How can I reduce the smell of stale dog urine in my yard?
I have an 13½ year old dog who is almost blind. She is still able to make her way outdoors to go potty but due to her age and poor eyesight, doesn't get very far before she squats down: essentially, off the porch, past the flowerbed, turn right. The upshot is that one spot in my yard gets "watered" a lot.
Since that spot is right by the porch, if I'm dining outside or just sitting enjoying the evening sun, I frequently get hit with a blast of stale dog urine. This is especially bad during the summer months because (a) I'm outside more, and (b) we get warm, dry summers here which means the urine doesn't get washed away quickly (even running the sprinkler in that area more than usual).
Is there anything I can do to reduce or eliminate the smell of her urine?
(My other dogs are grazers so any answers involving chemicals should take toxicity into account.)
The primary reason that the smell is so powerful is that urine contains Ammonia. It is that chemical that bonds with other chemicals in your dogs urine to produce that smell. Normally this would not be much of an issue as you noted because it would be spread out and Ammonia would get broken down by the plants and grass.
When it gets concentrated in one area though the plants some times can not keep up and sometimes the amount can even be so concentrated that the soil will be toxic to plants. Since this is a garden I would suggest first breaking up that soil and mixing in Garden Lime. The Lime will help the plants deal with the excess ammonia, and contains other minerals that help make a garden grow stronger. Lime is natural and mostly non toxic so you can dust the top of the area where your dog likes to urinate once a week(more if necessary) to help keep the smell down.
You can also use Vinegar and water or baking soda. Both of these work to bond with the ammonia and convert it into a chemical compound that is less pungent. These may be better options if your problem is from a larger area that is not easily tilled.
+1 nice... I didn't even think of garden lime, despite the fact that lime is often used in outhouses (at parks and camp locations) for this very purpose.