Roadside Revegetation

IMPLEMENTATION GUIDES
remote sites, as well as the availability and abundance of road right-of-way material that
is typically burned for disposal, this is an option that should be considered. If shredded or
chipped road right-of- way material is to be incorporated into the soil, it should be allowed
to age as long as possible in piles. To increase the rate of decomposition, the piles should be
moved several times a year to add oxygen.
Some organic sources have been stored in piles for long periods of time and are partially
decomposed. They are darker in appearance than fresh sources, but the appearance of the
original organic source can still be discerned (e.g., needles or leaves are still identifiable).
These materials are sometimes referred to as “aged.” Because only partial decomposition has
occurred, C:N is lower than fresh organic matter. Nitrogen immobilization, however, should
still be expected for a significant period of time after incorporation. Aged organic sources
have not typically undergone extensive heating, like composts, and they can contain seeds
of undesirable weeds.
Compost results from the controlled biological decomposition of organic material. The
resulting heat generated in the process sanitizes the material. The end product is stabilized
to the point that it is beneficial to plant growth (Alexander 2003a, 2003b). During the early
stages of composting, heat is generated at temperatures that are lethal to weed seeds, insects,
and pathogens (Inset 10-7). Fresh, moist compost piles will usually generate heat in the first
few days of composting, reaching 140 to 160 degrees F, which will kill most pathogens and
weed seeds (Epstein 1997; Daugovish and others 2006). The resulting material is a relatively
stable, sanitized product that is very dark brown to black in color. Composts are very suitable
materials for increasing the water-holding capacity of sandy soils, increasing nutrient supply,
and enhancing soil infiltration and permeability rates.
Inset 10-7 | Compost production
The production and use of compost in the United States has flourished in the last 20
to 30 years as a result of a ban in many of states on yard wastes in landfills. Since 1988,
the number of yard waste composting facilities in the United States has expanded from
less than 1,000 in 1988 to over 3,500 in 1994. With the formation of the Composting
Council in 1989, research in compost manufacturing has increased significantly.
Composting is the biological decomposition of organic matter under controlled
aerobic conditions. To start the composting process, there must be organic matter,
water, microorganisms, and oxygen (A). Heat is also needed, but is created by the
microorganisms as they proliferate. Temperatures exceed levels necessary to kill most
pathogens and weed species (B). With time, in a controlled composting environment,
microorganisms release carbon dioxide and water from the organic matter. The rate
at which these are released, and ultimately the composting time, is a function of the
type of material being composted and the composting method.
A variety of composting methods have been
developed over the years. State- of-the-art
facilities and equipment that control and
monitor oxygen, moisture, CO2, and temperature
levels throughout the composting
process can produce relatively uniform
products. The picture shown in (C) is of a
composting system that pumps oxygen
through a pipe centered in the wrapped
piles of compost. Temperature and carbon
dioxide are controlled through a venting
system (adapted from Epstein 1997).
˚F
160
140
120
100
80
60
40
32
˚C
70
60
50
40
30
20
10
0
Time (One to 12 Months)
Bacteria
Fungi and
Actinomycetes
Insects and
Worms
Pasteurization
Temperature
Compost
Water
25 to 50%
Green Wastes
(Nitrogen)
Microorganisms
1 to 12 Months
Compost
Oxygen
50 to 75%
Brown Wastes
(Carbon)
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