Americans spend crazy amounts of money on their lawn each year, much of this cost going to synthetic fertilizers. But you can do your lawn, and soil a great service by simply top dressing your grass with compost. I top dress parts of my lawn every year with compost to improve the soil and reduce compaction.
In this article I’ll go over some basics of compost, how it improves your soil. And I’ll show you how topdress my lawn, step by step.
The benefits of compost on soil
Compost is the final form of decomposed organic matter. As dead plant material, leaves and trees break down, they are ‘composting’. ‘Compost’ is the final, stable form of organic matter that has ‘broken down’. Think of it as what makes soils fertile, or at least a major component of it.
Compost has direct benefits soil in several ways :
- Organic matter in soil reduces compaction naturally, as well as the drainage
- The ability of your soil to hold nutrients is improved, thereby improving your soil’s fertility (via improved cation exchange capacity)
- Compost will improve the water holding capacity of your soil, improving your grass’s ability to withstand drought
But here is the thing – if you have clay soil, compost will break it up naturally. If you have sandy soil, compost will make it hold water better. And if you have some other kind of loam, or any other soil type, the addition of compost will make it more fertile.
Breaking down thatch
In addition to the direct benefits on soil, the addition of compost will also help break down thatch. Thatch is a layer of dead grass, roots, and stems that forms between soil and grass. A layer of thatch that is 1/4″-1/2″ thick is normal, but much more than that and nutrients will not reach soil.
Aeration of lawn will allow oxygen to penetrate into the soil. This combined with compost will feed the bacteria and micro-organisms necessary to break down thatch. The decomposed thatch in-turn will feed your soil and your grass more.
How to top dress your lawn with compost
Top dress your lawn with compost by first mowing, then aerating the lawn. Then, spread compost 1/4″-1/2″ thick (6-12 mm) with a shovel and wheelbarrow. Finally, rake the compost into the soil. It’s ok to see some compost between the grass blades. You just want to make sure that the blades can stick up through/around the compost.
Step 1 – Mow the grass
Cut your grass somewhat short to make spreading the compost easier. You will be able to see how well the compost is distributed.
Step 2 – Aerate the grass
If you really want the compost top-dressing to be effective, aerate the lawn by using a mechanical aerator or plugger. You can manually aerate the lawn with a manual aerator. Using an aerator that actually removes plugs of grass from the lawn is the most effective way to aerate, or reduce compaction.
Aeration also allows oxygen to get down into the soil, which the beneficial bacteria, fungi and micro-organisms in your soil need to survive.
But if you don’t want to spend the money renting an aerator or don’t have a manual foot aerator do not despair. I use a sturdy potato fork to aerate grass before top-dressing. The holes that are opened up will allow compost to get past the thatch and into the root zone of the grass.
Step 3 – Spread Compost
Spread compost liberally around the lawn using a shovel. Ideally you would like to have about 1/4″ (6 mm) of compost uniformly on top of the soil. This is enough compost to make a difference, but not too much where the grass will get smothered.
I just use a spade or a scoop-shovel and gently shake compost off the shovel, allowing it to fall in clumps around the area. Don’t worry about having a ‘uniform’ thickness, just do your best.
Step 4 – Rake Compost into the lawn
Finally, rake the compost into the grass. Take a simple rake and get to work! Just rake the compost until there are no obvious ‘clumps’ that may smother your grass.
Step 5 – Water the lawn
Watering the lawn after top-dressing can help get the compost to settle into the thatch and aeration holes. This will help everything look a bit more tidy than waiting for rain.
When should you top-dress your lawn?
The best times to topdress your lawn is in Early Spring and Summer. But, you can actually do this any time of year. Adding organic matter is always beneficial to your lawn, or just about any other plant. The increased fertility, water holding capacity, and drainage will have hidden benefits that you will reap without even realizing it.
Where can you get compost?
There are 3 ways most people can get compost. Make it, buy it, or be lucky and live in a municipality that gives it away for free.
Before you get your compost…
Know that if you are buying compost, make sure it is ‘finished’ and was composted at high temperatures. High temperatures will kill weed seeds. If compost was made at lower temperatures, then it is possible that viable weed seeds may be present.
Likewise, if you make compost, make sure you get it *hot*. Heat plus moisture breaks down a seeds natural defenses against decomposition, or kills it outright.
