After 14 years of lawn care I have learned a few things. One of those is you can have a beautiful yard, or a dog, but rarely both. It is best to lower expectations for your yard when you get a dog.
As for that age old question- Why is my dog's urine leaving those dark green or dead rings in my grass? It's my understanding every dog's urine contains a level of ammonia, which is a nitrite. Nitrogen is the main ingredient in fertilizer that makes your grass grow. However, too much of it, can be a bad thing. Think of when you go to Krispy Kreme and have one doughnut... It is delicious but inevitably you eat more and more, and while one doughnut is awesome, after 8 they start to turn on you and become a bad thing. You'll see a similar dead patch of grass with a dark green ring around the outside if you spill fertilizer on your grass. It doesn't make a difference if your dog is male or female, in heat or not, all dog urine contains different levels of ammonia. If you're lucky, your dog's urine has lower ammonia levels, and your grass will not be affected.