There is a pressing demand for methodology to validate claims of fertilizers labeled “suitable for organic production” in order to confirm their authenticity. A standard and vigorous protocol to address this urgent need will bring transparency and authentication to the array of organic fertilizer products on the market. In this study, the development of a potential systematic protocol that can be used by test laboratories and regulatory agencies to detect adulteration of organic fertilizers and soil amendments with synthetic nitrogen source is explained. By conducting a comprehensive literature review and analysis of 180 commercially available raw materials, organic fertilizers, soil amendments, and synthetic fertilizers, a comprehensive database of quantifiable properties has been compiled. In the developed protocol, ammonium content, C/N, δ¹⁵N stable isotope ratio and spectroscopic techniques were selected due to their effectiveness in identifying potential adulteration. A robust protocol of these metrics is presented for use by test labs and regulatory agencies for detection of adulterants in organic fertilizer.