A limeric I wrote in memory of a friend at school telling me that his uncle used to pee in a bucket and water the roses:

There was on old man from Nantucket,
Who would widdle into a bucket,
He spread it around,
All over the ground
Most especially around his roses he'd chuck it.

He wasn't from Nantucket, but it does rhyme with bucket.

Urea is actually one of the most potent fertilisers as it is approximtely 43% Nitrogen (or so I remember from my college days).

Over use will damage the plants though!