Gardening

Can you use pee to fertilize your garden plants?

Posted on September 17, 2019

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Last Updated on January 4, 2022 by Aaron von Frank

Can you use human urine to fertilize plants? Is it safe? How do you use it? Find the answers you’re looking for in this article!

Before we jump into whether (and how) you can use human pee to fertilize your yard and garden plants, we think it’s important to first provide some broader context…

Got biosolids?

We’ve got news that you may find disturbing: if you live in the US, you’ve eaten food that was fertilized with “biosolids.” That’s a nice way of saying “treated human waste.”

Every time you or the hundreds of millions of other Americans without septic tanks flush the toilet, wash dishes, shower, etc. that waste doesn’t just disappear into the ether. It goes to a waste treatment facility to be processed, before being reused as a fertilizer on farms, parks, forestland, and more.

Sign on the door at an American biosolid manufacturing facility, aka bathroom.

Sign on the door at a biosolid manufacturing facility, aka bathroom.

Sewage treatment is a sh… er, dirty job, but it’s actually quite important. A few decades ago, all of our untreated waste was simply dumped into the nearest creek, river, or ocean. The results?

Our waterways were horribly polluted. When Cleveland’s Cuyahoga River became so polluted with human waste and industrial runoff that it lit on fire in the summer of 1969, the American public was rightfully outraged.

A few years later in 1972, Congress passed the Clean Water Act, which put an end to the days of raw human sewage being dumped directly into US waterways.

If you enjoy seafood or vacations at the lake, you’ll probably appreciate that this practice is no longer allowed.

Biosolids are NOT allowed under USDA certified organic standards

Certified organic farmers (as well as conventional farms) are allowed to use composted animal manure on their farms. The composting techniques required under organic guidelines utilize heat created from microorganisms and the carbon-nitrogen ratios in properly-managed compost as a source to burn out the pathogenic organisms. (140 degrees is the magical temperature at which this happens.)

Interestingly, what’s left behind at the end of this process are the beneficial microorganisms that help boost soil and plant health.

USDA certified organic farmers are NOT allowed to human waste on their crops under section 205.105(g) of the National Organic Program (NOP) regulations. While it would be nice to “close the loop” by reusing this waste product, organic practitioners rightfully have some concerns considering some of the other goodies found in human biosolids after they’ve been treated.

Substances like antibiotics, hormones, steroids, flame retardants, pharmaceuticals, solvents, etc are found in treated human waste. These substances can bioaccumulate in soil, or in the case of antibiotics, cause a whole host of other problems.

Virginia Tech researchers are studying how such applications impact the increasingly deadly problem of antibiotic resistant bacteria:

“In the case of agricultural areas, excreted antibiotics can then enter stream and river environments through a variety of ways, including discharges from animal feeding operations, fish hatcheries, and nonpoint sources such as the flow from fields where manure or biosolids have been applied. Water filtered through wastewater treatment plants may also contain used antibiotics.

Consequently, these discharges become “potential sources of antibiotic resistance genes,” says Amy Pruden, a National Science Foundation (NSF) Faculty Early Career Development (CAREER) award recipient, and an assistant professor of civil and environmental engineering at Virginia Tech.

“The presence of antibiotics, even at sub-inhibitory concentrations, can stimulate bacterial metabolism and thus contribute to the selection and maintenance of antibiotic resistance genes,” Pruden explains. “Once they are present in rivers, antibiotic resistance genes are capable of being transferred among bacteria, including pathogens, through horizontal gene transfer.””

In short, if you grew up in the U.S., the only way you would have avoided eating foods that were grown using human waste is if you strictly stuck to certified organic foods and beverages.

Nutrient Cycling

If you’re like many people, you might have grown up thinking that food grows on a grocery store shelf or freezer. After reading this far, you’re now horrified to know that your food grew outdoors in soil—and that there’s a pretty good chance that soil was fertilized with processed human #1 and #2, aka biosolids.

And what’s in soil? Well, a single teaspoon of healthy, living soil is comprised of trillions of tiny microscopic organisms (aka microorganisms) that poop and pee all over the plants that become your food. Gahhhh!

Worm poop, or “food” as our plants call it. Worms don’t just eat manure and decomposing plant matter, they also eat nematodes, protozoans, rotifers, bacteria, and fungi—and all of those organisms produce waste too. As many microbiologists like to say, “the whole planet is covered in a thin layer of s**t.”

Now hang on… If those critters didn’t poop and pee around the rhizosphere of your food plants, your food plants wouldn’t be able to grow. (Your plants don’t call it “microbiosolids,” they just call it “food”.)

In exchange for these tiny gift packages, your plants offer their microbial friends a constant supply of delicious, carbohydrate-rich food through their root exudates that they make via photosynthesis. Yes, they feed each other and probably even swap love notes when nobody is looking.

Why Are You Telling Me This? I’ll Never Eat Anything Again!

