A woman raking over loose soil to smooth it prior to sod being laid.
In the final step of soil preparation for sod, rake fertilizer into tilled, amended soil and smooth the planting bed. Photo by Joey Williamson, Clemson Extension.

Heather N. Kolich, ANR Agent, UGA Extension Forsyth County

I’ve recently been in contact with a client who had questions about installing sod on the “gravel, clay, and dirt” yard of their new house. She was wondering if she should do a soil test. While the answer is yes, a soil test is only the first of several actions needed to prepare a construction site to sustain turfgrass sod.

Soil composition and layers

Healthy soil is a mixture of sand, silt, clay (all of which are minerals), and organic matter (material from plants, animals, and other living or once-living organisms) with plenty of pore space (small openings between soil particles) that hold air, moisture, and allow for root growth and movement of soil organisms. Undisturbed soil consists of different layers referred to as O, A, B, and C soil horizons.

The O horizon, consisting of fallen leaves and leaf litter, is the uppermost soil layer. Leaf litter helps protect soil from erosion and returns organic matter and nutrients to soil as it decomposes.

A graphic showing layers of soil and where the root activity is.
Soil has layers called horizons. Most root growth happens in the A horizon, topsoil. Image from NRCS.

The A horizon is topsoil, the layer in which roots grow. The deeper the topsoil is, the deeper the roots can move below the soil surface, into regions that are less likely to dry out.

The B horizon is subsoil. a mineral layer that’s usually heavy with clay and devoid of organic matter. Plant roots struggle to penetrate subsoil. The C horizon sits above the bedrock.

Soil inversion and compaction

Construction projects, including new home construction, involve a lot of soil movement. Prior to construction, valuable topsoil may be harvested and sold. Digging and leveling activities stir soil, bringing lower horizon layers to the surface and turning upper layers under. What we are left to plant in is subsoil or fill dirt that may have very different qualities than native soil.

On top of all this – literally – is heavy equipment that packs soil hard and presses closed the pore spaces that allow air and rain to move into soil.

Preparing soil for sod

staggered placement of sheets of sod.
Stagger sod pieces and fit them tightly together to slow water runoff and minimize gaps for weeds. Photo by Joey Williamson, Clemson Extension.

Sod needs to be in firm contact with the soil bed so that roots can grow into it. Ideally, the soil will have the proper pH and fertility for the turfgrass species, the soil bed will be free of rocks and weeds, and smooth and level with several inches of topsoil. Before installing sod:

  1. Collect soil samples for testing; I recommend the Basic and Organic Matter tests.
  2. Treat weeds with a broadleaf herbicide that is labeled for use with the turfgrass species to be installed.
  3. Rake and remove rocks, weeds, sticks, and debris.
  4. Apply lime and organic matter as recommended on soil test report and till it into the soil 2-4 inches deep.
  5. Level the soil; apply fertilizer as recommended in the soil test report and rake it in.
  6. Lay sod, fitting pieces tightly together and cutting to fit as needed.
  7. Press sod into the soil with a lawn roller.
  8. Water thoroughly; then water as frequently as needed during establishment to keep the soil moist.
  9. Gradually decrease watering to 1-inch per week after active growth begins. 

It’s also a good idea to make a record of the species and cultivar of the sod installed, such as Zoysia, Emerald or Bermuda, Tiftuf, so that when you need to replace a section, you’ll know what to purchase. Refer to the UGA Lawn Calendars and Georgia Pest Management Handbook for more information on lawn management.

Posted in: