Bacterial communities in soil are as resilient to human urine as they are to synthetic fertilizers, making it feasible to reuse this bodily fluid as fertilizer for agricultural crops, according to a new study. The following article presents a study conducted on the possibility of using human urine as an ecological fertilizer for crops.
The scientists found that even when applied at high doses, urine stored for a year had little impact on soil bacterial communities and produced minimal changes in soil pH and salinity.
However, the researchers found that urine fertilization increased the relative amounts of nitrifying and denitrifying groups compared to synthetic fertilizers, implying that more nitrogen oxides might be emitted when fertilizing with urine.
Preliminary results of using human urine as a fertilizer
Publishing their findings in the journal Applied Soil EcologyThe team of researchers from the University of Birmingham and L’Institut Agro Montpellier in France called for further studies into the long-term effects of urine fertilisation, particularly with regard to nitrogen oxide production and soil salinity.
Manon Rumeau, co-author of the study and a member of the University of Birmingham, commented: “Our research highlights the potential of recycling human urine to improve agricultural sustainability, reduce wastewater pollution and decrease reliance on synthetic fertilizers. Stored urine can be safely applied to a soil-plant system without negatively impacting the soil microbiome.”
Fresh urine is composed of 95% water, while the remaining 5% is composed of amino compounds such as urea or creatinine, organic anions and inorganic salts, making it a source of bioavailable nutrients and micronutrients for plant growth.
Need for further studies on the use of human urine as a fertilizer
There has been a lot of interest in repurposing human urine as a fertilizer for crops, but – until the publication of this study – a greater understanding of how urine can affect soil functions and microbial communities was needed.
The scientists fertilized a spinach crop with two different doses of stored and source-separated human urine, comparing them with a treatment with synthetic fertilizer and another treatment with water without fertilization, carried out in four soil tanks under greenhouse conditions.
Conclusion of the study related to the reuse of human urine as an ecological fertilizer
After 12 months of storage, urine had a reduced microbiome but contained few common urine strains. Thus, storing urine for several months, with the consequent increase in its pH value (approximately 9 instead of 6.5 in fresh urine) and its free ammonia concentration, is considered sufficient to inactivate most human pathogenic bacteria and break down extracellular DNA.
Soil bacterial communities were resistant to urine fertilization, with only 3% of organism groups being affected. High salt concentration in urine had little discernible effect on the bacterial community.
Notes
– The University of Birmingham is ranked in the world’s top 100 institutions. Its work attracts people from all over the world to Birmingham, including researchers, teachers and over 8,000 international students from over 150 countries.
– ‘Uncovering the impact of human urine fertilization on soil bacterial communities: A path towards sustainable fertilization’ – Manon Rumeau, Chiara Pistocchi, Nassim Ait-Mouheb, Claire Marsden, Brigitte Brunel is published in Applied Soil Ecology.
