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Human urine that has been matured in the sun for at least one month appears to be both a fertiliser and an effective pesticide. The findings could be particularly helpful for combatting insect infestations in West Africa, where soil quality is typically low and traditional pesticides are expensive.

Farmers taking part in a previous trial in Niger to investigate the use of urine as a fertiliser discovered that it was also having a pesticide effect, as plants treated with it had less pest damage than those that weren’t.

at the National Institute of Agricultural Research in Niger and his colleagues decided to test the findings on cowpeas (Vigna unguiculata), a vital crop in the country because of its drought tolerance.

Experiments were carried out in several villages across Niger to compare the effects of chemical pesticides and human urine on the crop’s pest resistance. Three applications were made at each site, with a week between treatments.

The team found that plots treated with synthetic pesticides had the lowest insect damage. But those treated with human urine had 20.5 times less infestation than control areas and their crop yields were 1.8 times higher.

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The urine was housed in large containers and fermented in the sun for one or two months to kill any pathogens. “The odour is very, very strong,” says Amadou. He says it isn’t yet clear exactly what causes the pesticide effect, but the smell is one contender.

The researchers hope to conduct more tests, including assessing different fermentation durations to see which has the best results for killing pathogens and inducing the pesticide and fertiliser effects. They also hope to shed light on the underlying mechanism behind the approach and how long the effects last.

Team member at the Dan Dicko Dankoulodo University of Maradi in Niger says that the pungent smell has no impact on the taste of the cowpeas. He believes the approach could be a lifeline for farmers in that part of Africa. “Soil fertility is very low in West Africa,” he says. “We have sandy soil and chemical fertilisers are very, very expensive.”