Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The Phosphorus Index: Changes afoot

06.11.2012
Phosphorus (P) is both an essential nutrient in agricultural fields and a contributor to poor water quality in surface waters. To encourage improved P management in fields, the P Index was proposed as a risk assessment tool in 1992. After 20 years of use, modifications, and growing pains, does the P Index accurately assess the risk of P loss?

A special section being published next month in the Journal of Environmental Quality addresses that question. The collection of papers grew out of a symposium at the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America 2011 Annual Meetings.

The section acknowledges the problems that have been encountered with P Index development and implementation, such as inconsistencies between state indices, and also suggests ways in which the indices can be tested against data or models to improve risk assessment and shape future indices.

The P Index was proposed in a 1992 symposium after people became aware of the environmental impacts of P loss from fields. Many farmers were applying manure or other biosolids to their fields at rates that over-applied P. Researchers realized that assessing the risk of P loss from those products was important to protect water quality.

The P Index tool was needed to connect various conditions because P loss is influenced by both site characteristics (e.g., soil test levels, connectivity to water) and the sources of P applied (e.g., inorganic fertilizer, organic sources). It was therefore a great improvement over the use of agronomic soil testing for P risk assessment.

"The objective of the original P Index was to identify fields that had high risk of P loss and then guide producers' decisions on implementing best management practices," says Nathan Nelson, ASA and SSSA member and co-author of the special section's introductory paper. "The P Index has developed into a widely used tool to identify appropriate management practices for P application and fields suitable for such application."

The original 1993 paper by Lemunyon and Gilbert laid out three short-term objectives for the P Index: 1) to develop a procedure to assess the risk for P leaving a site and traveling toward a water body; 2) to develop a method of identifying critical parameters that influence P loss; and 3) to select management practices that would decrease a site's vulnerability to P loss.

These objectives were to be met using fairly simple calculations that took into account both source factors and transport factors. Source factors included levels of P in the soil, rates of P fertilization, and methods or timing of P addition. Features such as soil erosion, runoff, and distance to streams composed the transport factors.

"P loss is high when you have both a lot of P present and an easy transport pathway," explains Nelson. "The index has been designed to evaluate the interaction between these different factors."

Because the P Index can be used to guide conservation practices, the USDA-National Resource Conservation Service (NRCS) adopted it as part of their management planning process. The NRCS, then, left it up to each state to develop their own P Index best suited for their environments and concerns.

"The P Index was meant to be something that could be easily computed with readily available data, so an NRCS agent would be able to obtain the necessary inputs," says Nelson. "But there are many different factors that influence P loss as you move from one physiographic region to the next. The differences in transport processes, soils, and landscapes in each state have led to 48 different versions of the P Index, and some of them are very different."

The inconsistencies of indices across states, along with a perceived lack of improvement in water quality in some regions, are now bringing the accuracy of the P Index into question. With different calculations in place, a set of factors may be categorized as low risk in one state and medium, or even high, risk in another. These discrepancies become especially obvious along state borders.

Researchers understand the need to improve P indices and have made it a priority to base any changes on sound scientific data. Efforts to preserve, evaluate, and improve the P index led the NRCS to release a Request for Proposals within the Conservation Innovation Grant Program. Three regional efforts were funded to evaluate and improve the indices in the Heartland, the Southern State, and the Chesapeake Bay regions of the U.S. Additionally, a national coordination project and two other state-level efforts (Ohio and Wisconsin) were recently funded through the Conservation Innovation Program.

While the final suggestions for the next generation of the P Index are likely a few years off, the research is currently underway. Due to variations in regional characteristics and the problems previously encountered by state boundaries, it is likely that suggestions for improved indices will be based on regional distinctions, Nelson says. The objective is that the evaluations will lead to optimized P indices and better management tools that accurately incorporate site and source characteristics to predict the risk of P loss from fields.

"The scientific community backs the P Index as the best method to assess P loss risk," says Nelson. "The challenge now is to develop consistency in P indices across state boundaries and quantify the accuracy of P index risk assessments."

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/41/6/1703.

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.

Caroline Schneider | EurekAlert!
Further information:
http://www.agronomy.org/publications/jeq/abstracts/41/6/1703

More articles from Agricultural and Forestry Science:

nachricht New research recovers nutrients from seafood process water
31.10.2018 | Chalmers University of Technology

nachricht Plant Hormone Makes Space Farming a Possibility
17.10.2018 | Universität Zürich

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: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>