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How to Top Dress Your Lawn with Compost

Ever wonder how your neighbor’s lawn is always better looking than yours? He or she is more than likely performing proper cultural practices on their lawn on an annual basis. Some of these cultural practices include proper irrigation schedulesmowing heightsfertilizer regimensaerating and dethatching and applying top dressing. In fact, there are many benefits to performing these cultural practices on a yearly basis.

Although the maintenance that goes into lawns can involve a lot of work and maybe even stress at times, it’s important to remember that the sole purpose for our lawns are to live on them and enjoy a beautiful home landscape. Backyard soccer games, playing fetch with the dogs…remember when we used to have people over for  backyard cookouts? Over time, these and other common activities combined with certain environmental conditions contribute to soil compaction. The hard work and effort that goes into them can be something you’re really proud of—especially if you’re a lawn care nut like us at Sod University.

Adding top dressing to your lawn will reap many benefits for your grass and the soil it grows in. Compacted soils or soils with a lot of thatch don’t receive the necessary nutrients they need because oxygen, water and other nutrients can’t get past the tough surface of your soil to reach the root zone. Although aerating and dethatching help with compaction issues, adding top dressing afterwards will actually give your grass the nutrients it needs to thrive.

The Problem with Compacted Soils and Thatch

Compacted soil or soils with a lot of thatch lead to many challenges including but not limited to: reduced water infiltration, reduced available pore space for oxygen and the inability for nutrients to reach your turf’s root zone. Homeowners are actually wasting time, effort and money when making fertilizer applications because the nutrients aren’t being absorbed into your grass. Core aeration is a great way to reduce soil compaction because it literally punches holes into your soil so that the surface loosens up and allows oxygen, water and nutrients to soak into the root zone. Top dressing with a compost product afterwards acts as a great amendment to reduce compaction long-term. Compost also contains a great amount of helpful nutrients such as carbon to promote microbial growth and overall turfgrass performance.

Pictured above from left to right: A compact lawn and turfgrass with a thick layer of thatch.

If you ever want to feel like a genuine turf nerd, go take a core out of your lawn and observe the area just above the soil surface. This is known as the “thatch layer”. A half inch of thatch or less is a good thing; however, excess thatch can lead to a reduction in water infiltration, increased disease activity, weed growth and other negative impacts. It also creates an ideal environment for harmful insects. Aeration and topdressing with compost attacks excess thatch on two fronts: the aeration physically breaks up the thatch layer, while the addition of compost aids in the chemical breakdown of thatch. This is nothing but beneficial for your lawn. You can learn more about the differences between aeration and dethatching here.

The Benefits of Top Dressing Your Lawn with Compost

The addition of a compost product after aeration will also increase a very important quality referred to as CEC (cation exchange capacity). In short, CEC is a measure of the ability of soil to hold nutrients. When soils have a low CEC, the application of fertilizer is much less effective. If you’re going to spend time and money on fertilizer applications, why not make them as effective as possible? When considering CEC, it is important to also consider pH because the two are closely related. Learn more about this in our Soil Management for Lawns and Gardens article.

We all love efficiency, and addressing these issues mentioned above leads to exactly that. Through reducing compaction and managing thatch we can significantly increase irrigation efficiency in addition to potentially reducing the need for herbicides and expensive fungicides. When we keep our CEC at acceptable levels, the nutrients we provide to our lawn through fertilizers are made available to the plant, instead of potentially being lost in various ways.

Lastly, compost contains a healthy amount of carbon for your lawn’s soil. Carbon, although largely undervalued, plays a huge role in the overall health of your soil:

  1. Carbon helps promote photosynthesis,
  2. Carbon feeds beneficial microbes, which affect soil structure, protects lawns from stress and breaks down nutrients in the soil,
  3. Assists with the healthy carbon to nitrogen ratio in your soil.

When the carbon to nitrogen ratio is optimal, plants have a better capacity to absorb more nitrogen and other nutrients. If you conduct a soil analysis and see there’s a lot of nitrogen in your soil but fertilizer applications aren’t making a big difference, it may be because you need more carbon. To learn more about the importance of carbon, read Why is Carbon Important to Your Lawn?. If you’re interested in starting your own compost pile, check out Composting 101.

How to Add Top Dressing to My Lawn

In the spring, apply 0.25–0.5 inches of top dressing after mowing your lawn low with compost, sand or topsoil. The best choice depends on your current soil and issues. Compost is a great all around option for both helping with drainage and providing organic material. The sand will help increase drainage and allow more air to access the root system while the topsoil will add organic material to your soil’s mixture. Sand will also help to maintain a leveled yard over time as it doesn’t compact easily. Be sure to mix the topsoil and sand so that it is fully blended if this is not already done.

It is estimated that turf makes up two percent of the land area in the United States, which equates to over 40 million acres. This would make it the largest irrigated crop in the country. For good reason, we all advocate for responsibility and sustainability in production agriculture and various other industries; but sometimes we forget the direct impact that we have on these things. Although it can be a bit of a workout, aeration and topdressing is a great way to utilize a truly sustainable maintenance practice on your own little grass farm. Be sure to check out a few related Sod University articles about top dressing like How to Level Your Lawn Without Ripping It Up and Eliminating Unattractive Hot Spots in Your Lawn.

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