Note that AFP keeps an Access Log and an Error log.
You can enable/disable the Access Log entirely (Server Admin->AFP-> Settings->Logging)
Here you can choose to Archive the log every X days
You can also select which events get logged: Login, Logout, Open File, Create File, Create Folder, Delete File/Folder
You can also set to archive the Error log every X days (or not at all), but you cannot disable the Error log entirely.
Can you log ownership and permissions changes?
Can you log failed log-in attempts?