Orthosulfamuron

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

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.
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.
A corresponding amount of acetone treated quartz sand was added to the control soil for carbon transformation test. The soil water content was adjusted to approximately 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.
Each treatment group was composed by three replicates.
A separate study was carried out using the reference items Dinoterb and Dinoterb Acetate, in order to check the expected level of effect in the soil (more than 25% stimulation / inhibition in nitrogen turnover and soil respiration).
The exposure period of carbon transformation test was of 28 days, while the exposure period of nitrogen transformation was of 42 days.

Test organisms (inoculum):

soil

Total exposure duration:

42 d

Moisture:

WHCmax (maximum water holding capacity): 43.5 %

Key result

Duration:

28 d

Dose descriptor:

other: Carbon mineralization

Effect conc.:

> 0.507 mg/kg soil dw

Conc. based on:

act. ingr.

Basis for effect:

respiration rate

Key result

Duration:

42 d

Dose descriptor:

other: nitrogen inhibition

Effect conc.:

> 0.507 mg/kg soil dw

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

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)

Conclusions:

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.

Executive summary:

IR5878 and its metabolites IR7863, IR7825 and IR8181 have no effects on soil microbial activity.

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. 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.

 

Description of key information

IR5878 and its metabolites IR7863, IR7825 and IR8181 have no effects on soil microbial activity.

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. 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.