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EC number: 206-992-3 | CAS number: 420-04-2
Biodegradation in soil
Administrative data
Link to relevant study record(s)
- Endpoint:
- biodegradation in soil, other
- Remarks:
- kinetic re-assessment
- Type of information:
- calculation (if not (Q)SAR)
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- accepted calculation method
- Qualifier:
- according to guideline
- Guideline:
- other: FOCUS groundwater scenarios in the EU review of active substances
- Version / remarks:
- Report of the FOCUS Groundwater Scenarios Workgroup, EC Doc. Ref. SANCO/321/2000 rev. 2; and “Generic guidance for FOCUS groundwater scenarios”. FOCUS Groundwater Scenario Workgroup, May 2001, Version.
- Deviations:
- no
- Test type:
- other: kinetic re-calculation
- Key result
- Soil No.:
- #1
- DT50:
- 0.78 d
- Type:
- not specified
- Temp.:
- 20 °C
- Remarks on result:
- other: geometric mean
- Transformation products:
- not specified
- Conclusions:
- Experimental DT50 values were normalised to standard conditions in accordance with FOCUS groundwater scenarios in the EU review of active substances (FOCUS, 2000). As a result, the DT50 for Cyanamide after normalisation to reference conditions was determined to be 0.78 days (geometric mean).
- Executive summary:
Experimentally determined DT50 values for the biodegradation of calcium cyanamide in soil were corrected according to FOCUS (2000). The models require DT50 values at normalised conditions so that they can be used as input parameters for the calculation of PECsoil, PECsw and PECgw. Laboratory degradation studies were undertaken at various moisture contents often between 40-50% MWHC (Maximum Water Holding Capacity) and at different temperatures (e.g. 10 °C, 12 °C, 20 °C). It has to be taken into account that the actual experimental conditions influenced the results of the studies. Therefore, according to FOCUS (2000) a special procedure called “normalisation” has to be performed before an average value can be calculated. After the normalisation procedure the DT50 at study conditions were transferred to the soil moisture at field capacity (FC). It was assumed that this reference soil moisture content is related to a pressure of 10 kPa (pF2). As a result, the DT50 for Cyanamide after
normalisation to reference conditions was determined to be 0.78 days (geometric mean).- Endpoint:
- biodegradation in soil, other
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- March/April 2018; report revised December 2018
- 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:
- - Principle of test: The aim of the procedure is to investigate the release and transformation kinetics of cyanamide after incorporation of PERLKA granules (> calcium cyanamide fertiliser) in soil.
Background:
In the study of Vilsmeier and Amberger (1978), the degradation of Perlka® (test substance) in soil has been investigated. The amount of cyanamide in soil was determined by extraction with water; however, during the extraction process, the remaining cyalcium cyanamide contained in Perlka® is hydrolysed to cyanamide. Thus, in the study conducted by Vilsmeier and Amberger (1978), the analysis of cyanamide includes systematically both the already formed cyanamide being present in the soil plus the cyanamide still present in the unreacted Perlka® in the form of calcium cyanamide. To date, no study from the scientific literature is known where this methodological drawback is solved. Therefore, AlzChem has developed in-house a new analytical approach which allows for the distinction between cyanamide and calcium cyanamide.
- Short description of test conditions:
Non-sterile, dry reference soil samples (REFESOL 01-A, corresponding to EU reference soil R2) were dosed with PERLKA® (in granular form and grinded). The investigations were conducted at 12 °C at a soil moisture of 5 % and 10 %. The soil concentration of cyanamide in the different samples was measured for 18 days. The cyanamide formed in the different soil samples was extracted with diethylether, which specifically extracts the free cyanamide but does not hydrolyse the unreacted Perlka®. By applying this method, one can differentiate between the amount of cyanamide formed in the soil under defined parameters (soil type, application rate, temperature, time and water content of the soil) and the unreacted calcium cyanamide in Perlka®. As reference, cyanamide F1000 (98%) is used as test item in order to follow its biodegradation under the same test conditions.
- Analysis: Upon contact with water calcium cyanamide is fast transformed to cyanamide. Extraction of soil samples with diethyl ether ensures the determination of free cyanamide only as calcium cyanamide is not dissolved by diethyl ether. The ether extract is then transferred to water and analyzed as ususal for cyanamide.
Extraction temperatures up to a maximum of 40 °C prevent dimerization of cyanamide to dicyandiamde that cannot be determined by the analyses used.
- Parameters analysed / observed: detection of free cyanamide
Soil: REFESOL 01-A (EU reference soil R2), dried, but not sterilised
Temperature: 12°C
Water content: a) 10 % (w/w), corresponding to 34 % WHC (water holding capacity)
b) 5 % (w/w), corresponding to 17 % WHC
Application rate: 500 kg Perlka® / ha with uniform incorporation into a soil layer of 5 cm, corresponding to 100 mg Perlka® / 100 g soil
Time: t = 0, 1 d, 2 d, 3 d ….18 d
Reference: Vilsmeier, K.; Amberger, A. (1978): Modellversuche zum Umsatz von gemahlenen Kalkstickstoff und Perlkalkstickstoff in Abhängigkeit von Bodenfeuchtigkeit und Applikationsform. In: Z. Acker- und Pflanzenbau 147, S. 68–77. - GLP compliance:
- no
- Remarks:
- The study was not carried out according to GLP.
- Test type:
- laboratory
- Specific details on test material used for the study:
- - Perlka: contains according to analysis 21.8 % dissociable cyanamide (14.5 % cyanamide-N)
- Reference substance cyanamide: purity 98.0 % - Radiolabelling:
- no
- Oxygen conditions:
- aerobic
- Soil classification:
- other: Reference soil REFESOL 01-A, dried (corresponds to EU reference soil R2). After-drying in a vacuum at 40 °C (delivery humidity approx. 0.5%), but not sterilized
- Year:
- 2 018
- Soil no.:
- #1
- Soil type:
- other: Reference soil REFESOL 01-A (corresponding to EU reference soil R2)
- Details on soil characteristics:
- No soil characteristics provided in report.
- Soil No.:
- #1
- Duration:
- ca. 18 d
- Soil No.:
- #1
- Initial conc.:
- ca. 1 000 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- PERLKA (corresponding to a theoretical cyanamide content of 218 mg/kg soil dw)
- Soil No.:
- #1
- Initial conc.:
- ca. 300 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- Cyanamide (98 %)
- Parameter followed for biodegradation estimation:
- test mat. analysis
- Soil No.:
- #1
- Temp.:
- 12
- Humidity:
- 5% or 10%
- Microbial biomass:
- not determined; non-sterile soil samples used
- Details on experimental conditions:
- 1. PRELIMINARY EXPERIMENTS:
100 g dry soil were added in 250 mL Duran bottle.
• Sample 1a / b / c: Addition of 10 g (10%) of water demin. (Blank)
• Sample 2a / b / c: Addition of approx. 22 mg Cyanamid F1000 dissolved in 10 g water demin. (Reference samples for recovery)
• Samples 3a / b / c: Addition of approx. 100 mg PERLKA (approx. 10 granules), shaking, then addition of 10 g water demin. (Target sample)
Thourough blending of the soil mixtures by shaking vigorously in the closed Duran bottle for 5 minutes.
• Samples 1/2/3 a: were placed in the vacuum drying oven at 40 °C after 1 hour of service and dried for 16 hours.
• Samples 1/2/3 c: were treated immediately after 1 hour (without drying) in the Soxhleth extractor
• Samples 1/2/3 b: were incubated for 4 days at 12 ° C (in the bath cryostat). Then further treated without drying analogously to sample series c.
Each soil sample was filled in a fresh extraction tube and placed in the Soxhlet apparatus. The 1-liter flask was charged with 400 mL (286 g) of diethyl ether. With a bath temperature of 70 °C, the Soxhlet was operated, so that a rapid distillation at 34 °C sump temperature resulted. A filling of the extraction room took about 8 minutes. After about 80 minutes (exactly 10 cycles), the extraction was stopped.
The diethyl ether extract was concentrated in a 1-liter flask on a rotary evaporator (bath temperature 40 °C) to about 30 mL. The contents of the flask were transferred to a 100 mL pear shaped flask and rinsed twice with fresh diethyl ether.
10 g of demineralized water were added to the pear-shaped flask. Then the diethyl ether was evaporated with a rotary evaporater. About 10 g of aqueous sample solution remained. This was transferred to a 25 mL volumetric flask, washed twice with water and made up to 25 mL.
These samples were analyzed for cyanamide by IC in the ANA laboratory. Expected value at 100% recovery: approx. 22 mg cyanamide in 25 mL solution, that is 0.9 mg cyanamide/mL.
2. MAIN EXPERIMENT 1: Time series Refesol 01-A at 10 % soil moisture
For the main experiment 1, 3 test series were applied:
• Test series 1.1 (Gü-HE 18 / 10.1): PERLKA granules
• Test series 1.2 (Gü-HE 18 / 10.2): Ground PERLKA
• Test series 1.3 (Gü-HE 18 / 10.3): free cyanamide, as a stock solution of Cyanamid F1000 in water
Approximately 100 mg of PERLKA or about 30 mg of cyanamide were weighed out on 100 g of soil and prepared with 10 g of water (= 10 % soil moisture). From each test series, a total of 9 identical vials were prepared at the same time and set aside for storage. The first evaluation took place after 1 hour, then in daily rhythm, later with longer intervals. The last sample was discarded without workup since the test series was terminated after 18 days.
3. MAIN EXPERIMENT 2: Time series Refesol 01-A at 5% soil moisture
For the main experiment 2 again 3 test series were scheduled:
• Test series 2.1 (Gü-HE 18 / 13.1): PERLKA granules
• Test series 2.2 (Gü-HE 18 / 13.2): Ground Perlka
• Test series 2.3 (Gü-HE 18 / 13.3): free cyanamide, as a stock solution of Cyanamid F1000 in water
Approximately 100 mg Perlka or approx. 30 mg cyanamide were weighed out on 100 g soil and applied with 5 g water (= 5 % soil moisture). From each test series, a total of 9 identical vials were prepared at the same time and set aside for storage at 12 °C. The first evaluation took place after 1 hour, then in daily rhythm, later with longer intervals. After 18 days, the test series was terminated.
As reference, Cyanamid F1000 (98 %) is used as test item in order to follow its biodegradation under the same test conditions. - Soil No.:
- #1
- % Recovery:
- 6
- Remarks on result:
- other: PERLKA granules, 12 °C, 10 % soil moisture, 18 days of incubation
- Soil No.:
- #1
- % Recovery:
- 7.6
- Remarks on result:
- other: PERLKA granules; 12 °C, 5 % soil moisture, 18 days of incubation
- Remarks:
- Cyanamide recovery
- Soil No.:
- #1
- % Recovery:
- 4.8
- Remarks on result:
- other: Ground PERLKA, 12 °C, 10 % soil moisture, 18 days of incubation
- Soil No.:
- #1
- % Recovery:
- 0.6
- Remarks on result:
- other: Ground PERLKA, 12 °C, 5 % soil moisture, 18 days of incubation
- Remarks:
- Cyanamide recovery
- Soil No.:
- #1
- % Recovery:
- 0.7
- Remarks on result:
- other: Cyanamide reference, 12 °C, 10 % soil moisture, 18 days of incubation
- Soil No.:
- #1
- % Recovery:
- 0.2
- Remarks on result:
- other: Cyanamide reference, 12 °C, 5 % soil moisture, 18 days of incubation
- Key result
- Soil No.:
- #1
- % Degr.:
- >= 92.4 - <= 94
- Parameter:
- test mat. analysis
- Remarks:
- Cyanamide
- Sampling time:
- 18 d
- Remarks on result:
- other: Release and transformation of cyanamide from PERLKA granules
- Remarks:
- 12 °C, 5 % and 10 % soil moisture
- Key result
- Soil No.:
- #1
- % Degr.:
- >= 99.3 - <= 99.4
- Parameter:
- test mat. analysis
- Remarks:
- Cyanamide
- Sampling time:
- 18 d
- Remarks on result:
- other: Release and transformation of cyanamide from ground PERLKA
- Remarks:
- 12 °C, 5 % and 10 % soil moisture
- Key result
- Soil No.:
- #1
- % Degr.:
- >= 99.3 - <= 99.8
- Parameter:
- test mat. analysis
- Remarks:
- Cyanamide
- Sampling time:
- 18 d
- Remarks on result:
- other: Degradation of cyanamide in reference soil samples
- Remarks:
- 12 °C, 5 % and 10 % soil moisture
- Key result
- Soil No.:
- #1
- DT50:
- ca. 1.1 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- ca. 12 °C
- Remarks on result:
- other: Release of cyanamide from PERLKA at 10% soil moisture
- Key result
- Soil No.:
- #1
- DT50:
- ca. 1.8 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- ca. 12 °C
- Remarks on result:
- other: Release of cyanamide from PERLKA at 5 % soil moisture
- Transformation products:
- yes
- No.:
- #1
- Details on transformation products:
- Degradation of cyanamide at 10 % soil moisture (12 °C): DT50 = 3.2 d
Degradation of cyanamide at 5 % soil moisture (12 °C): DT50 = 2.6 d - Evaporation of parent compound:
- no
- Volatile metabolites:
- no
- Residues:
- not specified
- Details on results:
- TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes
MAJOR TRANSFORMATION PRODUCTS
- Cyanamide
- Conclusions:
- The half-lives calculated from the experimental results are as follows:
For the transformation of CaNCN and release of cyanamide (K1):
• 1.1 days at 10 % soil moisture
• 1.8 days at 5 % soil moisture
For the breakdown of free cyanamide:
• 3.2 days at 10 % soil moisture
• 2.6 days at 5 % soil moisture
Revision: Degradation of the cyanamide as reference (Cyanamid F1000):
• 2.2 days at 10 % soil moisture
• 1.3 days at 5 % soil moisture - Executive summary:
Experiments with soil samples of REFESOL 01-A were conducted to investigate the release and transformation kinetics of cyanamide from the calcium cyanamide fertiliser product PERLKA. Soil samples were either incubated with PERLKA granules, ground PERLKA or 98 % cyanamide (reference samples) at 10 % or 5 % soil moisture at 12 °C. The content of cyanamide in different samples was determined by means of IC analyses after cyanamide extraction with diethyl ether, and the recovery of cyanamide in different treatments was followed for up to 18 days.
