Sod Lawns

The installation of sod is a popular way to establish a new lawn. Most sod lawns are a blend of different Kentucky bluegrass varieties. When installed correctly on properly amended soil, in appropriate light conditions, and where correct maintenance is provided, a sod lawn can be a valuable part of the landscape, otherwise there can be many potential problems.

Site Selection and Preparation

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 sun 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.

Control Weeds: If obnoxious perennial and/or annual weeds exist on the site it is best to consider controlling these before the sod lawn is installed.

Correct Drainage Problems: If excess water does not drain rapidly through the soil, the grass will have a poor root system and will grow weak. In some cases it may be necessary to install a drainage system to move excess water from problem areas in the yard.

Grading: Grade the soil away from fixed points on the yard (i.e. house, sidewalk, etc.)  with gradual, gentle slopes so that water will be directed away from the house and off the property. 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.

Soil Improvement: The need to acquire topsoil is not a necessity when installing a sod lawn. Have the soil tested for soil pH and nutrient levels; the test results will provide directions  on how to improve pH and nutrient deficiencies in the existing 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 or 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 clayey soil needs improvement work organic matter into it but do not add sand into a clay soil since this will cause it to pack harder than before, much like concrete.

Consider using 4 large (6-cubic foot) bales of peat or 2–3 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 topsoil is preferred, plan to add at least 4–6 inches of good topsoil, even though it is expensive, because a 6-inch layer of loose soil settles to about 5 inches. Grass roots will occupy approximately 5 or 6 inches of soil. So, if the topsoil layer is too thin the grass may actually be growing in pre-existing soil.

Final Soil Preparation: Sod should be installed on top of finely graded soil. After installing all drainage systems, adding topsoil and or soil amendments, and having rough graded the area it is time to final grade. Rake the soil to produce a smooth surface. A single trip with a light roller over the soil can be done in order to firm the soil and to  show any small humps and hollows which may need correcting. A mixture of soil granules and small clods of soil is preferred over a soil with a very powdery surface.

Installing Sod

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 usually has 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 that can be devastating to a lawn.

Make sure that the sod pieces are not dried out or wilted and are at least 1 inch thick. If the sod is not freshly cut and healthy do not accept it. Do not leave sod stacked in piles. If it can’t be installed immediately lay the pieces out in a shady location. For best results the sod should be laid 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 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.

Maintenance

Correct watering is critical to sod survival. The idea is to keep the soil under the sod moist as well as the  soil that comes with the sod piece. About 1 inch of water every 2 to 3 days applied early in the day is sufficient to keep the soil moist. Check on moisture conditions from time to time by lifting the corners of 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. Overwatering and saturating the sod/soil will prevent sod from re-rooting and cause the roots to rot.

After the sod has rooted to the soil (from 1–3 weeks) 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: A newly installed sod lawn will probably require mowing 4–7 days after it is installed. Avoid mowing too short; consider a length of approximately 2 inches for the lawn and never remove more than 1/3 of the leaf blade. It is not necessary to remove grass clippings. 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.

Adapted from Thomas Kowalsick, Cornell Cooperative Extension, 2001