heres a couple things i found in opies links at the top of this forum,
Human urine makes an excellent high nitrogen liquid fertiliser for most plants. Dilute it 10 to 1 and pour it over and or round fast growing plants once a week; like vegetables, Green manure crops and sugar cane. Indeed just about anything that you want to push along rapid green growth
Studies indicate that each person’s waste fluids can provide enough nitrogen, phosphorous and potassium to grow a year’s supply of wheat and maize for that person. According to some studies, human waste can be an even more effective fertilizer than animal manure.
Urine, which comprises 90 percent of human waste, contains about 80 percent of our waste’s fertilizer value. It can be applied to field crops without treatment because it is generally sterile. By the way "fresh urine" does not contain any bacteria, unless the person has a urinary tract infection, so you could even use it to wash out wounds without causing any infections,
Human urine can be used as an alternative to chemical fertilizer to reduce pollution in air, water and soil and help avoid or control other environmental hazards which surface due to the use of chemical fertilizer, Human urine contains nitrogen, phosphorous and potassium at a much higher ratio than in commercial fertilizers and is environmentally safe to use.
If you want to use urine to fertilize your gardens, keep in mind that when urea becomes ammonia, it also becomes volatile and part of it strips into the air. Both ammonia and nitrates are also very soluble and if not picked up by plant's root systems can enter groundwater with the irrigation water. So it would be best to keep gardens moist but not over watered, but these are similar problems faced by people who use other forms of fertilizers.
One advantage in using urine, as a fertilizer is that much of the urine is available in ideal chemical forms: nitrogen is in the form of urea (ammonia/ammonium which is present at concentrations of approximately 3.5 g/l), phosphorus as superphosphate and potassium as an ion. Urine is almost free from heavy metals - for example, cadmium - because even if we ingest them, they will tend to bind to the liver and kidneys, making the urine much lower in such contaminants than commercial fertilizers.
Urea outside the body quickly becomes ammonia and will be oxidized by special bacteria (called nitrifiers) into nitrates. All these 'reactive' nitrogen sources can be used to form amino groups for new amino acids, thus then being made into proteins
I still dont think i'd piss on my plants though....