Starting a compost pile is easy and will benefit the earth by reducing landfill waste. It is incredibly easy to begin, and you get free fertilizer! I have an extremely detailed guide on how to start a compost pile, which I suggest you read and watch the video (over 1 million views). I break it down in a simple manner that is easy for anyone to understand. After watching, you won’t be afraid to get started – I promise!
You can purchase compost. Many landscape companies sell compost on the side where you can buy it in bulk similar to mulch. But you can also purchase it ‘buy the bag’ at most garden centers.
Getting free municipal compost
Some municipalities pick up yardwaste and leaves throughout the year and compost them. In-turn, they offer the compost (or mulch) free to residents of the municipality. Check your local city or township to see if they offer free compost!
How is soil normally built?
You need to stop thinking of soil as just ‘dirt’. Soil is a living, breathing entity that is packed with microorganisms, bacteria, fungi and worms that all improve and naturally aerate your soil. The dead plant matter they consume is returned to the soil as nutrients and plant food. And the cycle continues….
A measure of fertility of soil is how much organic matter is present. And nice, healthy soils are packed with it. They have good tilth (how easy to till, crumbly), hold moisture but allow water to drain. Most of this organic matter comes in the form of roots that decomposed over many years. Organic matter in soil is something to be consumed by microorganisms and other plants, and must be replenished.
Think of the fertile prairies of the American Midwest. Acres and acres covered in tall grasses and forbs that developed deep fibrous roots each that die back each year. As these roots decompose, they are consumed by microorganisms, bacteria, fungi that make the nutrients available to other plants. This cycle occurring each year for centuries made some of the most fertile farmland the world has known.
Suburban soil is generally poor
A frequent practice during the construction of a new home is to strip the topsoil. Any layers of organic matter is often removed, leaving poor soil. I see this happening all the time when new subdivisions are constructed.
Turf-grass itself is also not ‘good’ for soil health. The deep fibrous roots of America’s prairies are replaced by the 2-3″ roots of turf grass. So, any organic matter that is deeper than 3″ will be consumed, and never replenished by the grass growing above it.
But, research has shown that compost could be one of the best ways to rejuvenate soil.  In addition to all the direct benefits that have been mentioned, the added infiltration of water could reduce runoff. This could help reduce effects of flash flooding, as well as reduce any potential fertilizer or herbicide runoff.
Compost is better than synthetic fertilizer
Compost, as an addition of organic matter to your lawn, has some really nice benefits that synthetic fertilizers cannot match. The improved nutrient holding capacity, water holding capacity, and improved drainage of organic matter cannot be matched by high-nitrogen fertilizers. In fact this has been shown by research!
In the late 90’s Dr. Daniel Garling and Dr. Michael Boehm of The Ohio State University conducted research on inorganic (synthetic) nitrogen fertilizers on golf courses versus organic composts. Their research found that organic compost applications in the Spring and late Summer had the largest effect on both color and duration of grass on golf courses. 
Synthetic fertilizers, while providing direct nutrients to your lawn can actually increase your thatch layer and compact your soil. This in turn means you need to keep adding expensive synthetic fertilizers to keep that lawn looking green. Increased thatch will reduce the amount of water absorbed by soil, and the added compaction will starve the micro-organisms of oxygen, further reducing fertility. It’s like a downward spiral for the health of your soil.
 – USDA-NRCS, Composting. “Part 637 Environmental Engineering-National Engineering Handbook.” Chapter 2 (2000): 2-4.
 – Harada, Yasuo, and Akio Inoko. “The measurement of the cation-exchange capacity of composts for the estimation of the degree of maturity.” Soil Science and Plant Nutrition 26.1 (1980): 127-134.
 – Craig G. Cogger (2005) Potential Compost Benefits for Restoration Of Soils Disturbed by Urban Development, Compost Science & Utilization, 13:4, 243-251, DOI: 10.1080/1065657X.2005.10702248
 Daniel Garling, Michael Boehm. Temporal Effects of Compost and Fertilizer Applications on Nitrogen Fertility of Golf Course Turfgrass, Agronomy Journal, Volume93, Issue3, May 2001,
Pages 548-555. https://doi.org/10.2134/agronj2001.933548x
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