T-4- 127 – Regulation of nitrification and urease inhibitors under the Fertilizers Act and Regulations

The 3 year regulatory transition period (October 26, 2020 to October 26, 2023) has now ended. As a result, regulated parties, including all manufacturers, importers, distributors and sellers of fertilizers and supplements must adhere to the amended Fertilizers Regulations. There are few notable exceptions for some product categories. Learn more about the implementation of the amended Fertilizers Regulations.

1. Purpose

Nitrification and urease inhibitors are nitrogen management products that can be applied with nitrogen-based fertilizers to improve nutrient use efficiency. These products have the potential to help limit greenhouse gas emissions and nitrogen run-off, thus reducing risk of harm to the environment from fertilizer use. Nitrification and urease inhibitors are regulated by the Canadian Food Inspection Agency (CFIA) as "supplements" under the Fertilizers Act and Regulations, and require registration prior to import and sale in Canada. The purpose of this document is to provide information on what is required to register nitrification and urease inhibitors in Canada.

2. Background

Nitrification inhibitors

Nitrification inhibitors act directly on soil bacteria to slow the conversion of ammonia to nitrate (this conversion is known as nitrification). Slowing or inhibiting nitrification is important in agricultural systems, where fertilizer is often applied as ammonia. The conversion of ammonia to nitrate increases nitrogen leaching, reducing the efficiency of fertilizer application and contributes to nutrient pollution of waterways. Inhibitors also control denitrification, a bacterial conversion of nitrate (NO3-) to molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products, including nitrous oxide (N2O), a greenhouse gas and key contributor to climate change.

Urease inhibitors

Urea is the most widely used form of nitrogen fertilizer. Ureases (naturally occurring enzymes in the soil – typically produced by soil bacteria) convert urea to ammonia and carbon dioxide, which is rapidly lost to the atmosphere through volatilization. Urease inhibitors reduce the activity of the enzyme and slow the rate at which urea is hydrolyzed.

3. Registration requirements for nitrification and urease inhibitors

Applications to register nitrification or urease inhibitors must follow the format described in the Guide to Submitting Applications for Registration under the Fertilizers Act. All information previously submitted to other jurisdictions is considered in the evaluation process.

3.1 Safety data requirements specific to nitrification and urease inhibitors

Nitrification and urease inhibitor products require a full safety assessment (Safety Assessment Level III), including Tabs 1-5 as outlined in the guide. In addition to providing a complete toxicological risk profile for the product, submissions must include data that substantiates all environmental safety claims made on the label of the product (for example, reduced nitrogen leaching, volatilization or runoff). There is a wealth of publicly-available, peer-reviewed data on the environmental performance of many nitrification and urease inhibitor chemicals. As a result of this extensive body of research, there are many well-established methodologies available to product proponents that can be used to substantiate the benefits of nitrification and urease inhibitors on environmental health endpoints. Due to the variety of environmental safety claims and modes of action associated with these technologies, there is no single methodology best suited for obtaining data to substantiate environmental safety claims. We also recognize the inherent variability of product performance and its dependence on soil and climatic conditions. Therefore, data requirements for substantiating environmental protection claims for the active ingredients in nitrogen stabilizer products are outcome-based (that is, do not prescribe specific methods or approaches). Examples of admissible data include but are not limited to:

  • nitrogen speciation curves
  • volatilization data / Nitrous oxide emissions (NH3, N2O). For N2O, both direct (emissions from the soil) and indirect (emissions from nitrate leaching, run-off and deposition of volatilized ammonia) measurement of emissions required.
  • nitrate leaching data
  • nitrogen use efficiency assessment

For both lab-scale and field-scale trials, good scientific practices must be employed. Methodologies should be repeatable, measurable, use appropriate controls, be of sound design and statistical evaluation, and test product performance in appropriate and representative scenarios. Experimental design must include an appropriate soluble control. In all cases, a description of the mode of action is required.

4. Research authorization

Individuals wishing to conduct research trials in Canada using unregistered nitrification or urease inhibitors must obtain a research authorization from the CFIA prior to import into Canada or release of the product into the environment. Please refer to T-4-103 – Guidelines for research authorizations for testing of novel supplements for more information.

5. Contact information

Fertilizer Safety Section
Canadian Food Inspection Agency
Phone: 1-855-212-7695
Email: cfia.paso-bpdpm.acia@inspection.gc.ca