Effects on Soil Microorganisms (OECD 217)

Soil Microorganisms - Carbon Transformation Test

This Test Guideline describes a laboratory test method designed to investigate long term potential effects of a single exposure of agrochemicals/non agrochemicals on carbon transformation activity of soil microorganisms.

A minimum of two test concentrations are recommended for agrochemicals (five for non agrochemicals). Sieved soil is divided into portions of equal weight (three for agrochemicals, six for non agrochemicals) including portions mixed with the carrier containing the product, and the control. A minimum of three replicates for both treated and untreated soils is recommended. After 0, 7, 14 and 28 days incubation, samples of treated and control soils are mixed with glucose, and glucose-induced respiration rates are measured for 12 consecutive hours. Respiration rates are expressed as carbon dioxide released or oxygen consumed. The mean respiration rate in the treated soil samples is compared with that in control and the percent deviation of the treated from the control is calculated. All tests run for at least 28 days. If, on the 28th day, differences between treated and untreated soils are equal to or greater than 25 % measurements are continued in 14 day intervals for a maximum of 100 days. Results are analysed using a regression model, and the ECx values are calculated. When the difference in respiration rates between the lower treatment and control is equal to or less than 25 % at any sampling time after day 28, agrochemicals can be evaluated as having no long-term influence on carbon transformation in soils. The EC50, EC25 and/or EC10 values are used for non agrochemicals.

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