Assessing the toxic effect of nitrapyrin on nitrogen transformation in soil

A 28 d N transformation test was developed according to the OECD guideline 216. In the laboratory-based test, a suitable soil was amended with powdered plant meal as an organic N source. Soil samples of 1 kg treated with five concentrations of nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine), in the range 1.0-100 mg kg⁻¹ dry weight were incubated for 28 d at 20±2 °C. A dose response was produced and the N mineralisation EC₅₀ (95% C.I.) for nitrapyrin was 3.1 (1.9-4.3) mg kg⁻¹ dry soil. The determined EC₅₀ was compared with literature figures for similar end points but using different methodology.