Being a agriculture buff the difference in the following fertilizers
Nitrogen
helps with green foliage growth
too much may prevent the plants from flowering or growing fruit.
Phosphorous(P)
Promotes root growth
Potassium(K)
Promotes flower and fruit growth
As for the subject of composting, urine is sterile and a good source of nitrogen. It needs to be diluted to a ratio of atleast 1 part urine to 5 parts water but up to a ratio of 1:10 is better before it can be added to the composting or plants.
Little fact though straight urine can be used as a weedkiller
![Grin ;D](http://hyperkat.com/scratchbox/Smileys/akyhne/grin.gif)