User capabilities and next generation phosphorus (P) indices

Purpose

The phosphorus (P) index is the primary approach to identify field management strategies and/or manure application strategies likely to lead to excessive risk of P loss. It has been over 40 years since the first research connecting agronomic P management and water quality and over 20 years since the initial publication defining a P Index. This session will consider opportunities to build on and expand existing P Index strategies to make them more effective at protecting water quality and friendlier to the target user.

What did we do?

Nutrient management is a process providing guidance on the rate, source, timing, and method of nutrient applications. After completing an initial one to five year strategic plan there are tactical adjustments for new information such as new soil and manure tests and changes in crop selection. Additional assessments are needed when implementing the plan such as determining if current weather and soil conditions are appropriate for application.

We initially reviewed current P Indices and the skills needed to implement those P Indices. We then considered how those requirements aligned with the likely users of the P Index at a particular steps in the development and implementation of a nutrient management of plan.

What have we learned?

Many current P Indices require using the soil erosion program RUSLE2 which is then a barrier to the use of these P Indices by anyone except planners with specialized planning. Such expertise is never available on some farms and unlikely to be available on most farms during tactical and implementation phases of the plan. There has also been suggestions that more complex strategies such as models should replace existing P Indices; this will lead to more complex P loss assessment tools.

Next generation P Indices will be more effective if we consider the capabilities and training of those likely to be making decisions at each critical juncture. Instead of “the” P Index we need to design a suite of tools that target key decision points. At each decision point, a first step of the development process must be defining who the likely decision maker is and what are their skills and training. We can only succeed if our tools are accessible to those that need to use them.

Future Plans  

Sessions like this one and regional efforts to evaluate and update P Indices are critical to the continued improvement of state P Indices. We all must recognize that the P Index concept is still relatively young; in comparison it took about a century to move from the first research on agronomic soil testing to our current soil test extraction methods and interpretation. We are still early in our journey to identify and implement the most effective tools to minimize P loss from agricultural fields.

Authors  

Dr. John A. Lory, Associate Professor of Extension, University of Missouri, Columbia, MO loryj@missouri.edu

Dr. Nathan Nelson, Associate Professor, Kansas State University, Manhattan, KS

Additional information            

Please contact the authors for more information about this topic.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

 

Estimation of phosphorus loss from agricultural land in the Heartland region using the APEX model: a first step to evaluating phosphorus indices

Purpose

Phosphorus (P) indices are a key tool to minimize P loss from agricultural fields but there is insufficient water quality data to fully test them. Our goal is to use the Agricultural Policy/Environmental eXtender Model (APEX), calibrated with existing edge-of-field runoff data, to refine P indices and demonstrate their utility as a field assessment tool capable of protecting water quality. In this phase of the project our goal is to use existing small-watershed data from the Heartland Region (IA, KS, MO and NE) to determine the level of calibration needed for APEX before using the model to generate estimates of P loads appropriate for evaluating a P Index.

What did we do?

APEX model is designed to simulate edge-of-field water, sediment, and nutrient losses. Our analysis included data from 19 watersheds at four sites in the Heartland Region representing a range of hydrologic conditions and including grazing, tilled row-crop, and no-till row-crop management systems.

We evaluated two strategies to optimize settings of model parameters: i. a watershed-specific parameterization based on full calibration/validation comparing measured data with simulated results of the model for runoff volume, sediment load and P load, ii. a minimal parameterization approach based on best professional judgment (BPJ) consistent with using APEX when measured runoff, sediment and P data are not available for model calibration. Model fitting for strategy (i) was done using event data in each watershed. The two parameterization strategies were evaluated based on the fit of “annual” totals where data at each location were summed by year (total of 97 site-years). The Nash-Sutcliffe model efficiency and regression methods were used to quantify model fit.

Figure 1. Examples of small watershed studies that generated runoff water quality used to assess APEX calibration strategies: a.Kansas; b. Missouri.

What have we learned?

