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Toxicity to soil microorganisms

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Description of key information

The NOEC for an inhibition of the nitrogen transformation in soil is ≥ 1000 mg test item/kg soil dry weight.


The test item had a stimulating, but not inhibiting impact on nitrogen transformation (nitrate-N content, nitrate-N formation rate) of soil microorganisms.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
1 000 mg/kg soil dw

Additional information

Test item effect on nitrogen activity of microorganisms was tested according to OECD TG216 and GLP. Soil nitrogen transformation was determined at concentrations of 10, 32, 100, 320 and 1000 mg test substance/kg soil dw in replicates of three after 28 days. The test item was dissolved in acetone and mixed with fine quartz sand before being mixed into biologically active agricultural soil (loamy soil) enriched with lucerne meal (0.92% Organic carbon, WHC  49-51%, sand 52.9%, silt 35.8%, clay 11.3%, pH: 7.4). The rate of nitrate formation between test item treated soil with a non-treated soil was compared. NO3-nitrogen formed in the nitrification process was determined by continuous flow analysis. Results: The variation between replicate control samples was less than ± 15% meeting the validation criteria. The test item had a stimulating, but not inhibiting impact on nitrogen transformation (nitrate-N content, nitrate-N formation rate) of soil microorganisms when applied at test item concentrations up to and including 1000 mg/kg soil dry weight treatment. Therefore, no ECx for inhibiting effects of the test item could be calculated. The statistical analysis showed the NOEC for an inhibition of the nitrogen transformation in soil is≥ 1000 mg test item/kg soil dry weight.