Human urine shows potential as eco-friendly fertilizer for crops

The research demonstrated that applying stored urine, even in high doses, had little effect on the composition of soil bacteria, soil pH, and salinity levels. However, it did show an increase in the presence of nitrifying and denitrifying bacterial groups compared to synthetic fertilizers, indicating that urine-based fertilization could result in higher emissions of nitrogen oxides.

Published in 'Applied Soil Ecology', the study calls for further investigation into the long-term impacts of urine fertilization, especially regarding nitrogen oxide emissions and soil salinity. Co-author Manon Rumeau from the University of Birmingham noted, "Our research highlights the potential of recycling human urine to enhance agricultural sustainability, reduce wastewater pollution, and decrease reliance on synthetic fertilisers. Stored urine can be safely applied to a plant-soil system without negatively impacting the soil microbiome."

Human urine, composed of 95% water and 5% amino compounds, organic anions, and inorganic salts, offers bioavailable nutrients essential for plant growth. The study examined the effects of applying stored urine to spinach crops in greenhouse conditions, comparing the results with synthetic fertilizers and non-fertilized water treatments.

After a year of storage, the urine showed a significant reduction in pathogenic bacteria and extracellular DNA, thanks to increased pH and ammonia levels. The study found that soil bacterial communities were largely resilient, with only 3% of bacterial groups showing any response to urine fertilization. Moreover, the high salt content of the stored urine did not significantly alter the soil's bacterial balance.