The granulated form of calcium cyanamide (PERLKA) does not release the maximum amount of cyanamide until nearly 48 hours have passed and the maximum is about 50 % of the total calcium cyanamide formulated. Grinding to a fine powder significantly increases the dissolution rate with ~80 % of the available cyanamide being released within the first hours of the test. The experiment with direct addition of cyanamide in aqueous solution demonstrates the rapid biodegradation of cyanamide in soil: the concentration of cyanamide in soil decreased to less than 50 % of initial within two days. Over time the cyanamide is transformed into other forms of nitrogen (urea, ammonium, nitrate, and dicyandiamide) and the measured amount of cyanamide decreases.
The half-lives calculated based on the experimental results are as follows:
For the transformation of CaCN2 and release of cyanamide:
· DT50 = 1.1 days at 10 % soil moisture
· DT50 = 1.8 days at 5 % soil moisture
For the breakdown of free cyanamide:
· DT50 = 3.2 days at 10 % soil moisture
· DT50 = 2.6 days at 5 % soil moisture
Revision: Degradation of the cyanamide as reference (Cyanamid F1000):
• 2.2 days at 10 % soil moisture
• 1.3 days at 5 % soil moisture
- Endpoint:
- biodegradation in soil: simulation testing
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- July - October, 2018
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- test procedure in accordance with generally accepted scientific standards and described in sufficient detail
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
- Deviations:
- yes
- Remarks:
- For details please refer to the field "Principle of method if other than guideline"
- Principles of method if other than guideline:
- - Principle of test: Aim of the study is to determine the release and transformation of cyanamide from PERLKA in soil. For this purpose, the DT50 of PERLKA and cyanamide in four different soil types were determined. The test substance is added to soil and is regularly sampled to determine the degradation of PERLKA.
- Short description of test conditions:
Test principle: PERLKA was incorporated in air-dried soils as granulate. A defined water concentration was adjusted by adding deionized water. At different times after incorporation the cyanamide formed in the different soil samples was extracted with diethyl ether, which specifically extracts the free cyanamide but does not hydrolyse the unreacted PERLKA. By applying this method, it can be differentiated between the amount of cyanamide formed in the soil under defined parameters (soil type, application rate, temperature, time and water content of the soil) and the unreacted calcium cyanamide in PERLKA.
The cyanamide content was determined photometrically after transfer in an aqueous solution. As reference, Cyanamid F1000 (98%) is used as test item in order to follow its biodegradation under the same test conditions.
- Parameters analysed / observed: The soil content of free cyanamide is analytically quantified.
Additionally, for one soil the content of the secondary transformation products of cyanamide, dicyandiamide (DCD), urea (CH4N2O), nitrate (NO3-), nitrite (NO2-) and ammonia (NH4+), at different sampling points was determined. Therefore the soil was treated with PERLKA respectively Cyanamid F1000 as described above but the extraction was performed with deionised water. Urea, nitrate, nitrite and ammonia were determined by using ion chromatography, DCD by LC-MS/MS. - GLP compliance:
- no
- Remarks:
- The test was performed as non-GLP-test based on OECD 307.
- Test type:
- laboratory
- Specific details on test material used for the study:
- Test item name: PERLKA
State of matter and appearance: granulate, grey to black
Storage conditions: in tightly closed containers, temperature < 10°C - Radiolabelling:
- no
- Oxygen conditions:
- aerobic
- Soil classification:
- other: EU reference soils which represent the soil types of the FOCUS scenarios R1 to R4.
- Year:
- 2 018
- Soil no.:
- #1
- Soil type:
- other: RefeSol 02-A (FOCUS type R1)
- % Clay:
- 15
- % Silt:
- 83
- % Sand:
- 2
- % Org. C:
- 1
- pH:
- 6.6
- Soil no.:
- #2
- Soil type:
- other: RefeSol 01-A (FOCUS type R2)
- % Clay:
- 7
- % Silt:
- 15
- % Sand:
- 73
- % Org. C:
- 0.9
- pH:
- 5.3
- Soil no.:
- #3
- Soil type:
- other: RefeSol 06-A (FOCUS type R3)
- % Clay:
- 48
- % Silt:
- 39
- % Sand:
- 13
- % Org. C:
- 2
- pH:
- 7.3
- Soil no.:
- #4
- Soil type:
- other: Dugliolo di Budrio (FOCUS type R4)
- % Clay:
- 14
- % Silt:
- 31
- % Sand:
- 55
- % Org. C:
- 0.4
- pH:
- 7.6
- Details on soil characteristics:
- The test was performed with each soil at two different water contents. The water contents were approx. 50 % and 25 % of the maximum water holding capacity. For Scenario R1 (RefeSol 02-A) the test was performed at 12 °C ± 2 °C, for the other scenarios the temperature during incubation was 20 °C ± 2 °C.
- Soil No.:
- #1
- Duration:
- 20 d
- Soil No.:
- #2
- Duration:
- 20 d
- Soil No.:
- #3
- Duration:
- 20 d
- Soil No.:
- #4
- Duration:
- 20 d
- Soil No.:
- #1
- Initial conc.:
- 1 000 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- PERLKA
- Soil No.:
- #2
- Initial conc.:
- 1 000 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- PERLKA
- Soil No.:
- #3
- Initial conc.:
- 1 000 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- PERLKA
- Soil No.:
- #4
- Initial conc.:
- 1 000 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- PERLKA
- Soil No.:
- #1
- Initial conc.:
- 300 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- reference material cyanamide (98 %)
- Soil No.:
- #2
- Initial conc.:
- 300 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- reference material cyanamide (98 %)
- Soil No.:
- #3
- Initial conc.:
- 300 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- reference material cyanamide (98 %)
- Soil No.:
- #4
- Initial conc.:
- 300 mg/kg soil d.w.
- Based on:
- test mat.
- Remarks:
- reference material cyanamide (98 %)
- Parameter followed for biodegradation estimation:
- other: analysis of free cyanamide in soil samples
- Soil No.:
- #1
- Temp.:
- 12 °C
- Humidity:
- 10.4 and 21 %
- Microbial biomass:
- not determined
- Soil No.:
- #2
- Temp.:
- 20 °C
- Humidity:
- 5 and 10 %
- Microbial biomass:
- not determined
- Soil No.:
- #3
- Temp.:
- 20 °C
- Humidity:
- 16 and 32 %
- Microbial biomass:
- not determined
- Soil No.:
- #4
- Temp.:
- 20 °C
- Humidity:
- 9 and 18.2 %
- Microbial biomass:
- not determined
- Details on experimental conditions:
- 1. EXPERIMENTAL DESIGN
- Soil condition: air dried
- Soil (g/replicate): 50 g of air-dried test soil were weighed into 48 (forty-eight) 250 mg glass bottles; 24 bottles each were used for the incubation of PERLKA and cyanamide, respectively.
- Control conditions, if used (present differences from other treatments, i.e., sterile/non-sterile, experimental conditions): same conditions except of no test item added
- No. of replication controls, if used: 3 bottles incubated with PERLKA per sampling; 8 samplings in total (see below)
- No. of replication treatments: 3 bottles incubated with cyanamide per sampling; 8 samplings in total (see below)
2. TEST PERFORMANCE
- Procedure:
For every single test (respective soil/water content combination) 50 g of air-dried test soil were weighed into 48 (forty-eight) 250 mg glass bottles. To 24 (twenty-four) of the bottles 50 mg PERLKA was added. These amounts represent a fertilisation rate of 500 kg PERLKA per hectare. To 24 (twenty-four) of the bottles 15 mg Cyanamid F1000 was added; this amount of cyanamide corresponds roughly to the cyanamide content at a fertilization rate of 500 kg PERLKA per hectare. Then the water content was justified by adding an appropriate amount of deionized water. The bottles were shaken for about five minutes to homogenize the mixture and then the bottles were closed.
For the determination of the secondary transformation products (DCD, urea, nitrate, nitrite and ammonia) RefeSol 01-A was used with about 50 % of maximum water holding capacity. 50 g of air-dried test soil were weighed into each of 48 (forty-eight) 250 mg glass bottles and treated as described above. At each sampling three bottles were used for extraction with deionised water. Additionally, for every sampling a soil sample without PERLKA or Cyanamid F1000 was used to determine the blank value of the secondary transformation products in the soil.
-Sampling: At each sampling three bottles were used for extraction with diethyl ether followed by determination of the cyanamide content in the diethyl ether fraction.
Sampling took place at different times after incorporation: 1 h after start of incubation, 1, 2, 3, 6, 9, 13 and 20 days after incubation.
- Analysis: After sampling the soils were extracted with diethyl ether using a Soxhlet equipment. The extract was transformed into an aqueous solution by using a rotary evaporator.
Cyanamide was determined photometrically. Secondary transformation products as DCD were analysed by LC/MS/MS and Urea, nitrate, nitrite and ammonia was determined using ion chromatography. Urea was
determined after transformation of urea to ammonia with urease. - Soil No.:
- #2
- DT50:
- 0.6 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 01-A, 10 % soil moisture
- Remarks:
- DT50 PERLKA
- Key result
- Soil No.:
- #2
- DT50:
- 0.95 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 01-A, 10 % soil moisture
- Remarks:
- DT50 cyanamide
- Key result
- Soil No.:
- #2
- DT50:
- 1.21 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 01-A, 5 % soil moisture
- Remarks:
- DT50 PERLKA
- Key result
- Soil No.:
- #2
- DT50:
- 0.82 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 01-A, 5 % soil moisture
- Remarks:
- DT50 cyanamide
- Soil No.:
- #1
- DT50:
- 0.87 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 12 °C
- Remarks on result:
- other: RefeSol 02-A, 21 % soil moisture
- Remarks:
- DT50 PERLKA
- Key result
- Soil No.:
- #1
- DT50:
- 1.15 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 12 °C
- Remarks on result:
- other: RefeSol 02-A, 21 % soil moisture
- Remarks:
- DT50 cyanamide
- Soil No.:
- #1
- DT50:
- 1.63 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 12 °C
- Remarks on result:
- other: RefeSol 02-A, 10.4 % soil moisture
- Remarks:
- DT50 PERLKA
- Soil No.:
- #1
- DT50:
- 1.63 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 12 °C
- Remarks on result:
- other: RefeSol 02-A, 10.4 % soil moisture
- Remarks:
- DT50 cyanamide
- Soil No.:
- #3
- DT50:
- 2.47 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 06-A, 32 % soil moisture, DT50 PERLKA
- Key result
- Soil No.:
- #3
- DT50:
- 0.55 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 06-A, 32 % soil moisture, DT50 cyanamide
- Soil No.:
- #3
- DT50:
- 2.51 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 06-A, 16 % soil moisture, DT50 PERLKA
- Key result
- Soil No.:
- #3
- DT50:
- 0.42 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: RefeSol 06-A, 16 % soil moisture, DT50 cyanamide
- Soil No.:
- #4
- DT50:
- 1.63 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: Dugliolo di Budrio, 18.2 % soil moisture, DT50 PERLKA
- Key result
- Soil No.:
- #4
- DT50:
- 0.79 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: Dugliolo di Budrio, 18.2 % soil moisture, DT50 cyanamide
- Soil No.:
- #4
- DT50:
- 1.61 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: Dugliolo di Budrio, 9 % soil moisture, DT50 PERLKA
- Soil No.:
- #4
- DT50:
- 1.21 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 20 °C
- Remarks on result:
- other: Dugliolo di Budrio, 18.2 % soil moisture, DT50 cyanamide
- Transformation products:
- yes
- No.:
- #1
- Details on transformation products:
- See in details on results below.
- Evaporation of parent compound:
- no
- Volatile metabolites:
- not specified
- Residues:
- not specified
- Details on results:
- Tests with Cyanamid F1000:
The content of free cyanamide in different the soil samples was measured in the diethyl ether fraction after extractions (CYextractF1000). The blue curves in Figure 1 to Figure 8 of the graphs shows the content of free cyanamide in comparison to the corresponding calculated total content of cyanamide added to the soil (CYaddedF1000) in dependence of relation to the incubation time.
Tests with PERLKA:
Analogously to the tests with Cyanamid F1000 tThe content of free cyanamide in different the soil samples was measured analysed in the diethyl ether fraction after extractions (CYextractPERLKA). The red curves in Figure 1 to Figure 8 of the graphs depict shows the content of free cyanamide in comparison to the corresponding calculated total content of cyanamide added to the soil (CYaddedPERLKA) in relation to dependence of the incubation time.
In this interim report the data for RefeSol 01-A (FOCUS Scenario R2), RefeSol 02-A (FOCUS Scenario R1), RefeSol 06-A (FOCUS Scenario R3) Dugliolo di Budrio (FOCUS Scenario R4) are presented.
Recovery of Cyanamide in RefeSol 01-A, 10 % soil moisture, 20 °C (see Figure 1)
The recovery for free cyanamide (measured as [CYextractF1000/CYaddedF1000] after one hour of incubation was close to 90 %. Within After six days of incubation less than 2 % of applied cyanamide could be found in the soil.
About 12 % of cyanamide were released from PERLKA after one hour of incubation.
The ratio [CYextractPERLKA/CYaddedPERLKA] increased to a maximum of 47 % after one day.
Subsequently Then the ratio [CYextractPERLKA/CYaddedPERLKA] decreased slowly until day 20.
