Calcium cyanamide

Field studies

Administrative data

Endpoint:

field studies

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997-11-28 until 1998-01-25 and 1998-01-12 until 1998-07-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Test guideline 1

Qualifier:

equivalent or similar to guideline

Guideline:

other: The study design is in compliance with EPA Pesticide Assessment Guidelines, Subdivision N, Section 164-1 “Field dissipation studies for terrestrial uses” (1982).

Deviations:

no

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

other: SETAC (Europe): Procedures for assessing the environmental fate and ecotoxicity of pesticides, March 1995. Part 3, 3.1 – “Soil Dissipation Study”, and meets good scientific practice.

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of measurement:

A terrestrial field dissipation study (field trials): The field soil dissipation of DORMEX (an 50.5 % (w/w) aqueous solution of cyanamide was measured at 2 location in 6 plots (at each location) after treatment with DORMEX (3 treated plots, 3 controls). In addition cyanamide concentrations in spiked soil samples were measured leading to measurments of the degradation rate of cyanamide under different controlled storage conditions (storage trials).

Media:

Soil in two locations in Phoenix, Arizona, USA: location A and location B. Soil. The characteristics of the solis of the different locations are detailed in the tables below in "Any other information on materials and methods incl. tables"

Test material

Test material information

Constituent 1

Reference substance name:

Cyanamide

EC Number:

206-992-3

EC Name:

Cyanamide

Cas Number:

420-04-2

Molecular formula:

CH2N2

IUPAC Name:

cyanamide

Test material form:

other: aqueous solution

Details on test material:

- Test material: DORMEX (50.5 % hydrogen cyanamide, w/w)
- Batch: 730901
- Appearance: Aqueous solution

Results and discussion

Any other information on results incl. tables

Cyanamide concentration in soil:

In none of the untreated control samples cyanamide could be detected above LOQ. Regarding the treated samples in case of location A cyanamide could only be found in sampling depth of 0-10 cm (0-4 inch). The cyanamide amounts in samples collected 1 hour after application were between 2.13 and 9.85 mg/kg. These amounts diminished rapidly at the following sampling dates. Three days after application only at two of three sites cyanamide could be detected in very small amounts. Already after one week no cyanamide was present in any sample. In the sampling depth of 10-20 cm (4-8 inch) there were no cyanamide findings at all at any sampling date.

The samples of location B showed a similar cyanamide pattern. The highest cyanamide concentration was found 1 hour after application (3.94 - 7.48 mg ai/kg). In contrast to location A, small cyanamide amounts were also found one week after application at two of three sites, however, cyanamide disappeared completely after two weeks at this location. Minor amounts of cyanamide (0.07 mg/kg) were found in the sampling depth of 10-20 cm one hour after application at two sites. Due to the fact that all other samples were free from cyanamide these single findings may be a consequence of the sampling procedure, by which cyanamide could be transferred from the upper cyanamide contaminated soil surface into deeper soil layers.

DT50 and DT90 values for cyanamide:

The DT50 values ranged from 7 to 39 hours and were calculated using linear regression analysis assuming first-order reaction kinetics. The overall mean DT50 value was calculated to be 24 hours. a sequential first-order kinetic equation. The DT90 values were not calculated but due to the fact that at location A cyanamide was not detectable after 1 week and at location after two weeks, the DT90 values are < 2 weeks.

Cyanamide concentrations in spiked soil samples:

For the spiked soil samples the recovery rate was determined to be < LOQ to 40.1 %. However, it has to be mentioned that the spiked soil samples were totally different from the actual soil samples, because they were extremely dry and were ground and passed through a 2 mm sieve. In contrary the actual samples were very humid and not treated in such a way at all. In order to explain the unexpected low recovery rates of the spiked soil samples, a series of storage stability tests were run using the untreated soil samples from the field tests. The samples were spiked with different cyanamide concentrations (4.2, 8.4 and 42.1 µg cyanamide) and immediately after spiking, the samples were put into the freezer (< 20°C), on dry ice or on dry ice for two days and then into the freezer. Only in two samples (2 days on dry ice, 42.1 µg, and 2 days on dry ice plus 6 days in the freezer, 42.1 µg) residues above the LOQ could be found and a recovery rate could be calculated. Though the storage periods were very short (2 and 8 days, respectively) the recovery rates were very low (16.7 % and 15.8 %, respectively). As the results of the storage tests did not help explaining the low recovery rates of the spiked field trial, a further series of tests was initiated, which was intended to examine the influence of temperature and storage time on cyanamide degradation in soil samples. For this purpose control samples were mixed together to form one bulk sample, spiked with 11.92 mg cyanamide/kg soil and stored at different temperatures. The samples were not thawed but extracted immediately after taking them out of the freezer. The results indicated that under ambient temperature conditions cyanamide was nearly completely degraded (99 %) within 2 days of storage. Samples stored at < 8°C showed a 92 % cyanamide degradation by day 3. Cyanamide degradation in samples kept in the freezer was also apparent but at a lower extent. After 10 weeks of storage (<-20°C) 35 % of the cyanamide had been degraded.

