Roadside Revegetation

IMPLEMENTATION GUIDES
The information can be graphed and used in a similar fashion to the example in Figure 10-30.
The SMP test is well adapted for soils with pH values below 5.8 and containing less than 10
percent organic matter (McLean 1973).
Apply Liming Materials
Limestone materials are commonly applied in powder form through fertilizer spreaders
or hydroseeding equipment. Fine limestone materials can be difficult to apply in dry form
through fertilizer spreaders. Pelletized limestone, which is very finely ground material that
has been processed into shot-sized particles, is easy to handle and can be used in fertilizer
spreaders. Hydroseeding equipment, however, is probably the best method for spreading
liming materials, especially very fine liming materials.
Since liming materials are relatively insoluble in water, surface applications of lime, without
some degree of soil mixing, renders the lime ineffective for immediate correction of subsoil
acidity. Several studies have indicated that it can take more than a decade for surface-applied
lime (not incorporated) to raise soil pH to a depth of 6 inches (Havlin and others 1999). It is
important, therefore, to incorporate liming materials into the soil at the depth where the pH
change is desired.
Incorporation can be accomplished on gentle slope gradients using tillage equipment, such as
disks and harrows (see Section 10.1.2, Tillage). Liming materials can be mixed on steep slopes
using an excavator. However, if equipment is not available for mixing on steep sites, applying
very fine liming materials through hydroseeding equipment is a possible way of raising pH.
This method requires the use of very finely ground limestone (Havlin and others 1999). This
product raises pH faster, and depending on the soil type, can move a short distance into the
soil surface. Nevertheless, with surface-applied limestone, it should be assumed that soil pH
will not change much deeper than 3 inches below the soil surface.
A
10.1.7 BENEFICIAL SOIL MICROORGANISMS
B
Background
Beneficial microorganisms are naturally occurring bacteria, fungi, and other microbes that
play a crucial role in plant productivity and health. Some types of beneficial microorganisms
are called “microsymbionts” because they form a symbiotic (mutually beneficial) relationship
with plants. In natural ecosystems, the root systems of successful plants have several microbial
partnerships that allow them to survive and grow even in harsh conditions (Figure 10-31).
Without their microsymbiont partners, plants become stunted and often die. Frequently,
these failures are attributed to poor nursery stock or fertilization, when the real problem was
the absence of the proper microorganism.
As discussed in Section 5.3.5, Mycorrhizal Fungi, beneficial microorganisms should be considered
as part of an overall strategy to conserve existing ecological resources on the site, including
existing beneficial soil microorganisms. These strategies include:
◾◾
Minimizing soil disturbance
◾◾
Conserving and reapplying topsoil and organic matter
◾◾
Leaving undisturbed islands or pockets on the project site
◾◾
Minimizing use of fast-release fertilizers
On projects where soil disturbance will be minimal, or where healthy topsoil is still present and
contains functional communities of beneficial microorganisms, reintroducing the organisms
will usually not be necessary. However, most road projects involve severe disturbances and
so healthy populations of beneficial microorganisms may be depleted or even absent. Soil
Figure 10-31 | Symbiotic
relationships of plants
Many plants rely on symbiotic relationships
to survive and grow in nature
(A). The mushrooms under this spruce
are the fruiting bodies of a beneficial
fungus that has formed mycorrhizae
on the roots (B).
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
268