Urea

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to terrestrial arthropods: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study was carried out at the experimental field of the Faculty of Agriculture, Kafr El-Sheikh University, during growing season of Jasmine (March- December, 2004).

The selected area for carrying out the present investigation was grown up with Jasminum grandiflorum shrubs of six years old at experiment time and was planted in rows of 2m apart and at a distance of 1.5 m between plants. The area (160m2) is divided into four plots.

The first plot was fertilizer – free plot which is considered as control plot. The second plot was fertilized by urea (46 % N) spraying over the green part of the plant (150 kg/fed.) and the third one was fertilized by NPK, N= ammonium sulphate(40 %), P=super phosphate(40 %) and K= potassium sulphate (60 %) added to the soil. The recommended fertilizer with NPK at the rate of 40 + 40 + 20 g/plant (64, 64, and 32 kg/fed.). The fourth plot was fertilized by the two fertilizers, urea spaying on the foliage plant and NPK added to the soil. The ratio between urea: N: P: K (150: 64: 64: 32 kg/fed.).

Urea was applied at the beginning of March 10th 2004 during the tested season. At the same time (NPK) was added to the second plot and to the third plot once during the experimental time. All of the tested treatments were replicated four times.

Sampling was carried out by the aid of steel quadrangular (10 x 10 x 5 cm). Soil samples were kept in plastic bags tightly closed and was carried directly to the laboratory. Soil samples were taken during three periods, April, August and December (early vegetative growth, vegetative growth/ blooming and blooming season, respectively).

The early vegetative growth is the period after the burning of the plant and ploughing the soil. The second period is the growing of the vegetation. The third period is the blooming growth.
Extraction of oribatid mites and Collembola took place by using modified Berlese funnels for 5 days, and were received in tubes containing fixative, oribatid mites and Collembola were sorted from other soil fauna using binocular microscope and preserved in a mixture of ethanol and lactic acid (1:1) then identified under high magnification.

Identification of mite was done in accordance with Balogh (1972) and Balogh and Mahunka (1983). Identification of Collembola was done using determination key of Hopkin (2007).

GLP compliance:

not specified

Remarks:

No information on GLP compliance provided.

Application method:

spray

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

other: various collembola species

Animal group:

Collembola (soil-dwelling springtail)

Details on test organisms:

field study (list of species found: see Table 2 of the publication)

Study type:

field study

Limit test:

yes

Total exposure duration:

9 mo

Remarks:

Urea was applied at the beginning of March 10th 2004 during the tested season. Soil samples were taken during three periods, April, August and December (early vegetative growth, vegetative growth/ blooming and blooming season, respectively).

Nominal and measured concentrations:

control; 150 kg urea/fed. (equals 357 kg urea/ha)

Reference substance (positive control):

no

Duration:

36 wk

Dose descriptor:

NOED

Remarks:

NOAEL

Effect conc.:

>= 357 000 g/ha

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: abundance

Results with reference substance (positive control):

Fertilized plots with 357 kg urea/ha recorded the higher abundance of Collembola and mites than the controls.

Validity criteria fulfilled:

not applicable

Conclusions:

Colembola NOAEC >= 357 kg/ha

Executive summary:

Fertilized plots (planted with Jasminum grandiflorum) with 357 kg urea/ha  recorded the higher abundance of Collembola and mites than the controls.

Reference 2

Endpoint:

toxicity to terrestrial arthropods: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study was carried out at the experimental field of the Faculty of Agriculture, Kafr El-Sheikh University, during growing season of Jasmine (March- December, 2004).

The selected area for carrying out the present investigation was grown up with Jasminum grandiflorum shrubs of six years old at experiment time and was planted in rows of 2m apart and at a distance of 1.5 m between plants. The area (160m2) is divided into four plots.

The first plot was fertilizer – free plot which is considered as control plot. The second plot was fertilized by urea (46 % N) spraying over the green part of the plant (150 kg/fed.) and the third one was fertilized by NPK, N= ammonium sulphate(40 %), P=super phosphate(40 %) and K= potassium sulphate (60 %) added to the soil. The recommended fertilizer with NPK at the rate of 40 + 40 + 20 g/plant (64, 64, and 32 kg/fed.). The fourth plot was fertilized by the two fertilizers, urea spaying on the foliage plant and NPK added to the soil. The ratio between urea: N: P: K (150: 64: 64: 32 kg/fed.).

Urea was applied at the beginning of March 10th 2004 during the tested season. At the same time (NPK) was added to the second plot and to the third plot once during the experimental time. All of the tested treatments were replicated four times.

Sampling was carried out by the aid of steel quadrangular (10 x 10 x 5 cm). Soil samples were kept in plastic bags tightly closed and was carried directly to the laboratory. Soil samples were taken during three periods, April, August and December (early vegetative growth, vegetative growth/ blooming and blooming season, respectively).

The early vegetative growth is the period after the burning of the plant and ploughing the soil. The second period is the growing of the vegetation. The third period is the blooming growth.
Extraction of oribatid mites and Collembola took place by using modified Berlese funnels for 5 days, and were received in tubes containing fixative, oribatid mites and Collembola were sorted from other soil fauna using binocular microscope and preserved in a mixture of ethanol and lactic acid (1:1) then identified under high magnification.

Identification of mite was done in accordance with Balogh (1972) and Balogh and Mahunka (1983). Identification of Collembola was done using determination key of Hopkin (2007).

GLP compliance:

not specified

Remarks:

No information on GLP compliance provided.

Application method:

spray

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

other: various mite species

Animal group:

Acari (soil-dwelling predatory mite)

Details on test organisms:

field study (list of species found: see Table 1 of the publication)

Study type:

field study

Limit test:

yes

Total exposure duration:

9 mo

Remarks:

Urea was applied at the beginning of March 10th 2004 during the tested season. Soil samples were taken during three periods, April, August and December (early vegetative growth, vegetative growth/ blooming and blooming season, respectively).

Nominal and measured concentrations:

control; 150 kg urea/fed. (equals 357 kg urea/ha)

Reference substance (positive control):

no

Duration:

36 wk

Dose descriptor:

NOED

Remarks:

NOAEL

Effect conc.:

>= 357 000 g/ha

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: abundance

Results with reference substance (positive control):

Fertilized plots with 357 kg urea/ha recorded the higher abundance of Collembola and mites than the controls.

Validity criteria fulfilled:

not applicable

Conclusions:

Colembola NOAEC >= 357 kg/ha

Executive summary:

Fertilized plots (planted with Jasminum grandiflorum) with 357 kg urea/ha  recorded the higher abundance of Collembola and mites than the controls.

Description of key information

NOEC field studies > 640 mg/kg dw (collembola, mites, acari and bees)

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:

640 mg/kg soil dw

Additional information

Several long-term field studies demonstrates that terrestrial arthropods are not sensitive to urea, i.e., the highest application rates had no adverse effect on this organism group. investigated groups were collembola, mites, acari and bees.

The highest application rate was 960 kg urea/ha corresponding to 640 mg/kg dw assuming that the upper 10 cm were treated since the studies were performed mainly in forests or during the growing season and hence, soil turn-over is unlikely. However, even if it is - more conservatively - assumed that urea has been distributed within the upper 20 cm, this would correspond to 320 mg/kg dw which indicates that these taxonomic groups are less sensitive than earthworms. Hence, from the regulatory aspect this group if less relevant.