Urine versus liquid plant food

Every year, the magazine Hemträdgården conducts a “gardening survey” in which readers are asked to carry out a cultivation project and then report on their experiences

The 2021 scout was a comparison of the cultivation results in three parallel trials, one using own urine as nutrient, another using Blomstra and the third using no nutrient at all.

Download the full report under the Files & Media tab

In this year’s gardening challenge, participants tested their own urine as a plant nutrient and compared it with the carefully formulated artificial fertilizer Blomstra in potted plants.
The results are astonishingly similar.
Fertilizing with urine in pots is poorly researched and, given that pesticide residues have been found in purchased, organic fertilizers, it’s time to take a closer look at our urine.
Our garden spotters have helped us with that!

Set-up of the survey
To participate in the survey, three equivalent pots with plants of the same variety and size were needed.
These would be grown under the same light, sun and wind conditions and with the same soil composition in the pots.
Both ornamental and edible plants could be grown, which would have time to grow, flower and harvest in one season.
The plants could have been purchased or raised at home but had to be in the same condition when planted in the pots they were finally allowed to grow in during the season.
During the reconnaissance, one of the plants would be watered only with water, as a control, one with its own urine and the third with Blomstra.
The nutrient solution would be added at each irrigation when the plants were established in their pots.
The application instructions were based on the nitrogen content of the respective nutrient and followed the concentration recommended when adding Blomstra at each irrigation.

Dosage according to nitrogen content
Blomstra contains 51 grams of nitrogen per liter and is about five times stronger than urine, which is assumed to have an average nitrogen content of 10 grams per liter.
The urine used was to be collected over a full day and then mixed in a ratio of 1:100 with water before use.
Blomstra was mixed in a ratio of 1:500. Diluted urine was to be used immediately and saved urine was to be kept cool in a closed container.

The spotters were given precise instructions to follow.
Three times during the growing season, the plants would be compared in terms of growth, leaf color, flowering/fruiting and infestation by any pests.
They would also check whether the urine caused odor problems.

The scouts
Of the 49 scouts accepted, 40 of them completed and submitted a full report.
Of these, six are vegetarians and the rest eat a mixed diet. The nutrient content of urine is affected by what you eat and a protein-rich diet gives more nitrogen in
the urine.
A third of the scouts had not fertilized with urine before and about half had never used Blomstra before.
Most have grown a fruit-bearing vegetable, most commonly tomato (27 scouts), peppers (5 scouts) and also eggplant, summer squash, cucumber and broccoli
have been scouted. Individual flowering plants such as flower tobacco, petunia and Indian cress have also been scouted.

The majority (35 spotters) have raised their own plants and most have grown this plant before.
23 spotters have had their pots outdoors and 17 have had them in a greenhouse or similar place.
Most have grown in plastic pots with a capacity of 10-20 litres.
Eight scouts have used their own soil mix in their pots, 20 have used only purchased soil products, the rest have mixed both their own and purchased products.
And many have mixed the potting soil with fertilizer products, which has affected the nutrient supply in the soil.

Evaluation
At the beginning of the survey, at the first evaluation session, about one month after the start of the survey, about half of the surveyors state that the three plants are similar in terms of growth, leaf color and flowering/fruiting.
At the second evaluation, the proportion of those who consider the plants to have developed differently increases and that proportion increases significantly at the third evaluation.
It is from the third occasion, about three months after the start, that the survey seeks answers to whether urine can give the same results as fertilization with Blomstra.

Growth, leaf color, flowering and fruit
By assessing the growth and leaf color of the plants, it is possible to get an idea of the nutrient availability of the plants. In the third evaluation, the 36
spotters who obtained different growth results on the plants gave 27 votes to the plant that had received urine, 21 to the one that had received Blomstra and 5 to the one that had received only water. The votes are more than the scouts and this is due to the fact that two options could be given if two plants developed equally.
Among the 26 scouts who scored the plants differently in terms of leaf color, the plants fertilized with urine received 21 votes and with Blomstra 20 votes.
No vote is given to the plant that has only received water.
It is remarkable that 14 scouts did not find any difference in leaf color between any of the three plants at the end of the survey.
Presumably, the nutrient content of the soil mixture was sufficient to satisfy even the plant that only received water during the entire reconnaissance period.
The 33 spotters who had different fruit set/flowering on the three plants gave the urine plant 26 votes, the flower plant 18 votes and the one that only received water five votes. On the other hand,
the water plant seems to have produced the earliest harvest.
Many people have also voluntarily compared the taste of the tomatoes, and which one they found tastier has varied.
But the interesting thing is that they noticed that the taste was affected by fertilization.
Since there are very few scouts who have been attacked by any pest on their plants, the basis for comparison is very small and no conclusions can be drawn.

During the course of the investigation, only three investigators could smell any urine from the pot fertilized with urine.
So troublesome odors are not a major problem in pot cultivation with this low dosage. However, the container where you store and mix the urine can start to smell if you do not rinse it out properly.

