Full proceedings available at: http://www.extension.org/72814 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.

1. User Capabilities and
Next Generation
Phosphorus Indices
Waste to Worth
April 2, 2015
John A. Lory
University of Missouri
Nathan O. Nelson
Kansas State University

2. Timeline of P Management Tools
Initial use of chemical extracts to predict crop
response to fertilizers (Anderson, 1960).
Development of current soil test phosphorus extracts
for agronomic assessment (Bundy et al., 2005).
Initiation of the environmental assessment era.
Resource
Assessment
1850
1900
1940
1985
2014

3. Timeline of P Management Tools
Initial research connecting soil test P to runoff water quality
(e.g. Romkens and Nelson, 1974; Sharpley et al. 1977; 1978).
Initial P Index framework (Lemunyon and Gilbert, 1993).
EPA-NRCS Unified national strategy for CAFO’s calling for P loss
assessment on agricultural fields.
CAFO rule requiring P loss assessment for regulated
applications.
Environmental
Assessment
1970
1994
1999
2008
2014

4. Apple Pie Effect
The term “P Index” has come to mean different things in different
places...
…but the differences are not always appreciated because all are
called “P Indices”.
We have an opportunity
sharpen our approach to P
loss assessment.

5. Opportunities as we Re-consider
P Loss Assessment Tools
• Regional approach.
• Focus on the user’s capabilities.
• Clarify water quality goal.
• Clarify temporal context of each P Index.
– Multiple tools to solve multiple challenges?
• Tools that promote voluntary adoption.
• Tools with applicability beyond manure.
We have an opportunity…

6. Opportunities as we Re-consider
P Loss Assessment Tools
• Regional approach.
• Focus on the user’s capabilities.
• Clarify water quality goal.
• Clarify temporal context of each P Index.
– Multiple tools to solve multiple challenges?
• Tools that promote voluntary adoption.
• Tools with applicability beyond manure.
We have an opportunity…

7. Soil sampling
protocol
Fertilizer recommendation
source
Crop N & P need
Manure sampling
protocol
P loss
assessment
protocol
Nutrient availability
coefficients
Manure nutrient valueP loss rating
Manure application rate
Manure rate calculations
Manure test
results
Soil test
results
Manure application
methodTillage
Yield goal
determination
Crop selection
Management Options: Green
Protocols: Red
Outcomes: Black
Nutrient Management:
A process, not a result.

8. Thinking About Time
NM Plan
Soil test result
Manure test result
P Loss assessment
1-5 year Plan (state dependent)
Sample every 3-5 years
Annually Annually Annually AnnuallyAnnually
<1 to 5-year assessment (state dependent)
Future application rate cannot be known…
Based on time sensitive information.
Therefore – Initial planning is a strategic process: what is feasible?
Nutrient Management: A process, not a result.

9. Strategic planning (1 to 5 years)
• Determine long-term goals (strategic goals) and mapping out a
strategy to attain those goals.
• Feasibility.
Tactical planning (1 to 12 months)
• Adjustments to strategic plan based on incoming information.
– New manure test results.
– Changes in cropping system.
Implementation (1 to 3 days)
• Are conditions today appropriate for P application.
Nutrient Management: A process, not a result.

10. Capabilities of the planner/decision maker
– Certified nutrient management planner
• Expectation for training and competency in use of complex
decision support tools.
• Experienced in sophisticated strategic nutrient management
planning.
– Farmer or farm manager
• Familiarity with computers.
• Experienced in strategic planning but not necessarily with
specifics related to nutrient management.
– Contract or professional manure applicator
• Uncertain computer skills.
• Experienced in short-term tactical assessments and
implementation decisions.
– Farm worker
• Limited computer skills.
• Experienced in implementation decisions.

11. Strategic Planning
Tactical Planning
Implementation
Dedicated
Planner
Farm
Manager
Contract
Applicator
Farm
Worker
?
?
?
Who is needs to make these decisions?
(Who needs to use the tool?)
?
?
?
?
?
?
?
?
?

12. Strategic Planning
Tactical Planning
Implementation
Dedicated
Planner
Farm
Manager
Contract
Applicator
Farm
Worker
Yes Yes? No? No
Yes YesYes?
Yes Yes Yes?
No
No
Who is needs to make these decisions?
(Who needs to use the tool?)

