The Danger of Nitrogen Burn
Dog urine is incredibly rich in nitrogen and natural salts. While a tiny amount of nitrogen is good for grass (it is the main ingredient in fertilizer), the concentrated dose in dog urine acts like a chemical burn, instantly scorching and killing the grass blades.
New Turf is Highly Vulnerable
An established lawn with deep roots can sometimes recover from mild urine burn. New turf, however, is already under massive stress from being harvested and transplanted. If a dog urinates on unrooted, fragile turf, that section of grass will die rapidly, leaving a permanent brown circle that will not grow back.
How to Protect Your Investment
For the first 3 to 4 weeks, you must keep dogs completely off the new lawn. This gives the roots time to anchor and the grass time to strengthen. Once the lawn is established and in use, the best defense is dilution. If your dog urinates on the grass, immediately follow them with a watering can or hose and heavily flush the area with fresh water to wash the concentrated nitrogen deep into the soil before it can burn the blades.