When a dog urinates on your lawn, you will likely have a brown spot if you leave the spot untreated. The reason dog urine will discolor and possibly kill your grass is the high concentration of nitrogen in urine. It's like a mega boost of fertilizer to your lawn, and can burn the grass. Both male and female dog urine contains nitrogen, though because male dogs seem to randomly distribute their urine in short bursts, male dog urine does not usually harm your grass. Female dogs tend to "squat" to urinate, leaving behind a large, concentrated area of urine which is more likely to damage your grass.
When It Is Your Dog
Train your dog to urinate in an area that is inconspicuous in your yard. To do this, begin by using a leash to lead your dog to the area you wish it to use to urinate. Keep your dog in that area until it does urinate, then praise your dog for doing a good job. Continue with this routine for at least two to three weeks. By then, your dog should be drawn to the area to urinate, not only because it is now habit, but also because of the smell of urine.
Encourage your dog to consume more water. When your dog drinks more water, its urine will be diluted with less concentration of nitrogen, and less damaging to your lawn. You can help your dog consume additional water by feeding it moist, canned dog food, soaking your dog's dry food with water for a half-hour or more before feeding, or adding a little broth to your dog's drinking water to make it more appealing.
Hose down the area your dog urinated in with water as soon as you can, or turn on your sprinklers for regular watering. By applying water to the urine area you will be diluting the urine, rendering it less potent. This is very effective if done within eight hours after your dog has urinated on your lawn.