Notice Bare Spots
The frequently appearance of bare spots in your lawn, small spots where grass just disappears, suggests a soil compaction problem. Areas of the lawn where there is routine foot traffic often become bare. The weight of passers by gradually compresses the soil, killing the grass in these spots--a good indicator compacted soil. See the file “Repairing The Lawn”.
Measure Thatch Layer
Thatch is the layer of dead organic material that accumulates on top of the soil at the base of the grass plants. It is composed of shallow growing grass roots, or stolons, that have started to grow on the soil surface and decomposing grass clippings. A certain amount of thatch, 1/4 inch or less, is desirable and should be no cause for concern. However, as you inspect your core of soil and grass, if there as much as 1/2 inch or more of thatch in the turf sample, then it is likely that your soil is compacted. Thick thatch can also indicate over-enthusiastic fertilizing and watering. See the file “Dealing With Thatch”.
Examine Discolored Spots in Turf
Circles or rings of yellow or brown anywhere in the lawn can mean any number of problems. Chapter Nine helps you diagnose whether those spots come from insects, disease, or even the neighbor's dog. Usually, dealing with discolored spots does not require renovating the whole lawn. At the same time, once you've diagnosed the problem, you may find you need to change the kind of grass you are growing to one that is more resistant to the insect or disease that is causing problems.