Orthosulfamuron

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 216 (January 21, 2000)

Qualifier:

according to guideline

Guideline:

other: OECD 217 (January 21, 2000)

Qualifier:

according to guideline

Guideline:

other: EPPO Bulletin 24: 1-16 (1994) SETAC Guideline, Soil micro-organisms, page 40-42 (March 1995)

GLP compliance:

yes

Specific details on test material used for the study:

Test material:
IR5878
Batch number: G 009/02
Purity: 98.56 ± 0.19 %

Details on sampling:

Carbon and nitrogen transformation tests were performed in two different experiments, applying 0.101 or 0.507 mg IR5878/kg soil dry weight to three replicates system per treatment group.Each treatment group was composed by three replicates.

Details on test solutions:

A stock solution was prepared by dissolving 25 mg of IR5878 in 50 mL acetone (acetone was used instead of water due to the low solubility of IR5878 in water). Afterwards, adequate amounts of the stock suspension were dropped onto the quartz sand. After evaporation of the solvent, the quartz sand was mixed to the soil using a laboratory mixer. In the course of the procedure the soil was ventilated and moistened with an adequate amount of deionised water. The soil water contents were adjusted to approximately 52 to 54% of the water holding capacity. For the nitrogen transformation test, additionally an amount of 0.5% Lucerne meal (related to soil dry weight) was added to the soil.

Test organisms (species):

other: Test soil

Nominal and measured concentrations:

Carbon and nitrogen transformation tests were performed in two different experiments, applying 0.101 or 0.507 mg IR5878/kg soil dry weight to three replicates system per treatment group.

Details on test conditions:

Test soil:
Clay < 2 µm: 10.3 %
Silt 63 µm to ≥ 2 µm: 37.5 %
Sand ≥ 63-2000 µm: 52.2 %
Cation exchange capacity: 70.5 mmol Ba/kg dry weight
Total organic carbon: 1.5 %
Microbial biomass: 287.6 mg C/kg soil dry weight (1.9 % of total organic carbon)
Optimum of glucose for respiration test: 3 g/kg natural soil
Dry weight: 81.7 ÷ 82.1 %
WHCmax (maximum water holding capacity): 43.5 %
pH: 6.8
NH4+ - N: below the limit of quantification
NO2- - N: 0.5 mg/kg dry weight
NO3- - N: 11.8 mg/kg dry weight
Total N: 12.3 mg/kg dry weight

Key result

Duration:

28 d

Dose descriptor:

EC50

Remarks on result:

other: no effects were observed

Findings

The differences in soil respiration rates between the control soil and the treated soil at both concentrations of IR5878 (0.101 and 0.507 mg IR5878/kg soil dry weight) were below the trigger value of 25% throughout the test.

At day 28 after application, the differences between the respiration rates of IR5878 treated soils and the control were 3.08% and 10.5% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively. The differences from the control were not statistically significant (p>0.05) at both test rates. The variation between the replicate control samples was clearly below the validity criterion of 15% throughout the test.

 

Table 8.10-1:  Effects of IR5878 on soil respiration in a loamy sand soil

	Soil respiration (mg CO2/ kg soil dry weight / h) (Mean values)
	Control	0.101 mg IR5878/kg soil dry weight		0.507 mg IR5878/kg soil dry weight
	Respiration rate	Respiration rate	Deviation^a	Respiration rate	Deviation^a
Day 0	13.595	14.092	3.66	10.884	-19.94
Day 7	16.222	16.830	3.75	17.367	7.06
Day 14	16.046	16.835	4.92	17.118	6.68
Day 28	15.722	16.207	3.08	17.371	10.49
^apercentage of deviation to control (+ = stimulating effect; - = inhibitory effect)

 

At day 28 after application, the differences between the soil nitrate content in the control soil and the treated soil at both concentrations of IR5878 (0.101 and 0.507 mg IR5878/kg soil dry weight) were below the trigger value of 25% throughout the test. The differences compared to the control were –15.5% and –17.0% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively, therefore the variation between the replicate control samples was clearly below the validity criterion of 15% throughout the test. The difference in nitrate formation rate was at –24.4% and –30.5% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively. Therefore the test was prolonged up to 42 days.

On day 42, the differences of nitrate content in treated samples compared to the control were –13.1 % (statistically significant, p < 0.05) and –14.9% (statistically significant, p < 0.05) at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively. The nitrate formation rate was below the trigger value of 25%(-18.1 and –22.9%, respectively).

