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Revegetation: Hydroseeding
Hydroseeding’s
main purpose is erosion control, this year will require
different applications and variations in hydroseeding products
and procedures.
Different Sites, Different Mixes
This year it is especially important to understand how different
sites may require different seed mixes. For quick revegetation,
during or after construction, annual grasses are often used, as
they will not be the permanent installation.
For quick post-construction revegetation, you want something to
grow quickly without watering, aside from rainwater or spray
from water trucks. It is important to select a very basic seed
mix that will establish quickly but not become invasive; select
an annual grass that will not reseed itself.”
After grading the client may want permanent vegetation, but if
they’re not going to build there for a while, consider a
temporary seed such as an inexpensive annual grass, or something
more site-specific. For most construction sites the landscape
architect has already specified the permanent species which will
have some type of irrigation.
Seasons for Changing the Mix
In Nevada exposed soil is forbidden. What happens on a site
that’s still under construction? Remember the 14-21 day rule.
According to NDEP, Stormwater General Permit, stabilization
measures must be initiated within 14
days of any construction activity having temporarily or,
permanently ceased. The size of the disturbed area is
irrelevant. For the disturbed area if earth disturbing
activities will be resumed within 21 days of the temporary
cease, then stabilization measures do not need to be
implemented. You have to put something down after grading to
save the soil. This can accomplished without seed by an erosion
control (EC ) blanket. H&C often covering the soil with a mix of
liquid glue and hydroseeding wood-fiber mulch. There are minimum
mixture rates for the amount of slope and the amount of
rainfall. The liquid glue looks like non-fat milk, and it’s the
texture of heavy cooking oil. When it hits the water it
activates and it’s awesome how it holds the soil. With the snow
melting, it is important to conduct an assessment of how
winterization efforts succeeded or failed? A site inspection
will allow you to assess any failures in the stormwater
pollution prevention plan (SWPP) and site best management
practices ( BMP’s).
Certain plants will germinate only during certain times of the
year. You can put a certain seed variety down at any time, but
it might not germinate. There’s a trend now to go to native
grasses, indigenous plants, most of which turn brown in summer.
The choices available for this ‘native seed’ varies region by
region. Seasonally, it depends on what your using for a nurse or
cover crop. Maybe some oats, or annual rye for cover in the
spring, using rye in the fall.
Steep Slopes, Deep Mixtures?
For steep slopes, hydroseeding professionals often use different
types of tackifiers or mixtures. Such as bonded fiber matric (BFM).
This shredded wood fiber is dyed green, so we can see where we
sprayed. The color lasts about a week in the sun. BFM forms
something similar to a plastic cast, a protective coating over
the dirt. Blankets are often used because of cost but a Terra
Novo product (EarthGuard Fiber Matrix) is competitive with
blankets.
It is designed to work directly with soil to maintain its
stability by both preserving existing soil structure and
flocculating fine sediment dislodged by stormwater or wind and
if properly applied doesn’t harden or prevent water from
entering the soil.
No matter what brand ask for ‘bonded fiber matrix’ or
‘stabilized fiber matrix,’ in a hydromix, because it works well
and extends the soil stabilization time.
Tackifiers are site-specific. The time of year factors in, too.
After the rainy season, you can use a lighter tackifier. If you
have an irrigated site, you can use a different tackifier. What
you use depends on the time of year, the soil type, the plant
material type, and whether the site is irrigated or not.
There are a wide range of tackifiers, such as guar – similar to
the guar gum you see used in food – or bonded fiber matrix,
which can put tackifiers, seed, and so on all in one package.
Even on non-slopes, if there’s wind and water erosion, consider
a tackifiers.
Another consideration, in addition to seed germination and
price, is how a product works with existing equipment. A common
complaint about hydraulic mulches relates to the level of
contamination.
Other
Comments
You can hydroseed under EC blankets so plants grow up through
them. The secret is planning the project, taking soil tests, and
making mixes that are site-specific leads to better success. A
‘shotgun’ approach just won’t work. You can also put straw over
our seed. Drill-seeding and land imprinting are also other
seeding techniques. Land imprinting uses a seed box atop a large
drum – like a giant waffle machine – which makes an impression
in the soil. The seeds fall into those impressions. In dry
years, germination takes place in the bottom of the impressions;
in wet years seeds terminate in the top part.
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