2-chloro-N-[[[4-(trifluoromethoxy)phenyl]amino]carbonyl]benzamide

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

May 26 1987.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

BBA Part VI, 1-1

Version / remarks:

1981

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Details on sampling:

The highest intended dosage rate for triflumuron is 0.25 kg a.s./ha. This amount may be used once per year. Calculated on the basis of a soil depth of 5 cm and a soil density of 1.5 g/cm (according to Chapters 5 and 6 of the Guideline for Testing the Influence of Plant Protectants on the Soil Microflora with Regard to the Carbon and Nitrogen Cycle, BBA-Braunschweig: Draft of Nov. 1981), 0.25 kg a.s./ha correspond to approx. 0.33 mg a.s./ha dry substance (DS) of soil. In the present studies soil samples were treated with 0.33 and 3.33 mg a.s. of triflumuron/kg DS soil.

Details on preparation and application of test substrate:

The soils were obtained from the field, passed through a sieve (2 mm) and stored at 20 + 2 °C for at least 7 but no longer than 14 days.

Treatment of soil:
The sieved soil (max. 5 kg dry weight) was thoroughly mixed with ground quartz sand (10 g sand/kg dry weight, control) or quartz sand and Alsystin (0.33 or 3.33 mg a.s./kg dry weight of soil) in 20 1 stainless steel containers by tumbling (14 min, 50 rpm) on an "Elte 650" rotator mixer (J. Engelsmann AG, Ludwigshafen, FRG). After treatment with sand or with sand and Alsystin the samples were divided into two equal amounts. The first part was mixed with pulverized alfalfa-grass green meal (5 g/kg dry weight of soil) for 14 min at 50 rpm, the second without alfalfa-grass green meal

Incubation of the soil:
From the thus treated soils, samples of 100 g dry weight were taken and placed in 6 x 6 cm (base area) and 14 cm high incubation vessels (brown glass bottles with screw cap and aeration system, total volume 350 ml). The samples were kept in the dark at 20 + 2 °C and at 45 - 50 % of the water holding capacity. The carbon dioxide released from the soil was drawn with carbon dioxide free-air at a rate of 60 + 6 ml/min through 40 ml of 0.5 N NaOH. Bottles with similar function were described by Greaves et al. (1978). The lye was replaced weekly and the amount of bound carbon dioxide was measured by titration with 0.1 N HC1 from pH 8.3 to pH 3.8 (Greaves et al). An automatic titrator with sample changer (Metrohm Co. Herisau, FRG) was used for these analyses.

Test organisms (inoculum):

other: soil respiration and the microbial mineralization of alfalfa-grass-green meal

Total exposure duration:

14 d

Test temperature:

20°C ±2

Organic carbon content (% dry weight):

2.6

Details on test conditions:

loamy sand (0.84 % org. C, pH (KC1) = 5.3) or a sandy silt soil (2.60 % org. C, pH (KC1) = 5.4).

Nominal and measured concentrations:

0.33 and 3.33 mg a.i. of Alsystin/kg dry weight of soil

Key result

Duration:

14 d

Dose descriptor:

other: Soil respiration or mineralization of grass green meal

Effect conc.:

0.33 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

respiration rate

Remarks on result:

other: Recommended amount of active

Key result

Duration:

14 d

Dose descriptor:

other: Soil respiration or mineralization of grass green meal

Effect conc.:

3.33 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

respiration rate

Remarks:

Nitrate formation rate also monitored.

Remarks on result:

other: For the 10-fold overdose, a slight (2%) increase in nitrate formation was seen at the higher concentration; no negative effects were seen on nitrification.