Full calibration provided excellent fit for runoff and total P (NSE>0.8 for each) and marginal fit for sediment (~0.3). In contrast, the BPJ resulted in unacceptable estimates of sediment and P load, and marginal fit for runoff volume (NSE~0.4). These results emphasize that failure to calibrate APEX with runoff and water quality data (the BPJ approach) will result in poor estimates of annual sediment and total P loads.

Future Plans      

We are testing a regional parameterization strategy as another possible way to extend the APEX model to locations where there is no runoff and water quality data. The next phase of this project will then use appropriately calibrated models to generate the long-term estimates of P loss needed to evaluate P indices in IA, KS, MO and NE.

Authors

Dr. John A. Lory, Associate Professor of Extension, University of Missouri, Columbia, MO loryj@missouri.edu 

Dr. Nathan Nelson, Associate Professor, Kansas State University, Manhattan, KS

Dr. Claire Baffaut, Research Hydrologist, USDA Agricultural Research Service, Columbia, MO

Dr. Anomaa Senaviratne, Post-doctoral Researcher, University of Missouri, Columbia, MO

Dr. Mike Van Liew, Watershed Modeling Specialist, University of Nebraska, Lincoln, NE

Ammar Bhandari, Doctoral Candidate, Kansas State University, Manhattan, KS

Dr. Antonio Mallarino, Professor, Iowa State University, Ames, IA

Dr. Matt Helmers, Professor, Iowa State University, Ames, IA

Dr. Ranjith Udawatta, Associate Research Professor, University of Missouri, Columbia, MO

Dr. Dan Sweeney, Professor, SE Agricultural Research Center, Kansas State University, Parsons, KS

Dr. Charles Wortmann, Professor, University of Nebraska, Lincoln, NE

Additional information 

Please contact the authors for more information about this project.

Acknowledgements      

This project is funded, in part, by a USDA-NRCS Conservation Innovation Grant.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

Nutrient Management Planners’ Feedback on New York and Pennsylvania Phosphorus Indices

Purpose 

The Phosphorus Index (PI) estimates the relative risk of P loss from agricultural fields and encourages the implementation of best management practices to reduce this risk. A majority of states designed their own PI version to address local conditions and priorities, resulting in a large variation in PI structures among states. Currently, multiple projects nationwide are evaluating if the different PIs are directionally and magnitudinally correct in ranking fields based in their potential for P loss. In the Chesapeake Bay, New York (NY), Pennsylvania (PA), Delaware (DE), Maryland (MD), Virginia (VA), and West Virginia (WV) are working cooperatively to fulfill this objective. Several approaches have been proposed to determine the effectiveness of the various PIs. The following results summarize one approach: a survey of certified nutrient management (CNMP) planners with questions specifically related to their perspectives on the NY and PA PIs. This approach recognizes that planners have experience with the PI and have a close knowledge of the landscape scenarios and management that have previously resulted in water quality violations.

What did we do? 

A total of 36 CNMP planners were surveyed in NY in the winter of 2013-2014. The survey included questions about (1) the relative importance of the different factors in the current PI; (2) the main reasons for water-quality violations; (3) the management practices the PI should encourage and discourage, (4) the use of a screening tool to identify fields that need and do not need a PI assessment; and (5) the PI assessment across and within geographic regions.

In PA, a survey structure and question content similar to NY was used to ensure comparability of results. Certified private and public nutrient management (NM) specialists as well as other members of the PA NM community received the survey in the spring of 2014.

What have we learned? 

All source and transport factors included in the NY PI were considered important by the CNMP planners. More than half of the planners indicated that the water quality violations were mainly driven by manure applications (1) just before snow melt or rainfall events, (2) on frozen or saturated soils, (3) too close to streams or ditches, or (4) without incorporation. Many nutrient management planners suggested that the PI should incentivize manure incorporation, implementation of cover crops, setbacks and buffers, and preferential manure applications to fields without connectivity. A high percentage of planners also suggested that the PI should discourage manure applications to saturated or frozen soils, to fields close to streams, to fields with steep slopes, manure spreading without incorporation, and high manure rates. Several CNMP planners in NY indicated the weighting of factors in the NY PI should be reevaluated, in particular, the timing of manure application. Some planners proposed to use real weather data to fine-tune the timing of manure application, while others suggested replacing the calendar year as a driver for PI weights by field conditions. Most of the CNMP planners in NY (1) did not support including a screening tool to quickly identify fields of no P runoff risk in the revised PI,(2) supported a physiographic-based PI (NY plus Northern PA), and (3) did not support multiple PIs within the NY. Some planners also raised concerns about the lack of systematic assessment of water quality, and the attempt to numerically predict P loss as opposed to predict the relative risk of P applications.

