Sounds like the sod was laid poorly...have you ever had the lawn "rolled" I have seen some outfits do this to even up ridges....this needs to be done in a way however that does not compact the soil to much.
Can you post a picture of the area Koren? I would like to take a look at possible water issues as well as the condition of the sod.
I can't say for sure, but a common cause of those rows of ridges is using a riding lawnmower and going through the same pattern each time running over the same paths with the wheels. As KMS said, you could have it rolled to flatten it out and then vary your mow pattern.
Yes, a photo would be helpful, Koren. What type of preparation was done before the sod was laid? When you say soft, do you mean that it actually gives when you walk on it?
do you remember if the soil was rolled flat before the sod was installed?
I cleared the yard of weeds. Put down top soil, then the sod was layed. It was not rolled. It actually gives when walked on,mushy. Thought I may have had moles or other burror that created the ridges.
Is the whole yard that way? If it was moles or voles you would be able to see raised paths, as in the photo in this link:
That is exactly how it looks
Maybe you have a grub problem that is attracting moles or voles. Do a test by pulling up a small section of sod. If you find more than six grubs in a square foot that's too many.
Try setting out traps and see if you catch any moles or voles. You can use mouse traps baited with peanut butter. If you have pets and are concerned about them getting in the traps, you can tuck them under an overturned flower pot that has been propped up on one side.
I bet that is why I had so few Japanese Beetles and a lumpy, soft lawn.
I checked for grubs,but didn't find any. I had already put down Bayers to kill grubs. No new problems. Do I put top soil down, and have it rolled to even out the yard?
I do not think rolling will have that much impact, Koren. You can try top-dressing, or adding a uniform layer of soil on top of the grass. Try to use soil similar to that underlying the turf and don't add more than 1/2 inch of soil at a time. Be sure to use soil that is free of weed seeds and nematodes and be careful not to exceed recommended topdressing rates, as this encourages large (brown) patch disease.