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Is Human Urine a Good Fertilizer? Yes, Diluted Heavily

Urine is a genuine nitrogen source and roughly an 11-1-2 feed. Undiluted it scorches plants and salts the soil, so 1:10 is the working ratio.

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Fresh vegetable waste piled in a slatted wooden compost bin
Photo: herb007, Pixabay Content License, via Pixabay
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Yes — diluted heavily. Roughly an 11-1-2 feed, strongly nitrogen-dominant, and close to sterile when fresh. Neat it scorches foliage and salts the soil, so 1:10 is the working ratio. On a compost heap it can go on undiluted.

Dilution, by use

This table answers the question on its own
UseDilution
Established plants in the ground1 : 10
Seedlings and young plants1 : 15–20
Containers1 : 20 — salts cannot wash through
Lawn1 : 10, watered in
Compost heapNeat — the material absorbs it

Apply to the soil around plants, not over the leaves, and water afterwards.

What it suits

Good for — brassicas, leafy greens, sweetcorn, grass, and hungry plants through mid season. Also an excellent compost activator for a heap that has stalled because it is too carbon-heavy.

Poor for — fruiting and flowering plants once they have set, since excess nitrogen pushes leaves at the expense of fruit. And legumes, which fix their own.

Use it fresh, within a day

Bacteria convert urea to ammonia in storage — which is both the smell and the loss of the nitrogen you wanted. Fresh urine barely smells. Dilute immediately; if you must hold it, keep the container sealed and cool, because an open bucket loses nitrogen to the air while getting steadily more unpleasant.

On food crops

Where to draw the line

Acceptable on crops where the edible part never meets the soil or the spray — fruiting plants, sweetcorn, climbing beans — with sensible hygiene and about a month before harvest.

Avoid salad leaves, root vegetables, and anything eaten raw close to the ground.

Use it from people in your own household who are well, and not from anyone on medication being excreted — that does pass through.

The long-term caution

Sodium and chloride in urine accumulate as salts, and repeated heavy application in one spot damages soil structure and root function — worst in containers and in dry climates, where nothing flushes them through.

All of that is prevented by the obvious things: dilute properly, rotate where it goes, water in afterwards, leave gaps between applications. Used occasionally and spread about, it causes no lasting problem.

Common questions

Is human urine a good fertilizer?

It is a genuinely effective nitrogen fertiliser and has been used as one for centuries. Fresh urine from a healthy person is close to sterile and carries nitrogen as urea plus useful phosphorus and potassium, giving roughly an 11-1-2 ratio — strongly nitrogen-dominant, which suits leafy growth and the activation of a compost heap. The catch is concentration: applied neat it scorches foliage and roots and leaves salts in the soil, so dilution is not optional.

How much should urine be diluted for plants?

Around one part urine to ten parts water for established plants in the ground, and weaker still at one to fifteen or one to twenty for seedlings and anything in a container, where salts accumulate rather than washing through. On a compost heap it can go on neat, since it is acting as a nitrogen activator rather than a feed and the material absorbs it. Apply to the soil around plants rather than over leaves, and water afterwards.

Is it safe to use on food crops?

On crops where the edible part does not contact the soil or the spray — fruiting plants, sweetcorn, climbing beans — it is widely considered acceptable with sensible hygiene and a gap before harvest of around a month. Avoid applying it to salad leaves, root vegetables and anything eaten raw and close to the ground. Use it from people in your own household who are well, and not from anyone on medication being excreted, which does pass through.

Why does urine smell so strongly after a while?

Because stored urine breaks down as bacteria convert urea into ammonia, which is both the smell and a loss of the nitrogen you wanted. Fresh urine barely smells at all. Use it within a day, dilute it immediately, and keep any storage container sealed and cool if you must hold it, since an open bucket loses nitrogen to the air while becoming increasingly unpleasant to be near.

What is it best used on?

Anything wanting nitrogen for leaf and stem growth — brassicas, leafy greens, sweetcorn, grass, and hungry plants in mid season. It is also an excellent compost activator, speeding up a heap that has stalled because it is too carbon-heavy. It is a poor match for fruiting and flowering plants once they have set, since excess nitrogen pushes leaves at the expense of fruit, and for legumes, which fix their own nitrogen.

Will it harm the soil over time?

Repeated heavy application in one spot will, because the sodium and chloride in urine accumulate as salts and that damages soil structure and root function, particularly in containers and in dry climates where nothing flushes them through. Rotating where it goes, diluting properly, watering in afterwards and leaving gaps between applications all prevent this. Used occasionally and spread about, it causes no lasting problem.

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