Lawn top dressing is when you apply a thin layer of material onto the lawn. Lawn dressing is often done with sand and that’s where the problem is.
Sand is used because people think it will improve air space and water infiltration and drainage. These are important organic gardening goals, but top dressing lawn with sand does not help achieve them.
No matter what your soil is composed of, putting sand on top can cause drainage problems and dry pockets in the soil. And there's more.
If you’re lawn top dressing with sand onto your clay soil, it can form a soil that is like concrete. And since sand doesn’t have any nutritional benefit or any ability to hold onto nutrients, you are decreasing the fertility of your organic soil.
It is not as bad to use sand on golf course greens because they are already made of sand, but even then, it is not very helpful. Regardless, in a residential lawn, it is harmful.
But in thinking about how to topdress a lawn, there is something else commonly used in organic gardening that you should absolutely use for lawn top dressing and that is 1/4 inch to 1/2 inch of good quality, well-screened compost! Well-made compost brings many benefits to the lawn and organic garden, including:
This method of lawn dressing is what should be done after aerating a lawn. One of my favorite organic gardening tips for if you want to do a really good job, after aerating and before adding the compost, you can add other soil-enhancing products such as mycorrhizal fungi, liquid kelp and any minerals that you need based on a soil test, such as calcitic lime and soft rock phosphate.
Doing all of these things is organic gardening heaven for your lawn.
It is best to do all of this after aerating because the amendments and compost get down into the root zone where they belong. While you shouldn’t need to aerate every year once your lawn is healthy, topdressing with compost is always a good idea. You can do it spring or fall or both.
You can rent a top dressing lawn machine to do this, but I have never had much luck with it using compost. I just do it with a shovel and rake.
As I discussed in Lawn Dethatching And Lawn Rolling, dethatching is a last resort to use only when the thatch is simply too much. The thatch will keep coming back until you address the root cause, which is inadequate soil microbial life. Continual dethatching will only exacerbate the problem.
Lawn rolling can be helpful during installation, but it is generally detrimental on an annual basis because it just compacts the soil, which is the opposite of what your organic gardening goals are.
As I discussed in Aerating A Lawn With A Lawn Core Aerator, lawn aeration can provide benefits if done during the fall or early spring by a machine with sharp tines that removes the soil cores. It must be followed by top dressing lawn with good compost and optional other amendments.
Lawn dressing with sand is detrimental, but a good 1/4 inch to 1/2 inch of compost annually provides many benefits.
So if you've been aerating your lawn, I hope you'll now top dress it after, and if you've been top dressing with sand, I hope you'll use compost instead. Let me know your thoughts below.