How to get rid of dog waste smell? Any suggestions

Hi folks,

I have 2 dogs, live in Santa Fe, New Mexico, where we get very little rain.
I have a problem with the smell left by the dog's waste. The dogs are
trained to relieve themselves on a gravel area away from the house in our
walled in courtyard. I clean it up every couple of days but the smell
remains. We don't get enough rain here to really wash it away on a regular
basis. Normally the sun helps a lot since it dries the area very quickly. I
thought lime might help, but after reading the caution on the side of the
bag I decided against using it for now. I don't want to contaminate the
ground with any dangerous chemicals either. One other factor is the cost. I
don't want to spend a fortune on this.

Is lime safe to put down on the gravel? Or does anyone have any other
suggestions on this topic?

Thanks in advance.
Tom
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