If you have dogs, dog urine has undoubtedly damaged your lawn. Dog urine contains ammonia and salts and these are hard on grass. The salts, especially, pull moisture from the grass roots and cause the grass to die. The ammonia causes the soil to be more acidic, which is also stressful for grass. One easy solution is to add dolomite lime to the urine spot. Dolomite lime helps to neutralize the acid in dog urine and restore the soil to a pH balance more favorable to the growth of new grass.
Water the spots on the lawn that dog urine killed. Water helps to dilute the ammonia, salts and excess nitrogen that the dog urine adds to the soil and helps prevent the dehydration that the urine salts can cause.
Rake off any dead grass from the affected areas with a hard rake. Allow the tines of the rake to scratch the surface of the soil.
Sprinkle a large handful of dolomite lime onto the raked area. One handful of lime per affected area will be sufficient. Water the area with a sprinkler after applying the lime. The lime will work its way into the soil and reduce the acidity caused by the urine, allowing new grass to grow over the spot.
Sprinkle a handful of grass seed over the area after you have watered in your lime if you wish to encourage the fast recovery of the area. Consult with your local nursery as to the best type of grass seed for your area and for the time of year. Water the grass seed and cover with a thin layer of straw or grass cuttings to hold in moisture and prevent birds from feasting on your seeds.
Wait 21 days to mow the affected areas if you added new seeds. If didn't add new seeds, continue on your normal schedule.