We don’t want to gross you out. We’re sharing this info with you for two reasons:

We want you to know that nature recycles everything and no matter what you eat, it was likely grown from the poop and/or pee of some other critter.
If you find out that you’ve already been eating food grown from the waste of other critters (including your own waste), you’re less likely to be grossed out by what we’re going to tell you next…

“Liquid gold,” aka pee, the homemade fertilizer you make daily

If you’re a human being, you make between 400 – 2,000 mL of pee every day. Human pee has a nitrogen-phosphorous-potassium (N-P-K) ratio of about 11-1-2.5, plus it contains lots of other trace nutrients.

Crunching the numbers, you make enough pee each year to grow every calorie of plant food your body needs in a given year. Wee! Time to free your pee!

Many a gardener we know refers to this magical substance as “liquid gold.” And rather than flushing it down the toilet, they use it to grow more food in a virtuous cycle.

5 things to consider when using pee on your garden plants

As with anything, there are good ways and not so good ways to use your liquid gold (human pee), and also info you might want to take into consideration before using it:

1. Do you have to dilute pee before using it as a fertilizer?

Yes, due to its high nitrogen content, human pee is far too concentrated to use directly on your plants without causing fertilizer “burn,” which can kill the plants. If you’ve ever seen dead spots in grass where dogs have pooped or peed, that’s actually fertilizer burn.

As such, be sure to dilute your pee somewhere between 6:1 – 10:1 with water before applying.

2. How often should you fertilize your plants with pee?

It depends on:

the plant(s) being fertilized (heavy feeder like citrus can be fertilized more frequently),
the plant(s) maturity (ex: seedling versus mature fruit tree), and
proximity to nearby waterways.

If you have healthy rich soil or your plants are right next to a creek, don’t use pee or other chemical/mineral fertilizers because much of it will end up in the water. (This is why Riparian buffers are used to mitigate water pollution.)

Just as with a chemical fertilizer, when you use liquid gold you are giving your plants a quick short-term boost of fertility in quantities and ratios that they might not need. What isn’t taken in by your plant’s roots or used by other soil critters will eventually be flushed through your soil and find its way into a nearby waterway or aquifer.

This is what causes massive fertilizer pollution in our waterways, such as the giant dead zones at the mouth of the Mississippi River. This is also why biologically active fertilizers (living composts) are much better for your plants and the environment than chemical fertilizers—they don’t wash away and they aid in nutrient cycling.

Overuse of chemical fertilizers also causes longterm, systemic soil imbalances and pest insect infestations. Think about it like this: if you take steroids, you might look great/muscular for a few years, but your body’s ability to produce its own testosterone are thrown out of whack and the long-term effects on your health can be devastating.

So if you’re using liquid gold, be sure to focus on building healthy living soil first, and your need for fertilizer inputs will be minimized or non-existent.

3. What are the best uses of pee as a fertilizer?

Homegrown blood oranges taste mighty good. Yes, our blood orange tree has benefited from homemade liquid gold as well.

a. Potted Plants – We grow a lot of citrus in pots.

There is only so much soil in a pot and only so much nutrition that can be cycled/reused within the confines of a pot. Since citrus is a heavy-feeding nutrient hog, liquid gold is a great, free source of fertilizer for our potted citrus plants.

If you have potted plants that require regular feeding, liquid gold is a great free fertilizer alternative.

b. Compost – If you have a big pile of carbon-rich leaves, straw, or wood chips that you’re composting, liquid gold is a great way to get nitrogen into the mix for composting. Pee away!

c. Struggling plants or plants that need a quick pick-me-up – If you notice a plant with yellowing leaves or that looks like it’s struggling for nutrition, diluted pee is a great way to give it a quick boost. Since it’s immediately bioavailable, you’ll notice a difference in the plant(s) within just a few days.

4. Are you taking medications?

Are you taking pharmaceuticals/medications? Psychotropics, antibiotics, and other drugs aren’t necessarily broken down in your body.

If you’re taking these medications, you probably don’t want to use your own liquid gold on your garden, because you could end up creating the next generation of antibiotic resistant bacteria—or get your earthworms hooked on Ritalin. (Ha.)

5. How do you “collect” liquid gold?

Got a large empty glass jar with a screw on lid? You’re ready to collect liquid gold.

Now, it might go without saying, but men are much better “equipped” to operate a liquid gold operation than women. We certainly don’t want to discourage women from participating in this activity, but just recognize and plan around your limitations here.

Now, go forth and use that beautiful homemade fertilizer to help your garden and potted plants flourish!

KIGI,

Update: Thanks to reader Alan Morse for pointing out that urine is, in fact, NOT sterile. New research from Loyola University has proven that human urine has lots of bacteria in it. “By using a technique called expanded quantitative urine culture (EQUC) and sequencing the subjects’ bacterial DNA, the team was able to identify bacteria not usually picked up by traditional urine cultures.”

Thanks for the correction, Alan!