Pet urine smell in yard

I am wondering if anyone else out there has noticed or had this problem, I have six dogs which usually use my backyard as their 'outlet'. I have begun to notice on humid days the urine smell is overwhelming, is there anything that anyone has used in their yard to help neutralize the smell? I am thinking vinegar, baking soda, charcoal, maybe something else??? that I can spread over the backyard. I have a nice size backyard and would like to try to keep the price within reason - I do support all six dogs and three cats so Im sure you can understand the need to keep it cheap :-) I use a scoop for poo but this method just doesn't work so well with the pee... as you can imagine:-) (edited to say - they are BIG dogs - all over 60lbs)

This message was edited Sep 8, 2008 12:20 PM