The rate constants were calculated as:
RefeSol 01-A (10 % soil moisture):
k1 (degradation of cyanamide): 0.72655
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 1.1632
thus, resulting in
DT50 cyanamide: 0.95 days
DT50 PERLKA: 0.60 days
Recovery of Cyanamide in RefeSol 01-A, 5 % soil moisture, 20 °C (see Figure 2)
k1 (degradation of cyanamide): 0.8450
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.5718
thus, resulting in
DT50 cyanamide: 0.82 days
DT50 PERLKA: 1.21 days
Recovery of Cyanamide in RefeSol 02-A, 21 % soil moisture, 12 °C (see Figure 3)
k1 (degradation of cyanamide): 0.6026
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.7944
thus, resulting in
DT50 cyanamide: 1.15 days
DT50 PERLKA: 0.87 days
Recovery of Cyanamide in RefeSol 02-A, 10.4 % soil moisture, 12 °C (see Figure 4)
k1 (degradation of cyanamide): 0.6533
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.4241
thus, resulting in
DT50 cyanamide: 1.06 days
DT50 PERLKA: 1.63 days
Recovery of Cyanamide in RefeSol 06-A, 32 % soil moisture, 20 °C (see Figure 5)
k1 (degradation of cyanamide): 1,2569
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.2811
thus, resulting in
DT50 cyanamide: 0.55 days
DT50 PERLKA: 2.47 days
Recovery of Cyanamide in RefeSol 06-A, 16 % soil moisture, 20 °C (see Figure 6)
k1 (degradation of cyanamide): 1.6389
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.5662
thus, resulting in
DT50 cyanamide: 0.42 days
DT50 PERLKA: 2.51 days
Recovery of Cyanamide in Dugliolo di Budrio, 18 % soil moisture, 20 °C (see Figure 7)
k1 (degradation of cyanamide): 0.8830
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.4241
thus, resulting in
DT50 cyanamide: 0.79 days
DT50 PERLKA: 1.63 days
Recovery of Cyanamide in Dugliolo di Budrio, 9 % soil moisture, 20 °C (see Figure 8)
k1 (degradation of cyanamide): 0.5744
k2 (degradation of calcium cyanamide (PERLKA) to cyanamide): 0.4293
thus, resulting in
DT50 cyanamide: 1.21 days
DT50 PERLKA: 1.61 days
Determination of secondary transformation products:
the amounts of free cyanamide (from the extraction with diethyl ether) and the secondary transformation products (from extraction with H2O) are described as recovery of total applied nitrogen (as Cyanamid F1000 or PERLKA).
- In the samples treated with Cyanamid F1000 only urea and ammonia could be observed in significant quantities. The amount of urea increased up to about 25 % until day two and then a decrease close to zero was observed until day 14. Ammonia increased slowly until day seven to about 17 % and remained on this level until the end of the experiment. The observed concentration for DCD, nitrate and nitrite were below 1 % of applied nitrogen.
- In the samples treated with PERLKA only nitrite was observed in concentrations below 1 % of applied nitrogen. The amount of urea increased up to about 15 % until day seven and then a slow decrease was observed to about 2 % until day 20. Also, DCD increased until day seven up to 20 %, remained on this level until days 14 and decreased then to 17 %. Ammonia increased slowly until the end of the experiment to about 19 %. Nitrate was determined with an amount of a 9 to 10 % of applied nitrogen which corresponds with the amount of nitrogen in PERLKA.
This study provides the basic rate constants and DT50 values in different soils for the degradation of cyanamide (Cyanamid F1000) and for the degradation of calcium cyanamide (PERLKA) to cyanamide. In this report the results for the soil types RefeSol 01-A, RefeSol 02-A, RefeSol 06-A and Dugliolo di Budrio which correspond to the soil types of the FOCUS scenarios R2, R1, R3 and R4, respectively are presented. According to Scenario R1 the test with RefeSol 02-A was performed at 12 °C ± 2 °C. For the tests with types RefeSol 01-A, RefeSol 06-A and Dugliolo di Budrio (corresponding to the scenarios R2, R3 and R4) the temperature during incubation was 20 °C ± 2 °C.
The transformation from cyanamide to secondary transformation products depend on the tested material. Whereas for Cyanamid F1000 only urea and ammonia in larger amounts could be detected, for PERLKA also nitrate and DCD were determined. The observed nitrate is not a transformation product but represents the original amount of nitrate in PERLKA. The observations on the amounts of transformation products were comparable to former study results (e. g. Vilsmeier & Amberger, 1978). - Results with reference substance:
- See details on results.
- Conclusions:
- The basic rate constants and DT50 values in four different soils for the degradation of cyanamide and for the degradation of calcium cyanamide (PERLKA) to cyanamide were determined.
The soils used in the experiment correspond to the soil types of the FOCUS scenarios R1 to R4. - Executive summary:
Upon contact with water calcium cyanamide is fast transformed to cyanamide. Calcium cyanamide is the main component of the fertiliser product PERLKA. To determine the rate constants and DT50 values for the release of cyanamide from PERLKA and the subsequent degradation of cyanamide, an experimental study was conducted. PERLKA was incorporated in four different soils as granulate at different soil moisture (50 % and 25 % of maximum water holding capacity) and temperatures (20 °C, 12 °C).
Samples were taken after1 h of incubation and at day 1, 2, 3, 6, 9, 13 and 20, and extracted with diethyl ether. The cyanamide content was determined photometrically after transfer in an aqueous solution. The derived half-lives are summarized below:
Soil
Focus Scenario
% of WHC
DT50 cyanamide
DT50 calcium cyanamide
RefeSol 02-A*
R1
50
1.15
0.87
25
1.06
1.63
RefeSol 01-A
R2
50
0.95
0.60
25
0.82
1.21
RefeSol 06-A
R3
50
0.55
2.47
25
0.42
2.51
Dugliolo di Budrio
R4
50
0.79
1.63
25
1.21
1.61
Additionally, for one soil the content of the secondary transformation products of cyanamide, dicyandiamide (DCD), urea (CH4N2O), nitrate (NO3-), nitrite (NO2-) and ammonia (NH4+), at different sampling points was determined. In this additional experiment, the soil was treated with PERLKA respectively Cyanamid F1000 as described above but the extraction was always performed with deionised water. Urea, nitrate, nitrite and ammonia were determined by using ion chromatography, DCD by LC-MS/MS.
The transformation from cyanamide to secondary transformation products depend on the tested material. Whereas for Cyanamid F1000 only urea and ammonia in larger amounts could be detected, for PERLKA also nitrate and DCD were determined. The observed nitrate is not a transformation product but represents the original amount of nitrate in PERLKA. The observations on the amounts of transformation products were comparable to former study results (e. g. Vilsmeier & Amberger, 1978).
Reference: Vilsmeier, K.; Amberger, A. (1978): Modellversuche zum Umsatz von gemahlenen Kalkstickstoff und Perlkalkstickstoff in Abhängigkeit von Bodenfeuchtigkeit und Applikationsform. In: Z. Acker- und Pflanzenbau 147, S. 68–77.
- Endpoint:
- biodegradation in soil: simulation testing
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- 1990-1991
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- other: EPA Pesticide Assessment Guidelines, Subdivision N, Section 162-1, Aerobic soil metabolism studies, October 1982
- Deviations:
- no
- GLP compliance:
- yes
- Test type:
- laboratory
- Radiolabelling:
- yes
- Oxygen conditions:
- aerobic
- Soil classification:
- not specified
- Soil no.:
- #1
- Soil type:
- sandy loam
- % Clay:
- 18
- % Silt:
- 26
- % Sand:
- 56
- % Org. C:
- 1.6
- pH:
- 6.8
- CEC:
- 11.6 meq/100 g soil d.w.
- Bulk density (g/cm³):
- 1.51
- Details on soil characteristics:
- The aerobic soil metabolism of [14C]-cyanamide was investigated in air-dried sandy loam soil collected from land located near Ashland, Nebraska, USA. Soil characteristics are listed in the above table. Additional characteristics:
Microbial activity: bacteria/fungal (colonies/g):
Day 0-control: 1.42 x 10E7 / 1.29 x 10E7
Day 0-test: 1.15 x 10E7 / 6.17 x 10E6 - Soil No.:
- #1
- Duration:
- 14 d
- Soil No.:
- #1
- Initial conc.:
- 33 mg/kg soil d.w.
- Based on:
- act. ingr.
- Parameter followed for biodegradation estimation:
- CO2 evolution
- radiochem. meas.
- test mat. analysis
- Soil No.:
- #1
- Temp.:
- 25 ± 1 °C
- Humidity:
- 75% of field capacity
- Microbial biomass:
- At day 0- control: 1.42 x 10E7 / 1.29 x 10E7. At day 0-test: 1.15 x 10E7 / 6.17 x 10E6
- Details on experimental conditions:
- - A preliminary test was performed in order to provide optimum experimental conditions for the definitive aerobic metabolism study. Therefore, the objectives of the preliminary study were to provide information on the rate of degradation of [14C]-cyanamide, on formation of volatile degradation products and on efficiency of extraction and TLC/HPLC methods. The conclusions drawn from the preliminary study were: The half-life of [14C]-cyanamide is short (approximately 0.5 days), requiring frequent sampling at the early stages of the study for an adequate evaluation of the degradation kinetics. The parent compound is nearly completely degraded to [14CO2] in a short period of time (approximately 7 days) requiring sufficient KOH traps.
Considering the results of the preliminary studies the definitive study was conducted as follows:
- The aerobic soil metabolism of [14C]-cyanamide was investigated in air-dried sandy loam soil collected from land located near Ashland, Nebraska, USA
- [14C]-cyanamide was dissolved in methanol (2.11 mg as/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 30 mg of non-radiolabelled cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 5.11 mg as/mL
- On the experimental start date 65 µL of the test solution were applied to 10 g dry weight of soil to give nominal concentrations of 33 mg as/kg soil (equivalent to 24.75 kg as/ha assuming incorporation into the top 5 cm).
- Soil samples were incubated under aerobic conditions in the dark at 25 ± 1 °C at a soil moisture content of 75 % of field capacity for up to 14 days
- Provisions were made for the trapping of organic volatiles and 14CO2 by the installation of a series of trapping solutions: ethylene glycol, 1N H3PO4, 2 x 5 N KOH
- Samples were taken immediately after application and after 4 h, 8 h, 24 h, 36 h, 3 d, 5 d, 7 d and 14 d. The microbial activity of the soil was measured at the beginning of the study. - Soil No.:
- #1
- % Recovery:
- 100
- Remarks on result:
- other: The total recovery ranged from 97.8 % to 108 % of initial measured dose (IMD).
- Key result
- Soil No.:
- #1
- % Degr.:
- 99.05
- Parameter:
- test mat. analysis
- Sampling time:
- 14 d
- Key result
- Soil No.:
- #1
- DT50:
- 1.26 d
- Type:
- (pseudo-)first order (= half-life)
- Temp.:
- 25 °C
- Soil No.:
- #1
- DT50:
- 1.94 d
- Type:
- other: DT90
- Temp.:
- 25 °C
- Transformation products:
- yes
- No.:
- #1
- Details on transformation products:
- TLC analysis of the soil extracts revealed the presence of cyanamide and one degradation product, which was identified as dicyandiamide. Dicyandiamide accounting for 0.431 % of applied radioactivity at maximum. Dicyandiamide decreased from 0.431 % at day 0 to 0.032 % at day 14.
- Evaporation of parent compound:
- no
- Volatile metabolites:
- yes
- Residues:
- yes
- Details on results:
- Material balance: The total recovery ranged from 97.8 % to 108 % of initial measured dose (IMD) with a mean recovery of 101 % of IMD. Extractable residues decreased from 96.7 % of IMD immediately after application to 0.37 % at day 14. Unextractable (bound) residues increased from 3.39 % of IMD at day 0 to 5.64 % at day 14. Cumulative volatile residues increased to 97.1 % of IMD at day 14. The majority (94.6 % of IMD) was identified as [14CO2] by precipitation with BaCl2. Radioactivity observed in the H3PO4 and ethylene glycol traps accounted for < 0.1 % and 2.63 % of IMD, respectively.
Principal degradation products: TLC analysis of the soil extracts revealed the presence of cyanamide and one degradation product, which was identified as dicyandiamide. Cyanamide decreased from 92.5 % of IMD at day 0 to 0.051 % at 14 days. Dicyandiamide decreased from 0.431 % at day 0 to 0.032 % at day 14.
DT50 and DT90 values: The degradation of cyanamide in a sandy loam soil was best described by first order degradation kinetics. The DT50 value was calculated to be 1.26 days. The DT90 value was not calculated within the report, but the data given in the report was taken to calculate the DT90 during the dossier compilation using the model ModelManager. The DT90 value of cyanamide was calculated to be 1.94 days assuming first order degradation kinetics. - Results with reference substance:
- No reference substance
- Conclusions:
- The primary aerobic pathway by which the parent compound disappears from soil is the final degradation to [14CO2] (complete mineralization). This fraction accounted for approximately 94.6 % of applied radioactivity after 14 days. The half-life of cyanamide was calculated using a first order kinetic and was found to be 1.26 days. The calculated time to 90 % degradation was 1.94 days. One minor degradation product was identified as dicyandiamide accounting for 0.431 % of applied radioactivity at maximum.
Due to the extensive mineralization and the low plateau of bound residues (< 10 %) cyanamide can be classified as low persistent (category I) according to the classification scheme of Beek et al. 2001. - Executive summary:
Considering the results of the preliminary studies the definitive study was conducted as follows: The aerobic soil metabolism of [14C]-cyanamide was investigated in air-dried sandy loam soil collected from land located near Ashland, Nebraska, USA. [14C]-cyanamide was dissolved in methanol (2.11 mg as/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 30 mg of non-radiolabelled cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 5.11 mg as/mL. On the experimental start date 65 µL of the test solution were applied to 10 g dry weight of soil to give nominal concentrations of 33 mg as/kg soil (equivalent to 24.75 kg as/ha assuming incorporation into the top 5 cm). Soil samples were incubated under aerobic conditions in the dark at 25 ± 1 °C at a soil moisture content of 75 % of field capacity for up to 14 days. Provisions were made for the trapping of organic volatiles and 14CO2 by the installation of a series of trapping solutions: ethylene glycol, 1N H3PO4, 2 x 5 N KOH. Samples were taken immediately after application and after 4 h, 8 h, 24 h, 36 h, 3 d, 5 d, 7 d and 14 d. The microbial activity of the soil was measured at the beginning of the study.
