SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Restructuring the P Index to better address P Management in New York 
Authors:Ketterings, Q.M., S. Cela, A.S. Collick, S.J. Crittenden and K.J. Czymmek 
Journal:Journal of Environmental Quality 
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URL (non-DOI journals): 
Model:TopoSWAT & SWAT 
Broad Application Category:pollutant only 
Primary Application Category:BMP assessment 
Secondary Application Category:phosphorus cycling/loss and transport 
Watershed Description:Dairy farm with 59 corn fields located in central New York, U.S. 
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Abstract:The New York Phosphorus Index (NY-PI) was introduced in 2001 after the release of the state’s first Concentrated Animal Feeding Operation (CAFO) Permit that required a nutrient management plan developed in accordance with NRCS standards. The stakeholder-based approach to development of the NY-PI, combined with a requirement for all regulated farms to determine a NY-PI score for all fields, ensured widespread adoption. While P management greatly improved over time, the initial NY-PI overemphasized soil-test P (STP), allowing for P addition if STP was low, even if the risk of P transport was high. Our goal was to develop a new PI approach that incentivizes implementation of best management practices (BMPs) where P-transport risk is high, building on feedback from certified planners (survey), analysis of a planner-supplied 33,000+ field database with NYPI information, and modeling of the impacts of specific BMPs on P runoff using data from a central NY CAFO farm. We propose a new NY-PI structure that identifies landscape-driven P-transport risk if P is surface applied when crops are not actively growing to reach a raw PI score that is multiplied by credits (factors £ 1.0) for implementation of BMPs effective in reducing the risk of P transport. In this “Transport ´ BMP” approach, STP is used as P application cutoff. This approach could reduce barriers to regionalization of PIs, as states can identify landscape risk factors, soil-test cutoffs, and BMPs while maintaining the same management categories (no manure, P-removal-based rates, or N-based management).