and deliver subsurface drainage directly to
streams. Wetlands constructed at tile outlets have been effective
in causing denitrification of nitrate and degradation of pesticides.
Wind Buffers
Windbreak/shelterbelts: plantings of single or multiple
rows of trees that are established for environmental purposes. While
the primary purpose of such buffers is to protect leeward areas
from troublesome winds, they may also provide separation of spraying
operations from adjacent areas, reduce drift due to lowered wind
speed, and intercept spray drift. Taller plantings provide the most
drift protection.
Cross Wind Trap
Strips:
areas of herbaceous vegetation, resistant to wind erosion, and grown
in strips perpendicular to the prevailing wind direction. These
strips trap wind-borne sediment and nutrients and pesticides carried
by sediment.
Herbaceous Wind
Barriers:
tall grasses, up to 5 feet, and other non-woody plants established
in 1- to 2-row narrow strips spaced across the field perpendicular
to the normal wind direction. These barriers reduce wind speed and
wind erosion and intercept wind-borne soil particles which may carry
pesticides and nutrients.
Other Barriers: other types of perennial vegetation
in the landscape can serve the function of a buffer. These include
CRP fields, wood lots, terrace back slopes, ditch banks, and wildlife
plantings.
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