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Toxicity to terrestrial plants

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Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Field test, very long test duration covering flowering state and may therefore be used for chronic assessment. Control described, no standard test organism. Results of two tests in two years.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Field test, performed two times (two replicates), appr. 10 months duration each
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Species:
other: other terrestrial plant: Boronia megastigma Nees
Plant group:
Dicotyledonae (dicots)
Test type:
other:
Study type:
field study
Substrate type:
natural soil
Limit test:
no
Remarks:
appr. 10 months
Key result
Species:
other: Boronia megastigma
Duration:
10 mo
Dose descriptor:
NOEC
Effect conc.:
323 kg/ha
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth and flowering
With IBDU, applied up to 100 kg N per ha to Boronia (a typical Australian native plant), toxicity did not occur, because the N amount from IBDU solubilized and available to the plants at any given time was supposed to be small and thus would have been within the assimilation capacity of the plant. At all application times, IBDU gave the highest flower yield.
Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Summary lacking experimental details. Cited in SIDS.
Principles of method if other than guideline:
other: field test
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Species:
Lolium perenne
Plant group:
Monocotyledonae (monocots)
Test type:
other:
Study type:
field study
Substrate type:
natural soil
Limit test:
no
Remarks:
appr. 4.5 months

A 2.2 kg N/are rate (approx. 700 kg IBDU/ha) of IBDU resulted in chartreuse green ryegrass when soil pH was above 7.0. At 3.3 to 7.3 kg IBDU-N/are definite toxicity symptoms were produced at 1 month after applicaton, regardless of soil pH (chartreuse-yellow ryegrass). In all instances, toxicity symptoms had disappeared at 3 months after IBDU application. Tissue analysis showed an inverse correlation with Mn content. There was no off-color response to sulfur-coated urea or ureaform applied at equivalent N rates. The toxic symptom exhibited by the ryegrass was not typical of that due to high ammonium. It was postulated that if ammonium rather than some toxic constituent unique to IBDU is involved, the symptoms are the result of the effect of an extended period (of otherwise nonlethal level) of ammonium on soil pH and thus Fe and Mn availability.

Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Summary lacking experimental details. Cited in SIDS.
Principles of method if other than guideline:
other: field test
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Species:
other: bermudagrass (Cynodon sp)
Plant group:
Monocotyledonae (monocots)
Test type:
other:
Study type:
field study
Substrate type:
natural soil
Limit test:
no

There was no toxic response of bermudagrass to IBDU at soil pH 5.2 to 7.3 or at any combinations of IBDU with Ca(OH)2 and/or urea.

Description of key information

NOEC (10 mo): 323 kg ha-1 (Boronia megastigma)

Effects were observed at 700 kg ha-1 (Lolium perenne)

Key value for chemical safety assessment

Additional information

No guideline studies are available on the toxicity of IBDU to plants. IBDU is used as a slow releasing N-fertilizer. In two field studies the effects of IBDU application to plant growth/ flowering were studied. Both studies significantly show that IBDU is rather promotive than inhibiting to plant growth and flowering. I.e. no toxic response was noted in bermudagrass (Cynodon sp.) after application of up to 1900 kg IBDU/ha every week, whereas off-color was observed in Lolium perenne after 1 month of application of approximately 700 kg IBDU/ha (Volk and Dudeck 1976, approx. 4 months duration). With IBDU, applied up to 323 kg per ha to Boronia megastigma, toxicity did not occur (Reddy and Menary 1989, approx. 10 months duration).