Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Probes Sources of Mississippi River Phosphorus

09.05.2011
In their eagerness to cut nitrogen and phosphorus pollution in the Mississippi River and Gulf of Mexico, people have often sought simple explanations for the problem: too many large animal operations, for instance, or farmers who apply too much fertilizer, which then flows into waterways.

But according to new modeling research that examined phosphorus loading from all 1768 counties in the Mississippi River Basin (MRB), the true causes aren’t nearly so straightforward. Livestock manure is widespread in many MRB counties, for example, but it shows little relationship to water quality, say researchers at the University of Illinois at Urbana-Champaign and Cornell University in the May-June 2011 issue of the Journal of Environmental Quality.

Moreover, areas that load the most phosphorus into the Mississippi are also places where farmers add less phosphorus to the soil than they remove each year in crop harvests, suggesting that overzealous fertilizer use is not the issue.

“If it were that, it would be easy to solve. But it’s not that,” says Mark David, a University of Illinois biogeochemist who led the research. “It’s much more complex. So I think in that sense addressing the problem is harder.”

Soil erosion and tile drainage contribute large amounts of phosphorus to the Mississippi and Gulf of Mexico each year, helping fuel a “dead zone” of oxygen-starved water in the Gulf that reached near-record size last summer. Local water quality may also decline due to phosphorus-driven algal blooms.

In an effort to pinpoint the most important sources of phosphorus across the entire MRB, David’s team calculated the yearly phosphorus inputs and outputs for every county in the basin from 1997 to 2006. After aggregating these and other data within 113 watersheds throughout the MRB, they then estimated the river load of phosphorus from every county between January and June for the same time period.

Not surprisingly, counties with intensive row crop agriculture, such as those in the Upper Midwest Corn Belt states of Iowa, Illinois and Ohio, contributed the most phosphorus to rivers. However, these same counties often showed negative phosphorus balances, meaning that phosphorus outputs in crops exceeded inputs by farmers.

In other words, farmers in these regions are actually mining stored phosphorus from the soil, rather than putting more into the system, David says. “But that negative balance doesn’t have much to do with the phosphorus that gets in the river.” Instead, the overall intensity of agriculture seems to matter most. “When I’m sitting here in Illinois in a watershed that’s 95% corn and soybeans, it’s going to lose some phosphorus,” he says, “whether the balance is negative or positive.”

In addition, although animal manure is considered a major phosphorus source to streams and rivers, it was relatively unimportant to phosphorus loading across the entire MRB. David suspects the reason is that most large-scale animal farms have moved to western states in the basin, such as Colorado, where there’s less precipitation to carry manure nutrients into the Mississippi.

Phosphorus from human waste did prove significant. Counties encompassing Chicago and other major metropolitan areas “showed up as hot spots,” David says, because most municipalities don’t remove phosphorus from the otherwise clean sewage effluent they discharge into streams. The team further found that about half of the variation in phosphorus loadings was not explained by their models, suggesting that other factors also contribute, such as stream bank erosion and phosphorus deposits in river sediments.

Overall, the findings suggest that reducing phosphorus pollution will require broad adoption of practices that limit nutrient runoff, such as cover crops, buffer strips, and incorporation of fertilizers. It will also require limits on phosphorus discharge from cities.

Achieving these objectives across the entire MRB won’t be easy, but David hopes the study helps people move beyond common assumptions about causes to focus on the real issues.

“To me the value of the study is that it helps shift the debate,” David says. “The problem is not as simple as two things. It’s not as simple as too much fertilizer or manure.”

The research was funded by the National Science Foundation’s Biocomplexity in the Environment/Coupled Natural-Human Cycles Program.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at https://www.agronomy.org/publications/jeq/abstracts/40/3/931.

The Journal of Environmental Quality is a peer-reviewed, international journal of environmental quality in natural and agricultural ecosystems published six times a year by the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and the Soil Science Society of America (SSSA). The Journal of Environmental Quality covers various aspects of anthropogenic impacts on the environment, including terrestrial, atmospheric, and aquatic systems.

The American Society of Agronomy (ASA) www.agronomy.org, is a scientific society helping its 8,000+ members advance the disciplines and practices of agronomy by supporting professional growth and science policy initiatives, and by providing quality, research-based publications and a variety of member services.

Sara Uttech | Newswise Science News
Further information:
http://www.agronomy.org

More articles from Agricultural and Forestry Science:

nachricht Cascading use is also beneficial for wood
11.12.2017 | Technische Universität München

nachricht The future of crop engineering
08.12.2017 | Max-Planck-Institut für Biochemie

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>