CALCIUM CYANAMIDE – AN IMPORTANT TOOL IN METHYL BROMIDE REPLACEMENT
STRATEGIES
Hans-Juergen Klasse, SKW Trostberg AG, Germany
After several years of international research it has become increasingly evident that methyl bromide cannot be replaced
with a single chemical exhibiting the same broad range effects but without harming the environment. As a consequence
strategies of Integrated Pest Management aim to combine several techniques and measures to suppress weeds and soil
borne pathogens. One of these measures to be considered is the use of the registered EC-fertiliser nitrogenous calcium
cyanamide.
For many years scientists have approved that the use of calcium cyanamide fertiliser helps to reduce soil borne diseases
like clubroot 3, Sclerotinia 6 and Fusarium1 and diminishes small weeds up to the stage of four true leaves 2. For this
reason the calcium cyanamide fertiliser PERLKA is used today by vegetable growers in all countries of the EU to
overcome the problems of insufficient crop rotation. How can a nitrogen fertiliser have such effects and how can these
effects be used in methyl bromide replacement strategies?
Metabolism of calcium cyanamide in the soil
To understand the effects of calcium cyanamide PERLKA we have to look on what happens in the soil after the
application of this unique fertiliser. The first intermediate, formed within hours after the product gets in contact with the
soil humidity is hydrogen cyanamide which dissolves and distributes in the soil water. Hydrogen cyanamide is
phytotoxic (herbicidal effects!) and has strong fungicidal properties by which it inhibits growth and sporulation of many
pathogenic fungi.
Metabolism of Calcium Cyanamide in the Soil
calcium cyanamide
Ca CN2
moisture required!
calcium dihydroxide
hydrogen cyanamide
Ca(OH)2
H2CN2
dicyandiamide
(H2N)2CNCN
urea
CO(NH2)2
ammonium
NH4
acts as an inhibitor
of the bacteria
Nitrosomonas
delayed nitrification!
nitrate
NO3
Hydrogen cyanamide is completely decomposed in soils within 7 to 14 days to urea and - to a certain extent - to
dicyandiamide which is known as a nitrification inhibitor and which is included in the EEC Council directive 93/69 as a
nitrogen form of EC -fertilisers. The dicyandiamide hinders the further decomposition of calcium cyanamide at the
stage of ammonium nitrogen. In combination with the liming effect of the calcium dihydroxide this leads to an
accumulation of ammoniacal nitrogen in the soil for a certain period of time before the ammonium is absorbed by clay
minerals or temporarily immobilized by the microflora. It has been found that increased concentrations of ammoniacal
nitrogen in the soil can reduce the number of nematodes 10.
Influence of calcium cyanamide on micro-organisms in the soil
Hydrogen cyanamide as the first metabolite of calcium cyanamide PERLKA has fungicidal properties. However,
laboratory research has shown that there are big differences between the pathogens in regard to their sensitiveness to
hydrogen cyanamide. Some of the Phytophthora-species have proved to be very sensitive 9. This has been confirmed in
open field trials in Turkey where Phytophthora capsici was controlled effectively on red pepper with applications of 500
to 600 kg calcium cyanamide two weeks before sowing 5.
However, even Fusarium species which seem to be relative tolerant to hydrogen cyanamide have been controlled in
greenhouses effectively when calcium cyanamide
was incorporated into the soil together with straw 1. Therefore besides the direct fungicidal effect of the cyanamide
there must be also an indirect effect of this treatment.
Mycelial growth of pathogenic fungi in the
presence of cyanamide
% Cyanamide in the culture medium
0,03-0,06
0,06-0,12
0,12-0,24
0,24-0,48
>0,48 %
Alternaria dianthi
Phytophthora cactorum
Phytophthora capsici
Colletotrichum lindemuthianum
Phytophthora parasitica
Pythium ultimum
Thielaviopsis basicola
Colletotrichum spinaciae
Sclerotium rolfsii
Verticillium albo-atrum
Cladosporium variabile
Gloeosporium olivarum
Fusarium spp.
According to Verona, 1970
Microbiologic research has shown that some of the non pathogenic fungi are more or less unaffected by increasing
concentrations of cyanamide. Above of this it has been found that some of these fungi - namely the Aspergillus- and
Penicillium species - can use the cyanamide molecule as a source of nitrogen for decomposing cellulose 7.
