Q. I have nice green circles on my lawn. Yes, I have three dogs!  The lawn was put in about nine months ago as sod.  It suffered from minor fungus last summer and those areas were resodded about three months ago which you can see in my photo.  About a week ago I added a nitrogen only fertilizer.  Do I need to add something else to the lawn?  I would like the lawn to look green like the circles which I assume are a result of my dogs!  Or is this some other issue? A. Thanks for telling me you have the dogs. You must read my column. Green spots or small circles can be from dogs. If it is from dogs, the spots are usually 6 to 10 inches in diameter with a smaller circle of dead grass in the center. Dog urine damage to lawn. If the lawn had been fertilized with a high nitrogen fertilizer at Thanksgiving the circles would not be as notieable             The concentrated dog urine kills the grass in the center of the green spot due to its concentration but acts like a high nitrogen fertilizer as it becomes more dilute further from the dead grass. The diluted dog urine causes the grass to become greener and grow more rapidly. So the dark green grass surrounding the brown dead center is frequently taller than the surrounding grass.             If it is warm outside, an application of high nitrogen fertilizer plus one or two mowings to remove the brown dead tips of grass should even the color out through your lawn. Nitrogen is the primary fertilizer responsible for having a green lawn. The other is iron. You cannot substitute one for the other. Nitrogen also stimulates growth. Adding more nitrogen means mowing more often.             Your lawn is very dense in the picture. This might also contribute to disease problems. You might try reducing your fertilizer applications to about half of what you are applying now to decrease its density and help improve air movement through the grass. This might help reducing disease potential when it is hot outside.             You could also try mowing your lawn a bit shorter in the summer months, no shorter than 1 1/2 inches. This might also help reduce disease potential. Make sure you are irrigating your lawn in the early morning hours, not at night where the water can sit on the lawn for several hours before it evaporates.             I have a class coming up on lawn care management on Sunday, February 26 at noon at Plant World Nursery.