Research reveals that phosphorus is being washed from U.S. soils into rivers, driven by climate change and agricultural practices.
This leads to ecological disruptions and poses challenges to food security, requiring innovative agricultural technologies for mitigation.
Phosphorus Depletion in U.S. Soils
Phosphorus, a critical nutrient in soil necessary for sustaining most forms of life, is increasingly being lost from farmland and ending up in waterways across the United States. This alarming trend was uncovered in a new study led by researchers at Penn State.
Published today (November 18) in the Proceedings of the National Academy of Sciences, the study analyzed data from 430 rivers across the U.S. over four decades. The findings reveal that phosphorus loss from agricultural lands has risen significantly, despite ongoing efforts to curb it. This loss threatens crop yields, which could lead to higher food prices, the researchers warned.
Impact of Weather and Soil Erosion on Phosphorus Levels
“We’ve seen from recent weather events that water quantity, the amount of water that storms and waterways carry, can lead to dangerous flooding and mudslides,” explained Li Li, professor of civil and environmental engineering at Penn State and corresponding author on the study. “What we wanted to understand is what happens to the land when these storms pull the subsurface of the soil into rivers and streams. What we found is an alarming loss of this finite element that lets soil sustain life.”
Phosphorus plays an essential role in various biological processes, like creating DNA structure and facilitating the energy transfer between cells, Li explained. But unlike nitrogen, another critical soil nutrient, phosphorus is a non-renewable resource with limited geological deposits, meaning that once it moves from land to water, it can’t get back into the land.
Challenges of Phosphorus Management
“This is a problem for many reasons,” Li said. “When it’s lost from farmland, it can reduce crop yields, potentially leading to higher food prices. Then, when phosphorus enters our waterways, it can cause harmful algal blooms that can make water unsafe for swimming and fishing — and can even reduce oxygen levels in water and kill fish and other aquatic life. It also makes it more expensive to treat drinking water, which means higher water bills for all of us.”
The study used a sophisticated deep learning model to analyze four decades of data, from 1980 to 2019, from 430 rivers throughout the contiguous United States. It revealed that while 60% of the rivers studied showed declining levels of phosphorus, the overall amount of phosphorus flowing into rivers has increased. Agricultural areas are the biggest contributors to the problem, with phosphorus levels increasing in most rivers near agricultural areas, even as they decline in rivers near urban areas.
Addressing the Issue Through Innovation
“This suggests that efforts to control phosphorus pollution from sources like agricultural runoff are not as effective as we thought,” Li said. “But declining levels of phosphorus, particularly in rivers flowing through urban areas, suggests that efforts to control phosphorus pollution from point sources such as wastewater treatment plants are working.”
Despite these targeted efforts, Li said the overall increased amount of phosphorus flowing into rivers is due to the increased frequency of extreme weather events that lead to heavier rainfall and higher river flows — with that increased flow comes more phosphorus.
“This means that even though we’re doing a better job at limiting phosphorus pollution from urban areas, the problem is getting worse overall, due to factors largely beyond the control of just one region,” Li said. “This is a problem that is tied to climate change.”
Going forward, the study’s authors said phosphorus pollution from agriculture needs better prevention and mitigation, which will be a challenge, especially as wetter storms drive increased rainfall and river flows. They said that this will likely require a combination of new technologies and changes to farming practices.
Innovative Solutions to Address Phosphorus Pollution
One such technology was invented at Penn State and is currently garnering support from the agricultural technology sector to address the problem at scale. Hunter Swisher, a 2016 Penn State alumnus, is the founder and chief executive officer of Phospholutions, a fertilizer formulated to increase phosphorus efficiency in the soil.
He developed the company’s technology during his undergraduate studies in plant sciences at Penn State. The company recently announced the results of a study proving that the product reduces runoff potential by 78% compared to conventional phosphorus fertilizers. Phospholutions is actively commercializing throughout the Americas, Europe, and India.
“We are advocating for more innovation, more creativity and more urgency,” Li said. “The connection between water and land is essential and that balance is growing increasingly fragile.”
Reference: “Increasing phosphorus loss despite widespread concentration decline in US rivers” by Wei Zhi, Hubert Baniecki, Jiangtao Liu, Elizabeth Boyer, Chaopeng Shen, Gary Shenk, Xiaofeng Liu and Li Li, 18 November 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2402028121
Other Penn State authors are Wei Zhi, former assistant research professor of civil and environmental engineering at Penn State and currently a professor in Hohai University in China; Jiangtao Liu, a doctoral student in civil and environmental engineering; Elizabeth Boyer, professor of environmental science; Chaopeng Shen, professor of water resources engineering; and Xiaofeng Liu, associate professor of civil engineering. Other authors are Hubert Baniecki of University of Warsaw in Poland and Gary Shenk of the United States Geological Survey.
This work was supported by the Barry and Shirley Isett Professorship at Penn State, the High Performance Computing Platform of Hohai University, the U.S. National Science Foundation, the U.S. Department of Energy, and the Polish Ministry of Education and Science.
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5 Comments
This effect is not due to climate change. It’s called the phosphorus cycle.
This is not a study. It’s a commercial for Penn State’s Phospholutions, a phosphorus fertilizer you can buy that combines both phosphorus and pollutions, I assume.
The phosphorus decline in rivers has been a decades-long effort to reduce agricultural runoff, preventing increased phosphorus causing algal blooms that eutrophy and end lakes. Storms will not consistently increase phosphorus levels as they are not constant. Agriculture depletes soil phosphorus, so farmers add it using phosphates or manure, as has been the case for at least 8000 years. Maybe Penn State should stick to cheesing steak and leave farming to universities in the Midwest.
I agree with your observation about this being a commercial for *Phospholutions”.
The midwest has nothing over central PA concerning agricultural however.
“A Penn State-led study analyzed data from 430 rivers across the U.S. and found that phosphorus loss from agricultural lands has increased over the past four decades, despite efforts to reduce it.”
You two beat me to complaining that the association with the company appears to be a financial conflict of interest that taints the veracity of the claims.
They claim that the depletion of phosphorus in the fields has been occurring for 4 decades and warn that it “can potentially lead to decreased crop yields, which can possibly drive up the cost of food.” The problem is, from USDA data for field crops, such as corn over the last nearly 30 years, corn production (in bushels per acre) has increased from 113.5 to 183.1. That is, during most of the time that they claim an increased loss in phosphorus, there has been a steady increase in corn and essentially flat production of wheat. Therefore, it would appear to be speculation that there is a potential problem with phosphorus leading to reduced yields because there is no empirical evidence to support the speculated effect. I think that they should be looking for alternative explanations. However, with a link to a company poised to make money from the ‘problem,’ there probably isn’t a big incentive to look for other explanations. That is the essence of a “conflict of interests” in scientific research.
Are we ignoring the fact that all the concrete and pavement and buildings in urban areas also prevent this runoff?
Anybody who reads the studies and actual data understands full well there are problems with our soil and the effects it is having as well as the effects that are coming, but that’s not limited to phosphorus and this article was definitely nothing more than a biased advertisement.
Have we forgotten that in times past soil nutrients were incorporated by tillage. The application of manure and fertilizer nutrients on the soil surface is necessary for notill plans to be implemented. Could it be that Phosphorus is more readily moving from field to waterway as a result? Plant uptake of Phosphorus from deeper soil horizons that do not receive incorporated nutrients could be a cause of the observed depletion.
Perhaps notill farming has some drawbacks that chemical companies would not like to discuss.