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The installation of sod is a popular way to establish a new lawn.
Most of the sod purchased is a blend of different Kentucky bluegrass
varieties or a mixture of other common turfgrass types (i.e., fine
fescue, perennial ryegrass, tall fescue). When installed correctly
on properly amended soil, in the appropriate sunlight conditions
and where correct maintenance is provided, a sod lawn can be a valuable
part of your landscape.
There
can be many potential problems in installing a sod lawn. Sod is
often installed on top of soil that has had little or no preparation,
for example. Inadequate consideration is often given to the sunlight
requirements of each turfgrass species. Many new lawn owners are
misadvised as to the maintenance requirements of Kentucky bluegrass
as well--although Kentucky bluegrass does require a certain level
of maintenance to perform at its best and to offer its best aesthetic
qualities, it does not require the wasteful practices we often see
property owners providing (i.e., exceeding recommended fertilizer
rates and frequency, frequent over watering, excessive use of pesticides
when problems don't exist, etc.).
With
a little planning, preparation and correct maintenance Kentucky
bluegrass sod (and other types) can be an asset to your property.
Site Considerations
Survey the site before selecting the grass type and/or varieties
that will dominate the sod you purchase. Most of the Kentucky bluegrass
varieties grow best in sites receiving full sunlight all day. There
are a few varieties that will tolerate moderate amounts of shade.
If the site is too shady you will need to consider another type
of grass for best results. See our GreenShare Factsheet on Selection
of Grasses for more information.
Control
Weeds
If obnoxious perennial and/or annual weeds exist on the site it
is best to consider controlling these (if possible) before the sod
lawn is installed.
Correct
Drainage Problems
Drainage problems need to be addressed before
installing sod. If excess water does not drain rapidly through the
soil, the turfgrass will have a poor root system and will grow weak.
In some instances you may need to consider installing a drainage
system to move excess water from problem areas in your yard to areas
where the water will not cause a problem.
Grading
Be sure to grade the soil away from fixed points on your yard (i.e.
your house, the sidewalk, etc.). You should do this with gradual,
gentle slopes so that water will be directed away from your home
and off your property.
Soil Improvement
The need to acquire topsoil is not a necessity when installing a
sod lawn. Often existing soil is suitable for sod or can be improved
to make it suitable. Have your soil tested for soil pH and nutrient
levels (see GreenShare factsheet on soil
testing for information on submitting soil samples for testing).
The test results will direct you in how to improve your existing
soil. The soil pH should be between 6.0 and 7.0 for best results.
Limestone is used to increase the soil pH and should be mixed with
the top 6 inches of soil before the soil is final graded. This is
also the time to correct any nutrient deficiencies.
If
you do not test the soil you will have to rely on certain "rules
of thumb" in regard to additions of limestone and fertilizer. Add
50 lbs. of dolomitic limestone per 1000 square feet. Starter fertilizers
in 1-2-1 or 3-4-1 ratios (i.e. 10-20-10 or 18-24-6) should be added
at the rate of 1 lb. of nitrogen per 1000 square feet. The limestone
and fertilizer should be mixed with the top 6 inches of soil.
Most
soils benefit from additions of organic matter. To improve a sandy
soil, work about 1-2 inches of organic matter into the top 4-6 inches
of soil. Another method is to thoroughly mix 1 inch of heavier soil
with the top 4 inches of sand. A better alternative is to add both
organic matter and heavier soil rather than one or the other.
If a heavy or "clay-like" soil needs improvement you should work
organic matter into it. Do not add sand into a clay soil, since
this will cause it to pack harder than before much like concrete.
Organic matter sources vary. Consider using 4 large (6-cubic foot)
bales of peat or 2 to 3 cubic yards of well-rotted manure or cultivated
peat. Similar amounts of finished compost could also be considered.
These volumes should be evenly spread across 1000 square feet and
mixed with the top 4-6 inches of soil.
Topsoil
If you decide to bring in topsoil you should plan on adding at least
4-6 inches of good topsoil, even though it is expensive. You need
to consider at least this amount since a 6-inch layer of loose soil
settles to about 5 inches. Turfgrass roots will occupy approximately
5 or 6 inches of soil. If the topsoil layer is too thin the turf
may actually be growing in the pre-existing soil. If possible plan
ahead when purchasing topsoil. In this case you will have adequate
time to have the soil tested for pH, nutrients and physical analysis.
