If you notice spots of dead grass in the yard where your dog plays, your pooch is likely the culprit, because his urine is a natural grass killer. This doesn't indicate any problems with his diet -- in fact, you can't make his urine stop killing the grass by changing what he eats. It's a matter of the chemicals naturally found in his waste, which can make grass turn brown and die.
Urine's Chemical Makeup
Dog urine is high in nitrogen compounds and salt, which can kill grass naturally when applied in a large volume. When your dog deposits urine in a small, concentrated spot, the high dose of nitrogen and salt overwhelms and kills the grass. This is why dogs who squat to urinate leave more distinct patches of dead grass in their wake -- their urine is deposited in more concentrated areas, whereas dogs who spray may distribute it widely enough for the harmful chemicals to make less of a visible impact on the grass.