13. P Index Implementation
State STP Erosion Rate
Application
Method? Timing Apparent time step
IA Yes RUSLE2 Total P Yes No By year
KS Yes RUSLE2 Fertilizer/Manure Yes Yes By year, use highest
year (5-yr plan)
MO Yes RUSLE2 No No No 5-yr plan
MD Yes RUSLE Fertilizer/Manure Yes Yes By year
MS Yes RUSLE2 Fertilizer/Manure Yes No By year
NC Yes RUSLE/
RUSLE2
Fertilizer/Manure Yes No Based on most
erosive in 5-yr plan
NY Yes RUSLE2 Fertilizer/Manure Yes Yes By year for 1-yr plan
PA Yes RUSLE/
RUSLE2
Fertilizer/Manure Yes Yes By application for 1-
yr plan

14. Examples of P Assessment Tools
Existing Approaches Examples Complexity Data Needs
Regional Strategic Risk: Which farms? Which fields in a watershed?
Watershed models APEX, SWAT, SPARROW High Extensive
Nutrient Balance Cornell Whole Farm Nut. Bal. Moderate Moderate
Field Strategic/Tactical Risk: Which fields? Which strategies? Changes to my plan?
Simplified model Nutrient Tracking Tool High Extensive
APLE Moderate Moderate
Decision support P Indices Low-Moderate Low-Moderate
Implementation Risk: Application today?
Decision support WI Runoff Risk Advisory
Forecast
Low Low
BMP List NRCS Nutrient Mgt. Std. Low Low

15. Strategic Planning
Tactical Planning
Implementation
Dedicated
Planner
Farm
Manager
Contract
Applicator
Farm
Worker
RUSLE2 Challenge: Often needed for strategic and tactical decisions.
Ideally who is makes these decisions?

16. Opportunities as we Re-consider
P Loss Assessment Tools
• Regional approach.
• Focus on the user’s capabilities.
• Clarify water quality goal.
• Clarify temporal context of each P Index.
– Multiple tools to solve multiple challenges?
• Tools that promote voluntary adoption.
• Tools with applicability beyond manure.
We have an opportunity…

17. P Index Implementation
State STP Erosion Rate
Application
Method? Timing Apparent time step
IA Yes RUSLE2 Total P Yes No By year
KS Yes RUSLE2 Fertilizer/Manure Yes Yes By year, use highest
year (5-yr plan)
MO Yes RUSLE2 No No No 5-yr plan
MD Yes RUSLE Fertilizer/Manure Yes Yes By year
MS Yes RUSLE2 Fertilizer/Manure Yes No By year
NC Yes RUSLE/
RUSLE2
Fertilizer/Manure Yes No Based on most
erosive in 5-yr plan
NY Yes RUSLE2 Fertilizer/Manure Yes Yes By year for 1-yr plan
PA Yes RUSLE/
RUSLE2
Fertilizer/Manure Yes Yes By application for
1-yr plan

18. Strategic Planning
Tactical Planning
Implementation
Long-term
Average
Rotational
Losses
Long-term
Annual or
Seasonal
Losses
Seasonal
Forecasting
Short-term
Weather
Forecast
Your choices have direct implications on how you develop and validate
your tools
Establish Temporal Context

19. Event-based loss
Long-term average
loss by year
Long-term average
rotational loss
0
1
2
06/27/11
08/17/11
11/10/11
11/27/11
04/06/12
04/15/12
04/30/12
05/02/12
05/05/12
05/07/12
10/24/12
11/12/12
04/09/13
05/21/13
05/28/13
TotalPhosphorus
(kgha-1)
Measured
Simulated Best Judgment
Simulated Calibrated
Establish a Temporal Context: Some Examples

20. Agronomic Soil Testing
Farm- and field-level Strategic Assessment
What fields will respond to phosphorus?
What fertilizer rate should I apply to this field?
Potential users
Farmers
Consultants/Ag. advisors

21. Our Challenge
• Clearly define goals as a first step.
• Tools must be accessible to those who need to use them.
• We are not developing “the P Index”.
Our goal is a suite of tools targeted at key decision points.
Our tools can be complex – but they must be simple to use.