Soil
grade changes have the potential to damage and kill existing trees
on your property. If you are going to add topsoil over the roots
of existing trees it is imperative that you take the appropriate
steps necessary to prevent damaging and killing trees. A simple
"well" constructed around the trunks of trees is not sufficient.
See our GreenShare Factsheet on Protecting
Trees during Construction for more information.
Final Preparation
Sod should be installed on top of finely graded soil. After you
have installed all drainage systems, added topsoil and or soil amendments
and have rough graded the area it is time to final grade. The soil
should be raked to produce a smooth surface. This firms the soil
and allows any remaining small humps and hollows to show in the
soil, which should be corrected at this time. A mixture of soil
granules and small clods of soil is preferred over a soil with a
very powdery surface. You may want to make a single trip with a
light roller over the soil in order to firm the soil and to show
any small humps and hollows which may need correcting.
Proper
Time
With proper irrigation sod can be installed almost anytime
during the growing season when the ground is not frozen. It is desirable
to plan ahead, however, and consider installing sod in the late
summer to early fall. As with seeding, this time of the year is
usually very conducive to the environmental conditions needed for
rapid establishment. Although possible, it is best to avoid installing
sod during very hot, dry and humid conditions of mid-summer. The
frequent watering needed to establish new sod during this time may
encourage diseases such as Pythium blight, which can be devastating
to a lawn.
Installing
The Sod
Make sure that the sod pieces are not dried out or wilted. Also
be sure that the pieces are at least 1 inch thick. If the sod is
not freshly cut and healthy do not accept it. Do not leave the sod
stacked in piles. If you can not install it immediately lay the
pieces out in a shady location. For best results the sod should
be laid as soon after delivery as possible, preferably no more than
36 hours after it is cut.
The
soil should be flat and moderately moist. If needed, water the soil
ahead of time very lightly. This improves the ability of the sod
to survive and knit in faster. Lay the sod strips on the prepared
soil tightly together, edge to edge, with staggered joints like
bricks in a wall. Fill cracks with soil if necessary. Immediately
soak the newly laid sod thoroughly.
As
soon as it is dry enough to walk on, lightly roll or tamp the sod
to give a good contact with the soil beneath. This is necessary
to remove any air pockets that will interfere with proper rooting.
Watering
Correct watering after installing the sod is critical to its survival.
The idea is to keep the soil under the sod moist as well as the
soil that comes with each sod piece. This does not mean constantly
wet and soggy. Usually 1 inch of water every 2 to 3 days applied
in the early part of the day will be sufficient to keep the soil
moist. Measure 1 inch of water by placing several straight sided
coffee cans in the sprinkler output pattern. Check on the moisture
conditions from time to time by lifting the corners of the sod pieces.
If the sod/soil seems excessively wet by the second day then delay
watering until the third day. Water only as frequently as necessary
to keep the soil/sod moist, not soggy and wet. It is most important
that you do not over-water and avoid saturating the sod/soil since
this will prevent the sod from re-rooting and cause the roots to
rot.
After
the sod has knitted (rooted) to the soil (from 1-3 weeks) it is
important to change the watering schedule. Watering should be done
thoroughly to soak the root zone (top 4-5 inches of soil) but infrequently.
Providing 1 inch of supplemental irrigation every 4-7 days (depending
on soil, temperatures and rainfall) should be adequate for most
lawns. There is no need for daily watering of a sod lawn.
Mowing
Normally a newly installed sod lawn will probably require mowing
4 to 7 days after it is installed. Avoid over-mowing; consider a
length of approximately 2 inches for the lawn. Never remove more
than 1/3 of the leaf blade when mowing the lawn. It is not necessary
to remove or pick up grass clippings after mowing if you mow the
lawn as frequently as is necessary. Grass clippings do not cause
thatch layers.
Fertilizing
The lawn will probably require fertilizing approximately 4-6 weeks
after it is installed. Apply a complete fertilizer with a ratio
of 2-1-1 or 4-1-3 at the rate of 1 pound of nitrogen per 1000 square
feet. Lightly water in the fertilizer after it is applied. See our
GreenShare Factsheet on Developing Fertility
Programs for Lawns for more information.
Adapted
from Thomas Kowalsick, Cornell Cooperative Extension, 2001
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