Soil samples were extracted three times with methanol:water (10 mL of 80:20, v/v). After each addition of extraction solvent the soils were mechanically shaken for one hour. The extracts were combined and aliquots taken for LSC analysis and reverse phase thin layer chromatography (TLC). Transformation products were identified by co-chromatography with authentic standards. Extracted soil samples were combusted to determine levels of unextractable residues. Radioactivity in the KOH was confirmed to be CO2 by precipitation as BaCO3. Radioactivity in the trapping solutions was quantified by LSC.
The rate of degradation of cyanamide in soil was determined using linear regression assuming first-order reaction kinetics. The primary aerobic pathway by which the parent compound disappears from soil is the final degradation to [14CO2] (complete mineralization). This fraction accounted for approximately 94.6 % of applied radioactivity after 14 days. The half-life of cyanamide was calculated using a first order kinetic and was found to be 1.26 days. The calculated time to 90 % degradation was 1.94 days. One minor degradation product was identified as dicyandiamide accounting for 0.431 % of applied radioactivity at maximum.
Due to the extensive mineralization and the low plateau of bound residues (< 10 %) cyanamide can be classified as low persistent (category I) according to the classification scheme of Beek et al. 2001.
- Endpoint:
- biodegradation in soil: simulation testing
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- 1990-1991
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- other: EPA Pesticide Assessment Guidelines, Subdivision N, Section 162-2, Anaerobic soil metabolism studies, October 1982
- Deviations:
- no
- GLP compliance:
- yes
- Test type:
- laboratory
- Radiolabelling:
- yes
- Oxygen conditions:
- anaerobic
- Soil classification:
- not specified
- Soil no.:
- #1
- Soil type:
- sandy loam
- % Clay:
- 18
- % Silt:
- 26
- % Sand:
- 56
- % Org. C:
- 1.6
- pH:
- 6.8
- CEC:
- 11.6 meq/100 g soil d.w.
- Bulk density (g/cm³):
- 1.51
- Details on soil characteristics:
- The aerobic soil metabolism of [14C]-cyanamide was investigated in air-dried sandy loam soil collected from land located near Ashland, Nebraska, USA. Soil characteristics are listed in the above table. Additional characteristics:
Microbial activity: bacteria/fungal (colonies/g):
Day 0-control: 1.20 x 10E7 / 1.70 x 10E4
Day 0-test: 3.60 x 10E7 / 1.00 x 10E4 - Soil No.:
- #1
- Duration:
- 60 d
- Soil No.:
- #1
- Initial conc.:
- 33 mg/kg soil d.w.
- Based on:
- act. ingr.
- Parameter followed for biodegradation estimation:
- CO2 evolution
- radiochem. meas.
- test mat. analysis
- Soil No.:
- #1
- Temp.:
- 25 ± 1 °C
- Humidity:
- 75% of field capacity
- Microbial biomass:
- At day 0- control: 1.20 x 10E7 / 1.70 x 10E4. At day 0-test: 3.60 x 10E7 / 1.00 x 10E4
- Details on experimental conditions:
- - A preliminary test was performed in order to provide optimum experimental conditions for the definitive anaerobic metabolism study. Therefore, the objectives of the preliminary study were to provide information on the rate of degradation of [14C]-cyanamide, on formation of volatile degradation products and on efficiency of extraction and TLC/HPLC methods. The most important conclusion drawn from the preliminary study was: The half-life of [14C]-cyanamide is short (approximately 0.5 days). The half-life of 0.5 days was used as the point at which the definitive samples were flooded to establish anaerobic conditions.
Considering the results of the preliminary studies the definitive study was conducted as follows:
- The anaerobic soil metabolism of [14C]-cyanamide was investigated in the same soil used in the aerobic soil metabolism study (see table below in "Any other information on materials and methods incl. tables". The microbial activity of the soil was measured at the beginning of the study
- [14C]-cyanamide was dissolved in methanol (2.11 mg as/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 30 mg of non-radiolabelled cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 5.11 mg as/mL. On the experimental start date 65 µL of the test solution were applied to 10 g dry weight of soil to give nominal concentrations of 33 mg as/kg soil (equivalent to 24.75 kg as/ha assuming incorporation into the top 5 cm)
- After 12 hours of aerobic incubation in darkness at 25 ± 1 °C at a soil moisture content of 75 % of field capacity the soil samples were flooded with 30 mL of well water. A 1 % glucose amendment (0.1 g) was added to ensure a substrate for anaerobic bacteria and the flask atmosphere was replaced by nitrogen. Samples were incubated under anaerobic conditions in the dark at 25 ± 1 °C for 60 days
- Provisions were made for the trapping of organic volatiles and [14CO2] by the installation of a series of trapping solutions: ethylene glycol, 1N H3PO4, 2 x 5 N KOH
- Samples were analysed immediately after application and after 6 hours and 12 hours of aerobic incubation. Subsequently, samples were analysed after 15, 30, 45 and 60 days of anaerobic incubation.
- Soil No.:
- #1
- % Recovery:
- 97.8
- Remarks on result:
- other: The % recovery indicated above is the mean recovery. The total recovery ranged from 87.2 % to 102 % of initial measured dose (IMD).
- Key result
- Soil No.:
- #1
- % Degr.:
- 86.5
- Parameter:
- test mat. analysis
- Sampling time:
- 60 d
- Soil No.:
- #1
- DT50:
- 0.52 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: The DT50 value under aerobic conditions.
- Soil No.:
- #1
- DT50:
- 34.7
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: The DT50 value under anaerobic conditions
- Soil No.:
- #1
- DT50:
- 105
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: The DT90 value under anaerobic conditions.
- Transformation products:
- yes
- No.:
- #1
- No.:
- #2
- No.:
- #3
- No.:
- #3
- No.:
- #4
- Details on transformation products:
- TLC analysis of the soil extracts revealed the presence of cyanamide and four degradation products, which were identified as dicyandiamide, guanylurea, guanidine and urea.
Dicyandiamide decreased from 4.53 % at day 0 to 3.52 % after 12 hours of aerobic conditions, then increased to 5.72 % after 60 days. Guanylurea appeared after 15 days of anaerobic conditions at 4.62 % of IMD, increased to 8.06 % at day 30, then decreased to 5.59 % at 60 days. Guanidine and urea were also first detected after 15 days of anaerobic conditions at 0.25 % and 0.29 % of IMD, respectively, and increased to 2.74 % and 1.39 % after 60 days, respectively. - Evaporation of parent compound:
- no
- Volatile metabolites:
- yes
- Residues:
- yes
- Details on results:
- Material balance: The total recovery ranged from 87.2 % to 102 % of initial measured dose (IMD) with a mean recovery of 97.8 % of IMD. Extractable residues decreased from 96.7 % of IMD immediately after application to 63.4 % after 12 hours of aerobic incubation, and to 4.31 % after 60 days of anaerobic conditions. Residues in the test water decreased from 37.6 % of IMD at day 15 to 27.2 % after 60 days. Unextractable (bound) residues increased from 3.30 % of IMD at day 0 to 6.93 % at day 60 with a maximum value of 9.55 % after 12 hours of aerobic conditions. Cumulative volatile residues increased to 23.7 % of IMD after 12 hours of aerobic conditions, and to 54.5 % of IMD after 60 days of anaerobic conditions. The majority (53.1 % of IMD) was identified as [14CO2] by precipitation with BaCL2. Radioactivity observed in the H3PO4 and ethylene glycol traps accounted for up to < 0.2 % and 1.29 % of IMD, respectively.
Principal degradation products: TLC analysis of the soil extracts revealed the presence of cyanamide and four degradation products, which were identified as dicyandiamide, guanylurea, guanidine and urea . Cyanamide decreased from 88.03 % of IMD at day 0 to 43.1 % after 12 hours of aerobic conditions, and to 13.5 % after 60 days of anaerobic conditions. Dicyandiamide decreased from 4.53 % at day 0 to 3.52 % after 12 hours of aerobic conditions, then increased to 5.72 % after 60 days. Guanylurea appeared after 15 days of anaerobic conditions at 4.62 % of IMD, increased to 8.06 % at day 30, then decreased to 5.59 % at 60 days. Guanidine and urea were also first detected after 15 days of anaerobic conditions at 0.25 % and 0.29 % of IMD, respectively, and increased to 2.74 % and 1.39 % after 60 days, respectively.
DT50 and DT90 values: The degradation of cyanamide in soil both under aerobic and anaerobic conditions was best described by first order degradation kinetics. Cyanamide was found to degrade rapidly under aerobic soil conditions, but relatively slow under anaerobic soil conditions. The DT50 value under aerobic conditions was calculated to be 0.517 days and the DT50 value under anaerobic conditions was calculated to be 34.7 days. The DT90 value was not calculated within the report, but the data given in the report was taken to calculate the DT90 during the dossier compilation using the model Model-Manager. The DT90 value of cyanamide under anaerobic conditions was calculated to be approximately 105 days assuming first order degradation kinetics.
Additional work represented in the supplemental report.
Iron content: The iron content of the test soil was determined because the degradation of cyanamide is assumed to be sensitive to the iron content of soils. The iron content of the soil was found to be 10.751 ppm total iron, and 32.4 ppm DTPA extractable iron. While the iron content of soil is not the only factor in determining the soil degradation of cyanamide, comparisons can be made among soils using the obtained data to determine if the iron content is responsible for differences in observed reaction rates.
Non-extractable residues: The test soils in the definitive study were initially extracted with methanol:water (80:20, v:v). Following this extraction, bound residue level increased from 3.30 % of IMD at day 0 to 9.55 % at 12 hours (aerobic phase), then decreased to 6.93 % at day 60 of the anaerobic phase. Supplemental extractions with hexane and 0.005 M phosphate buffer (pH 4) were performed to determine the identity of the non-extractable residues. No additional residues were extracted with hexane. This is not surprising, due to the fact that cyanamide and its degradation products are very well water soluble, are relatively polar, and have limited solubility in hydrocarbon solvents. An additional 2 - 5 % of IMD was extracted with the phosphate buffer. Characterisation of the extracted radioactivity by TLC revealed it to be residues of cyanamide and guanylurea.
Volatile residues: The phosphoric acid and ethylene glycol trapping solutions were analysed by TLC, and the radioactivity was determined to represent residues of the parent compound. LC/MS analysis confirmed the presence of dicyandiamide, guanylurea, guanidine and urea in the selected water sample (day 30 of the anaerobic phase) and thus confirms the results previously obtained by TLC. - Results with reference substance:
- No reference substance
- Conclusions:
- Cyanamide seems to undergo a rapid degradation under aerobic soil conditions, with conversion to CO2. The degradation was slower under anaerobic conditions (DT50anaerobic = 34.7 days), and mineralization did not occur to the same extent as under aerobic conditions. Four minor degradation products occurred and were identified as dicyandiamide, guanylurea, guanidine and urea. None of the degradation products exceeded the trigger value of 10 % of applied radioactivity. Guanylurea was found with 7.5 % of TAR at maximum value.
Regarding anaerobic conditions, cyanamide can be classified as moderately persistent (category II) according to the classification scheme of Beek et al. (2001). - Executive summary:
Following a preliminary test an anaerobic soil metabolism of [14C]-cyanamide was investigated in a Sandy loam soil (same soil used in the aerobic soil metabolism study). On the experimental start date 65 µL of the prepared radiolabled test solution were applied to 10 g dry weight of soil to give nominal concentrations of 33 mg as/kg soil (equivalent to 24.75 kg as/ha assuming incorporation into the top 5 cm). After 12 hours of aerobic incubation in darkness at 25 ± 1 °C at a soil moisture content of 75 % of field capacity the soil samples were flooded with 30 mL of well water. A 1 % glucose amendment (0.1 g) was added to ensure a substrate for anaerobic bacteria and the flask atmosphere was replaced by nitrogen. Samples were incubated under anaerobic conditions in the dark at 25 ± 1 °C for 60 days. Provisions were made for the trapping of organic volatiles and [14CO2] by the installation of a series of trapping solutions: ethylene glycol, 1N H3PO4, 2 x 5 N KOH. Samples were analysed immediately after application and after 6 hours and 12 hours of aerobic incubation. Subsequently, samples were analysed after 15, 30, 45 and 60 days of anaerobic incubation. Flood water from the anaerobic samples was separated from the soil prior to initiation of extraction. Soil samples were extracted three times with methanol : water (10 mL of 80:20, v/v). Extractions were subjected to LSC and TLC analysis. Radioactivity in the KOH was confirmed to be CO2 by precipitation as BaCO3. Radioactivity in the trapping solutions was quantified by LSC. The rate of degradation of cyanamide in soil was determined using linear regression assuming first-order reaction kinetics.
Cyanamide undergoes rapid degradation under aerobic soil conditions with conversion to CO2. A DT50aerobic was calculated although the aerobic phase of the study was only 12 h and only 3 data points were used for the calculation (for a sound regression analysis in calculating DT50, at least 5 sampling times are required including zero time). However, the figure confirms the rapid aerobic biodegradation of cyanamide.
Cyanamide decreased from 88.03 % of IMD at day 0 to 43.1 % after 12 hours of aerobic conditions, and to 13.5 % after 60 days of anaerobic conditions. The degradation was slower under anaerobic conditions (DT50anaerobic = 34.7 days), and mineralization (conversion to CO2) did not occur to the same extent as under aerobic conditions. The obtained calculated DT90anerobic was 105 days. Cumulative volatile residues increased to 23.7 % of IMD after 12 hours of aerobic conditions, and to 54.5 % of IMD after 60 days of anaerobic conditions. The majority (53.1 % of IMD) was identified as [14CO2] by precipitation with BaCL2.
Four minor degradation products occurred and were identified as dicyandiamide, guanylurea, guanidine and urea. None of the degradation products exceeded the trigger value of 10 % of applied radioactivity. Guanylurea was found with 7.5 % of TAR at maximum value.
