Wikipedia actually has a large discription of urine's use as a fertilizer...wow,its actually better then I thought....
http://en.wikipedia.org/wiki/Urine

Here's 'part of' what wikipedia said.....

Agriculture: Fertilizer
Urine contains large quantities of nitrogen (mostly as urea), as well as significant quantities of dissolved phosphates and potassium, the main macronutrients required by plants, with urine having plant macronutrient percentages (i.e. NPK) of approximately 11-1-2 by one study[20] or 15-1-2 by another report,[21] illustrating that exact composition varies with diet. Undiluted, it can chemically burn the roots of some plants, but it can be used safely as a source of complementary nitrogen in carbon-rich compost.[22]

When diluted with water (at a 1:5 ratio for container-grown annual crops with fresh growing medium each season,[23] or a 1:8 ratio for more general use[22]), it can be applied directly to soil as a fertilizer. The fertilization effect of urine has been found to be comparable to that of commercial fertilizers with an equivalent NPK rating.[24] Urine contains most (94% according to Wolgast[20]) of the NPK nutrients excreted by the human body.