Roadside Revegetation

IMPLEMENTATION GUIDES
The literature is scant and inconclusive on the benefits of hydraulic mulch to seed germination
and seedling establishment in wildland conditions. Carr and Ballard (1980) found no difference
in plant establishment when seeds were applied with and without hydraulic mulches, but only
low rates of hydromulches were compared. One approach to increasing seed germination
that is often used in drying climates is a two pass application system, where seeds and a
minimum amount of hydraulic mulch are applied in the first pass, then covered by a thick
application of hydraulic mulch in a second pass. While this application method appears to
have some advantage over a one pass operation because the seeds are covered with a greater
thickness of hydraulic mulch, it is not known what the difference in germination and seedling
establishment rates might be. The benefits from a germination standpoint are probably not
seen until the hydromulch rates are high (3,000 lb/ac or greater). Even then, on arid sites
receiving less than 6 inches precipitation, higher hydraulic mulch rates can intercept the low
amount of precipitation that is received, preventing moisture from reaching the seeds (see
Section 5.2.2, Rainfall Interception). Since it is uncertain whether hydraulic mulches improve
germination, it is better to base mulch rates on surface stability objectives than on seeding
objectives and use other methods to improve seed germination. For example, it might be
more effective to reduce the amount of hydraulic mulch to the minimum amount necessary
to apply seeds and, with the costs savings, apply a long- fibered mulch in a second operation.
Identify Hydroseeding Areas
Hydroseeding should take place after the final slope shaping and topsoil placement have been
completed. Several months before hydroseeding is to take place, the site must be visited to
finalize an implementation plan that includes the locations of where the plants or cuttings are
to be installed and where seeding will take place. While most of the hydroseeding areas will
conform to the revegetation units developed during planning, things always look different
after construction. In this field review, the exact locations of the areas that will be hydroseeded
are drawn on a road map and areas are identified where different seed mixes, fertilizer types/
rates, or hydraulic mulch rates will be applied.
The acreage for each hydroseeding area is calculated using methods described in Figure 9.2
in Chapter 9. This method partitions the cuts lopes and fill slopes into rectilinear units by road
stations and calculates acreage between each unit. This information is then summarized and
used to develop task orders. It can also be used in the field for keeping record of acreages
and location of hydroseeding operations.
The proximity to streams must be considered when locating hydroseeding areas. If hydroseeding
areas are adjacent to ditches or waterways that drain into live streams, a buffer
should be included around these features to avoid entry of fertilizers into the stream system.
Fertilizers applied to these sites have the potential of entering the ditches during rainstorms
and eventually reach a stream course as nutrient pollution. Road runoff can be a significant
contributor of nutrients to water systems (Reuter and others 1998).
Determine Seeding Rates
Sowing rates for hydroseeding are calculated using the same method outlined in Figure 10-96
in Section 10.3.1, Seeding. The reader is referred to this section for determining seeding rates
for any type of sowing method. These sowing calculations assume that the method of sowing
does not cause damage to seeds. This might not be a good assumption with hydroseeding,
which has been shown to increase the risk of seed breakage in the hydraulic seeder tank
during mixing (Kay and others 1977; Wolf and others 1984; Pill and Nesnow 1999). Additions
of fertilizers further increase the risk by exposing seeds to high salt levels when seeds are
in the slurry tank and also after they are applied to the soil surface (Brooks and Blaser 1964;
Carr and Ballard 1979; Brown and others 1983). Taking precautions to reduce the risk of seed
damage during hydroseeding will increase the seed germination rates and reduce the amount
of seed needed for the project.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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