Regarding anaerobic conditions, cyanamide can be classified as moderately persistent (category II) according to the classification scheme of Beek et al. (2001).
- Endpoint:
- biodegradation in soil: simulation testing
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- 1978
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- other: BBA-Merkblatt Nr. 36, 2. Auflage, Juni 1976 (Unterlagen zum Verhalten von Pflanzenbehandlungsmitteln im Boden im Rahmen des Zulassungsverfahrens)
- Deviations:
- no
- GLP compliance:
- no
- Remarks:
- study was conducted prior to the implementation of GLP
- Test type:
- laboratory
- Radiolabelling:
- no
- Oxygen conditions:
- aerobic
- Soil classification:
- not specified
- Soil no.:
- #1
- Soil type:
- loamy sand
- % Clay:
- 8.8
- % Silt:
- 42.9
- % Sand:
- 48.3
- % Org. C:
- 2.19
- pH:
- 5.6
- CEC:
- 8.4 other: mval/100 g
- Soil no.:
- #2
- Soil type:
- loamy sand
- % Clay:
- 10.6
- % Silt:
- 50.5
- % Sand:
- 38.9
- % Org. C:
- 1.1
- pH:
- 7.2
- CEC:
- 8.2 other: mval/100 g
- Soil no.:
- #3
- Soil type:
- sand
- % Clay:
- 5.5
- % Silt:
- 36.3
- % Sand:
- 58.2
- % Org. C:
- 0.48
- pH:
- 6.5
- CEC:
- 4 other: mval/100 g
- Details on soil characteristics:
- 3 kind of soils were obtained at LUFA Speyer: a loamy sand with high organic matter content, a loamy sand with low organic matter content, and a sand. Soil characteristics are listed in the above field.
- Soil No.:
- #1
- Duration:
- 14 d
- Soil No.:
- #2
- Duration:
- 14 d
- Soil No.:
- #3
- Duration:
- 14 d
- Soil No.:
- #1
- Initial conc.:
- 0.173 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #1
- Initial conc.:
- 0.346 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #1
- Initial conc.:
- 0.52 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #2
- Initial conc.:
- 0.173 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #2
- Initial conc.:
- 0.346 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #2
- Initial conc.:
- 0.52 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #3
- Initial conc.:
- 0.173 g/kg soil d.w.
- Based on:
- act. ingr.
- Soil No.:
- #3
- Initial conc.:
- 0.52 g/kg soil d.w.
- Based on:
- act. ingr.
- Parameter followed for biodegradation estimation:
- test mat. analysis
- Soil No.:
- #1
- Temp.:
- 20 ± 2°C
- Humidity:
- 40 % of the maximum water capacity.
- Soil No.:
- #2
- Temp.:
- 20 ± 2°C
- Humidity:
- 40 % of the maximum water capacity.
- Soil No.:
- #3
- Temp.:
- 20 ± 2°C
- Humidity:
- 40 % of the maximum water capacity.
- Details on experimental conditions:
- The air dried soils were re-moistened to 40 % maximum water holding capacity. ALZODEF ® was applied to each soil at three different concentrations: (1) 0.5 l ALZODEF/m³ soil, (2) 1.0 l ALZODEF/m³ soil, and (3) 1.5 l ALZODEF/m³ soil corresponding to nominal concentrations of 0.173 g ai/kg soil, 0.346 g ai/kg soil and 0.52 g ai/kg soil. These application rates are equivalent to field application rates of ca 130 kg ai/ha, ca 260 kg ai/ha, and ca 390 kg ai/ha, respectively, assuming incorporation into the top 5 cm and a soil bulk density of 1.5 g/kg. Soil samples were incubated for up to 14 days. Incubation conditions were not specified, but it was stated that the test was performed in all details according to the guideline. Thus, it can be assumed that the soil samples were incubated under aerobic conditions in the dark at 20 +/- 2°C at a soil moisture content of 40 % of the maximum water capacity.
- Soil No.:
- #1
- DT50:
- 1 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In Loamy sand with high organic carbon content applied with 0.5 l ALZODEF/m³.
- Soil No.:
- #1
- DT50:
- 1 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: Loamy sand with high organic carbon content, applied with 1.0 l ALZODEF/m³.
- Soil No.:
- #1
- DT50:
- 3 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In Loamy sand with high organic carbon content, applied with 1.5 l ALZODEF/m³.
- Soil No.:
- #2
- DT50:
- 2 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: Loamy sand with low organic carbon content, applied with 0.5 l ALZODEF/m³.
- Soil No.:
- #2
- DT50:
- 3 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In Loamy sand with low organic carbon content, applied with 1.0 l ALZODEF/m³.
- Soil No.:
- #2
- DT50:
- 3 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In Loamy sand with low organic carbon content, applied with 1.5 l ALZODEF/m³.
- Soil No.:
- #3
- DT50:
- 6 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In sand, applied with 0.5 l ALZODEF/m³.
- Soil No.:
- #3
- DT50:
- 12 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In sand, applied with 1.0 l ALZODEF/m³.
- Key result
- Soil No.:
- #3
- DT50:
- 12 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: In sand, applied with 1.5 l ALZODEF/m³.
- Transformation products:
- not specified
- No.:
- #1
- Evaporation of parent compound:
- not measured
- Volatile metabolites:
- not measured
- Residues:
- not specified
- Details on results:
- DT50 and DT90 values: On the basis of the cyanamide concentrations in soil at various time points after application regression curves were fitted and the DT50 values were calculated from the regression curves using a graphical estimation method. The DT50 values of the two loamy sand soils were in a range from 1 to 3 days. These results were in good agreement with the values obtained in the aerobic soil metabolism study and during the aerobic phase of the anaerobic soil metabolism study where the DT50 values ranged from 0.517 to 1.26 days. Only in the sand soil with a very low organic carbon content the DT50 values ranged from 6 to 12 days.
The degradation of cyanamide was slower in the soil samples receiving the high application rates of 1.0 and 1.5 l ALZODEF/m³ than in the soil samples receiving the lowest application rate of 0.5 l ALZODEF/m³ indicating a dependence of the degradation rate from the application rate.
- Results with reference substance:
- no reference substance
- Conclusions:
- The DT50 values of cyanamide ranged from 1 to 3 days in two loamy sand soils with different organic carbon content and from 6-12 days in a sand soil with a very low organic carbon content. The results show that the degradation of cyanamide in soil is influenced by the organic carbon content indicating that the biotic degradation prevails in soils. Furthermore, the degradation rate of cyanamide in the test soils depended on the application rate with a faster degradation observed in the test soils receiving the lowest application rate.
- Executive summary:
The rate of degradation of cyanamide, applied as formulated product ALZODEF, was investigated in 3 additional soils which were obtained at LUFA Speyer: a loamy sand with high organic matter content, a loamy sand with low organic matter content, and a sand. ALZODEF ® was applied to each soil at three different concentrations: (1) 0.5 l ALZODEF/m³ soil, (2) 1.0 l ALZODEF/m³ soil, and (3) 1.5 l ALZODEF/m³ soil corresponding to nominal concentrations of 0.173 g ai/kg soil, 0.346 g ai/kg soil and 0.52 g ai/kg soil. These application rates are equivalent to field application rates of ca 130 kg ai/ha, ca 260 kg ai/ha, and ca 390 kg ai/ha, respectively, assuming incorporation into the top 5 cm and a soil bulk density of 1.5 g/cm³. Soil samples were incubated for up to 14 days under aerobic conditions in the dark at 20 2°C at a soil moisture content of 40 % of the maximum water capacity. Soil samples were extracted three times with 0.1 N hydrochloric acid (HCl) (30 g soil with 100 mL acid). Afterwards the extracts were adjusted to pH 7 using NaOH and analysed by TLC and a spectrophotometrical method.
On the basis of the cyanamide concentrations in soil at various time points after application regression curves were fitted and the DT50 values were calculated from the regression curves using a graphical estimation method. The DT50 values of the two loamy sand soils were in a range from 1 to 3 days. These results were in good agreement with the values obtained in the aerobic soil metabolism study and during the aerobic phase of the anaerobic soil metabolism study where the DT50 values ranged from 0.517 to 1.26 days. Only in the sand soil with a very low organic carbon content the DT50 values ranged from 6 to 12 days.
The degradation of cyanamide was slower in the soil samples receiving the high application rates of 1.0 and 1.5 l ALZODEF/m³ than in the soil samples receiving the lowest application rate of 0.5 l ALZODEF/m³ indicating a dependence of the degradation rate from the application rate.
The results show that the degradation of cyanamide in soil is influenced by the organic carbon content indicating that the biotic degradation prevails in soils. Furthermore, the degradation rate of cyanamide in the test soils depended on the application rate with a faster degradation observed in the test soils receiving the lowest application rate.
Referenceopen allclose all
Table: Temperature normalisation of DT50 values of cyanamide to reference conditions (20 °C)
| Name | Reference | Soil type | exp. temperature (°C) | exp. soil moisture* | DT50 at study conditions (days) | Normalisation factor | DT50 after normalisation to 20 °C (days) |
| Refesol 01-A | Güthner (2018) | Loamy sand | 12 | 10% | 2.2 | 0.532 | 1.17 |
| Refesol 01-A | Güthner (2018) | Loamy sand | 12 | 5% | 1.3 | 0.532 | 0.69 |
| Refesol 01-A | Weinfurtner (2019) | Loamy sand | 20 | 10% | 0.95 | 1.000 | 0.95 |
| Refesol 01-A | Weinfurtner (2019) | Loamy sand | 20 | 5% | 0.82 | 1.000 | 0.82 |
| Refesol 02-A | Weinfurtner (2019) | Silt loam | 12 | 21% | 1.15 | 0.532 | 0.61 |
| Refesol 02-A | Weinfurtner (2019) | Silt loam | 12 | 10.40% | 1.06 | 0.532 | 0.56 |
| Refesol 06-A | Weinfurtner (2019) | Silty clay | 20 | 16% | 0.42 | 1.000 | 0.42 |
| Refesol 06-A | Weinfurtner (2019) | Silty clay | 20 | 32% | 0.55 | 1.000 | 0.55 |
| Dugliolo di Budrio | Weinfurtner (2019) | Silt loam | 20 | 9.10% | 1.21 | 1.000 | 1.21 |
| Dugliolo di Budrio | Weinfurtner (2019) | Silt loam | 0.2 | 18% | 0.79 | 1.000 | 0.79 |
| Ashland | EFSA (2010) | Loamy sand | 20 | - | 0.7 | 1.000 | 0.70 |
| SP 257 | EFSA (2010) | Loamy sand | 20 | - | 0.96 | 1.000 | 0.96 |
| SP 357 | EFSA (2010) | Loamy sand | 20 | - | 1.24 | 1.000 | 1.24 |
| Geometric mean | 0.95 | 0.78 | |||||
* this information was not considered for the normalisation
Interpretation of the results:
The two main experiments show the following effects:
• The decomposition curves show certain fluctuations, which i.a. based on the processing of individual samples per sampling point. The soil samples contain only a few PERLKA granules, variations in the composition (i.e., recovery value) cannot be excluded.
• The release of cyanamide from PERLKA granules is retarded.
• The cyanamide content in reference samples decrease exponentially. At 5 % soil moisture cyanamide degradation is faster under the given experimental conditions than at 10 % soil moisture.
• Cyanamide from PERLKA granules is slowly released, the maximum concentration is reached in both main experiments after about 2 days. At 10 % soil moisture, the maximum amount of free cyanamide is about 45 % of the total releasable amount. At 5 % soil moisture, the maximum is lowered to about 35 % due to the faster cyanamide degradation.
• The fact that the cyanamide recovery curve of PERLKA samples (granules and ground) overshoots the recovery curve of cyanamide reference samples is based on the retarded release of cyanamide from PERLKA.
Kinetic modeling:
The degradation of free cyanamide (test series x.3) was based on a simple first-order kinetic model. The cyanamide concentration should thus decrease with time t according to an exponential function, where K2 is the rate constant of cyanamide degradation:
[Cyanamide free] = [cyanamide free, zero] * exp (-K2 * t)
A logarithmic plot of cyanamide concentrations versus time should therefore be a straight line. The corresponding correlation coefficients are very good (10 % humidity) and satisfactory (5 % humidity), respectively, hence the above-mentioned assumption could be confirmed. From the slope parameters K2, a half-life for free cyanamide of 2.6 days at 10 % soil moisture or 1.9 days at 5% soil moisture can be calculated according to t1 / 2 = ln (2) / K2.See also graphic 1 (section 'Illustration').
To model the degradation of PERLKA, a more complex kinetic model was developed:
Calcium cyanamide in PERLKA is hydrolyzed to free cyanamide with a rate constant K1. The equation of first order is thus:
[CaNCN] = [CaNCN, zero] * exp (-K1 * t) (equation 1)
Normalized to 100 % recovery, i. [CaNCN, zero] = 1
[CaNCN] = exp (-K1 * t) (equation 2)
Since 1 mol of cyanamide is liberated from 1 mol of CaNCN, the normalized equation for free cyanamide is thus:
[Cyanamide liberated] = (1-exp (-K1 * t)) (equation 3)
Free cyanamide is now degraded with a second rate constant K2 (see above). The first order equation is:
[Cyanamide] = [cyanamide released] * exp (-K2 * t) (equation 4)
Equation (3) inserted in equation (4) gives our kinetic model with two parameters K1 and K2:
[Cyanamide] = (1-exp (-K1 * t)) * exp (-K2 * t) (equation 5)
This equation has now been numerically adjusted to the PERLKA granule measurement points using the solver module in Microsoft Excel, using the least squared sum method. K1 and K2, the system was overdetermined.
The results are shown graphically as follows (red dots or red curves): see graphics 2 and 3 below.
The determined half-lives for the degradation of cyanamide released from PERLKA (K2) are consistent with the half-times for free cyanamide determined above by regression.
From the numerically determined kinetic model parameters K1 and K2, the concentration profile of further species was modeled only with the above equations:
Calcium cyanamide (black curves, see graphics below) is degraded according to equation (1).
