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Technical Notes
<br />ten cubic yards of compost are needed per 1,000 square
<br />feet of lawn that is amended.
<br />Helpful specifications on determining the proper
<br />amount of compost are provided in Chollak and
<br />Rosenfeld (1998), as well as guidance
<br />on selecting compost of the right
<br />source and age. It may also be neces-
<br />sary to add dolomitic lime at a rate 100
<br />lbs /1,000 square feet to control acid-
<br />ity. After compost amendment, grass
<br />is then reestablished by seeding or
<br />sodding. The process for amending
<br />compost into new lawns is slightly
<br />different; more detailed information can be found in
<br />Chollak and Rosenfeld (1998) and McDonald (1999).
<br />Compost amendment can also
<br />provide benefits for the lawn
<br />owner.
<br />„i,
<br />While compost amendment seems like an ideal
<br />practice, there are a number of situations where it is not
<br />feasible. These include sites that have steep slopes, a
<br />high water table, wet saturated soils, or downhill slope
<br />toward the house foundation (these areas are usually
<br />are poor candidates for a traditional lawns, as well). In
<br />addition, deep tillage within three feet of the drip line
<br />of trees and shrubs should be avoided.
<br />The cost to install a compost amended lawn on a
<br />new residential lawn is about 72 cents per square foot,
<br />according to Chollak and Rosenfeld (1998), but can
<br />drop to 66 cents per square foot if applied across all the
<br />lawns in a new subdivision. For a typical quarter -acre
<br />lawn, the cost of installing a compost- amended lawn is
<br />about $7,200, including labor, equipment rental, com-
<br />post and hydro- seeding. This is about twice the cost of
<br />traditional methods to establish a new lawn (Chollak
<br />and Rosenfeld, 1998). However, the cost of compost
<br />amendment drops to about 20 cents per square foot if
<br />labor is excluded (assuming compost is available at
<br />$12 /cy, delivered, rental of tiller /spreader, soil test,
<br />lime and grass seed). Thus, if a homeowner were to do
<br />it himself, the cost of amending an existing quarter acre
<br />lawn might run about $2,200, with the time investment
<br />of two or three weekends.
<br />A faster and less costly compost amendment prac-
<br />tice has been recently introduced in the Pacific North-
<br />west. It involves aeration of existing soil (but not deep
<br />tillage), followed by the placement of about three
<br />inches of compost over the surface of the lawn in the
<br />fall. The lawn is then seeded in the spring. Initial results
<br />indicate that this simplified practice produces good
<br />turf, but the hydrologic benefits have yet to be quan-
<br />tified. If future monitoring indicates that this simpli-
<br />fied practice works, it will sharply reduce the costs and
<br />effort for the individual homeowner to restore his or her
<br />yard.
<br />Benefits of Soil Compost Amendments
<br />A number of recent research studies have explored
<br />the potential hydrologic benefits of compost - amended
<br />soils. Kolsti et al. (1995) monitored test plots of
<br />amended and unamended soils over ten storm events
<br />in Seattle, and reported that compost - amended soils
<br />reduced surface runoff by 29 to 50 %, depending on the
<br />amount and type of compost used. Even higher reduc-
<br />tions in lawn runoff (53 to 74 %) were predicted if
<br />compost amendments were implemented across a small
<br />watershed, according to amodel developed by Hieliema
<br />(1999). Chollak and Rosenfeld (1998) estimated that
<br />stormwater detention basin volumes could be reduced
<br />by 5 to 15% if compost amendments were incorporated
<br />into new subdivisions in glacial tills soils near Seattle,
<br />Washington.
<br />Compost amendment can also provide benefits for
<br />the lawn owner. For example, compost- amended lawns
<br />generally have a fraction of the summertime irrigation
<br />needs of a normal lawn. In addition, the organic matter
<br />in compost supplies meets all of the lawn's fertilization
<br />needs, at least for the first year (Landschoot, 1996).
<br />Grass also appears to grow better on compost- amended
<br />soils. Indeed, researchers have reported that compost -
<br />amended lawns exhibit more rapid turf coverage, denser
<br />root networks, greater rooting depths, lower bulk den-
<br />sity and higher organic matter (Harrison et al., 1996
<br />and Kolsti et al., 1995).
<br />Compost Amendments as a Stormwater Management
<br />Strategy
<br />The compost amendment practice should be con-
<br />sidered an element of better site design, and could be
<br />a useful technique to reduce stormwater at the residen-
<br />tial lot level. It is likely that its benefits would be
<br />amplified in conjunction with lawns also designed to
<br />treat rooftop, driveway and sidewalk runoff. Several
<br />creative designs to integrate compost amendments
<br />with other on -site practices in residential areas are
<br />described in Konrad et al. (1995). Compost amend-
<br />ments could also be used to improve the performance
<br />of grass swales, biofilters and filter strips. Communi-
<br />ties may want to encourage developers to install com-
<br />post amendments during new lawn and landscape
<br />construction (possibly through stormwater credits).
<br />Compost amendments might also prove to be an
<br />effective tool for watershed restoration, particularly in
<br />watersheds where other stormwater retrofit options are
<br />not feasible. The cumulative hydrological benefits of
<br />restoring soil quality on hundreds of lawns, athletic
<br />fields, and vacant lots could potentially be significant.
<br />The critical management issue is determining how to
<br />deliver lawn and landscape compost amendment ser-
<br />vices to homeowners in a cost - effective manner across
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<br />Watershed Protection: Techniques • Vol:. 3; No -2. •. January: 2000
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