AOAC ERP Fertilizers - March 2019

3/14/2019

AOAC EXPERT REVIEW PANEL FOR FERTILIZERS  OMA 2015.15: Nitrogen, Phosphorus and Potassium Release  Patterns of Slow and Controlled‐Release Fertilizers  Presenter & Method Author: William Hall, N‐P‐K Consulting, LLC 

THURSDAY, MARCH 14, 2019 1:00PM – 4:00PM GAITHERSBURG MARRIOTT WASHINGTONIAN CENTER GAITHERSBURG, MARYLAND 20878 USA

AOAC INTERNATIONAL 2275 Research Blvd, Suite 300 Rockville, Maryland 20850 USA

AOAC EXPERT REVIEW PANEL FOR FERTILIZERS

BACKGROUND AND SUMMARY OF METHOD INCLUDING METHOD SCOPE/APPLICABILITY • SLV Medina et al – Journal of AOAC International Vol. 97, No. 3, 2014, pp. 643‐686  (OPEN ACCESS) • AOAC Method – OMA 2015.15 • Two extraction methods are described, one is an accelerated laboratory method that can be completed in 4‐7  days. The alternate method is an ambient soil based extraction method that is conducted over 180 days . • Typically nitrogen is the analyte, but other nutrients are described and applicable to the accelerated method.  In both cases a series of extractions are performed over time, the extracts are analyzed for nutrient content  and the results expressed as percent of total nutrient released over time (hours for the accelerated extraction,  or days for the ambient extraction.  • The results of the two methods can be correlated to allow for use of the accelerated data to assess/predict  the release of nutrients using the ambient extraction method. Thus saving the months of time required for the  ambient test to be conducted on every material.  • Scope Accelerated Laboratory Extraction – This method is applicable for the determination of N, P, and K in Slow  and Controlled Release Fertilizers  • Scope Alternative A, Ambient Soil Method – This method is applicable for the determination of N in Slow and  Controlled Release Fertilizers

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