The differences between the mineral nitrogen content in the control soil and the treated soil at both concentrations of IR5878 (0.101 and 0.507 mg IR5878/kg soil dry weight) were also clearly below the trigger value of 25% at day 28. At day 28 the differences were –13.1 and –14.8%, respectively.

The variation between the replicate control samples was clearly below the validity criterion of 15% throughout the test.

The reference items Dinoterb and Dinoterb Acetate produced in the soil the expected level of effect (more than 25% stimulation / inhibition in nitrogen turnover and soil respiration).

 

Table 8.10-2:  Effects of IR5878 on soil nitrogen transformation in a loamy sand soil – Nitrate content

	NO3– N (mg / kg soil dry weight / h) (Mean values)
	Control	0.101 mg IR5878/kg soil dry weight		0.507 mg IR5878/kg soil dry weight
	Nitrate-N content	Nitrate-N content	Deviation^a	Nitrate-N content	Deviation^a
Day 0	14.033	13.750	-2.02	14.612	4.13
Day 7	17.288	14.455	-16.39	15.831	-8.43
Day 14	23.414	18.588	-20.61	19.319	-17.49
Day 28	36.985	31.245	-15.52	30.700	-16.99
Day 42	48.721	42.335	-13.11	41.465	-14.89
^apercentage of deviation to control (+ = stimulating effect; - = inhibitory effect)

 

Validity criteria fulfilled:

yes

Executive summary:

Effects of on O2 consumption after 28 days of exposure and effects on NO3 nitrogen production after 42 days exposure were investigated. IR5878 was tested on biologically active agricultural soil; loamy sand. A BSB-Sensomat System system was used to determine the CO2 production over a period of up to 24 hours at different sampling intervals. Nitrogen transformation was determined in soil enriched with lucerne meal with test item soil compared with non treated soil. Soil carbon turnover was sampled at 0, 7, 14 and 28 days after treatment and soil nitrogen turnover was sampled at 0, 7, 14, 28 and 42 days.

The test item was tested at 0.101mg and 0.507 mg IR5878 /kg soil dry weight.

At day 28 after application, the differences between the respiration rates of IR5878 treated soils and the control were 3.08% and 10.5% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively.

At day 28 after application, the differences between the soil nitrate content in the control soil and the treated soil at both concentrations of IR5878 (0.101 and 0.507 mg IR5878/kg soil dry weight) were below the trigger value of 25% throughout the test. The differences compared to the control were –15.5% and –17.0% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively, therefore the variation between the replicate control samples was clearly below the validity criterion of 15% throughout the test. The difference in nitrate formation rate was at –24.4% and –30.5% at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively. Therefore the test was prolonged up to 42 days.

On day 42, the differences of nitrate content in treated samples compared to the control were –13.1 % (statistically significant, p < 0.05) and –14.9% (statistically significant, p < 0.05) at 0.101 and 0.507 mg IR5878/kg soil dry weight, respectively. The nitrate formation rate was below the trigger value of 25%(-18.1 and –22.9%, respectively).

The differences between the mineral nitrogen content in the control soil and the treated soil at both concentrations of IR5878 (0.101 and 0.507 mg IR5878/kg soil dry weight) were also clearly below the trigger value of 25% at day 28. At day 28 the differences were –13.1 and –14.8%, respectively.

The variation between the replicate control samples was clearly below the validity criterion of 15% throughout the test.

Based on the results of this study, IR5878 had no significant impact on soil carbon mineralisation and a tolerable impact on soil nitrogen transformation when applied at concentrations up to 0.507 mg/kg soil dry weight (corresponding to 5 times the recommended application rate). It can be concluded that IR5878 will not have any long term influence on soil microflora.

Description of key information

A study was carried out in order to assess the effects of IR5878 on the activity (carbon mineralisation and soil nitrogen transformation) of the soil microflora in the laboratory. Carbon and nitrogen transformation tests were performed in two different experiments, applying 0.101 or 0.507 mg IR5878/kg soil dry weight to three replicates system per treatment group.

IR5878 had no significant impact on soil carbon mineralisation and a tolerable impact on soil nitrogen transformation when applied at concentrations up to 0.507 mg IR5878/kg soil dry weight (corresponding to 5 times the recommended application rate). Therefore, it can be concluded that IR5878 will not have any long term influence on soil microflora.