
We don't have grass at home, but do where we have the static van and have the brown patches too. I follow Isla around with a watering can and try and get her to wee is the same area so it can all go brown in the same spot, but it doesn't always work. I'm trying dog rocks that are put in the dogs water bowl, but haven't been staying long enough at the static this year to really test them. I've heard votes both for and against them as to whether they actually help, but I thought it worth trying.
I suspect in the long run they won't as Isla's wee seems particularly virulent, if I could find a way of collecting it I could sell it as grass killer as it would be remarkably effective. I've wondered if food is the cause of such acidic wee or is it just this dog as I can't say I particularly noticed the brown patches with the last dog of the same breed.
The only thing left is to have a sand area and train the dog to only go there.