Dog pee kills grass primarily because it contains a high concentration of nitrogen, which is a byproduct of the dog's digestion of protein. While nitrogen is a nutrient that plants need to grow, too much nitrogen concentrated in one small area overwhelms the grass's root system and essentially "burns" the grass, causing it to die and turn brown or yellow. This concentrated nitrogen comes from urea and other nitrogen compounds in the urine. The damage is more noticeable when dogs repeatedly urinate in the same spot, leading to brown patches on the lawn. It is a misconception that the acidity (pH) of dog urine is what kills the grass; the real culprit is the nitrogen concentration. Factors such as a dog's diet, how much they drink, and their urination style (female dogs or male dogs that squat tend to cause more localized damage) influence the severity of the damage. Different grass types also vary in sensitivity to urine nitrogen.
