1-[2-(2-chloroethoxy)phenylsulfonyl]-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea;triasulfuron (ISO)

Toxicity to soil microorganisms

Description of key information

28-d NOEC for the respiration and nitrogen transformation：0.335 mg/kg soil dw (Plücken 1986).

Additional information

Studies required in Annex VII and some other studies required for higher tonnage are available. All the studies available have been included in the dossier for this endpoint. There are two studies available for this endpoint, both are included as supporting studies. The study by Schulz was performed according to the OECD TG 216 and 217. The study was conducted in compliance with GLP criteria. The test substance formulation was added to a biologically active agricultural soil (loamy sand) as a solution in deionised water. The treatment rates were 0.05 and 0.5 mg/kg soil dw Control soil was treated in the same way, but without the addition of test substance. Positive control, Dinoterb (6.8, 16 and 27 mg/kg soil dw) was tested in separate studies. For nitrification aliquots (200 g dw) were dispensed into 500 mL flasks closed with air permeable screw caps (3 replicates per treatment/control), which were incubated at 18.5 - 20.1 °C. Soil moisture was maintained at 43.09 - 45.00% soil WHC. Soil was amended with lucerne meal (0.5%). For carbon transformation in soil after addition of glucose aliquots (1000 g d.w.) were dispensed into 4 L steel test vessels closed with air permeable lids (3 replicates per treatment/control), which were incubated at 18.5 - 20.1 °C. Soil moisture was maintained at 42.67 - 44.57% soil WHC. Respiration and nitrification were determined for all treatments at 0, 7, 14 and 28 days after treatment. The 28-d NOEC value for the respiration and nitrogen transformation was determined to be 0.5 mg formulation /kg soil dw (0.1 mg substance/kg soil dw) (Schulz 2010).

The study by Plücken was performed without the use of a standard guideline and it was not conducted under GLP. Two agricultural soils, a sandy soil and a silty loam were incubated under various conditions. The test concentrations in the soils were 0.0335 and 0.335 mg per kg of soil. Control soil was treated in the same way, but without the addition of test substance. For nitrification aliquots of 50 g dw (2 replicates per treatment/control) of both soil types were incubated at 25 ± 1 °C. The soil samples (treated and untreated) were amended with 23.6 mg ammonium sulfate per 50 g dry soil dissolved in the water needed to moisten the soil. This quantity of ammonium sulfate corresponded to 100 ppm of nitrogen. Respiration was determined for all treatments at 1, 3, 7, 14, 21 and 28 days after treatment. For carbon transformation aliquots of 100(Schulz 2010). g dw (2 replicates per treatment/control) of both soil types were incubated at 25 ± 1 °C. Additional replicates of untreated and treated soils mixed with 0.5% lucerne meal on a dry weight basis before adjustment of the moisture content were also included. Nitrification was determined for all treatments at 0, 3, 7 days and after 2, 3 and 4 weeks of treatment. The 28-d NOEC value for the respiration and nitrogen transformation was determined to be 0.335 mg/kg soil dw (Plücken 1986).