Full proceedings available at: http://www.extension.org/72793 The revision of the USDA-NRCS national standard for nutrient management in 2011 was driven, in part, by inconsistencies in state phosphorus (P) indices, rekindling debates over standardizing indices at regional or national scales. Reasonable arguments exist for maintaining the status quo, which allows for state specific site assessment approaches, as well as for regional and national P Indices, which would take advantage of expertise, resources and technologies that may not exist locally. In addition, a diversity of site assessment approaches have now been proposed that differ from the original P Index. Understanding the benefits and limitations provided with these approaches is key to advancing site assessment for P management.

1. Checking Ambition with Reality
Where do we go with the P Index and site assessment?
Pete Kleinman
D. Beegle, A. Sharpley, D. Osmond, J. Lory,
P. Vadas, J. Weld, T. Veith, A. Collick

2. P Site Assessment tool
(on the books)
*
One national approach, 50 state options?
Uniformity vs. flexibility

3. One national approach, 50 state options?
NATIONAL
+ National resources
+ Consistency
 Regulatory, bureaucratic
 Uniform changes
 Equity?
STATE
+ Flexibility
 Regulatory, bureaucratic, political
 Nimble in responding to needed
change
 Local sensitivity

4. Something in between?
Regional approaches
Existing regional groups
SERA-17
Mule Barn Group
Other?
National P index assessment
Physiographic Regions
Allegheny Plateau
Ridge and Valley
Coastal Plain
Piedmont

5. Resistance to change
Nutrient management planning in Pennsylvania
Before 2006
No standardized format to PA plans
After 2006
Standardized formats (Word
docs) with manual calculation
2009 - Spreadsheet automation
- Supported by nutrient
management planning
community
- Exemptions allowed (most
big firms with existing
automation/interfaces)
Farmer
Private
Planner
Public
sector
review

6. Successes
• Improved consistency
 Internal (e.g., N and P recommendations)
 Plan review and oversight
• Ensures current agronomic information is used
 e.g., manure N availability changes in Agronomy guide automatically
updated in spreadsheet
• Efficiency - automated calculations and facilitated information entry
Barriers
• Meeting all end-user needs with standard output (farmer, private, public)
 Integration with existing private sector approaches and tools
• Learning curve
 spreadsheet tool
 Implementing, updating, and understanding Excel
Resistance to change
Pennsylvania’s NMP Standard Format Spreadsheet

7. So we want to improve things. What are our
objectives?
Getting lost in the possibilities
• Education
• Predicting outcomes
• Satisfying regulators, public perception
• Implementation of recommendations
• Improved water quality
• Sustainable agriculture

8. Who are the end users and what do they want?
Getting lost in the possibilities
In actuality
Action agencies, regulators,
consultants, public
 Affect change/ minimize
adverse impacts
 Implementation
• Consistent with other
approaches/rules
• Data, resources
• Readily applied
 Improves water quality
• quantifiable results?
Intended
Farmers, turf industry, home
owners, land managers
 Industry specific recs
 Understand issues and
management options
 Actionable guidance

9. P Index
Watershed model
What is the best tool?
Simple index or complex model

10. Complex
Simple
vulnerability
assessment
IFSM
SWAT
APEX
AnnAGNPS
CBM
P Index
User friendly,
water quality
predicting
APLE
WI Snap-Plus
OK PPM
TX TBET
Current options
Simple index or complex model
Farm to
Watershed
FieldField
SCALE OF APPLICATION
TYPE OF TOOL

11. How much is lost?
How much is
transferred?
What’s the impact?
Vulnerability to P loss or predicting effects
What do we want to know?

12. Simple P Index
Modifying current indices and making new ones
Modeled P loss (kg/ha)
SOURCE Factor
• Soil Test
• Fertilizer
• Rate
• Method
• Manure
• Rate
• Method
• PSC
X
Transport Factor
• Erosion
• Runoff
• Leaching
• Distance
• Modified
Connectivity
= P Index
Each Source Factor
weighted
Each Transport
Factor weighted
Current
r2=0.52
X =
P Index
Sediment P SOURCE
• Soil Test
Sediment Transport
• Erosion
Sediment P
Factor
Soluble P SOURCE
• Manure P
• Fertilizer P
• Soil Psat
X
Runoff Transport
• Runoff = Runoff Soluble P
Factor
X
Leaching Transport
• Leaching = Leaching Soluble
P Factor
Each Source Factor
weighted
Each Transport
Factor weighted Distance
Connectivity
Soluble P SOURCE
• Manure P
• Fertilizer P
• Soil Psat
r2=0.65
Modeled P Loss (kg/ha)
Revised“Component”PI
X =
Adapted from Bolster et al. (2012)

13. Appropriate
 Making management decisions
 Education about important factors of P loss, in format that
makes sense and is conceptually correct
 Directionally correct – If I do “X”, will P loss go up or
down?
Not appropriate
 Quantitative uses (unless proven otherwise)
 How much PI score changes not same as or
consistently proportional to actual P loss
 Challenge to meaningfully compare to measured P loss
data
 Event-based, spatial, beyond edge-of-field evaluations
Best Use of the P Index

14. r2 0.78 0.15
Correct 83% 53%
Low 10% 11%
High 7% 35%
High erosion, low
P application
Low runoff, erosion
high P application
Simple Index
Require the verification of complex models

15. SWAT Ratings
P Index Ratings
without Distance Factor
Medium
High
Very High
P loss vulnerability
Low
SWAT vs P Index:
Field-by-field ratings

16. Complex models
How do we make them user friendly and adapt them to state needs?
• SWAT interface for conservation planners
• No GIS - Little or no training required
• Evaluate practices funded by TSSWCB
• Quantitative sediment & nutrient reductions
• Extensively validated
Texas BMP Evaluation Tool
• Simulates management practices, cropping
systems, and other land uses across range of
agricultural landscapes (whole farms and small
watersheds)
• Represents suites of practices: filter strip,
intensive rotational grazing scenarios, vegetated
grassed waterways, and land application of
manure
• GIS‐based or Windows‐based interfaces
available
• Not yet in an interface such as TBET

17. Appropriate
 What areas and land uses contribute the most P?
 How will field changes affect water quality downstream?
 Where do changes need to be made to have the most
impact?
 How much land needs new practices?
Not appropriate
 Spatial BMP placement
 Farm and field-scale management
• Not designed to evaluate specific practices or fields
Complex models

18. Are we delivering advice that the farmer needs?
Forecasting Models

19. Pete Kleinman
USDA Agricultural Research Service
University Park, PA 16802
peter.kleinman@ars.usda.gov
Thank you