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Using urine as fertilizer in the garden

Applying urine to the gardenCarol Steinfeld's Liquid Gold presents a wide array of methods to use urine in your garden.  Since urine has a C:N ratio of 0.8:1, it is far too high in nitrogen to be used as a straight fertilizer in most instances or you'll burn your plants.  Instead, dilute one part urine in three to ten parts water, at which concentration urine can be used like a chemical fertilizer.  However, keep in mind that diluted urine has all of the same pitfalls for disrupting soil microorganisms as other chemical fertilizers do, and use it with care.  The only place that I would feel comfortable applying diluted urine directly to our plants is our potted citrus since they crave nitrogen and are too isolated from the soil to get their full nutritional requirements from compost.

Peeing on the compost pileIn my opinion, a better use of urine is as a high nitrogen source to round out your compost pile.  You can simply pee onto a big pile of wood chips, leaves, sawdust, or a bale of straw turned so that the cut ends go up, and you'll have a smaller but richer pile of compost in six months to a year.  One experimenter put a lot of cardboard vertically in a plastic container and filled the container with urine, ending up with rich compost in a year.  For a lower work option, Carol Steinfeld recommends peeing directly onto woody mulches (three or more inches deep) around your trees and shrubs --- the high carbon mulch will mitigate the high nitrogen urine and your woody plants will get a slower meal.

Graywater bedFor those of you with small city gardens (or who want to pee in the bathroom and forget it), you might consider building a graywater bed.  Channel the urine from a urine-diverting toilet in your bathroom to a garden bed with a layer of sand and pea gravel on the bottom topped by good garden soil and plants.  The urine filters out through holes in the bottom of the pipe while air comes in from the other end of the pipe to keep aerobic bacteria happy.  Replacing the sand and pea gravel with bales of straw captures any urine leaching away and provides high quality compost, but you have to turn and rebuild this type of bed once a year to add in new straw bales and take out the excess compost.  For best results, consider diverting laundry water or other graywater into the bed to dilute the urine.

Graywater gardenBe aware that using fresh urine to grow your own food is pretty safe since you can't give yourself a disease you don't already have, but if you find a way to collect a whole community's urine and apply it to your farm, you'll probably want to sterilize it first.  The simplest way to sterilize urine is to store it in a sealed container for six months.  (Don't let air come in contact with the urine or a lot of the nitrogen will turn into ammonia and escape, which smells bad and also lowers the nutritional quality of your pee.)  For added safety, apply urine to crops where edible parts don't touch the ground or wait one month after applying urine before harvesting the crops.  The absolute safest way to apply urine is below the soil surface (such as in the graywater beds in the last paragraph or by drip irrigation) since a healthy soil food web will make short work of any pathogens that might happen to be present in your pee.

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This post is part of our Urine Fertilizer lunchtime series.  Read all of the entries:





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Haha! I love the photography for this one. I appreciate knowing what ratio to use... though I'm worried that using urine to fertilize my potted citrus will tell my cats it's okay for them to do it, too.
Comment by Eliza @ Appalachian Feet Thu Jan 20 13:33:33 2011

I snagged those great photos off the internet --- click on them to see the sources.

It seems to me that if you could teach your cat to pee on the plants, and then add a bit of water to dilute the urine, you'd be in great shape!

Comment by anna Thu Jan 20 16:41:32 2011
Is this legal? I know there are lots and lots of regulations about disposal of human waste.
Comment by Frederic Thu Jan 20 18:41:47 2011
That's a good question, and I don't 100% know the answer, but from the vague things I've read, I would say it's legal. Although I'd like to say the reason it's legal is because it's safe (which I think it is), I think the real reason it's legal is because the health department regulates the systems you build to deal with human waste, not whether you use them. As long as you have your state-approved septic system, composting toilet, plain toilet, or whatever, I don't think they can mandate that you have to put all of your urine in it. On the other hand, if the health department was in a really bad mood, I can see how they would say it is illegal to add a urine-diverter to your toilet. But I don't think they could tell you not to pee in a milk jug, dilute it, and pour it on your roses.
Comment by anna Thu Jan 20 19:15:42 2011
The city of Bristol, TN, composts all human waste--and sells it.
Comment by Errol Thu Jan 20 19:26:30 2011
It's definitely not illegal to compost human waste if you jump through all of the hoops. That said, there are a lot of hoops!
Comment by anna Thu Jan 20 20:14:49 2011

Our place came with an 8 year old crape myrtle that had never bloomed but after several months of mixed species urine it put on a stellar show and now it's sending up suckers. Cats pee in the ficus trees every autumn between the time I bring them in and get some moss over the soil. Stinks a while but seems not to hurt them even at the awful concentration I think Miss Lilly gave them last winter.

If noting else, use it on ornamental plants.

Comment by April Thu Jan 20 20:19:21 2011
Pee
When I read your first post about urine as fertilizer I thought- you need a milk cow! Every time I left the dogs loose when I milked Molly, she'd send out a generous stream of fresh, steamy pee. The rule I heard is to dilute cow urine with 5 parts water for plants. Another cool collection fact: cows and horses can poo while walking, but have to stand still to pee.
Comment by Karen Fri Jan 21 02:19:54 2011

April --- Woody plants with a woody mulch do seem to be the safest place to apply urine. They seem much more able to cope with pee even undiluted. I'm very glad to hear some firsthand data!

Karen --- Sounds like you need to be collecting that cow urine!

Comment by anna Fri Jan 21 11:06:30 2011

Hey there...I have been glancing about for a while, and not found anything...

Have you seen any studies or reports on medication half-lives? How long doe sit take for these things to break down? (This has been a question I have had for a while now...interested in humanure and in urine for plant fertilization, but have yet to find any information on this. (I know I will not have any of these things in mine, but what happens if you are designing a homestead and folks need to take medications?

Comment by Geoffrey Fri Feb 18 22:06:01 2011

Someone else asked me this on facebook, and my gut reaction was "why should I care about medications? We never take anything." :-) But it's a very valid point since the majority of Americans are much less medicine-shy than we are, and you're right that a lot of the drugs go right through you.

I tried to do a bit of research online, but kept coming to pages about how to pass a urine drug test. :-) So, no hard data here, just speculation. If I was concerned about medicines in urine, I would probably use the urine on a compost pile or in a deep, woody mulch around a fruit tree. Fungi seem to be very good at breaking pollutants down, so I suspect if you pee into areas with lots of fungi, they would take care of it for you. That's just a guess, though!

Comment by anna Sat Feb 19 08:51:46 2011

I was doing general research on human urine as a fertilizer for our backyard urban garden and found this detailed experiment. It's for an larger scale but it answers the question for medications and possible disease microbes.

http://www2.gtz.de/Dokumente/oe44/ecosan/en-human-urine-nutrient-recovery-2007.pdf

Comment by cuber88 Fri Apr 1 03:05:45 2011
That's an odd document --- halfway through, it delves into a specific product made by the author's company. That said, it does show one experiment where concentrations of erythromycin in urine were halved during eight weeks in storage.
Comment by anna Fri Apr 1 08:58:15 2011