One of the largest uses for compost in the landscape business is
amending soils intended to be seeded or sodded with turf. Home lawns,
and turf areas in parks, golf courses, commercial developments,
and highway strips all need to be seeded or sodded at some point
in time during new construction. Many states are now choosing to
include compost in their procurement legislation in hopes of creating
markets for locally produced compost products. However, there is
still a gap in many states, especially when it concerns specifications.
Although procurement legislation is extremely helpful in the total
market development picture, the landscape foreman or designer close
to each job needs a more detailed point of reference, a specification,
to follow. The specification must be simple and easy to follow without
a lot of cumbersome red tape.
Why use compost for turf establishment? There are a number of agronomic
and economic benefits which have become rather well known. Agronomic
benefits include reducing compaction, increasing drainage, increasing
nutrient exchange capacity, increasing moisture retention, reducing
erosion potential of soils, and a host of others. Many contractors
also claim using compost helps increase speed and total % germination
of turf seed and increased knitting of roots for sodded projects.
Economic benefits include offering a product capable of enhancing
project performance while reducing total costs. Because most soils
lack the ideal level of organic matter, compost can provide this
missing link while remaining quite affordable compared to alternatives
like peat moss. The project outlined below is a typical example
of economic savings possible.
Planting bed preparation
Flower bed preparation has become more popular among contractors
seeking that extra performance for their customers. Compost, along
with peat and cow manure, have filled the need for some type of
soil amendment to be used in most high end bed prep projects. Additionally,
the trend of raised beds has increased the need to import volumes
of materials to achieve an elevated status, increasing the need
for blended topsoils or soil amendments.
Besides the trends of increasing activity in the flower garden,
scientific evidence of increased performance from using compost
has been demonstrated through research conducted at the Ohio State
University. Dr. Elton Smith, Professor Emeritus of Horticulture,
determined that annuals and perennials grown in compost amended
soils were 30% larger on average. Most beneficial results were found
at application rates of 1-2" of compost incorporated to a depth
of 5" native soil.
Although Smith1s research pointed out obvious agronomic benefits,
it is clear that locally produced compost normally has an economic
advantages compared to imported peat moss. Compost may often be
as much as 50% less expensive than peat. However, many leading perennial
experts agree that compost mixed with peat moss in a 50-50 blend
offers the best of both worlds, especially for those plants which
thrive best in slightly acidic soils. The pH of peat moss, normally
about 5.0, helps balance out the pH of compost, normally between
7 and 8.
Homeowners instinctively seem to seek the perfect soil for their
annual and perennial flower beds. While I was writing this article,
a stranger knocked at our door in the pouring rain and started into
a story about how she normally gets horse manure for free, but it
was apparent from our garden near the road that the "black,
crumbly humus was far superior". Her ten semi trailers will
be delivered next week.
How would a homeowner learn about such products? Homeowners are
extremely observant, especially when they visit parks like Sea World,
Disney, and other theme parks where flowers and greenery have increased
in popularity over the last ten years. Rob McCartney, Horticulturist
for Sea World of Ohio, has developed a team of experts responsible
for making landscaping the highest rated attraction at the park...ahead
of Shamu, Dolphin Cove and other animal attractions. In part, it
is these attractive landscapes in public places which drive consumer
demand to obtain similar results at home.
In the commercial landscape business, specifications for bed prep
are less common than for turf or mulch projects, because beds usually
take up less time and attention in an overall project. Projects
which tend to have all the bases covered usually have included a
spec for each part of the project, including bed prep, turf seeding
and mulching. However, on a large portion of projects, no specification
for bed prep is included.
Since adding compost to a flower bed may be the last chance to
incorporate organic matter for a number of years, it stands to reason
to add a good amount. Most soils are low in organic matter, even
if they have been worked for a number of years. For that reason,
our specs call for addition of 2" of compost which needs to
be incorporated to a final depth of at least 5". Most rototiller
tines are about 5", so this spec is easily accomplished in
Using Compost as a mulch
Finely screened compost is not the best product to use for weed
control in flower beds. Dr. Elton Smith again proved this with research
conducted several years ago, comparing compost mulches with standard
bark mulches. However, using compost for a mulch has become more
popular in recent years because of favorable pricing, availability
and other aesthetic benefits.
At Sea World of Ohio, Rob McCartney first tried compost to use
as a mulch for the dark color, offering contrast and a dark background
to the splashes of annual and perennial color. For those using compost,
concern with weed control seems to be balanced out with other benefits,
including added nutrient exchange and the ability to incorporate
the compost/mulch into the soil at the end of the growing season
(see fall bed prep, LLM, Oct., '95).
To reach common ground between weed control and the desire to add
valuable humus to the landscape beds annually, the specification
below outlines an acceptable product.
Notice the particle size includes all material passing a 2"
screen, which will make the product have a large rage of particle
sizes, with minimal unattractive long pieces of woody material.
Many material yards and garden centers are starting to create a
special blend of 1/3 compost and 2/3 hardwood bark mulch to obtain
the dark color the retail customer wants without sacrificing the
weed control they need.
The compost-mulch mixture makes a lot of economic sense. Hardwood
barks are often delivered to supply yards for $10-$15 per cubic
yard whereas compost may range from $5-$10/yd. Economic benefits
aside, there are significant agronomic advantages in adding compost
to a hardwood bark mulch. Hardwood mulches often are acidic, sometimes
reaching a pH of 4.5 (this is when it usually takes your breath
away). Compost, with a slightly alkaline pH, can help buffer this
sour mulch and avoid potential plant damage when applied in the
From a nutrient standpoint, compost-amended mulches offer a better
overall package and tend to rot down faster in the landscape, requiring
re-application each year. These products tend to be more popular
with the serious gardener looking for a higher level of performance.
Active gardeners also tend to move various landscape plants around
alot, which is harder to accomplish if mulches containing more actual
wood fiber are used.
Although compost can be combined with other mulches successfully,
hardwood barks seem to be the leading choice for the mixture described
above. Pine bark has a larger lignin content and is naturally longer
lasting in the landscape and is normally used by itself, without
If you have not used compost on a project because it has not been
listed in the specification, contact the project architect or owner
and inquire about the feasibility of submitting an alternate bid.
You should be able to find some level of expertise locally available,
either from your local extension service, testing laboratory, land
grant university or private compost vendors.
The lack of specifications in a variety of compost applications
have been targeted as one of the roadblocks to the successful development
of markets in the composting industry. We hope you can use the examples
above to promote the correct use of quality composts in your local
communities. If you are not able to directly influence the projects,
consider passing along a copy of the specs to an influential decision
maker who may be able to help. If you have further questions about
use guidelines, specifications or other compost related matters,
contact the Composting Council at 440-989-2748.
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