Urine compared to Blomstra
The question was whether our own urine could be as good a liquid fertilizer as the chemically produced complete fertilizer Blomstra for our potted plants.
Based on the overall result of this survey, those who have received differences on the plants are of that opinion.

The result between the votes even weighs over in favor of urine.
According to the overall survey result, human urine is a good fertilizer even in pot cultivation during the growing season.
On the other hand, with the individual surveyor, the result has gone both ways, but the differences between urine and Blomstra have generally been small.
With a longer culture, the outcome may have been different. Some have suggested symptoms of magnesium deficiency on the leaves of tomato plants watered with urine and even pistil rot has been mentioned. For
most, the scouting has lasted up to 15 weeks.

Continuing with urine
32 scouts will continue to fertilize with urine, six scouts hesitate and two will refrain. Following the instructions for urine handling in the reconnaissance,
was initially perceived as cumbersome and messy, but gradually it became a routine.
Some suggest that urine use will be rationalized in the future.

The advantages of urine, which many mention, can be summarized in three words, free, easily accessible and environmentally friendly.
There is no burden on the treatment plants and no unnecessary manufacturing, packaging and transport of artificial products if you use urine
as fertilizer, some comment.
It feels most ecological and the result does not differ significantly from Blomstra, is a comment. I think everyone can agree
that urine is locally produced. Then some are hesitant to use their own urine if they also eat medicines or sprayed food.
Eating food fertilized with urine can also arouse feelings of discomfort, it is a question of ethics, says a spotter.
And although few noticed any odor with this dosage, there is a concern about odor problems. Someone has been sneaking their urine fertilizer.

Twelve scouts will continue to use Blomstra as a nutrient solution, ten will refrain and 18 may continue to use it. Advantages of Blomstra
mentioned are that it is a concentrated, reliable nutrient that is guaranteed odorless and has given good results. The disadvantage is that it is not organic
and costs money.

Scouting reflections
Many factors, conditions and circumstances affect scouting in a home environment with different growers. For example, the plants that have been outside have also received natural rainfall and therefore have not needed to be watered as often as if they had grown in a greenhouse.
It has also been difficult to ask someone else to water the fertilizer according to the instructions when you have been away.
And many have found it difficult to dose correctly, and you may have both over- and underdosed the nutrients of both types.
Then the composition and content of the potting soil has affected the outcome of the fertilization experiment.
A scout who grew petunia in lean seed soil got the most beautiful plant with urine fertilization. However, petunia plants other than spanning, which were grown in Hasselfors P-soil, became more vigorous even
without added nutrients.

The basic content of the soil is important, as is the volume of soil.
Another scout believes that the addition of neither urine nor Blomstra is necessary in his own, well-composed soil mixture.
The scout who grew broccoli in compost and sand, a lean soil, got the best plant with urine fertilization. The scout who grew beefsteak tomatoes in only potting soil had a similar result between urine and blossom.
The blossom plant was slightly more vigorous, but the harvest was greater for the urine plant. So was the harvest of summer squash watered with urine.

The scout who also grew tomatoes in a sand bed with grass clippings as cover and nutrient supply got significantly better development and yield on these plants than those fertilized with urine or Blomstra. Another grower has found the same result for a tomato plant that was fertilized with leachate from bokashi.

A scout growing eggplant in ordinary, cheap potting soil got the best yield on the plant fertilized with urine. However, non-scout plants grown with drip irrigation and given urine at a rate of 1:20 once a week grew better, but still yielded slightly less than the scout’s urine plant.

Dosage of urine
The assumption that human urine contains 10 grams of nitrogen per liter is a guideline value that may be in excess according to some data where nitrogen values can vary between 5 and 12 grams.
In my own reconnaissance, I therefore had a fourth plant that received a double dose of urine, that is, a concentration of 1:50 at each irrigation.

The tomato plant that received this dosage became significantly more vigorous than the other three plants included in my scouting, the nitrogen supply had increased. The harvest was delayed and the tomatoes were significantly fewer, but twice as large as on the other plants.

A urine dosage in the ratio 1:50 gave me a completely different result than the 1:100 of the span.
That dosage was enough for the urine plant to almost match the Blomstra plant in mine as well as in most other people’s scans. But the exact nitrogen content of human urine
varies. A scout would have increased the amount of urine if he had done as usual and taken into account how the plants were doing and fertilized accordingly.

For a well-balanced dosage with your own urine and the amount of nitrogen you apply, it is important to follow the development of the plants with regard to the result you want to achieve. And following your plants in this way is fun, interesting and instructive, as one scout put it, and contributes to both your own and the collective knowledge bank.

In most cases, your own urine works well as a liquid nutrient, even in seasonal pot cultivation, as the survey can confirm. If the urine is given at each irrigation, a mixture of 1:100 is a good guideline.