Fertilizing Plants With Urine

“This tree looks like it could use a shot of nitrogen!” Photo: www.amazon.ca

Comment: I think you should write about using urine in the garden as fertilizer. I’ve been doing it for several years now and it gives really good results. I even used it to resuscitate an old rose bush that had been vegetating for years. Now it’s 6 ft (2 m) tall and blooming again. 

I started using it after seeing a TV report on Africans who collect urine from public toilets, dilute it, then water the fields with that rather than buying chemical fertilizers from BASF or Monsanto they can’t really afford!

And it’s so simple: I just pee into my watering can, then fill with rainwater. That way, I’m conserving drinking water and not applying chemical fertilizers to my gardens that will end up polluting the water table.

How about it? You’ve written about just about everything else!

Julien Cr

Answer: Yes, I have. But I have to confess something: I’ve been avoiding the issue.

Yes, I know about the virtues of human urine in the garden, but the yuck factor just … overwhelms me. What can I say, but that I’m squeamish? I keep telling myself I’m being priggish and that my readers deserve to know about this. Several times I’ve even set a date to write about it, but always found another good idea at the last minute. Well, there it was yet again on my agenda. So, this time I’m doing it.

In the garden, urine has been called liquid gold! Photo: SuSanA Secretariat, Wikimedia Commons

So, in a few words: urine makes an excellent fertilizer. Indeed, one of the very best ones. 

It’s instantly available for plants to soak up and it’s particularly rich in nitrogen, the mineral most often deficient in soils. The ratio of minerals actually varies according to a whole range of factors, including the “provider”’s diet, but, for a Westerner with standard eating habits, you could estimate an NPK ratio of 11:1:2, that is 11% nitrogen, 1% phosphorus and 2% potassium. That’s as good as many commercial fertilizers! And it’s a complete fertilizer: urine also contains all the trace elements (iron, boron, zinc, etc.) that plants need, but almost no heavy metals.

However, on the down side, urine is so rich in salts (especially sodium) that the standard recommendation is to dilute it in 10 to 15 parts of water. (20 parts for seedlings.) Also, not to apply it to any particular garden space more often than once every 2 or 3 weeks. 

You’ll all seen the damage dog pee can do to a lawn due to excess salt, right? Well, you wouldn’t want to have the same problem in your garden!

What About the Stink?

There won’t be any, not if you use it fresh. Fresh urine is essentially odorless (unless you’ve just eaten asparagus: more about that here) or you have a urinary tract infection (in which case, see a doctor). But if you leave urine sitting around, bacteria start breaking down the odorless urea into ammonia and that smells. Once in the ground (and dilute to boot), soil microbes will prevent any smell.

Peeing in the Compost

There’s reason you find the letter P in compost. Photo: u/l1231, reddit.com

Alternatively, urine can be used in your compost bin where it’s high nitrogen content will stimulate faster decomposition. It isn’t even necessary to dilute urine when you apply it to compost. Send the menfolk out and they can apply it directly!

Is Urine Safe?

Urine is considered sterile when it leaves the body, so using fresh urine is not a problem. When it’s stored, that’s a different story. However, there are pros and cons about the use of stored urine. I’ll let you look into that yourself, but be forewarned, even scientific opinions vary widely.

Just water urine in to fertilize your garden. Photo: www.thespec.com

Can you apply urine to edible plants (vegetables, herbs, etc.)? Sure! The recommendation is to apply it to the soil at the base of the plants, not to the foliage. Also, it’s best to stop fertilizing with urine 3 to 4 weeks before harvest.

But what if you are taking medication or know you have a UTI (urinary tract infection)? Again, opinions vary. Some experts say not to worry, that the drug residues and microbes the urine might contain will degrade on contact with the soil which is, after all, full of greedy microbes. But other experts recommend against using urine in the garden if you are on medications or know you have a UTI. So, who to believe?

Personally, I would tend to err on the side of caution in this case and to avoid the use of urine if you’re taking medications or have a UTI.

Will I personally be using urine in my own gardens? No, but at least I have a good excuse now: I seem to be taking a whole host of medicines due to my doddering old age. Just a few years ago, though, I could logically have done it… but I never dared to. Yep, I confess: the yuck factor held me back. 

So, be braver than me and save the planet one pee at a time.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, laidbackgardener.blog will continue its mission of demystifying gardening and making it more accessible to all.

7 comments on “Fertilizing Plants With Urine

  1. cow manure, horse manure, chicken manure ( not a yuck)….. (URINE) a yuck! lol

  2. The thing is, old civilization, and in some rural asian regions in the modern times have been using human wastes to make their lands fertile.

  3. It makes more sense that walking through the garden to get to the outhouse. Just do not apply it directly (undiluted), but onto the mulch on the soil near to the ‘target’ plants. Since it should not be applied too frequently, it does not do much to repel rabbits. (Enough to repel rabbits would likely be toxic to roots.)

  4. Bob flowerdew pees in the compost and I’ll admit that during Covid when our allotment toilets have been closed it was necessary to do the same. For girls it’s a bit more tricky though but it’s amazing what you can do with a polytunnel and a bucket ??

  5. Christine Lemieux

    Yes, Yuck! But great to know. Glad you shared!

  6. This post certainly grabs one’s attention and makes you sit up and take notice. 🙂 Interesting topic though and I appreciate the pros and cons. I won’t be trying it, but it is always good to know.

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