Gardeners happily use cow and horse manure to fertilize their plants. Gardeners pay a premium for Milorganite — a fertilizer that is the end result of the Milwaukee sewerage wastewater treatment process. So, why not use urine to fertilize your plants?
Eww, yucky is your first thought. Because of the squeamishness associated with using urine to grow crops, its use has been limited. Urine was one of the go-to fertilizers of ancient civilizations and is still in use by cultures around the globe. University of Michigan scientific studies have shown urine is a safe and highly effective fertilizer. Germany, England, and various African countries have ongoing studies for its potential to increase the global food supply without reliance on expensive, ground-water polluting, synthetic fertilizers.
Instead of flushing precious elements downstream, where they cause nutrient pollution and harmful algal blooms, we can reclaim these nutrients to grow gorgeous crops. Cabbage, beans, tomatoes, okra, corn, pumpkin, beets, and cucumbers as well as ornamentals respond well to diluted urine fertilizer. Urine contains large amounts of nitrogen, and some phosphorus and potassium, the three primary macronutrients in traditional fertilizers. It also includes micronutrients and trace minerals like calcium, magnesium, and sulfur. Thanks to the human digestive process, they’re all present in a form that’s readily available to plants.
After use, any noticeable odor dissipates quickly. Unlike solid waste, urine is typically free of harmful pathogens. Deer and other suburban pests are known to avoid areas marked by another’s urine.
Using urine in place of synthetic fertilizers is considered safe and effective if it’s applied properly. Of course, do not use your garden as a toilet. If applied fullstrength, urine’s high salt and nitrogen content would burn your plants, just as your dog’s urine burns beige patches in your neighbor’s lawn. A safe dilution is nine parts water to one part urine.
Don’t throw away your fireplace ashes. Add a small handful, 1/4 cup of wood ash to each container to boost potassium, which is present in urine in only low amounts. Finnish researchers discovered that adding wood ashes to urine fertilizer for tomato plants resulted in sweeter fruit — and four times as much fruit! Adding wood ashes also boosted beet root size.
Collect urine in a covered container or watering can. If you wish, feel free to pee directly into the compost pile; it’ll help the decomposition process. What a way to start the day; get fresh air, sunshine and save on toilet flushing water. Urine has uric acid which speeds up the compost process and gets you to the end product faster. The National Trust in England provides “pee bales” in strategic places in public gardens and parks that the male horticulture staff can use.
In Europe, where a lot of research is focusing on closing the nutrient cycle and decreasing environmental costs, you can purchase a standard-looking toilet that has a urine diversion bowl, which makes the whole collection process hands-off. Less of this is going on in the U.S. Urine diversion toilets are available through specialty plumbing supply houses if you want to make the investment.
Urine should be applied after the soil heats up to 50 degrees which is standard for all fertilizers. You can store it for up to 6 months. Apply diluted urine directly to the soil. Avoid contact with leaves or splashing on plant parts. Never use urine as a foliar spray. Water plants between treatments as you would with any fertilizer to prevent salt build up in the soil.
Stick with applying once every two weeks. As a precaution, stop use one month before harvesting edibles. Wash fruits and vegetables before consuming them, especially if eating them raw. This is good practice regardless of fertilizer use. Adults produce around 125 gallons of urine per year, containing 9 pounds of nitrogen and 0.8 pounds of phosphorus. Used to fertilize grain, this is enough to grow wheat for making a loaf of bread every day of the year.
Like mama used to say, “Waste Not, Want Not.”