Improving Drainage and Leveling Lawns with Heavy Clay Soil

I built a house during Covid and due to various issues related to drainage plans and builder agreements am dealing with the same thing. They scraped the existing great soil from the lot, brought in red inert clay and laid St Aug directly on top.

I spent two years working with lawn care experts at UF, aerating, topdressing and even using a bulb drill to do large core aerations trying to get it right.

None of it worked despite perfect watering via irrigation, using top dressing soil amendments like humichar and following best practices for fertilizing and other treatments.

Simply put if your soil is poor and overly compacted it will take years to fix it from the top down for St Aug because the roots don’t effectively get deep in hard pan clay resulting in yellow, stunted grass and root rot where the water sits on the roots because it can’t penetrate.

I’m about to completely til the front yard, amend with a sand/compost mix and level prior to resodding.

I’ve been told Bermuda does better with compaction, but St Aug simply won’t work with the red clay and it will take years of repeated aeration, topdressing and amendments to fix the soil to a degree that will allow your lawn to look the way you want it to.

Same situation. Basically turns into concrete when I add sand. I’m just dumping a couple yards of compost on it every early spring and maybe one day I’ll be able to actually work it. Bermuda grows fine but I’d really like it more level to get down under an inch one day.

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I'm starting to kick myself in the arse for not seeding bermuda

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The only person who kicks themselves in the arse is the one who seeds Bermuda.

Sod or sod/sprig combo

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you need to till the soil to get your amendments down into the clay to help break it up some.

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I really think with clay it has to be mechanically broken up so the amendments can have a place to go.

The reality of core aeration is that it helps but is so shallow that you aren’t really going to fix the deeper compaction issues in a year or two that way,

If you want real results I think it has to be tilled and amended deep enough to allow the st aug roots to get down 4-6” minimum.

If you just til it it’ll compact back together with foot traffic and regular mowing.

If you just top dress the good soil can’t penetrate.

Again with Bermuda you might be able to cheat, but St Augustine reflects its roots and I just don’t think you can grow healthy roots for that grass without 4-6”of healthy non compacted soil.

Till it in October and plant annual ryegrass and daikon radish. It works in food plots with red clay soil in the Florida parishes. Let it decay in spring then reseed with Bermuda.

I built 6 years ago and had lots of clay soils from the pond they dug. Used this product from Andersons. Took about 2 years to see the results.

Elaborate please.

First, gypsum is not going to be effective in improving drainage in calcium clay dominate soils in south LA, or elsewhere, it is soil physics-soil chemistry thing (can be effective in high sodium clay, or sodic clay soils, which you are not finding in this region). Don’t waste your time or money with that amendment. This LSU AgCenter article will help with some common soil myths LINK

Fill in low spots in the lawn with mason sand (no weed seeds), you can add up to 2 inches at a time and St Augustine will grow through. LINK Then you can add more sand later as needed to bring soil level to grade.

Soil aeration is good - won’t help with drainage - but good for lawn grass health. True mineral-based top soil is fine if you can get it, just remember bagged “top soil” found at the box stores & many garden centers is simply composted forestry products - organic mater - with a little bit of sand - not what you want to fill in low spots. Honestly, mason sand only, in low spots will be adequate.

And of course a potential option, depending on the severity of the problem, is to install a lawn drainage system, placing catch basins in larger, low areas and diverting the water to a ditch, the street, etc. by gravity flow if feasible, and if gravity flow is not doeable because of lawn grade relative to the street, or elsewhere, then you can add a central larger catch basin with a sewerage pump where accumulated water diverted to it from low areas in the lawn can be pumped to the street. This was the approach I used (use) to remove large amounts of standing water from my heavy, calcium clay soil backyard.

Apple Drains on YouTube has dozens of good videos on various lawn drainage approaches.

Same problem. No top soil. Builder put centipede sod directly on hard packed clay.

First I top dressed it with 20 CY of compost. Then I bought a 2” soil auger that attaches to a cordless drill and drilled holes in the areas that were holding water and filled them with topsoil/compost/peat moss mixture. I would or drill 10 or so holes in the backyard whenever I went outside. Probably drilled more than 1,000. I eventually started using my 6” post hole auger for this. I also added some topsoil, fixed the grade, and installed a couple of pallets of zoysia in the back yard when I added a patio and outdoor kitchen. I haven’t drilled very many holes in the front yard because underground utilities are not fun to drill through like irrigation lines are.

I’ve gradually been transferring plugs to the back and front yard to let the zoysia take over. I’ve found that a golf cup cutter works much better than any sod plugger, but it’s still an enormous pain in the arse and takes forever. Backyard is now 75% zoysia. Front yard is 10% zoysia at best . If I had to do it all over again, I would’ve paid the $15,000 I was quoted to have my yard completely topsoiled and re-sodded with zoysia.

I also tried almost everything else as well: gypsum, mechanical aeration, liquid aeration, humic acid, etc. only thing I haven’t done is install underground storm drainage due to the sidewalk in the front