Urine as Garden Fertilizer

Using Urine in the Garden

I wish that all of my neighbours would come to my property to urinate. I’d keep individual graduated buckets for them, and then give a prize for the largest donation at the end of the year.

Much of the information that follows comes from, or was verified by, Carol Steinfeld’s book “Liquid Gold: The Lore and Logic of Using Urine to Grow Plants.” It’s a slim volume, only 95 pages, but if you need to see something in print before you’re convinced to make the shift to urine-based gardening, then the $15 dollars will be money well spent.

During this past summer, I planted ten new blueberry plants (8 varieties) in the back garden. They appeared healthy and happy for the first few weeks, but then developed red spots on their leaves – which is often an indication that a blueberry plant is nitrogen-deficient. This got me wondering whether nitrogen-rich urine could be used to help balance the nutrients in the garden soil.

When Tova was still living here with me, we both peed in the gardens regularly, but not too close to the plants. I had noticed that where I peed off the deck, often from the same location, the grass below had died away. That raised some concern as to whether urine would help or hurt a growing plant. Steinfeld’s book answered many of my questions.

The message, at its simplest level, is that urine can be one of the single most important inputs into a garden. Over the course of a year, an adult excretes approximately 116 gallons of urine. If that healthy individual is consuming and digesting both plant and animal proteins, then his/her annual urine production will contain enough fertilizer to grow “50-100% of the food requirement for another adult” In the book, Anna Edey from the Solviva garden states that she grew “200 full-grown onion in one square yard, fertilizing only with urine… also (using) wood ash, which is alkaline, to balance the pH of urine,.. and to supply extra potassium to plants.”

That said, the nutrients in urine must be supplemented by other organics - carbon, fibres and beneficial micro-organisms – in order to maintain and improve the health of your garden soil. While perhaps Anna Edey was able to grown 200 onions using urine fertilizer, it likely relied also on the established health of the existing soil – which would require a broader compost mix if that health is to be maintained.

In order that the nutrients in urine can be best utilized by garden plants, the urine must be oxidized to a nitrate form by aerobic soil bacteria. There are a number of ways to accomplish this, but the common goal is to combine the nitrogen and nutrient rich urine with carbon-rich materials to create a C:N (Carbon:Nitrogen) ratio of 25:1.
On its own, urine has a C:N ratio of only 0.8:1, which is too low for microbes to effectively use and process into beneficial forms. So carbon rich materials such as sawdust (400:1) or brown leaves and garden clippings, straw, wood shavings or peat moss are all perfect mediums to absorb and balance urine for garden use.

On my property, I have a large pile of wood shavings from milling logs for building materials. I didn’t want to add these on their own directly to the gardens because the C:N ratio would have likely depleted much of the existing soil nitrogen during the decomposition process. Now, with the urine added, the shavings should be a positive addition. Come to think of it, information I’d read last summer had suggested that I mulch heavily over the newly-planted blueberries using wood shavings. So this might have been what caused the original problem I had that eventually led me to this new resource (newly-realized resource).

Three other methods suggested for combining urine to grow garden produce include, 1) combining urine with greywater draining into an “aerobic garden bed” (check online for the “Washwater Garden” at www.ecowaters.org)
2) dilute the urine at least 8:1 and then it can be applied directly to garden plants. And 3) pour urine (probably should still be diluted) onto “well-mulched aerated soil, covered with 3” of wood shavings or leaf mulch and containing plenty of humus material.

By separating urine from feces, the fertilizer becomes a lot easier and safer to handle and use. There are many high-tech separating toilets on the market, but we simply keep a plastic jug or small bucket to pee into. This in turn is either diluted and then added to the garden, or else taken and poured directly onto the compost bin section that contains largely carbon materials. As well, by separating, the remaining feces doesn’t develop the same foul odour that occurs when the two are combined.
The feces collected in the compost toilet is also now drier and easier to store for composting. However, because of possible pathogens in feces, the processing time is much longer and so it is preferable to do this as a separate project. As well, while humanure will eventually decompose and become a valuable input, it is urine that contains up to 90% of the nitrogen and potassium found in combined wastewater. So don’t just flush it away.

On those days when nothing else seems to be going right – everything I touch is breaking or dying or just not happening – then at least I get the satisfaction of adding to the future garden cycle. Peeing into the bucket, or walking over to stand in front of the compost bin and directly add my 11 grams of nitrogen daily to the cycle of life. That’s comforting. Some days it seems like it’s about as much as I manage to accomplish.