Details on results:

Soil respiration (release of carbon dioxide from the soil without the addition of substrate): In the loamy sand soil the highest recommended rate of triflumuron causes a retardation of the soil respiration of around 38% in comparison to the untreated control soil in the 2nd week after treatment. The 10-fold overdose of the insecticide causes an increase of the carbon dioxide formation of about 10% in the first week after treatment and a decrease of about 21% in the second week. In the sandy silt soil both rates of triflumuron cause an insignificant stimulation of the soil respiration (17 and 21%, resp., in comparison to the untreated control). Three weeks after treatment the latest, identical amounts of carbon dioxide are liberated from the treated and the untreated samples of both soils.`

Mineralization of alfalfa-qrass-green meal: In the loamy sand soil the mineralization of alfalfa-grass-green meal is insignificantly increased (13 and 15%) in the 2nd week after treatment with the highest recommended rate of Alsystin and the 10-fold overdose in comparison to the untreated control soil. In the sandy silt soil both rates of the insecticide have no influence on the mineralization of the added substrate.

The single and the 10-fold application rate influenced the mineralization
of soil carbon and of added substrate only slightly and for a short
time. An impairment of the carbon cycle in the soil is therefore not to be expected.

Validity criteria fulfilled:

yes

Conclusions:

The effects of triflumuron (0.33 and 3.33 mg/kg dry weight) soil were investigated on soil respiration and the mineralisation of lucerne grass green meal. Effects were investigated in two soil types. A slight (2%) increase in nitrate formation was seen at the higher concentration; no negative effects were seen on nitrification.

Executive summary:

The recommended amount of triflumuron and a 10-fold overdose (equivalent to 0.33 and 3.33 mg a.s./kg dry wt. soil or 0.25 and 2.5 kg a.s./ha) had no meaningful influence on soil respiration or the mineralization of lucernegrass green meal in a loamy sand (0.84 % org. C, pH (KC1) = 5.3) or a sandy silt soil (2.60 % org. C, pH (KC1) = 5.4). Applied under practical conditions, the insecticide should have no negative influence on carbon transformations in soils.

Reference 2

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

BBA Part VI, 1-1

Version / remarks:

1987

Deviations:

not specified

GLP compliance:

no

Analytical monitoring:

not specified

Details on sampling:

The highest projected dosage rate is 0.25 kg a.s./ha, applied once per year. Calculated on the basis of a soil depth of 5 cm and a soil density of 1.5 g/cm (according to the Guidelines for the Official Testing-of Plant Protectants, part VI, 1-1 influence upon the activity of the soil microflora, BBA Braunschweig, March 1987) 0.25 kg a.si./ha correspond to approx. 0.33 mg a.s./kg dry wt. soil. In the present studies soil samples were treated with 0.33 and 3.33 mg a.s./kg dry wt. soil.

Details on preparation and application of test substrate:

The sieved soil (max. 5 kg dry weight) was thoroughly mixed with ground quartz sand (10 g sand/kg dry wt. soil, control) or a mixture of quartz sand and Alsystin (0.33 or 3.33 mg a.s./kg dry wt. soil) in 20 1 stainless steel containers by tumbling (14 min, 50 rpm) on an "Elte 650" rotator mixer (J. Engelsmann AG, Ludwigshafen, FRG). After treatment with sand or with sand and Alsystin the samples were divided into two equal amounts. One part was mixed with pulverized ammonium sulfate (1000 mg/kg) and quartz sand for 14 min at 50 rpm, the second part only with quartz sand.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Details on test conditions:

Extractions: Immediately after the treatment and 7, 14, 21 and 28 days later, soil samples (equivalent to 50 g dry weight) were removed. After thorough mixing, portions corresponding to 10 g of dry weight of each sample were weighed and extracted with 50 ml of KCl for 60 min on a mechanical shaker (approx. 200 rpm). The soil extracts were filtered to remove soil particles and analyzed for their content of ammonium-N and nitrate-N plus nitrite-N on a Technicon Autoanalyzer. Soil samples or soil extracts which could not be extracted or analyzed immediately, were stored in the deep-freezer at -20 ± 2 °C.

