Our Lawn Is Doing Something Weird!

[karyn]

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My husband nor I don't know much about lawncare, other than to mow, trim and water. We now have a huge problem and we don't have any idea of what it is or what's causing it. We have a lovely, large backyard. Over the past ten or so years, the soil has shifted. We have many holes that are anywhere from 1/2" to 4" in depth.
The larger holes are about the same size of an adult's foot. We didn't pay it much mind for a long while but, this spring, it was overwhelmingly obvious. Where there aren't holes, there are hundreds of hard ridges about 1" to 2" high. I fell in the yard, which is sad, because I can't run around with my dog any longer!
The only thing different about our yard is a large, round metal drain in a far corner all the way to the back~the ground around it gradually slopes down a couple of feet. Would that have anything to do with it?
I am really hoping someone knows of something we can do to remedy this problem.
Thank you all for reading this and am looking forward to someone helping us. Oh, I almost forgot...for the past 5 years we've had professional lawn services. Funny they didn't notice the ground sinking and rising! We stopped the service months back because we got no bang for our buck...just not worth it. You all take care!!

[Scaper-S2k]

Did you have any trees removed from the yard (a long time ago)? Over time, the old roots start to rot and the ground can give away like you mentioned.

[Sammy]

..... Where there aren't holes, there are hundreds of hard ridges about 1" to 2" high. .....

Moles ?

[hardboiled]

AS well as the moles and roots, if your lawn service repeatedly mowed in the same directions without ever overlapping their paths, they may have worn ruts and ridges in the turf/soil. Does it seem to follow a pattern?

Earthworms can cause lots of mounds of soil in the wet season. Heavy tree canopy and rain runoff from branches may be causing large consistent drops of water to hit the ground and erode it in areas.

Here are some tips if your condition is what I am imagining. A season or two of these practices could restore it at little expense. You could topdress it in the spring with compost from the falls leaves and good topsoil. Spread a half inch or so of soil over the entire area and use a drag mat or hand rake it to level it into the low spots. Aerating regularly in the spring and fall over time can help to level out and thicken the turf. Pulling a drag mat or section of weighted chain link fence over the lawn will knock down the worm mounds if that is the issue. You could do this after heavy worm activity and a week to two after aerating. That or rolling may help with the ridges over time too. Rolling can also compact soil though if done too heavily which can be detrimental to root growth, thus thinning the turf and allowing more erosion.

You want to strive for thickening the turf. Cutting height, fert schedule and type of fert, soil makeup, watering schedule all can have negative impact if done wrong. You might start with a soil sample and see if you need to amend the soil with organic matter or sand, for example. Look into the things above and see if you notice a pattern that mey be causing the condition. A good book to read, that you would probably be able to find at the library, is Building a Healthy Lawn by Stuart Franklin/Storey Books. Good Luck.

As I reread you post I came up with some questions. Did this roughness exist before you let the lawn services go? Did they handle the fertilizing or was that up to you? Did you have bare spots show up after last years drought? Have you noticed lots of moths fluttering around over the surface as you mow in the evenings? You don't have to answer these here, but knowing the answers may help you diagnose the problem. There can be so many things that can cause it. It would be helpful if you can post some pictures, but your best bet would be to either study some books yourself or try a reputable lawn service again and see that they are doing things properly and addressing the whole lawn and it's condition, not just mowing and trimming it.