Overall, responding NM specialists indicated a need to revise the PA PI and favored the continued use of a screening tool. State boundary was the preferred regional basis for revising and implementing the PA PI, but some respondents showed support for using physiographic region. Current, PA PI source and transport factors were considered important and reliable in assessing fields for vulnerability to P loss. However, many NM Specialists recognized other potential PA PI factors such as flooding frequency, concentrated flow, leaching potential, and degree of soil P saturation as important for consideration in revising the PA PI. Based on their experience, respondents reported water quality violations typically resulted from manure spills, manure discharge events, and erosions events. Management practices to be encouraged by the PA PI include buffers, cover crops, and erosion control practices such as no tillage. In turn, management practices to be discouraged by the PA PI include winter manure application and manure application to land without suitable cover.

Future Plans 

The management practices identified by CNMP planners will be evaluated in the revised version of the NY PI.

The information obtained from the PA survey will be considered in the PA PI revision process. Similarities in responses between PA and NY especially with respect to practices to be encouraged or discouraged by the PI demonstrate the need for continued cooperative regional work and PI evaluation.

Authors

Quirine M. Ketterings, Professor, Cornell University qmk2@cornell.edu

Sebastian Cela, Postdoctoral Associate Cornell Univ.,Karl J. Czymmek, Senior Extension Associate Cornell Univ., Jennifer Weld, Graduate Student Penn State, Douglas Beegle, Distinguished Professor Penn State, Peter Kleinman, Research Leader USDA-ARS PSWMRU

Additional information 

For additional information, contact Quirine M. Kettertings at qmk2@cornell.edu

Acknowledgements

This project is funded by a USDA-NRCS CIG Grant.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

Modeling Phosphorus Runoff in the Chesapeake Bay Region to Test the Phosphorus Index

Purpose

To assess and advance site assessment for P based management. This presentation is part of a symposium addressing the P Index.

What did we do?

The revision of USDA-NRCS’s standard for nutrient management coincided with significant assessment of the performance of Phosphorus (P) Indices in the six states that are tied to the Chesapeake Bay watershed. The 64,000 square mile watershed is the focus of unprecedented activity around nutrient management as a result of a 2011 Total Maximum Daily Load for P, nitrogen (N), and sediment under the Clean Water Act. In addition, the state of Maryland had required updates to it’s original P Index, resulting in broad scrutiny by various interest groups. Within this setting, USDA-NRCS funded a multi-state project to help advance the testing and harmonization of P-based management in the Chesapeake region.

States in the Chesapeake Bay region have had a long history of collaboration over P management. As a result, participants in the project decided to employ a unique approach to evaluating site assessment and P-based management on the basis of physiographic groupings. Expert panels were established for each of the major physiographic provinces in the region: (1) the Allegheny Plateau (NY, PA and WV); (2) the Appalachian Valley and Ridge (PA, MD, VA, WV) and the Appalachian Piedmont (PA, MD, VA); (3) and the Atlantic Coastal Plain (DE, MD, VA). Panels were comprised with representatives from the nutrient management planning community, the conservation community, the action agency community (state and federal), the farming community and researchers.

At the beginning of the project, each physiographic panel was charged with helping to identify the primary P management concerns for a province and the range of conditions that are most appropriate for site assessment. As the project evolves, panels will be expected to provide feedback on results, look for consistencies and differences between state approaches to site assessment, and, for states working to modify they site assessment approaches, offer input on suitable options.

