1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)propane-1,3-dione

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 6 October 2021 to 15 March 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Version / remarks:

2000

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: The soil for the study was prepared for storage (premoistening to about 42 % and incorporation of lucerne-grass-green meal).

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: The test item was weighed out onto quartz sand (1 % of the total soil amount per treatment) for each test concentration separately, mixed thoroughly and applied to the surface of the soil. Additional demineralized water was added to adjust the humidity of the soil. Afterwards, the soil was mixed with a mixer to ensure a homogeneous distribution of the test item in the soil and portioned into replicates.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

19.5 - 20.2 °C

Moisture:

42.8 - 44.9 % of MWHC

Organic carbon content (% dry weight):

0.616

Nitrogen content (% dry weight):

11.2

Details on test conditions:

TEST SYSTEM
- Testing facility: Noack Laboratory, The soil was pre-adjusted to about 42 % of its maximum water holding capacity with demineralized water before storage. Drying out of the soil was prevented by moistening with demineralized water as necessary. The soil amounts were amended with powdered lucerne-green-grass-meal (0.5 % of soil dry weight).
- Origin of lucerne-green-grass-meal: Futtermittel & Naturkost Mühle Gladen, Bahnhofstraße 42, 46286 Dorsten, Germany
Total nitrogen content: 28.5 g/kg
Total carbon content: 43.2 % C/N ratio: 15.1
- Test container: Plastic boxes (volume 1.0 L, food grade) with perforated tops to enable gas exchange.
- Amount of soil: 400 g dw (Control - 10 - 31.6 - 100 - 316 mg/kg), 350 g dw (1000 mg/kg dw)
- No. of replicates per concentration: 3
- No. of replicates per control: 3
- Photoperiod: dark

SOIL INCUBATION
- Method: Incubation was performed in bulk and subsamples were taken.

SOURCE AND PROPERTIES OF SUBSTRATE
- Geographical reference of sampling site: Offenbach, “rechts der Landauer Str.“ Nr. 826/7, Rheinland-Pfalz, Germany; Gauß-Krüger-Coordinates: R-439683; H-5449554; LUFA-soil 2.3; Batch No. F2.32821
- History of site: Cultures: 2017 - 2021: uncultivated; Fertilisation: 2017 - 2021: none
- Treatments with pesticides or fertilizers: No crop protection products applied during the year of sampling and 4 preceding years. No organic fertiliser was applied for at least six months prior use.
- Dry weight (dw) before application (g/100 g soil): 87.1
- Depth of sampling: ca. 0 - 20 cm
- Soil texture
- % sand: 2.4 ± 0.2 (2.0 - 0.63 mm), 29.0 ± 1.4 (0.63 - 0.2 mm), 26.2 ± 0.8 (0.2 - 0.063 mm)
- % silt: 19.4 ± 0.7 (0.063 - 0.02 mm), 10.9 ± 0.9 (0.02 - 0.006 mm), 4.8 ± 0.5 (0.006 - 0.002 mm)
- % clay: 7.4 ± 0.9 (< 0.002 mm)
- Soil taxonomic classification: silty sand (LUFA standard soil 2.3)
- Soil classification system: German DIN
- pH: 6.2 ± 0.3
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight): 10.2
- Inital Ammonium-N (mg NH4-N/kg dw): 0.989
- Maximum water holding capacity (in % dry weigth): 45 %
- Cation exchange capacity (meq/100 g): 6.0 ± 0.9
- Pretreatment of soil: The soil was manually cleared of large objects and then sieved to a particle size of up to 2 mm. The maximum water holding capacity and the pH value were determined.
- Storage: 62 days in the dark at 4 - 6 °C in a climatic room.
- Initial microbial biomass as % of total organic C: 1

DETAILS OF PREINCUBATION OF SOIL: The soil was pre-incubated at room temperature (ca. 20 °C) for 19 days to adapt the microorganisms to test conditions before the start of the study.

EFFECT PARAMETERS MEASURED: During the test period the metabolic activity of the microbial biomass, measured as quantity of nitrate formed / formation rate, was determined 0, 7, 14 and 28 days after test item application and compared to that of an untreated control group.

RANGE-FINDING STUDY
- Test concentrations: Control, 10, 100, 1000 mg/kg dw
- Results used to determine the conditions for the definitive study: Inhibition (%) of Nitrate-N Formation rates after 28 days compared to control : 2, -7, -19, respectively.

