This study presents a method to detect whether organic fertilizers have been mixed with synthetic fertilizers or chemical nutrients. The approach is low-cost and straightforward, making it suitable for regulators and laboratories testing commonly sold organic fertilizers.

The authors describe several basic tests that measure ammonia, total carbon, and nitrogen, which soil testing labs, including those at the California Department of Food and Agriculture, can easily perform. These tests are likely to identify over 90% of samples that contain synthetic nitrogen. Anyone who suspects their fertilizer might be adulterated can submit a sample to a commercial soil test lab or the Department to determine its authenticity. More advanced tests can further enhance the detection of mixed fertilizer samples. Since these advanced tests are not commonly used in soil labs, the California Department of Food and Agriculture may consider accepting these samples for additional analysis.

Legitimate fertilizer producers will benefit from clear testing guidelines to ensure their products meet quality standards, while those producing adulterated fertilizers will face necessary scrutiny to confirm the authenticity of their products.