A recent study from Penn State reveals that phosphorus, a crucial soil nutrient for supporting life, is increasingly being washed away into waterways across the United States.
The research, published on November 18 in the Proceedings of the National Academy of Sciences, examined data from 430 U.S. rivers and discovered that phosphorus loss from agricultural land has risen over the last 40 years, despite attempts to mitigate this issue. According to the researchers, the erosion of phosphorus could result in lower crop yields, leading to higher food prices.
“Recent weather patterns indicate that water volume from storms can cause severe flooding and mudslides,” stated Li Li, a civil and environmental engineering professor at Penn State and the study’s lead author. “Our aim was to investigate the impacts on land when storms wash the subsurface soil into rivers and streams. What we uncovered is a concerning depletion of this finite element that enables soil to nurture life.”
Li emphasized that phosphorus is vital for numerous biological functions, such as forming DNA and facilitating cellular energy transfer. Unlike nitrogen, which is another important nutrient, phosphorus is a finite resource with limited natural reserves, which means that once it is washed away from land to water, it cannot return.
“This presents several challenges,” Li said. “Its loss from farmland can lead to decreased crop yields and consequently, higher food costs. When phosphorus makes its way into our water bodies, it can trigger harmful algal blooms, rendering water unsafe for recreational activities like swimming and fishing. It can also diminish oxygen levels in the water, harming fish and other aquatic life, and increase the costs associated with treating drinking water, resulting in higher bills for consumers.”
The study utilized an advanced deep learning model to analyze 40 years of data (1980-2019) from 430 rivers across the contiguous United States. Results indicated that while 60% of the rivers showed decreasing phosphorus levels, the total phosphorus entering rivers has actually risen. Agricultural regions were highlighted as the primary source of this issue, with phosphorus concentrations increasing in many rivers adjacent to agricultural land, even as they decreased in urban river areas.
“This indicates that our attempts to manage phosphorus pollution from sources like farm runoff may not be as effective as we had believed,” Li noted. “On the other hand, the decline in phosphorus levels in urban rivers implies that our measures to control pollution from direct sources such as wastewater treatment plants are paying off.”
Li pointed out that, despite these focused efforts, the rising phosphorus levels in rivers are largely attributed to more frequent extreme weather events that bring heavier rainfall and higher river flows, leading to elevated phosphorus transport.
“Even though we are improving phosphorus pollution management in urban settings, the overall situation is worsening, driven by factors that exceed the control of any single area,” Li explained. “This is a broader issue linked to climate change.”
For the future, the study’s authors stress the need for enhanced strategies to prevent and reduce phosphorus pollution from agriculture, which poses a significant challenge as wetter storms lead to increased rainfall and river flow. They believe solving this issue will require a mix of innovative technologies and alterations in farming practices.
One of these innovations, currently receiving backing from the agricultural tech industry, was developed at Penn State. Hunter Swisher, a 2016 alumnus, is the founder and CEO of Phospholutions, a company focused on creating fertilizers that improve phosphorus efficiency in soil.
Swisher created the technology while studying plant sciences at Penn State, with recent results showing that their product can reduce runoff by 78% compared to traditional phosphorus fertilizers. Phospholutions is now working to expand its presence throughout the Americas, Europe, and India.
“We are calling for more innovation, creativity, and urgency,” Li said. “The interconnection between land and water is vital, and this balance is increasingly at risk.”
Other contributors from Penn State include Wei Zhi, a former assistant research professor now at Hohai University in China; Jiangtao Liu, a doctoral candidate; Elizabeth Boyer, a professor of environmental science; Chaopeng Shen, a professor of water resources engineering; and Xiaofeng Liu, an associate professor of civil engineering. Additionally, Hubert Baniecki from the University of Warsaw in Poland and Gary Shenk from the United States Geological Survey are among the authors.
This research was funded by the Barry and Shirley Isett Professorship at Penn State, the High Performance Computing Platform at Hohai University, and grants from the U.S. National Science Foundation, the U.S. Department of Energy, and the Polish Ministry of Education and Science.