What have we learned?

Modeling P runoff plays a fundamental role in the Chesapeake project. For each physiographic region, watersheds were identified where the SWAT model and the local P Index would be run to compare results. This objective has proven challenging to the SWAT model, as it requires a common scale of spatial inference with the P Index, i.e., the field. At the start of the project, the performance of SWAT was evaluated with regard to its representation of hydrologic and P cycling processes. It was determined that a version of SWAT that better represents variable source area hydrology, TOPO-SWAT, is best suited to the uplands of the Chesapeake Bay region. In addition, it was determined that the original P routines in SWAT are insensitive to the key nutrient management factors considered by the P Index (rate, timing, method and form of P application). Therefore, a new set of P routines was developed to correct the problem.

To-date, SWAT has been applied to watersheds in all of the physiographic regions of the Chesapeake Bay watershed: Factory Brook (NY) and Dressler Run (PA) in the Allegheny Plateau; Spring Creek (PA), Mahantango Creek (PA), Conewago Creek (PA), Upper Potomac (VA) in the Appalachian Mountains (Valley and Ridge as well as Piedmont). On the Atlantic Coastal Plain, where subsurface P losses to artificial drainage dominate, existing models were deemed inadequate. Therefore, an empirical approach to describing P transfers has been used that includes the application of geophysical imagining techniques to describe the flow paths connecting fields with drainage ditches.

Future Plans

Next steps of the project are to begin comparing P Index output with SWAT output for select field conditions under an array of management scenarios. At that point it is expected the physiographic panels will be re-engaged to work through the assessment of P Index performance and generate insight into the potential for regionally consistent approaches to P-based management.

Authors

Peter Kleinman, Research Leader, USDA-ARS Pasture Systems and Watershed Management Research Unit peter.kleinman@ars.usda.gov

D. Beegle, Z. Easton, A. Collick, Q. Ketterings, D. Fuka, T. Veith, A. Shober, S. Cela, M. Reiter, A. Allen, J. Liu and T. Basden

Additional information

Information on this project can be obtained by contacting the corresponding author.

Acknowledgements

This project is funded, in part, by a USDA-NRCS Conservation Innovation Grant.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

Wisconsin Producer Perspective on the Phosphorus Index

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Why Evaluate the P-Index from the Farmer’s Perspective?

The phosphorus index is a risk management tool, designed to evaluate the potential for runoff from a field based on the conditions and management of that field. Based on many years of work with farms in Wisconsin, the author sees the P-Index as valuable tool for comparing fields and management on the same farm and influencing choices that will lead to the lowest risk of runoff. The tool should not be used to compare between farms, as differing management and geography can cloud those comparisons. Another aspect of the p-index that causes concern is its use as a regulatory tool. When the p-index is applied from a distance–without contact with the farm or farmer, a disconnect can develop.

Author

Dennis Frame, University of Wisconsin drframe@wisc.edu

Additional Information

UW Discovery Farms http://uwdiscoveryfarms.org/

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

What’s the P Index?

The P Index is the Phosphorus Index, a risk assessment tool to quantify the potential for phosphorus runoff from a field. The P Index helps to target critical source areas of potential P loss for greater management attention. It includes source and transport factors. Source factors address how much P is available (for example, soil test P level and P fertilizer and manure application amounts). Transport factors evaluate the potential for runoff to occur (for example, soil erosion, distance and connectivity to water, soil slope, and soil texture). The P Index allows for relative comparisons of P runoff risk. When the P Index is high, recommendations are made either to apply manure on a P basis or not to apply manure at all. When the P Index is low, manure can be applied on a N basis. Also, if the P Index is high, the factors that are responsible for the higher risk of P loss are identified, and this information provides guidance for management practices to reduce the risk. For example, if the P Index is high because of high soil erosion, a recommendation to implement soil conservation best management practices (BMPs) may lower the risk and allow safe manure application.

For additional information:

To find your state’s P Index, do a web search for “phosphorus index” plus your state name.

Author: Jessica Davis, Colorado State University