Total releasable cyanamide is the sum of CaNCN and free cyanamide (blue curves).
Degradation products of cyanamide (in the first step urea, further to ammonium) are modeled with the following equation (blue curves, see graphics below):
[Urea] = 1 - ([CaNCN] + [cyanamide free])
It can be seen from the model curves that total amount of cyanamide released decreases exponentially with a half-life of approx. 4 days, irrespective of the moisture content. Cyanamide, which is present in free form, shows its maximum after approx. 2 days, whereby this is at 45 % (10% moisture) or 35 % (5 % moisture) of the theoretically amount of cyanamide that can be released from PERLKA.
At 10 % soil moisture the recovery for Cyanamide F1000 at the beginning of the test is 97.1 %. The results of the other time points show the degradation curve of cyanamide under these specific conditions (see green line in Figure 1). The release of cyanamide from Perlka® (granular form; see blue lines in Figure 1 and Figure 2) is delayed and is in its maximum below 50 % of the total cyanamide that could theoretically be released from Perlka®.
All tables below show the measured free cyanamide concentration in the extract (individual results of three replicates, the mean value, standard deviation and coefficient of variation), the corresponding calculated concentration of cyanamide in soil and the recovery (ratio of the measured cyanamide concentration to the added resp. theoretical concentration).
Table A1: RefeSol 01-A, 10 % soil moisture
Incubation time | Free Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery/Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 544.40 | 499.20 | 524.80 | 522.80 | 22.67 | 4.34 | 13.07 | 87.13 |
1.00 | 242.50 | 235.80 | 204.73 | 227.68 | 20.15 | 8.85 | 5.69 | 37.95 |
2.00 | 138.70 | 140.00 | 126.50 | 135.07 | 7.45 | 5.51 | 3.38 | 22.51 |
3.00 | 78.10 | 77.10 | 70.04 | 75.08 | 4.39 | 5.85 | 1.88 | 12.51 |
6.00 | 9.81 | 9.12 | 7.61 | 8.85 | 1.13 | 12.72 | 0.22 | 1.47 |
9.00 | 1.11 | 0.66 | 0.81 | 0.86 | 0.23 | 26.64 | 0.02 | 0.14 |
13.00 | 0.37 | 0.26 | 0.19 | 0.27 | 0.09 | 33.20 | 0.01 | 0.05 |
20.00 | 0.26 | 0.2 | 0.24 | 0.23 | 0.03 | 13.09 | 0.01 | 0.04 |
|
|
|
|
|
|
|
|
|
Incubation time | Free Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery/Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 44.57 | 46.51 | 61.83 | 50.97 | 9.46 | 18.55 | 1.27 | 11.69 |
1.00 | 206.80 | 215.40 | 200.87 | 207.69 | 7.31 | 3.52 | 5.19 | 47.63 |
2.00 | 160.35 | 177.70 | 174.52 | 170.86 | 9.24 | 5.41 | 4.27 | 39.19 |
3.00 | 159.48 | 138.54 | 136.70 | 144.91 | 12.65 | 8.73 | 3.62 | 33.24 |
6.00 | 56.30 | 54.02 | 58.69 | 56.34 | 2.33 | 4.14 | 1.41 | 12.92 |
9.00 | n. d. | 10.96 | 25.87 | 18.41 | 10.54 | 57.23 | 0.46 | 4.22 |
13.00 | 21.22 | 13.72 | 8.09 | 14.35 | 6.59 | 45.92 | 0.36 | 3.29 |
20.00 | 3.40 | 1.91 | 5.08 | 3.46 | 1.59 | 45.82 | 0.09 | 0.79 |
Table A 2: RefeSol 01-A, 5 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery/Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 571.00 | 572.60 | 558.80 | 567.47 | 7.55 | 1.33 | 14.19 | 94.58 |
1.00 | 228.60 | 216.60 | 212.40 | 219.20 | 8.41 | 3.84 | 5.48 | 36.53 |
2.00 | 89.20 | 102.95 | 97.51 | 96.55 | 6.92 | 7.17 | 2.41 | 16.09 |
3.00 | 88.10 | 100.95 | 96.30 | 95.12 | 6.51 | 6.84 | 2.38 | 15.85 |
6.00 | 1.59 | 3.02 | 1.22 | 1.94 | 0.95 | 49.00 | 0.05 | 0.32 |
9.00 | 0.77 | 0.30 | 0.16 | 0.41 | 0.32 | 77.93 | 0.01 | 0.07 |
13.00 | 0.47 | 0.19 | 0.07 | 0.24 | 0.20 | 83.94 | 0.01 | 0.04 |
20.00 | 0.21 | 0.45 | 0.12 | 0.26 | 0.17 | 65.61 | 0.01 | 0.04 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Stddev. | CV | Free Cyanamide | Recovery/Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 20.75 | 27.83 | 29.29 | 25.96 | 4.57 | 17.60 | 0.65 | 5.95 |
1.00 | 147.60 | 136.58 | 128.06 | 137.41 | 9.79 | 7.13 | 3.44 | 31.52 |
2.00 | 144.07 | 158.15 | 151.25 | 151.16 | 7.04 | 4.66 | 3.78 | 34.67 |
3.00 | 141.70 | 123.15 | 120.50 | 128.45 | 11.55 | 8.99 | 3.21 | 29.46 |
6.00 | 65.25 | 49.06 | 48.63 | 54.31 | 9.47 | 17.44 | 1.36 | 12.46 |
9.00 | 19.30 | 38.59 | 28.71 | 28.87 | 9.65 | 33.42 | 0.72 | 6.62 |
13.00 | 14.78 | 17.00 | 29.75 | 20.51 | 8.08 | 39.39 | 0.51 | 4.70 |
20.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0 | 0.00 | 0.00 |
Table A 3: RefeSol 02-A, 21 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 507.78 | 499.20 | 489.90 | 498.96 | 8.94 | 1.79 | 12.47 | 83.16 |
1.00 | 283.00 | 282.50 | 273.00 | 279.50 | 5.63 | 2.02 | 6.99 | 46.58 |
2.00 | 148.60 | 144.20 | 136.95 | 143.25 | 5.88 | 4.11 | 3.58 | 23.88 |
3.00 | 85.50 | 79.70 | 77.65 | 80.95 | 4.07 | 5.03 | 2.02 | 13.49 |
6.00 | 11.74 | 18.12 | 14.60 | 14.82 | 3.20 | 21.56 | 0.37 | 2.47 |
9.00 | 2.47 | 2.20 | 0.71 | 1.79 | 0.95 | 52.81 | 0.04 | 0.30 |
13.00 | 0 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
20.00 | 0 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 38.77 | 46.20 | 52.04 | 45.67 | 6.65 | 14.56 | 1.14 | 10.47 |
1.00 | 218.10 | 195.20 | 201.20 | 204.83 | 11.87 | 5.80 | 5.12 | 46.98 |
2.00 | 190.94 | 176.94 | 202.70 | 190.19 | 12.90 | 6.78 | 4.75 | 43.62 |
3.00 | 179.87 | 174.70 | 204.70 | 186.42 | 16.04 | 8.60 | 4.66 | 42.76 |
6.00 | 123.65 | 106.38 | 92.08 | 107.37 | 15.80 | 14.72 | 2.68 | 24.63 |
9.00 | 57.30 | 71.35 | 55.51 | 61.39 | 8.67 | 14.13 | 1.53 | 14.08 |
13.00 | 29.70 | 54.46 | 23.70 | 35.95 | 16.30 | 45.35 | 0.90 | 8.25 |
20.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Table A 4: RefeSol 02-A, 10.4 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 458.64 | 441.74 | 461.76 | 454.05 | 10.77 | 2.37 | 11.35 | 75.67 |
1.00 | 233.09 | 234.39 | 221.13 | 229.54 | 7.31 | 3.18 | 5.74 | 38.26 |
2.00 | 102.40 | 134.15 | 137.05 | 124.53 | 19.22 | 15.44 | 3.11 | 20.76 |
3.00 | 56.10 | 80.02 | 69.01 | 68.38 | 11.97 | 17.51 | 1.71 | 11.40 |
6.00 | 14.04 | 7.25 | 11.24 | 10.84 | 3.41 | 31.46 | 0.27 | 1.81 |
9.00 | 9.76 | 2.72 | 2.35 | 4.94 | 4.18 | 84.47 | 0.12 | 0.82 |
13.00 | 1.39 | 0.36 | 0.45 | 0.73 | 0.57 | 77.79 | 0.02 | 0.12 |
20.00 | 0 | 0.03 | 0.00 | 0.01 | 0.02 | 173.21 | 0.00 | 0.00 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 |
| 16.55 | 24.67 | 20.61 | 5.74 | 27.84 | 0.52 | 4.73 |
1.00 | 111.99 | 139.54 | 133.85 | 128.46 | 14.55 | 11.32 | 3.21 | 29.46 |
2.00 | 143.89 | 117.52 | 141.13 | 134.18 | 14.49 | 10.80 | 3.35 | 30.78 |
3.00 | 147.76 | 154.43 | 166.49 | 156.23 | 9.49 | 6.08 | 3.91 | 35.83 |
6.00 | 88.63 | 87.64 | 68.68 | 81.65 | 11.24 | 13.77 | 2.04 | 18.73 |
9.00 | 42.65 | 65.00 | 46.04 | 51.23 | 12.04 | 23.51 | 1.28 | 11.75 |
13.00 | 26.60 | 23.71 | 22.56 | 24.29 | 2.08 | 8.57 | 0.61 | 5.57 |
20.00 | 3.34 | 4.48 | 6.02 | 4.61 | 1.34 | 29.15 | 0.12 | 1.06 |
Table A 5: RefeSol 06-A, 32 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 277.97 | 288.39 | 288.52 | 284.96 | 6.06 | 2.13 | 7.12 | 47.49 |
1.00 | 69.43 | 79.48 | 76.09 | 75.00 | 5.11 | 6.82 | 1.88 | 12.50 |
2.00 | 15.50 | 20.94 | 53.18 | 29.87 | 20.36 | 68.17 | 0.75 | 4.98 |
3.00 | 9.11 | 8.28 | 6.51 | 7.96 | 1.33 | 16.68 | 0.20 | 1.33 |
6.00 | 0.62 | 0.92 | 1.09 | 0.88 | 0.24 | 27.60 | 0.02 | 0.15 |
9.00 | 1.18 | 0.57 | 0.72 | 0.82 | 0.32 | 38.33 | 0.02 | 0.14 |
13.00 | 0.49 | 0.77 | 0.70 | 0.65 | 0.14 | 22.15 | 0.02 | 0.11 |
20.00 | 0.24 | 0.43 | 0.00 | 0.22 | 0.21 | 96.67 | 0.01 | 0.04 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 23.45 | 25.26 | 24.66 | 24.46 | 0.92 | 3.78 | 0.61 | 5.61 |
1.00 | 100.40 | 78.43 | 48.58 | 75.80 | 26.01 | 34.31 | 1.90 | 17.39 |
2.00 | 71.25 | 67.84 | 49.03 | 62.70 | 11.96 | 19.08 | 1.57 | 14.38 |
3.00 | 46.27 | 30.74 | 45.60 | 40.87 | 8.78 | 21.48 | 1.02 | 9.37 |
6.00 | 61.72 | 33.80 | 22.06 | 39.20 | 20.37 | 51.97 | 0.98 | 8.99 |
9.00 | 10.48 | 17.46 | 7.26 | 11.73 | 5.21 | 44.46 | 0.29 | 2.69 |
13.00 | 15.90 | 11.92 | 2.75 | 10.19 | 6.74 | 66.16 | 0.25 | 2.34 |
20.00 | 0.36 | 2.02 | 4.90 | 2.43 | 2.29 | 94.58 | 0.06 | 0.56 |
Table A 6: RefeSol 06-A, 16 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 382.72 | 390.78 | 383.50 | 385.67 | 4.45 | 1.15 | 9.64 | 64.28 |
1.00 | 72.80 | 65.30 | 67.00 | 68.37 | 3.93 | 5.75 | 1.71 | 11.39 |
2.00 | 22.73 | 16.26 | 17.42 | 18.80 | 3.45 | 18.35 | 0.47 | 3.13 |
3.00 | 3.60 | 4.82 | 4.10 | 4.17 | 0.62 | 14.74 | 0.10 | 0.70 |
6.00 | 1.86 | 1.52 | 1.36 | 1.58 | 0.26 | 16.27 | 0.04 | 0.26 |
9.00 | 1.52 | 1.54 | 1.31 | 1.46 | 0.13 | 8.71 | 0.04 | 0.24 |
13.00 | 1.41 | 1.21 | 1.33 | 1.32 | 0.10 | 7.49 | 0.03 | 0.22 |
20.00 | 1.27 | 1.52 | 1.36 | 1.38 | 0.13 | 9.17 | 0.03 | 0.23 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 13.09 | 14.60 | 16.22 | 14.63 | 1.57 | 10.72 | 0.37 | 3.36 |
1.00 | 58.96 | 87.40 | 54.10 | 66.82 | 17.98 | 26.92 | 1.67 | 15.33 |
2.00 | 75.73 | 7.56 | 62.28 | 48.52 | 36.11 | 74.42 | 1.21 | 11.13 |
3.00 | 39.11 | 49.11 | 53.44 | 47.22 | 7.35 | 15.56 | 1.18 | 10.83 |
6.00 | 17.11 | 16.70 | 13.37 | 15.73 | 2.05 | 13.02 | 0.39 | 3.61 |
9.00 | 20.37 | 16.39 | 12.83 | 16.53 | 3.77 | 22.83 | 0.41 | 3.79 |
13.00 | 6.54 | 10.73 | 5.68 | 7.65 | 2.70 | 35.33 | 0.19 | 1.75 |
20.00 | 1.65 | 1.55 | 9.42 | 4.21 | 4.52 | 107.31 | 0.11 | 0.97 |
