Objective of the study

The study is designed to investigate the long-term effects of a pesticide on nitrogen transformation activity of soil microorganisms, after a single  exposure.

In the case of pesticides intended for soil sterilisation, the study shall be designed to measure rates of recovery of microbial activity following treatment.

Circumstances under which the study is recommended to be required

Data with the active ingredient are recommended for all terrestrial outdoor uses.

Test organism

The study is conducted with a natural soil. Permanent pastures, fields with annual cereal crops (except maize) or densely sown green manures are suitable.

The selected sampling site should not have been treated with pesticides for a minimum of one year before sampling, nor should organic fertiliser have been applied for at least six months. Mineral fertilisers may be used as long as soil samples are not taken until at least three months after fertiliser application. The use of soil treated with fertilisers with known biocidal effects (e.g. calcium cyanamide) should be avoided.

Test substance

• Technical grade active ingredient
• A study with the end-use product is recommended to be required if the toxicity of the pesticide product cannot be reliably predicted on the basis of the active ingredient alone.

Typical endpoints of the study

• Quantity of nitrate formed (mg nitrate/kg dry weight soil/day)
• Percent deviation of the nitrate formation rate in each treatment compared with that in the control
• EC₂₅, EC₁₀ or NOEC, or EC₅₀

Testing guidelines

• OECD Guidelines for the Testing of Chemicals. Test No. 216: Soil Microorganisms: Nitrogen Transformation Test
• US EPA Ecological Effects Test Guidelines. OCSPP 850.3200: Soil Microbial Community Toxicity Test
• US EPA Ecological Effects Test Guidelines. OCSPP 850.3000: Background and special considerations – Tests with terrestrial beneficial insects, invertebrates and microorganisms