Nominal and measured concentrations:

Nominal concentrations: 10, 31.6, 100, 316, 1000 mg/kg soil dry weight

Reference substance (positive control):

yes

Remarks:

Cyanoguanidine is tested yearly at a concentration of 50 mg/kg soil dry weight

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

other: LOEC

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: yes

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: Inhibition >25 % after 7 days.

Reported statistics and error estimates:

see "attachment"

Validity criteria: Variation between control replicates was < 15 % at days 0, 7, 14 and 28 for the determination of inorganic nitrogen (quantity of nitrate-N formed).

 

 

 

Validity criteria fulfilled:

yes

Conclusions:

The NOEC was determined at ≥ 1000 mg/kg dw and the LOEC, EC25 and EC50 was determined at > 1000 mg/kg dw after 28 days.

Executive summary:

The effects of Butyl methoxydibenzoyl methane on the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216 (2000).The test guideline presents alternative testing procedures that apply to agrochemical and non-agrochemical substances. The approach for non-agrochemical substances, which entails a dose-response test design and focuses primarily on inhibitory effects was adopted in this study performed with Butyl methoxydibenzoyl methane. The test item was applied via quartz sand at concentrations of 1000, 316, 100, 31.6, 10 mg/kg soil dry weight. Untreated field soil, adjusted to a moisture content corresponding to nominally 45 % of its maximum water holding capacity and mixed with a source of organic nitrogen (lucerne-greengrass-meal), was tested as the control under the same test conditions as the test item replicates. In the presence of a viable community of soil microflora, organic nitrogen undergoes conversion to mineralised nitrogen and a sequence of microbially mediated transformations that result in the formation of a series of inorganic nitrogen species: ammonification (product = NH₄ + -N), followed by stage 1 nitrification (product = NO₂ - -N) and finally stage 2 nitrification (product = NO₃ - -N). The effects of the test item on nitrogen transformation by soil microflora were determined by comparing rates of formation of the final transformation product, nitrate-nitrogen (NO₃ - -N), in soil treated with Butyl methoxydibenzoyl methane against the rate observed in the untreated control. Measurements of nitrate-nitrogen concentrations in soil were made in all treatments and the control on the day of treatment application (day 0) and after 7, 14 and 28 days. No inhibition was observed compared to control group, therefore the NOEC was determined at ≥ 1000 mg/kg dw and the LOEC, EC25 and EC50 was determined at > 1000 mg/kg dw after 28 days.

Description of key information

The NOEC was determined at ≥ 1000 mg/kg dw and the LOEC, EC25 and EC50 was determined at > 1000 mg/kg dw after 28 days.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw

Additional information

The effects of Butyl methoxydibenzoyl methane on the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216 (2000).The test guideline presents alternative testing procedures that apply to agrochemical and non-agrochemical substances. The approach for non-agrochemical substances, which entails a dose-response test design and focuses primarily on inhibitory effects was adopted in this study performed with Butyl methoxydibenzoyl methane. The test item was applied via quartz sand at concentrations of 1000, 316, 100, 31.6, 10 mg/kg soil dry weight. Untreated field soil, adjusted to a moisture content corresponding to nominally 45 % of its maximum water holding capacity and mixed with a source of organic nitrogen (lucerne-greengrass-meal), was tested as the control under the same test conditions as the test item replicates. In the presence of a viable community of soil microflora, organic nitrogen undergoes conversion to mineralised nitrogen and a sequence of microbially mediated transformations that result in the formation of a series of inorganic nitrogen species: ammonification (product = NH₄ + -N), followed by stage 1 nitrification (product = NO₂ - -N) and finally stage 2 nitrification (product = NO₃ - -N). The effects of the test item on nitrogen transformation by soil microflora were determined by comparing rates of formation of the final transformation product, nitrate-nitrogen (NO₃ - -N), in soil treated with Butyl methoxydibenzoyl methane against the rate observed in the untreated control. Measurements of nitrate-nitrogen concentrations in soil were made in all treatments and the control on the day of treatment application (day 0) and after 7, 14 and 28 days. No inhibition was observed compared to control group, therefore the NOEC was determined at ≥ 1000 mg/kg dw and the LOEC, EC25 and EC50 was determined at > 1000 mg/kg dw after 28 days.