What type of odor are you getting and when does it occur?
If it's poop odor and occurs right after the drop, then you might look into a different food for Annie. My Moose-dog didn't digest chicken & rice well - his poop would smell something awful and the scent would linger even after the poop was removed. I ended up changing him to a lamb & rice food and the smell has minimized greatly.
If it's pee scent, then you might do some surveillance and see if any other dogs are using the area.
Also, how big of an area does she use to do her business. The smaller the space, the less "airing out" it will get between uses. Allowing her a larger area might be enough to let the ground recover from the deposits.
The last thing is what type of ground cover is there? The flatter and more solid the ground, the less chance that bits will get left behind.