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Checking ambition with reality the pros and cons of different approaches to site assessment


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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.

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Checking ambition with reality the pros and cons of different approaches to site assessment

  1. 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. 2. P Site Assessment tool (on the books) * One national approach, 50 state options? Uniformity vs. flexibility
  3. 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. 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. 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. 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. 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. 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. 9. P Index Watershed model What is the best tool? Simple index or complex model
  10. 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. 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. 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. 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. 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. 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. 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. 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. 18. Are we delivering advice that the farmer needs? Forecasting Models
  19. 19. Pete Kleinman USDA Agricultural Research Service University Park, PA 16802 Thank you