Once the urine is out of the body and exposed to the air the urine turns to ammonia in 24 hours.
As an experiment you can take a disposable diaper if you have a baby and after removing the wet diaper put it somewhere exposed to the air and then 24 hours later come back to the diaper and smell it.
The wet diaper will smell like ammonia.
Or pee in a jug and leave the urine exposed to the air and come back in 24 hours and smell it and it will or should smell like ammonia.
That's one reason why if a child is in diapers you need to change their diapers often when they pee and wipe up any pee on their body.
The leftover pee can turn to ammonia and cause rashes.
The Romans actually used to use old urine when it turned to ammonia to brush their teeth with.