It’s mid-summer 1966 and the whole of England is preparing for the soccer World Cup final against Germany. England had never reached the final before and with the match being played at Wembley Stadium in London, there’s no shortage of excitement in the air.
Meanwhile, in a small house in a rural village in the English Midlands, pre-final preparations are proceeding. A new black-and-white TV (younger readers might reach for Google at this point) has arrived and taken pride of place in the lounge, while a sturdy playpen is under construction to limit my interference with the event.
Nearly two years old at this stage and a ferocious climber, my parents faced an uphill struggle making the playpen “Seán-proof.”
During one road test, I escaped both the playpen and the house. I was found relieving myself in the hedge of our aged neighbor Mrs. Newton. An event she was keen to prevent from reoccurring and one which my relatives still remind me (and others) of today.
However, 58 years later and following publication of research carried out by an Anglo-French research team based at Birmingham University in the U.K., I can now claim the moral high ground. It turns out I was trailblazing sustainable fertilization.
Nutrients in Fresh Urine
Published in a recent issue of Applied Soil Ecology, researchers from Birmingham’s School of Geography, Earth and Environmental Science and L'Institut Agro at the University of Montpellier in France have confirmed that recycling human urine as a fertilizer for agricultural crops is a viable proposition.
Fresh urine is composed of 95% water with the remaining 5% made up of amino compounds, such as urea or creatinine, organic anions and inorganic salts. This makes it a source of bioavailable nutrients and micronutrients for plant growth, and as such, an ideal fertilizer.
However, the authors note that while there has been great interest in using human urine as a crop fertilizer, theirs is the first study to deliver more understanding about how it affects soil functions and microbial communities.
This is important for several reasons. For example, urine application, by enhancing nitrification and volatilization, could significantly acidify soils, and soil pH is a key determinant of bacterial community structure. It also can increase soil salinity, potentially leading to a decrease in bacterial diversity and the emergence of halotolerant taxa.
What the Research Says
Another concern is that the concentration of carbon and micronutrients such as iron, copper, manganese and zinc could stimulate microbial growth and modify the bacterial community structure.
To investigate these issues, the researchers fertilized a spinach crop with two different doses of source-separated and stored human urine (170 kg N/ ha + 8.5 kg P/ ha and 510 kg N/ ha + 25.5 kg P/ ha) and compared this with a synthetic fertilizer treatment (170 kg N/ ha + 8.5 kg P/ ha) and a water treatment without fertilizer. The experiment was carried out in four soil tanks in greenhouse conditions.
They found that even when applied in high doses, one-year stored urine (which has a pH of 9 compared to about 6.5 for fresh urine) had little impact on soil bacterial communities and produced minimal change in soil pH and salinity.
However, the researchers did discover that urine fertilization increased the relative amounts of nitrifying and denitrifying groups compared to synthetic fertilizer — implying that more N2O and NO could be emitted when fertilizing with urine.
The urine's high salt concentration had little discernible effect on the bacterial community.
Sustainable Gold?
In a broader context, the experiment provides evidence that one-year-stored urine can be applied to a plant-soil system without negatively impacting soil bacterial communities in the short term.
Co-author and University of Birmingham researcher Manon Rumeau commented: “Our research highlights the potential of recycling human urine to enhance agricultural sustainability, reduce wastewater pollution and decrease reliance on synthetic fertilizers. Stored urine can be safely applied to a plant-soil system without negatively impacting the soil microbiome.”
The study calls for further studies on the long-term effects of urine fertilization — particularly regarding nitrogen oxide production and soil salinity.
Note: the current world market for synthetic fertilizer is somewhere north of $200 billion annually and growing.
Soccer enthusiasts might like to know that England won that match 4–2, with striker Geoff Hurst scoring the first-ever hat trick in a World Cup final.
I met Hurst at a control and automation conference in Birmingham in the mid-1990s when he was hired to attract potential customers to one of the vendor’s booths. I can’t remember what the automation product was, but I certainly remember beating him — 4–2 — at foosball. I still have the autographed postcard and football he gave me afterward.