Table A 7: Dugliolo di Budrio, 18 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 611.75 | 387.40 | 390.31 | 463.16 | 128.70 | 27.79 | 11.58 | 77.19 |
1.00 | 207.81 | 164.56 | 155.19 | 175.85 | 28.07 | 15.96 | 4.40 | 29.31 |
2.00 | 80.51 | 69.90 | 92.17 | 80.86 | 11.14 | 13.78 | 2.02 | 13.48 |
3.00 | 44.31 | 61.73 | 64.25 | 56.76 | 10.86 | 19.13 | 1.42 | 9.46 |
6.00 | 12.24 |
| 6.01 | 9.12 | 4.40 | 48.24 | 0.23 | 1.52 |
9.00 | 4.92 | 0.94 | 1.60 | 2.49 | 2.13 | 85.79 | 0.06 | 0.41 |
13.00 | 4.42 | 1.37 | 0.70 | 2.17 | 1.98 | 91.45 | 0.05 | 0.36 |
20.00 | 0.32 | 0.89 | 0.71 | 0.64 | 0.30 | 46.15 | 0.02 | 0.11 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 43.27 | 46.90 | 41.70 | 43.96 | 2.67 | 6.07 | 1.10 | 10.08 |
1.00 | 177.45 | 141.54 | 152.96 | 157.32 | 18.35 | 11.66 | 3.93 | 36.08 |
2.00 | 170.90 | 214.27 | 117.28 | 167.48 | 48.59 | 29.01 | 4.19 | 38.41 |
3.00 | 119.67 | 98.61 | 86.05 | 101.44 | 16.99 | 16.75 | 2.54 | 23.27 |
6.00 | 87.48 | 81.72 | 102.95 | 90.72 | 10.98 | 12.10 | 2.27 | 20.81 |
9.00 | 42.25 | 67.10 | 45.63 | 51.66 | 13.48 | 26.08 | 1.29 | 11.85 |
13.00 | 16.65 | 10.50 | 58.15 | 28.43 | 25.92 | 91.17 | 0.71 | 6.52 |
20.00 | 2.13 | 2.17 | 3.33 | 2.54 | 0.68 | 26.87 | 0.06 | 0.58 |
Table A 8: Dugliolo di Budrio, 9 % soil moisture
Incubation time | Cyanamide from F1000 | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 337.45 | 183.90 | 441.40 | 320.92 | 129.55 | 40.37 | 8.02 | 53.49 |
1.00 | 131.64 | 174.33 | 174.01 | 159.99 | 24.56 | 15.35 | 4.00 | 26.67 |
2.00 | 128.84 | 82.18 | 78.38 | 96.46 | 28.10 | 29.13 | 2.41 | 16.08 |
3.00 | 74.73 | 72.20 | 91.02 | 79.31 | 10.21 | 12.88 | 1.98 | 13.22 |
6.00 | 26.63 | 25.78 | 20.79 | 24.40 | 3.15 | 12.92 | 0.61 | 4.07 |
9.00 | 5.44 | 5.80 | 6.32 | 5.85 | 0.44 | 7.56 | 0.15 | 0.98 |
13.00 | 0.86 | 1.37 | 0.43 | 0.90 | 0.67 | 74.00 | 0.02 | 0.15 |
20.00 | 0.21 | 0.18 | 0.13 | 0.17 | 0.04 | 21.60 | 0.00 | 0.03 |
|
|
|
|
|
|
|
|
|
Incubation time | Cyanamide from PERLKA | Std. dev. | CV | Free Cyanamide | Recovery /Ratio | |||
days | mg/l | mg/l | mg/l | mg/l |
| % | mg/50g soil | % |
| a | b | c | Mean |
|
|
|
|
0.04 | 24.21 | 38.83 | 28.52 | 30.52 | 7.51 | 24.62 | 0.76 | 7.00 |
1.00 | 158.51 | 179.05 | 142.58 | 160.05 | 18.28 | 11.42 | 4.00 | 36.71 |
2.00 | 139.53 | 133.27 | 147.73 | 140.18 | 7.25 | 5.17 | 3.50 | 32.15 |
3.00 | 115.86 | 98.93 | 105.53 | 106.77 | 8.53 | 7.99 | 2.67 | 24.49 |
6.00 | 119.54 | 98.62 | 93.31 | 103.82 | 13.87 | 13.36 | 2.60 | 23.81 |
9.00 | 71.92 | 67.16 | 63.55 | 67.54 | 4.20 | 6.21 | 1.69 | 15.49 |
13.00 | 26.72 | 31.73 | 25.46 | 27.97 | 3.32 | 11.87 | 0.70 | 6.41 |
20.00 | 3.10 | 3.89 | 9.90 | 5.63 | 3.72 | 66.05 | 0.14 | 1.29 |
Table A 9: Blank values for Ammonia, urea, DCD, nitrate and nitrite in RefeSol 01-A, 10 % soil moisture, 20°C.
Incubation time | Ammonia | Urea | DCD | Nitrate | Nitrite |
days | mg/L | mg/L | mg/L | mg/L | mg/L |
1 | 0.95 | 0.83 | 0 | 8.45 | 0.051 |
2 | 1.09 | 0.96 | 0 | 8.27 | 0.043 |
3 | 1.27 | 1.17 | 0 | 9.93 | 0.061 |
6 | 1.44 | 1.3 | 0 | 11.12 | 0.048 |
7 | 0.95 | 0.58 | 0 | 8.82 | 0.032 |
13 | 1.26 | 0.88 | 0 | 7.54 | 0.051 |
20 | 1.28 | n.d | 0 | 8.41 | 0.054 |
average | 1.18 | 0.95 | 0 | 8.93 | 0.049 |
The tables A 10 to A 12 show the recovery of total applied nitrogen with PERLKA or Cyanamid F1000 based on the technical data sheet of PERLKA and the certificate of analysis of Cyanamid F1000.
Table A 10: Recovery of applied nitrogen as nitrate and nitrite in RefeSol 01-A, 10 % soil moisture, 20°C.
Incubation time | Nitrate from Cyanamid F1000 | Nitrite from Cyanamid F1000 | ||||||
days | a | b | c | mean | a | b | c | mean |
0.04 | -0.62 | -0.65 | -0.65 | -0.62 | -0.01 | 0.00 | -0.01 | -0.01 |
1.00 | -0.28 | -0.79 | -1.16 | -0.74 | 0.00 | 0.03 | 0.01 | 0.01 |
2.00 | -0.35 | -0.75 | -0.73 | -0.61 | 0.03 | 0.05 | 0.04 | 0.04 |
3.00 | -0.27 | -0.87 | -0.70 | -0.61 | 0.05 | 0.07 | 0.06 | 0.06 |
6.00 | -0.63 | -0.31 | -0.77 | -0.57 | 0.07 | 0.01 | 0.03 | 0.04 |
7.00 | -0.60 | -0.43 | -0.12 | -0.38 | 0.04 | 0.05 | 0.04 | 0.04 |
13.00 | -0.64 | -0.54 | -0.61 | -0.60 | 0.04 | 0.04 | 0.03 | 0.04 |
20.00 | -0.50 | -0.72 | -0.58 | -0.60 | -0.01 | 0.00 | 0.00 | 0.00 |
Incubation time | Nitrate from PERLKA | Nitrite from PERLKA | ||||||
days | a | b | c | Mean | a | b | c | Mean |
0.04 | 9.41 | 9.07 | 9.80 | 9.43 | 0.02 | 0.01 | 0.02 | 0.02 |
1.00 | 9.78 | 9.64 | 8.06 | 9.16 | 0.02 | 0.01 | 0.01 | 0.01 |
2.00 | 9.27 | 9.20 | 10.27 | 9.58 | 0.00 | 0.00 | 0.00 | 0.00 |
3.00 | 9.65 | 10.02 | 9.72 | 9.80 | -0.00 | 0.00 | 0.00 | 0.00 |
6.00 | 9.48 | 9.62 | 9.54 | 9.55 | 0.00 | 0.00 | 0.00 | 0.00 |
7.00 | 9.42 | 9.90 | 9.42 | 9.58 | 0.00 | -0.01 | -0.01 | -0.01 |
13.00 | 8.84 | 9.52 | 9.68 | 9.35 | -0.01 | 0.00 | 0.00 | 0.00 |
20.00 | 9.90 | 9.88 | 9.66 | 9.81 | -0.01 | -0.01 | -0.01 | -0.01 |
Table A 11: Recovery of applied nitrogen as DCD and urea in RefeSol 01-A, 10 % soil moisture, 20°C.
Incubation time | DCD from Cyanamid F1000 | Urea from Cyanamid F1000 | ||||||
days | a | b | c | Mean | a | b | c | Mean |
0.04 | 0.47 | 0.44 | 0.35 | 0.42 | 1.43 | 1.44 | 1.57 | 1.48 |
1.00 | 0.59 | 0.68 | 0.59 | 0.62 | 12.88 | 12.49 | 12.41 | 12.59 |
2.00 | 0.64 | 0.68 | 0.69 | 0.67 | 39.93 | 18.33 | 18.80 | 25.69 |
3.00 | 0.69 | 0.72 | 0.73 | 0.71 | 21.53 | 17.65 | 14.46 | 17.88 |
6.00 | 0.80 | 0.76 | 0.79 | 0.78 | 16.06 | 20.12 | 7.41 | 14.53 |
7.00 | 0.82 | 0.72 | 0.72 | 0.75 | 11.64 | 17.97 | 12.88 | 14.16 |
13.00 | 0.91 | 0.92 | 0.87 | 0.90 | <1 | <1 | <1 | <1 |
20.00 | 0.79 | 0.84 | 0.85 | 0.83 | <1 | <1 | <1 | <1 |
Incubation time | DCD from PERLKA | Urea from PERLKA | ||||||
days | a | b | c | Mean | a | b | c | Mean |
0.04 | 1.85 | 1.30 | 1.33 | 1.49 | 4.82 | 4.98 | 5.41 | 5.07 |
1.00 | 5.76 | 6.81 | 3.30 | 5.29 | 5.85 | 5.60 | 5.65 | 5.70 |
2.00 | 15.87 | 14.99 | 13.82 | 14.90 | 7.86 | 7.39 | 7.15 | 7.47 |
3.00 | 16.51 | 17.96 | 16.12 | 16.86 | 9.29 | 10.45 | 8.44 | 9.39 |
6.00 | 20.27 | 20.27 | 22.73 | 21.09 | 15.25 | 14.36 | 14.99 | 14.87 |
7.00 | 19.31 | 21.32 | 20.22 | 20.28 | 14.03 | 16.57 | 15.95 | 15.51 |
13.00 | 17.93 | 23,50 | 21.45 | 20.96 | 8.01 | 10.13 | 10.85 | 9.66 |
20.00 | 18.02 | 18.02 | 15.91 | 17.32 | 1.70 | 1.46 | 3.89 | 2.35 |
Table A 12: Recovery of applied nitrogen as ammonia and cyanamide in RefeSol 01-A, 10 % soil moisture, 20°C.
Incubation time | Ammonia Cyanamid F1000 | Cyanamid from Cyanamid F1000 | ||||||
days | a | b | c | mean | a | b | c | mean |
0.04 | -0.50 | -0.65 | -0.41 | -0.52 | 90.73 | 83.20 | 87.47 | 87.13 |
1.00 | 2.02 | 2.53 | 2.38 | 2.31 | 40.42 | 39.3 | 34.12 | 37.95 |
2.00 | 4.44 | 5.68 | 5.37 | 5.16 | 23.12 | 23.33 | 21.08 | 22.51 |
3.00 | 6.72 | 9.48 | 9.14 | 8.45 | 13.02 | 12.85 | 11.67 | 12.51 |
6.00 | 19.36 | 11.78 | 14.10 | 15.08 | 1.64 | 1.52 | 1.127 | 1.47 |
7.00 | 14.44 | 19.64 | 17.03 | 17.04 | 0.19 | 0.11 | 0.14 | 0.14 |
13.00 | 16.65 | 16.85 | 16.53 | 16.68 | 0.06 | 0.04 | 0.03 | 0.05 |
20.00 | 15.17 | 15.83 | 16.31 | 15.77 | 0.04 | 0.03 | 0.04 | 0.04 |
Incubation time | Ammonia from PERLKA | Cyanamide from PERLKA | ||||||
days | a | b | c | Mean | a | b | c | Mean |
0.04 | -0,42 | -0.40 | -0.35 | -0.39 | 9.29 | 9.70 | 12.89 | 10.63 |
1.00 | 0.39 | 0.37 | 0.36 | 0.36 | 43.12 | 44.91 | 41.88 | 43.30 |
2.00 | 1.24 | 0.96 | 1.07 | 1.09 | 33.43 | 37.05 | 36.39 | 35.62 |
3.00 | 2.86 | 2.53 | 2.42 | 2.60 | 33.25 | 28.89 | 28.50 | 30.21 |
6.00 | 6.11 | 6.46 | 3.96 | 5.41 | 11.74 | 11.26 | 12.24 | 11.75 |
7.00 | 8.04 | 5.02 | 4.21 | 5.76 | n.d | 2.29 | 5.39 | 3.84 |
13.00 | 13.53 | 13.28 | 17.15 | 14.65 | 4.43 | 2.86 | 1.69 | 2.99 |
20.00 | 19.89 | 19.74 | 17.56 | 19.07 | 0.71 | 0.40 | 1.06 | 0.72 |
Recovery and extraction of radioactivity from aerobic soil treated with [14C]-cyanamide at a nominal level of 33 ppm (results expressed as % of initial measured dose):
Days after application | Total [14C] | Cumulative volatile residues | Total extractable | Cyanamide | Dicyan- diamide | Non- extractable |
0 | 100 | 0 | 96.7 | 92.5 | 0.431 | 3.39 |
4 h | 102 | 6.7 | 86.0 | 77.7 | 0.420 | 9.46 |
8 h | 98.7 | 14.8 | 76.4 | 68.5 | 0.389 | 7.48 |
1 | 97.8 | 60.2 | 29.7 | 26.2 | 0.189 | 7.87 |
1.5 | 98.7 | 73.2 | 18.1 | 14.9 | 0.131 | 7.26 |
3 | 101 | 88.9 | 2.8 | 2.05 | 0.032 | 8.95 |
5 | 108 | 94.3 | 5.6 | 3.98 | 0.096 | 7.74 |
7 | 105 | 95.5 | 2.0 | 0.732 | 0.083 | 7.80 |
14 | 103 | 97.1* | 0.37 | 0.051 | 0.032 | 5.64 |
Recovery and extraction of radioactivity from anaerobic soil treated with [14C]-cyanamide at a nominal level of 33 ppm (results expressed as % of initial measured dose):
Days after application | Total14C | Cumulative volatile residues | Water residues | Total extractable | Non-extractable |
Aerobic phase | |||||
0 | 100 | - | - | 96.7 | 3.30 |
6 h | 102 | 12.4 | - | 82.8 | 6.45 |
12 h | 96.6 | 23.7 | - | 63.4 | 9.55 |
Anaerobic phase | |||||
15 | 100 | 48.6 | 37.6 | 4.79 | 8.83 |
30 | 102 | 50.3 | 39.0 | 4.28 | 8.34 |
45 | 87.2 | 52.1 | 25.4 | 3.19 | 6.69 |
60 | 92.8 | 54.5* | 27.2 | 4.31 | 6.93 |
* 53.1 % were identified to be CO2by precipitation with BaCL2.