Cyanamide concentrations in soil after application of 37.42 l DORMEX/ha corresponding to 19.83 kg cyanamide/ha (location A):

Time after application	Plot 1		Plot 3		Plot 6
	0-10 cm	10-20 cm	0-10 cm	10-20 cm	0-10 cm	10-20 cm
1 hour	2.13	< LOQ	3.64	< LOQ	9.85	< LOQ
1 day	0.47	< LOQ	0.62	< LOQ	1.83	< LOQ
3 days	0.36	< LOQ	0.55	< LOQ	< LOQ	< LOQ
1 week	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ
2 weeks	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ
4 weeks	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ

Cyanamide concentrations in soil after application of 37.42 l DORMEX/ha corresponding to 19.83 kg cyanamide/ha (location B):

Time after application	Plot 1 (site 1+2)		Plot 3 (site 3+4)		Plot 6 (site 5+6)
	0-10 cm	10-20 cm	0-10 cm	10-20 cm	0-10 cm	10-20 cm
1 hour	5.08	0.07	3.94	< LOQ	7.48	0.07
1 day	2.12	< LOQ	3.48	< LOQ	2.24	< LOQ
3 days	1.18	< LOQ	1.56	< LOQ	0.53	< LOQ
1 week	0.3	< LOQ	0.1	< LOQ	< LOQ	< LOQ
2 weeks	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ
4 weeks	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ	< LOQ

DT₅₀values for cyanamide in soil under field conditions:

Test Site		DT50(hours)	R^2	Kinetic
Loc. A	Plot 1	23	0.975	first order
	Plot 3	22	0.969	first order
	Plot 6	7	0.996	first order
Loc. B	Plot 1	39	0.995	first order
	Plot 3	36	0.989	first order
	Plot 6	18	0.998	first order

Applicant's summary and conclusion

Conclusions:

Under field conditions cyanamide was degraded with a mean DT50field value of 1 day and a worst-case DT50 field value of 1.6 days. Two weeks after application no cyanamide residues could be detected any more and thus, the DT90field is less than 2 weeks. Degradation rates of cyanamide under different controlled storage conditions it has been proved that the compound is significantly degraded even if the samples are kept below –20°C. The study as performed (field trials, storage trials) gives enough evidence for the conclusion that cyanamide is rapidly degraded in the upper soil layers and will not leach into deeper soil layers.

Executive summary:

Cyanamide, applied as formulated product DORMEX (an 50.5 % (w/w) aqueous solution of cyanamide) to a set-up of soil plots in 2 locations in Phoenix, Arizona, USA: location A and location B, was degraded very fast in soil. After one week only traces could be determined in the upper soil layer (0–10 cm / 0–4 inch) and after two weeks it had completely disappeared. In the lower soil layer (10–20 cm / 4–8 inch) traces of cyanamide were only found in two cases one hour after application. Except these two incidents probably caused by the sampling procedure, in no other samples of this sampling depth cyanamide was detectable. The DT50 values were found to be in a range from 7 to 39 hours with an overall mean value of 24 hours.

By measuring the degradation rate of cyanamide under different controlled storage conditions it has been proved that the compound is significantly degraded even if the samples are kept below –20 °C. Despite the fact that the recovery rates of the spiked soil samples were very low, the study as performed (field trials, storage trials) give enough evidence for the conclusion that cyanamide is rapidly degraded in the upper soil layers and will not leach into deeper soil layers.