There's a lot of info available online on the subject of human urine as fertiliser
This is a good introduction:
Aside from the associated water saving -- flushing less -- advantage, there is a scientific case that urine may be the answer to a looming global shortage of phosphorus, a key component in fertilisers.
Despite the 'yuk' factor, human urine is actually a relatively clean substance. It should be sterile when produced at the body factory. Compared to other sources of manure fertiliser -- cow, horse, sheep, chicken -- it carries much less chance of contamination by pathogens.
Indeed, in-house human urine -- rather than the other solid stuff -- is where most of the good nutrients are at.
The downside is the smell. However, if urine is diluted and spread on soil or mulch within 24 hours of its production, the odour issue won't register significantly in the process. Although some commercial system do -- the preferred domestic management approach rule should be don't store your urine: use it fresh.
In situations of drought or water restrictions, recycling urine can save a significant amount of water. Even low-flow toilets use approx 6 litres per flush (as opposed to 13.2 litres for the full) so that a visit to pee on average 5 times per day will use up a daily quotient of 30 litres of water.
After working as a nurse for many years, especially in geriatric facilities, urine doesn't scare me at all. I also recall the time before sewerage connections were installed in houses and folk relied on outback 'can' toilets and under bed 'potties' -- just like kids' toilet training hardware-- to get them through the night without en suites.
I've been experimenting. So far so good. While it takes some dedication to collect and distribute human urine -- production is easy -- compared to other exotic gardening activities, like making manure teas and composting, it has its efficacy merits.
Why bother with pee, you ask?
I think the core advantage with urine harvesting is that it can contribute to your water budget by reducing usage. It won't impact on your water bill much given the way the utilities currently charge, but each week you could be saving 300 litres of drinkable water from being flushed away. Scandinavians are building townships that recycle urine as a form of sustainable sewerage management.
Is the effort worth it for the plants?
Hypothetically you'll save on input costs as you won't be importing fertilisers.Aside from the phosphorus advantage, research is very supportive:
Indeed if you were feeling a bit low on any day and feeling a tad worthless as a human being , you can take heart from the fact that you could supply enough urine to fertilize roughly 6,300 tomato plants a year.
There's power in pee!
It's not actual burn, but the plant tissues desiccate due to osmotic stress.
Generally, I find that in my usage conditions, this only occurs when several consecutive doses are deposited on the one plant or grassed area.
Pee on your lawn the same spot night after night and see what happens...
That I have not suffered from 'burn' confuses me --as I'd certainly expect it from poultry manures, and human urine is high in urea. I gather that this is probably due to the fact that the urine must first wet out the mulch layer.In the process the microbes change the Nitrogen.
This is why I broadcast/splash it. I prefer the under-arm bowl in spurts.
"The nitrogen in urine is in the form of urea, creatine, and ammonia; when mixed with carbon-rich materials, the aerobic bacteria convert it into nitrates, which the plants can then uptake."
And any unconverted liquid solution seeps through the sand below.On clay soils, the whole process would be very different.
Also, if using urine, underground watering isn't necessarily a good idea as you always want a reserve 'flush' of salts if they perchance build up. So if it doesn't rain, give the urine area of your garden a good squirt.
As the Veganics point out:
This is the easiest method. Just pee on the mulch. The mulch will stop the plants from receiving an overly-concentrated blast of urine, as well as helping to break down the nitrogen into a source the plants can use. Peeing between two layers of mulch will lessen nitrogen losses from conversion to ammonia gas. (LINK)
The other problem with fertilizer Nitrogen/Urea (such as from urine) is that with over use it will acidify your soil. (LINK) But my massive number of worm proletariat is telling me that my pH range is excellent:A pH between 6.0 to 7.0 is a good pH for worms.
I would have thought that my persistent usage would significantly acidify my soil over time,due to nitate build up, but the consequences thus far have been benign, even advantageous -- so long as I keep adding carbon in the form of mulch and keep sifting urine through that layer separate from the plants themselves.
If your garden smells -- you are doing it wrong. Very wrong.
As I say: fresh is always best.
The 'burn' is the result of a liquid outside of the plant cells that is more concentrated than the liquid inside the plant cells. The plant then tries to equalise the concentration by pumping water outside of itself to the liquid which surrounds it. Then the plant looks burned because it is now short of water inside its cells. Thank you Dave. 'Osmosis' is the word I was looking for.