Method analysis: The determination of the ammonium-nitrogen is based on the indophenol-green-reaction. The colour develops with the transformaton of ammonium, sodium salicylate,
potassium-sodium-tartrate, sodium-nitroprusside and sodium hypochlorite in a buffered medium at pH 12.8 to 13.3. The colour complex is measured at 660 nm.

For the determination of nitrate plus nitrite, nitrate ions are reduced to nitrite ions by hydrazine sulfate in the presence of Cu-II-sulfate in the alkaline environment. The nitrite ions react in the acid medium with sulfanilic acid and N-1-naphthyl ethylene diamine hydrochloride to a diazo dyestuff. The extinction of the formed diazo dyestuff is measured at 520 nm. Soil physico-chemical properties are indicated.

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

3.33 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Details on results:

During the 28-day experiments it was found that the concentrations 0.33 and 3.33 mg triflumuron/kg soil dry weight. had no meaningful influence on the turnover of nitrogen (effects =25 %) in either a loamy sand or a silt soil.

The stimulation of the mineralization of native soil nitrogen can be explained by a slight microbicidal action of the test material. After treatment of the soil part of the soil microorganisms are killed. The surviving microflora uses the dead cell material as source of nutrients. During this process, ammonium, nitrate and carbon dioxide are liberated. Since the nitrogen being bound in the cell material was mineralized to ammonium and nitrate without delay, an impairment of the nitrogen turnover is not to be expected.

Due to the stimulation of the nitrogen mineralization, the nitrate content of the treated samples of the loamy sand increased in comparison to the control and was even 14 and/or 25% above the level of the control at the end of the experiment (day 28). An accumulation of nitrate in the soil is, however, not to be expected since the formation of nitrate was no longer stimulated in the 4th week after treatment. The influence on the nitrification of added ammonium in loamy sand was low and is therefore of no ecological significance. Triflumuron is not expected to have any negative influence on the nitrogen cycle in the field when applied as recommended.

Validity criteria fulfilled:

not specified

Conclusions:

The effects of triflumuron (0.33 and 3.33 mg/kg dry weight) soil were investigated on the ammonification and mineralization of soil nitrogen, and the nitrification of added ammonium. Effects were investigated in two soil types. A slight (2%) increase in nitrate formation was seen at the higher concentration; no negative effects were seen on nitrification.

Executive summary:

The highest recommended dosage of Triflumuron(0.33 mg a.s./kg dry wt soil, equivalent to 0.25 kg a.s./ha) and a 10-fold overdose (3.33 mg a.s./kg dry wt soil, equivalent to 2.5 kg a.s./ha) induced an increase in soil nitrogen mineralization in a loamy sand soil (0.84% org. C, pH (KCl) - 5.3). At the end of the experiment (28 days), the nitrate content of the treated samples was slightly higher (14 and 25%, resp.) than of the untreated control soil. In the 4th week after treatment, however, quantities of nitrate formed were the same as in the control. In a silt soil (1.23% org. C, pH (KCl) - 4.8) the highest recommended dosage of the insecticide had no meaningful influence on nitrogen mineralization. Treatment of soil had no influence on nitrification of added ammonium in a silt soil and no meaningful influence on nitrification in a loamy sand soil. In field soils, Triflumuron should have no negative effects on the nitrogen cycle.

Description of key information

Based on a weight of evidence assessment, Triflumuron has no adverse effect on the mineralisation or nitrogen cycles in soil. 

In the first study, the effects of triflumuron (0.33 and 3.33 mg/kg dry weight) soil were investigated on soil respiration and the mineralisation of lucerne grass green meal. Effects were investigated in two soil types. A slight (2%) increase in nitrate formation was seen at the higher concentration; no negative effects were seen on nitrification.

During the second 28-day study it was found that the concentrations 0.33 and 3.33 mg triflumuron/kg soil dry weight had no meaningful influence on the turnover of nitrogen (effects =25 %) in either a loamy sand or a silt soil.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

3.33 mg/kg soil dw