Please help me fix my lumpy lawn

[HipGnosis]

I need help with my lumpy lawn.
I'm in Wisconsin - the ground (below the top soil) is mostly clay.
I had a couple small trees (one very small), but they've been gone for years.

The 'lumps' are actually dips, which are very random - some holes and some like a small ditch.
The lawnmower (gas, walk/push mower) wheels drop in some of them and I have to push quite hard to get the mower going again.   Very frustrating.

I have done / tried;
I put a dethatching blade on my mower, lowered the mower a bit and ran it over the lawn to scrape down the high spots - hoping that what was scrapped went into the low spots.
I did that quite a few times, over a few yrs.
I called a 'Lawn Service' guy (from a community bulletin board) - he spread 2 yards of top soil  (over < 1K sq ft)  He wanted to do 3.   It was nice, for a yr or two...
I called a landscaper.  He would re-sod - after rototilling.  $$$$   Not gonna happen.

Now, the dips are back...
What are my options and which is most permanent fix?

[uniwelder]

Not knowing any more, I would just get dirt and fill the low spots.  However, if you already did this and the same holes and ditches have appeared again within a couple of years, do you know why?  Are you on a steep hillside or over a sinkhole or have animals digging?

[GilesMM]

Fill with sand (uncompressible) then top with soil.

[HipGnosis]

Fill with sand (uncompressible) then top with soil.

Which type (types) of sand is 'uncompressible'??

[GilesMM]

Fill with sand (uncompressible) then top with soil.

Which type (types) of sand is 'uncompressible'??

Pretty much all.  Just get a bag or two at the home store.  $5-6/bag.

[uniwelder]

Fill with sand (uncompressible) then top with soil.

Which type (types) of sand is 'uncompressible'??

Pretty much all.  Just get a bag or two at the home store.  $5-6/bag.

2 cubic yards of dirt have already been added. It sounds like another few yards are needed again. That’s a pretty good amount of fill required.

[Boll weevil]

My concern with sand would be it may not hold the grass all that well.

It may just be something you have to keep addressing until it’s fixed. My recollection of our front yard when I was a kid was that one of the first things we did after moving in was to cut down a big tree and grind the stump below grade. My dad was adding soil and grass seed for years. I think part of the problem was that the stump grinding didn’t remove the entire root system, so as it slowly rotted out, the area would keep collapsing.

[HipGnosis]

My concern with sand would be it may not hold the grass all that well.

It may just be something you have to keep addressing until it’s fixed. My recollection of our front yard when I was a kid was that one of the first things we did after moving in was to cut down a big tree and grind the stump below grade. My dad was adding soil and grass seed for years. I think part of the problem was that the stump grinding didn’t remove the entire root system, so as it slowly rotted out, the area would keep collapsing.

I think you're onto something there....  lucky me..

[lthenderson]

I'm in Wisconsin - the ground (below the top soil) is mostly clay.

What are my options and which is most permanent fix?

Unfortunately, there is no permanent fix for clay soil in a place that sees frost heaving. You will always get a bumpy lawn over time.

To help keep things at bay as long as possible, aerate your lawn well and often. Then top dress with soil as needed.

[deborah]

Rototilling will help because it will redistribute the soil as well as aerating it. It's actually the most permanent fix. Adding soil (or sand) each year in the dips will do something too, but it will take a number of years. If your soil is clay, sand will help make it into loam, as will compost.

[BudgetSlasher]

Does your state have an agency that does a geological survey? Our state does and it tells us what are underlying geological formations and strata are. That will give you a very good clue if permanent is even possible.

My ground is mostly orange/brown clay and glacial till overlaying a blue-gray submarine clay (about 4 to 5 feet down) with a scattering of organic rich top soil. That blue-gray clay is prone to settling/sliding and over my several acres we have a few locations that slowly sink as a result. The only think we can do is fill every few years.

Also has already been said frost heaving in freezing climates will constantly shift shift anything above the frost line. There really is no fix for that... short of replacing everything above the frost line.