News and knowhow for farmers

Human urine gives equal crop yields to chemical fertilisers

Reuse of urine fertilised and not fertilised basil experiment part I

By George Munene

According to a guide on The Use Of Urine In Crop Production by the Stockholm Environment Institute, urine is a well-balanced nitrogen-rich fertilizer that can replace and normally gives the same yields as chemical fertilisers in crop production.

In field research done in Burkina Faso, the yields from urine-fertilized crops did not differ from mineral fertilized crops.

Urine from one person during one year was found sufficient to fertilize 300-400 m2 of crop to a level of about 50-100 kg N/ha.

As a fertiliser, it adds nitrogen, phosphorus, potassium, and sulphur as well as micronutrients — elements that accelerate plant growth.

Urine fertiliser can come in handy for net fertiliser importing countries such as Kenya as it can help mitigate poverty and malnutrition at a local level, and improve the trade balance of countries importing chemical fertilizers if adopted on a large scale.

Food security can be increased with a fertilizer that is available free for all, regardless of logistic and economical resources.

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Urine is not a major carrier of the disease, meaning it does not require heavy processing for use in agriculture. The World Health Organization (WHO) advises letting it rest for at least a day before use.

Per a study conducted by the University of Michigan, urine stored for 24 hours showed a 99 per cent drop in the passing of urinary tract infections uptake and bacterial DNA from humans which can cause antibiotic-resistant infections in humans and spread other bacteria in the environment.

“I think this is an important step in demonstrating that we have methods where we can reduce the risks that the things in urine pose,” said Dr. Krista Wigginton, a co-author of the research from the University of Michigan.

Urine can be applied neat or after dilution with water to reduce odor and the risk of over-application. A commonly recommended rate of dilution is 1:3, though this varies with local conditions.

The nutrient content in urine is dependent on a diet that varies between countries and individuals. According to a paper on the Guidelines on the Use of Urine and Faeces in Crop Production an average adult produces 500 L of urine yearly; approximately 4 kg of Nitrogen (N), 0.5 kg of Phosphorus (P), and 1 kg of Potassium (K) per person per year; making urine a nitrogen-rich liquid fertiliser. Due to having comparably high N and low organic matter content it’s advised to supplement urine with other nutrients and sources of organic matter.

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Experiments on separating urine from toilets for industrial agricultural applications are being carried out in South Africa, Ethiopia, India, the United States, Mexico, Switzerland, and Germany.

Sanitation systems based on source separation of human urine also help in the environmental sustainability of wastewater management.

Social acceptability remains the biggest hurdle to the widespread adoption of urine-based fertilisers. It is high in countries such as Uganda, China, France, but low in Portugal and Jordan.

According to a study evaluating support for urine recycling among 1252 Indian consumers, though 68% of people surveyed supported the recycling of human urine, only 44 per cent would be open to consuming food grown using it. 

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