Most people plant sod because it is an easy way to enjoy an instant lawn. Rot can be an issue, though, particularly if the roots become waterlogged.
1. Amend the Soil
The best way to prevent root rot on new soil is to make sure you lay it on well-draining, nutrient-rich soil. This means working in some organic matter, such as compost, into the top foot or so of the soil. Clay soil, in particular, can drain poorly and cause rot issues, so use plenty of compost to help break up the clay for better drainage. Performing a soil test before amending can help you guide you on what to amend with and how much to use.
2. Aerate Deeply
Aeration adds porosity to the soil, which prevents it from draining poorly or holding too much water and too little air. Tilling and amending will aerate the site quite well, but you might need to aerate again if you prepare the lot but then don't plant for several weeks (such as when prepping a site in fall for spring sod installation). A core aerator is a simple tool that can quickly break up the soil before sodding, or you can go over it again with a tiller right before planting.
3. Watch the Weather
Don't install sod if extremely wet weather is in the forecast. Some rain and drizzle is fine and possibly even beneficial since it prevents the sod from drying out. Torrential rains, though, can lead to saturated and waterlogged soils that will drown the young grass roots before they have time to establish.
4. Ensure Root Contact
Sod roots quickly due to root contact with the soil beneath. If there is an air space between the sod and the soil, the roots won't be able to spread and establish. Worse, moisture often gets trapped in this space and leads to root rot. When installing sod, make sure that the roots are in full contact with the soil beneath. This is done by first leveling the soil before rolling out the sod, and then using a lawn roller to press the sod firmly against the soil.
5. Water Correctly
Don't over soak the new sod, as this can also lead to rot. Instead, water lightly twice per day, providing up to 1 inch of water daily. Once the sod is established and the roots have penetrated into the soil beneath, you can resume the normal watering schedule for your climate and grass type.
Contact a sod installation service for more assistance and to ensure healthy rooting of your new lawn.