Top Dressing - St Augustine Lawn - Ask Extension
HelloI plan to hire a service to aerate my lawn due to compacted clay soil. After that I plan to apply a compost/sand mixture to top dress the lawn - ...
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Top Dressing - St Augustine Lawn #772064
Asked September 17, 2021, 1:29 PM EDT
HelloI plan to hire a service to aerate my lawn due to compacted clay soil. After that I plan to apply a compost/sand mixture to top dress the lawn - front yard is extremely bumpy with some major low spots. It is in dire need of leveling.(St Augustine)Question is - what time of year is best for these two things?Thanks
Dallas County Texas
Expert Response
When you aerate your lawn, be sure the service uses "core aeration." The aerator device should remove plugs of soil from the holes and leave little cylinders of the removed soil on the surface. Spread compost after aeration and water it in. This will wash some of the compost into the holes and improve the aeration of the entire column of soil. You aerate and compost now or wait until spring.
Add soil to areas that need fill while the grass is actively growing and not subject to heat stress. This means spring or early September around here. Use either a top soil or a sandy loam for the job but mix in some compost with whatever you use. Don't use sand as it can combine with clay and make a very hard mixture and sand is deficient in nutrients. You may need to do this over more than one growing season because you should add only a half inch maximum at one time.
Good luck!
Rick Coke
Add soil to areas that need fill while the grass is actively growing and not subject to heat stress. This means spring or early September around here. Use either a top soil or a sandy loam for the job but mix in some compost with whatever you use. Don't use sand as it can combine with clay and make a very hard mixture and sand is deficient in nutrients. You may need to do this over more than one growing season because you should add only a half inch maximum at one time.
Good luck!
Rick Coke
Thank you so much.
I've read a lot about mixing the sand and compost for top dressing to level my lawn but I assume you are recommending no sand because of my clay dirt?
Thanks again - I will look to the Spring !
Rather than sand, I'd use a soil that provides some nutrients and improves the texture of the lawn. And compost is always good. It provides nutrients, beneficial microbes, improved texture, aeration, water holding capacity, etc etc. It's almost magic.
Rick
Rick
Sounds great. Thank you for your help!
Josh—
I find mixed reviews concerning adding sand to clay soil. Some say it's great, others that it's a disaster and makes the clay slower to drain and more like concrete. I've avoided it because of the mixed reviews.
Two additives to clay soil that have unanimously positive reviews are compost and expanded shale. Expanded shale usually is tilled into the soil, for example when preparing a new flower or vegetable bed. And it's expensive. Compost can be used as a top dressing, added to an area after aeration, tilled into a new bed—there really isn't a wrong way to use it.
If I were in your shoes I'd aerate now and add a generous layer (1/2" or so) of compost and water it in. When the grass takes off growing next spring and you've had to mow it a couple of times, apply a fertilizer (no weed and feed, just feed only). When the grass responds to the fertilizer, apply a layer of compost and topsoil (black dirt if you can get it, sandy loam topsoil if you can't) to start the leveling process. Repeat the leveling in early September next year and again the following spring if needed.
Rick
I find mixed reviews concerning adding sand to clay soil. Some say it's great, others that it's a disaster and makes the clay slower to drain and more like concrete. I've avoided it because of the mixed reviews.
Two additives to clay soil that have unanimously positive reviews are compost and expanded shale. Expanded shale usually is tilled into the soil, for example when preparing a new flower or vegetable bed. And it's expensive. Compost can be used as a top dressing, added to an area after aeration, tilled into a new bed—there really isn't a wrong way to use it.
If I were in your shoes I'd aerate now and add a generous layer (1/2" or so) of compost and water it in. When the grass takes off growing next spring and you've had to mow it a couple of times, apply a fertilizer (no weed and feed, just feed only). When the grass responds to the fertilizer, apply a layer of compost and topsoil (black dirt if you can get it, sandy loam topsoil if you can't) to start the leveling process. Repeat the leveling in early September next year and again the following spring if needed.
Rick
