Which Soil Mix to Use for Sod?

Q. We have an area that is about 20×20. We are planning to install sod in this area. We need to bring in about 6 inches of soil before we install the sod. I just called about of your soil mixes and you gave me a lot of good info. But I need all the options in written form how to mix the soil before to installing the sod.

Viragrow Garden Soil containing compost and washed silica sand

A. I gave you two options; the first was to use our Garden Soil Mix which is a mixture of compost and washed silica sand and apply enough to bring it up to finished grade. Your 20×20 area would require 8 cubic yards at a cost of $35 per yard plus sales tax and delivery.

You can layer our Garden Soil Mix on top of your existing fill IF water drains through your existing soil fast enough. However, if your soil does not drain quickly then it is best not to layer them. If the area that you needed to fill was 12 inches deep or more, then there would be no problem layering our Garden Soil Mix on top and you would not need to go through this next step.

If soil particles do not have the correct air and water
balance between them, roots will not grow.

To find out if water drains fast enough so you can layer them

•  Dig a hole at least 12 inches deep in the existing soil. I use a posthole digger.
• Fill this hole twice with water. The first time allow the water to drain then fill the hole a second time.
• Time how long it takes for the water to drain after the second filling. If water drains from the hole in less than four hours, you can layer our Garden Soil Mix on top of your existing soil. If water drains a lot slower than this then you will create a problem if you layer the two mixes on top of each other.

Ammonium phosphate, a traditional 'starter'er"
fertilizer

When two soils that drain differently are layered on top of each other it is difficult for roots of plants to grow from one layer into the deeper layer. Instead, the roots become shallow because they prefer the mixture of water and air in the top layer. Turfgrass with shallow roots are more prone to diseases, lack heat tolerance and develops dry spots.

If you think the soils should not be layered, you can still use Garden Soil Mix on top of your existing soil with this modification. 

Apply a 2 to 3 inch layer of Garden Soil Mix on top of your existing soil and cultivate or rototill it into the existing soil, mixing the two together. Lay the remaining garden soil on top of this mix and sod over the top of it.

Mixing the two soils together where they interface helps water movement transition from one soil type to another soil type that is very different.

Soil that is prepared for sod or seed should be firmed and not “fluffy”. When walking across the surface your feet should not sink more than ½ inch deep. If your feet sink more than this, roll the soil to firm it up before sodding or seeding. Use a starter fertilizer such as 16-20-0 before seeding or sodding to encourage rooting. After laying sod, immediately apply water to the sod that has been laid.