Roadside Revegetation

IMPLEMENTATION GUIDES
A general rule for tillage work is to operate equipment on the contour to reduce the potential of
water concentrating in the paths of the furrows and creating soil erosion problems. Operating
equipment on the contour (cross slope) is limited to gentler slopes (Table 10-4). To optimize
the use of equipment on steep slopes, down-slope operation of equipment must not create
long, continuous furrows. It is also important to consider that if cuts and fills are left less
compacted, there will be deeper rills and gullies created if concentrated flows of water are
directed onto these slopes. These features are unsightly and can deliver high quantities of
sediment to watercourses. Therefore, on slopes that have been tilled, it is important to redirect
any concentrated flow of water that might enter the top of the cut to areas that are designed
to handle this water. While it is not the job of the revegetation specialist to walk the tops of
cuts and fills to determine whether concentrated water might flow into areas that are not
designed for it, the success of the tillage project might depend on it.
Most soil shattering equipment is attached to a tractor toolbar and is limited to slope gradients
of 3H:1V or less. Subsoilers and rippers are best used for projects that consist of gentle terrain
or obliterated road sections. Newer equipment, such as the subsoiling grapple rake, has been
developed to overcome these limitations. Attached to the arm of an excavator, this equipment
can reach 35 feet up and down slope and specifically rip targeted areas of compacted soil
(Figure 10-10).
Incorporate Soil Amendments
Tilling is used to incorporate fertilizers, organic matter, lime, and other amendments evenly
throughout the soil, while loosening compacted soils. Tilling with these objectives requires
equipment that mixes soil, such as plows, tillers, disks, chisels, and soil spaders. This equipment
is tractor-drawn and limited to gentle slope gradients (5H:1V or greater) and soils low in rock
fragments. These tools are not designed to break up deep compaction. Under most disturbed
soil conditions, the best that can be expected this equipment is tillage to a depth of 8 to 12
inches.
Rippers and subsoilers are not very effective in incorporating materials such as fertilizers or
organic matter into the soil. Nevertheless, spreading mulch on the soil surface prior to ripping
or subsoiling usually incorporates enough organic matter into the soil surface to enhance
infiltration rates (Luce 1997). In the same manner, fertilizers applied to the soil surface, especially
those containing immobile nutrients, will be mixed into the top several inches of soil and
made available to surface roots. On projects where topsoil has been salvaged and reapplied,
subsoilers or rippers are the preferred equipment. Using equipment that mixes soils runs the
risk of incorporating salvaged topsoil with the infertile subsoil.
A more recent set of specialized revegetation tools that mix and incorporate amendments
have been developed for the tracked excavator. The arm of the excavator can reach 35 to
40 feet on steep cut and fill slopes and work soils that were previously inaccessible to most
equipment. The simplest excavator attachment is the bucket which can be used to move
topsoil or organic matter to concentrated locations and creating mounds or planting islands
(see Section 10.1.8, Topographic Enhancements). When islands are created for deep-rooted
species, such as shrubs and trees, soil can be excavated several feet deep with the excavator
bucket and incorporated with organic matter amendments to create a deep rooting profile.
The subsoiler grapple rake (Figure 10-10) adds several design features to the excavator bucket.
In addition to mixing organic amendments into the soil, the subsoiler grapple rake can remove
large rock with the grapples and loosen soils with the winged subsoiling tines.
C
B
Figure 10-10 | Subsoiling
grapple rake
The subsoiling grapple rake is a
quick-mounting attachment to excavating
machinery that combines several
operations in one: (A) subsoiling with
winged tines, (B) soil incorporation with
bucket, and (C) removal of rock and slash
with grapples (Photo courtesy of Mike
Karr, Umpqua National Forest).
A
Roughen Soil Surfaces
Tilling is often done to roughen the soil surface for erosion control and to create a more optimum
seedbed (see Section 5.6.7, Surface Roughness).Surface Roughness). The micro-topography
of a roughened surface consists of discontinuous ridges and valleys. The valleys become the
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