Characterisation of radioactivity in water and soil extracts from anaerobic soil treated with [14C]-cyanamide at a nominal level of 33 ppm (results expressed as % of initial measured dose):
Days after application | Cyanamide | Dicyandiamide | Guanylurea | Guanidine | Urea | |||||
SE | W | SE | W | SE | W | SE | W | SE | W | |
Aerobic phase | ||||||||||
0 | 88.03 | 4.53 | - | - | - | |||||
6 h | 73.8 | 3.97 | - | - | - | |||||
12 h | 43.1 | 3.52 | - | - | - | |||||
Anaerobic phase | ||||||||||
15 | 2.93 | 25.0 | 0.62 | 5.28 | 0.41 | 4.21 | 0.03 | 0.22 | - | 0.29 |
30 | 1.61 | 20.4 | 0.38 | 5.59 | 0.54 | 7.52 | 0.45 | 2.70 | 0.44 | 1.27 |
45 | 1.79 | 12.7 | 0.30 | 2.84 | 0.32 | 5.62 | 0.06 | 2.24 | 0.03 | 0.83 |
60 | 1.84 | 11.7 | 0.34 | 5.38 | 0.42 | 5.17 | 0.49 | 2.25 | 0.34 | 1.05 |
SE: Soil extract
W: Water
Cyanamide concentration in three soils after application of 0.5, 1.0, and 1.5 l ALZODEF/m³ (expressed in mg cyanamide/kg soil):
Days after treatment | SP257 Loamy sand with high organiccontent | SP357 Loamy sand with low organic matter content | SP1106 Sand | ||||||
| 0.5 | 1.0 | 1.5 | 0.5 | 1.0 | 1.5 | 0.5 | 1.0 | 1.5 |
0 | 250 | 388 | 551 | 170 | 318 | 600 | 190 | 390 | 607 |
2 | 42 | 138 | 314 | 75 | 220 | 380 | 144 | 328 | 535 |
4 | 35 | 123 | 277 | 29 | 63 | 205 | 120 | 258 | 363 |
7 | 18 | 63 | 89 | 5 | 33 | 86 | 87 | 235 | 347 |
10 | - | 15 | 66 | - | 25 | 73 | 65 | 205 | 347 |
14 | - | - | - | - | - | - | - | - |
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Cyanamide concentration in three soils after application of 0.5, 1.0, and 1.5 l ALZODEF/m³ (expressed in % of applied):
Days after treatment | SP257 Loamy sand with high organiccontent | SP357 Loamy sand with low organic matter content | SP1106 Sand | ||||||
| 0.5 | 1.0 | 1.5 | 0.5 | 1.0 | 1.5 | 0.5 | 1.0 | 1.5 |
0 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
2 | 16.8 | 35.57 | 56.99 | 44.12 | 69.18 | 63.33 | 75.79 | 84.10 | 88.14 |
4 | 14 | 31.70 | 50.27 | 17.06 | 19.81 | 34.17 | 63.16 | 66.15 | 59.80 |
7 | 7.2 | 16.24 | 16.15 | 2.94 | 10.38 | 14.33 | 45.79 | 60.26 | 57.17 |
10 | - | 3.87 | 11.98 | - | 7.86 | 12.17 | 34.21 | 52.56 | 57.17 |
14 | - | - | - | - | - | - | - | - | - |
DT50values of cyanamide concentration in three soils after application of 0.5, 1.0, and 1.5 l ALZODEF/m³ (expressed in days):
Application rate | SP257 Loamy sand with high organic carbon content | SP357 Loamy sand with low organic carbon content | SP1106 Sand |
0.5 l ALZODEF/m³ | 1 | 2 | 6 |
1.0 l ALZODEF/m³ | 1 | 3 | 12 |
1.5 l ALZODEF/m³ | 3 | 3 | 12 |
- The test concentrations of ca 130 kg ai/ha, ca 260 kg ai/ha, and ca 390 kg ai/ha were significantly higher than the maximum recommended application rate of 20.8 kg/ha. Even the lowest test concentration was 6-fold higher than the maximum recommended application rate. Therefore, it can be assumed that the DT50 values of cyanamide when applied according to the GAP are even shorter than the DT50 values obtained in this study.
- Aerobic degradation at 10°C
The rate of aerobic degradation in soil at 10°C can be extrapolated from data received at 20°C by using the „Q10-method“ which was developed by the FOCUS Group (Forum for the co-ordination of pesticide fate models and their use). For the calculation of the DT50lab(10°C) the above-mentioned DT50labvalues (20°C) are multiplied with the Q10value of 2.2. This Q10value derived from different aerobic degradation studies and provides the best extrapolation from 20°C to 10°C.
The extrapolated DT50lab(10°C) were in the range of 2.2 to 26.4 days. But due to the fact that the DT50labvalues (20°C) were determined for application rates which were at least 6-fold higher than the recommended field application rates in can be expected that the real DT50values for cyanamide when applied according to GAP are even shorter.
Description of key information
The following DT50 and DT90 values were calculated for the aerobic and anaerobic degradation of cyanamide in soil under laboratory conditions.
DT50 aerobic : 0.7 days – 4.6 days
DT90 aerobic: 2.4 – 15.2 days
DT50 anaerobic: 34.7 days
DT90 anaerobic: 105 days
The normalised DT50 value of 0.78 days at 20°C (Klein et al., 2019) is used for the risk assessment according to Regulation (EC) No 1907/2006 (REACH).
Key value for chemical safety assessment
- Half-life in soil:
- 0.78 d
- at the temperature of:
- 20 °C
Additional information
Reliable experimental information on the biodegradation of cyanamide in soil is available (Heß, 1978; Schmidt, 1990/91). In addition, experimental studies on the biodegradation of calcium cyanamide (Günther, 2018; Weinfurther, 2019) is presented below. The experimental DT50 values obtained by Günther (2018) and Weinfurther (2019) were re-calculated by Klein et al. (2019) to reference conditions in accordance with FOCUS (2000). The available information is discussed in a weight of evidence approach.
In the work of Schmidt (1990/91) few collected studies examined the biodegradation of cyanamide in soil under aerobic and anaerobic conditions (the studies were applied to IUCLID as two study record summaries, one for the aerobic biodegradation studies and the other for the anaerobic biodegradation). The work of Heß (1978) examined the biodegradation of cyanamide in soils that contain low and high amounts of low organic carbon.
The primary pathway of cyanamide dissipation during under both aerobic and anaerobic conditions is the degradation to 14CO2 (i.e. complete mineralisation). Apart from the final degradation product CO2 no other major degradation products (> 10 % of applied radioactivity) occurred, neither under aerobic conditions nor under anaerobic conditions.
Cyanamide degradation in soil both under aerobic and anaerobic conditions can generally be best described by using first order degradation kinetics. The following DT50 and DT90 values were calculated for the aerobic and anaerobic degradation of cyanamide in soil under laboratory conditions.
DT50 aerobic : 0.7 days – 4.6 days
DT90 aerobic: 2.4 – 15.2 days
DT50 anaerobic: 34.7 days
DT90 anaerobic: 105 days
DT50 values of up to 12 days were found in one sand soil with a very low organic carbon content and with the lowest test concentration ca. 13-fold higher than the maximum recommended application rate. Therefore these values can be considered as unrealistic worst case values. Cyanamide degradation in soil is influenced by the organic carbon content of soils indicating that biotic degradation plays an important role in soil.
For comparison (although the study is not included in this section) under field conditions cyanamide was degraded with a mean DT50field value of 1 day and a worst-case DT50field value of 1.6 days. Two weeks after application no cyanamide residues could be detected anymore and thus, the DT90field is less than 2 weeks.
These DT50 values show that cyanamide is degraded very fast in soil.
For the agricultural application of calcium cyanamide the substance is formulated in a slow dissolving granule (PERLKA) that is applied to agricultural fields as a fertiliser. In contact with soil moisture, PERLKA granules will slowly release cyanamide.
Hence, experiments conducted with the calcium cyanamide fertiliser are included. Upon contact with water calcium cyanamide is fast transformed to cyanamide. In contrast, upon contact of the granules with soil moisture the release of cyanamide from calcium cyanamide is time-dependent. To determine the rate constants and DT50 values for the release of cyanamide from PERLKA and the subsequent degradation of cyanamide, two studies were conducted by Güthner (1018) and Weinfurtner (2018).
Weinfurtner (2019) incorporated calcium canamide (PERLKA) in two different soils as granulate at different soil moisture (50 % and 25 % of maximum water holding capacity) and temperatures (20 °C, 12 °C). Samples were incubated for up to 20 days. The derived half-lives are summarized below:
Soil | Focus Scenario | % of WHC | DT50 cyanamide | DT50 calcium cyanamide |
RefeSol 02-A* | R1 | 50 | 1.15 | 0.87 |
25 | 1.06 | 1.63 | ||
RefeSol 01-A | R2 | 50 | 0.95 | 0.60 |
25 | 0.82 | 1.21 | ||
RefeSol 06-A | R3 | 50 | 0.55 | 2.47 |
25 | 0.42 | 2.51 | ||
Dugliolo di Budrio | R4 | 50 | 0.79 | 1.63 |
25 | 1.21 | 1.61 |
* Test performed at 12 °C, all others at 20 °C
Additionally, for one soil the content of the secondary transformation products of cyanamide, dicyandiamide (DCD), urea (CH4N2O), nitrate (NO3-), nitrite (NO2-) and ammonia (NH4+), at different sampling points was determined. In this additional experiment, the soil was treated with PERLKA respectively Cyanamid F1000 as described above but the extraction was always performed with deionised water. Urea, nitrate, nitrite and ammonia were determined by using ion chromatography, DCD by LC-MS/MS.
The transformation from cyanamide to secondary transformation products depend on the tested material. Whereas for Cyanamid F1000 only urea and ammonia in larger amounts could be detected, for PERLKA also nitrate and DCD were determined. The observed nitrate is not a transformation product but represents the original amount of nitrate in PERLKA. The observations on the amounts of transformation products were comparable to former study results (e. g. Vilsmeier & Amberger, 1978).
These values are further supported by the half-lives calculated based on the experimental results by Günther (2018) in the standard soil RefeSol 01-A which are as follows:
Soil type | Soil moisture [%] | Temperature [°C] | DT50 PERLKA [d] | DT50 cyanamide [d] |
RefeSol 01-A | 10 | 12 | 1.1 | 3.2 |
RefeSol 01-A | 5 | 12 | 1.8 | 2.6 |
The DT50 values from these studies are relevant with regard to the exposure calculations in relation to the agricultural application of PERLKA. The DT50 values were normalised to a standard temperature of 20 °C by means of a Q10 factor of 2.2 as recommended by FOCUS (2000). Subsequently, these values were used as input for the exposure calculations of the predicted environmental concentrations in surface water, groundwater and soil performed with FOCUS Step 3 + Step 4, FOCUSPEARL, and ESCAPE V2.0, respectively.
For FOCUS Step 3 + Step 4 and FOCUSPEARL, DT50 PERLKA values were additionally normalized to a standard soil moisture of pF 2 (= field capacity) using an exponent of 0.7 as the model requires degradation at optimised moisture conditions. Also, the moisture correction was done according to FOCUS (2000).
Please note: the DT50 values for the subsequent degradation of cyanamide are independent of soil moisture and no correction has been performed. The value represents the geometric mean of all experimental data after normalisation to 20 °C but without soil moisture normalisation.
Furthermore, in accordance with the model requirements DT50 input values for ESCAPE V2.0 were not normalized to standard soil moisture.
An overview of the relevant DT50 input values per model is given below:
Exposure model | DT50 PERLKA [d] | DT50 cyanamide [d] |
FOCUS Step 3 + 4 | 0.721 | 0.78 |
FOCUSPEARL | 0.721 | 0.78 |
ESCAPE V2.0 | 0.740 | 0.766 |
Conclusion
Reliable information on the biodegradation of cyanamide in soil is available. The following DT50 and DT90 values were calculated for the aerobic and anaerobic degradation of cyanamide in soil under laboratory conditions.
DT50 aerobic : 0.7 days – 4.6 days
DT90 aerobic: 2.4 – 15.2 days
DT50 anaerobic: 34.7 days
DT90 anaerobic: 105 days
Additionally, information on the transformation and fate of calcium cyanamide in soil matrices is available. It was demonstrated that upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide. Thus, for industrial manufacture and use, release of calcium cyanamide to water will result in potential environmental exposure of hydrogen cyanamide. Any subsequent potential soil exposure via sludge and air will be by cyanamide, not calcium cyanamide.
The normalised DT50 value of 0.78 days at 20°C (Klein et al., 2019) is used for the risk assessment according to Regulation (EC) No 1907/2006 (REACH). It is concluded that cyanamide is rapidly degraded in soil and that there is hence no indication for persistency regarding this environmental compartment.
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