FAQ: Should I use compost or topsoil to establish a new lawn?
Mixing compost with native soil makes topsoil. So instead of either/or, when you use compost to establish a new lawn, you get both.
Simply incorporate the compost into the top few inches of in situ soil according to the manufacturer’s recommendations. (Click here for McGill’s use instructions.)
Et voilà … a new layer of topsoil.
You can also broadcast compost with the seed or put down a layer under new sod. The compost will accelerate establishment and green-up. Compost use has been shown to encourage earlier green-up in the spring and extend the green season in the fall, too.
If you insist on buying topsoil, have it tested for organic matter content before application. Because so much true topsoil has been lost over the years, especially in developed areas, that load of dirt may not be topsoil at all, but scraped up, nearly-inert subsoil. If the product is mostly sand or mostly clay, you may need to add compost to boost its organic matter content.
Still not convinced? Instead of buying topsoil and fertilizer, it can be cheaper to make your own topsoil, too.
But don’t make the mistake of using 100% compost when the job calls for topsoil. Most plants will need the weight/density of soil to provide support and keep the plant upright throughout the growing season(s).
Planting in 100% compost may be too rich for some plants, as well.
Remember, compost is intended to be used as a soil amendment, not a soil replacement.