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Toxicity to terrestrial plants

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Endpoint:
toxicity to terrestrial plants: long-term
Data waiving:
other justification
Justification for data waiving:
other:
Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 850.4230 (Early Seedling Growth Toxicity Test)
Principles of method if other than guideline:
The objective of this study was to evaluate the effect of intermediate to high rates of granulated mineral or organomineral fertilizers on onion N uptake, nutrient balance, root growth and water influx. Onions were grown on four natural soils with different concentrations of ammonium sulfate applied. Test duration was 84 days.
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
Four Quebec soils (specified in table below) were used in this study. Soils were air dried, sieved to 2-mm aggregate size, moistered to 80% of water-holding capacity, transferred to plastic pots (3.2L volume) in amounts of 3.6 - 4.4 kg, depending on bulk density.
Seeds of onion were sown in flats containing moist vermiculate. On the 14th day, four uniform seedlings were transplanted to each pot. To prevent P, K and Mg deficiency, 40 mg P * kg-1 as Ca(H2PO4)2, 90 mg K*kg-1 as K2SO4, and 40mg Mg*kg-1 were mixed with the soils. Hydrated lime was added to the Beaurivage and the St. Jude soils to raise the pH to near 6.5.
Humic peat, containing 600 g H2O * kg-1 wet peat and 13.6 g total N * kg-1 on a dry-weight basis, was ammoniated with 50 g NH3 as ammonia liquor * kg-1 of peat (i.e., 41.2 g NH3-N * kg-1) on a dry weigh basis and pelleted to 2mm granules. Peat-ammonium sulfate pellets were made of the same peat as described above and reagend-grade AS particles of < 1mm diameter. The fertilizers were mixed with soils 4 days before the seedlings were transplanted.
Species:
Allium cepa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: Common onion
- Plant family: Alliaceae
- Variety: Norstar 210B
Test type:
early seedling growth toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Remarks:
4 types
Limit test:
no
Total exposure duration:
84 d
Test temperature:
18 - 22 °C
pH:
5.0 - 6.6
Moisture:
65% relative humidity
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): plastic pots (3.2 L)
- Amount of soil: 3.6-4.4 kg
- Method of seeding: Seeds of onion were sown in flats containing moist vermiculite.
- No. of plants (retained after thinning): 4 per pot
- No. of replicates per treatment group: 3
- No. of replicates per control: 3

GROWTH CONDITIONS
- Photoperiod: 16:8 light:dark
- Light source: incandescent and coolwhite fluorescent lamps
- Light intensity and quality: 300 µE/m²/s photon flux density at plant height
- Relative humidity (%): 65 %

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : N uptake, root length, water uptake, nutrient balance, dry matter yield
Nominal and measured concentrations:
Nominal: 0 (control), 133, 266, 399, and 532 mg N per kg soil
Reference substance (positive control):
no
Species:
Allium cepa
Duration:
84 d
Dose descriptor:
LOEC
Effect conc.:
513.3 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
other: NH4
Basis for effect:
other: yield (dry weight)
Key result
Species:
Allium cepa
Duration:
84 d
Dose descriptor:
NOEC
Effect conc.:
342 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
other: NH4
Basis for effect:
other: yield (dry weight)
Details on results:
Yield (dry weight per pot) was greatest for 133 mg N per kg soil. An inhibitory effect was found at 399 and 532 mg N per kg soil (corresponding to 513.3 and 685.1 mg NH4 / kg soil), except for the sandy soil where only the 532 mg N per kg soil ammonium sulfate was inhibitory.
Results with reference substance (positive control):
No positive control was included.
Validity criteria fulfilled:
not applicable
Conclusions:
In a 84 d seedling growth toxicity test, seeds of onion (Allium cepa) were grown in 4 different natural soils amended with ammonium sulphate. An inhibitory effect on yield (dry weight) was found at 399 and 532 mg N/kg soil dw (corresponding to 513.3 and 685.1 mg NH4/kg soil), and a NOEC of 299 mg N/kg soil dw (nominal) can be derived, which corresponds to a 84 d NOEC of 342 mg NH4/kg soil dw (nominal) for ammonium.

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