Human urine has been used as a garden fertilizer for thousands of years, but fell out of favor in the age of modern sewage systems and chemical fertilizers. Urine contains important nutrients for plant growth, including carbon, phosphorous, potassium and nitrogen, and when handled properly, it makes a darn fine plant food. Plus it’s free, in a time when commercially-produced plant foods cost more every day.
If you’re icked out, you’re not alone. In Niger it is taboo for some women to speak of urine, so a research project among women farmers renamed it oga, which means “boss” in Igbo. When the farmers applied home-produced Oga fertilizer to pearl millet every two weeks, yields rose by 30 percent. Oga has since become a regionally popular fertilizer because it works well, costs very little, and is socially acceptable.
Safe Pee-Cycling Practices
I first wrote about using urine in the garden in Mother Earth News more than 10 years ago, and readers immediately started asking questions about its safety for people and the planet. Of special concern was what might happen if bits of antibiotic-resistant bacteria lurking in human bodies got introduced into soil, and thus into the food chain. Modern problems, for sure, but recent research from the University of Michigan found that aging urine makes it lethal to the worst bacteria. When urine is set to age in plastic jugs for six months or more, it becomes increasingly inhospitable to a wide range of microbes. Six months at cool room temperature is the current aging recommendation from the World Health Organization.
Large-scale agriculture is eager to develop urine-based fertilizer systems, which have additional environmental benefits. Less water is needed for flushing, and less dirty water enters the waste stream. In France, research is ongoing using urine to grow grains and other crops, and steady progress is being made developing urine-based packaged fertilizer products in France and Sweden.
Adults produce about 1.7 liters of urine per day, but unless you have a special toilet, collecting all of it is impractical. Then again, it is easy enough to collect urine in a labeled plastic jug when you’re in the mood or in a convenient outdoor space. Once collected, just screw on the cap and leave it in an out-of-the-way place. It’s okay for stored urine to freeze in winter.
Where privacy permits, you can collect urine outdoors in straw bales, which are then used as mulch or added to compost. We have no facilities in our workshop building, so there is always a pee bale stationed on the hidden side. I’ve used rotting pee bales to mulch everything from asparagus to tomatoes, with consistent success.
Before World War II, people did this sort of thing all the time. An elderly British friend says when he was a boy, a bale of peat would be placed in a trough in the boy’s toilet at school. When the headmaster thought it was ready, the bale would be moved to the school’s vegetable garden to enrich the soil. Pee-cycling is far from new!
Using Urine in the Garden
In the US, the non-profit Rich Earth Institute has turned the area around Battleboro, VT into a pee-cycling hub. Local farmers use urine to grow everything from flowers to giant ears of corn using pee collected by interested residents and stabilized at Rich Earth facilities. They estimate that one adult pee-cycler can support a 1/10th acre food garden.
Whether fresh or time-stabilized for six months or more, urine must be diluted because of its potent supply of salts and nutrients. Salts in urine are the reason why grass dies when dogs pee on it repeatedly. Early advice on pee-cycling advised diluting urine with water at a ratio of more than 1:10, but the gardeners at Rich Earth have found that nitrogen-hungry crops like sweet corn respond well to a stronger 3:1 mixture. A 5:1 dilution is good for broccoli, peppers, tomatoes and other vegetables that benefit from booster feedings, as well as container-grown flowers.
Once diluted, the mixture is applied directly to the root zones of actively growing plants and then watered in to distribute the nutrients into the soil. Don’t worry - any odor present at application time will dissipate within minutes, and you will have come a step closer to growing a great garden with fewer outside inputs.