Consequently these fungi will be promoted by the presence of both, cyanamide nitrogen and straw, in the soil.
Some of these fungi are known to suppress others by natural antagonism and therefore they are used commercially for
biological pest control. In Italy products are sold containing Aspergillus spp. (against Sclerotinia and Rhizoctonia spp.)
and Penicillium spp. (against Pythium and Phytophthora spp.) for biological control of soil borne diseases 4. A similar
effect can be achieved if these fungi, which are present in every soil, are promoted by favourable living conditions.
Incorporating calcium cyanamide PERLKA together with straw changes the balance of the soil microflora in favour of
these beneficial, non parasitic types and thus results in a biological disease suppression.
Practical experience with calcium cyanamide PERLKA for methyl bromide replacement
In recent years the incorporation of calcium cyanamide fertiliser (500 to 1000 kg/ha) and shredded straw (10 t/ha) into
the soil followed by a soil solarisation has been successfully used as a replacement of methyl bromide in some
Mediterranean greenhouse areas. It has been found that in regard to fungal diseases this combination performs better
than solarisation alone and is similar effective as methyl bromide 1. On the other hand, nematicidal effects of calcium
cyanamide, which often had been observed in pot trials, could not be achieved in greenhouse trials in Sicily on
tomatoes. This could be due to the fact that the cyanamide does not penetrate deep enough into the soil.
Weeds are most susceptible to cyanamide from the stage of germination up to 4 true leaves. Hence the diminution of
weeds is most effective if the soil has kept humid for 7 to 10 days before and if not all the calcium cyanamide PERLKA
is mixed into the soil but if at least 300 kg/ha are applied to the soil surface before covering the soil with the PE sheets.
Influence of different soil treatments on
marketable yield of open-field fennel
Salerno (I) ,Mean of 2 years
Marketable bulbs
in % of plants
85
80
75
70
65
60
55
50
45
40
75,5
78
78,5
Solarisation
Methyl
51,5
Control
Solarisation
+ PERLKA (500 kg/ha Bromide
+ Straw (10 t/ha)
According to Palumbo et al. 1999
These results from northern Italy on fennel are showing a good yield response even with a low rate of 500 kg/ha of
calcium cyanamide PERLKA and even under open field conditions in a region with more moderate summer
temperatures 8.
Influence of different soil treatments on
marketable yield of open-field iceberg lettuce
Salerno (I) , 1996/97 (1 year)
Marketable heads
in % of plants
90
85
80
75
70
65
60
55
50
45
40
85
79
a
a
61
ab
46
b
Control
Solarisation
Solarisation
Methyl
+ PERLKA (500 kg/ha Bromide
+ Straw (10 t/ha)
According to Palumbo et al., 1999
The same trial was performed also on iceberg lettuce. Calcium cyanamide plus straw significantly increased the efficacy
of the solarisation. Similar findings have been made in Crete, where calcium cyanamide PERLKA improved the
efficacy of soil solarisation against Fusarium solani on greenhouse cucumbers and allowed to reduce the period of
solarisation from 6 to 3 weeks1.
Soil solarisation with calcium cyanamide and straw
1. Soil activation
2. Soil treatment
3. Soil preparation and planting
cyanamide
1. Removing previous crop 1. Application of calcium
2. Application of straw
2. Powerharrowing
3. Rotary cultivator
3. Irrigation
4. Irrigation
5. Soil covering
Solarisation
Activation
-2
-1
1. Removing plastic sheets
2. Irrigation
3. Planting of the crop
0
Week
1
2
3
4
5
Summary
Calcium cyanamide fertiliser PERLKA is an environmentally benign product which helps to reduce the infestation of
soils with soil borne pathogenic fungi and weeds. It gives a slow release of nitrogen and improves soil fertility. In
particular in combination with soil solarisation and organic matter but even alone calcium cyanamide PERLKA is a
valuable tool in methyl bromide replacement strategies.
References:
1.
Bourbos, V.A., M.T. Skoudridakis, G.A. Darakis and M. Koulizakis: Calcium Cyanamide and soil solarisation for
the control of Fusarium solani f. sp. Cucurbitae in greenhouse cucumber.
Crop Protection Vol. 16, pp. 383-386, 1997
2.
Cornforth, I.S.: Calcium cyanamide in agriculture.
Soils and Fertilizers, Vol. 34, No.5, pp 463 – 469, 1971
3.
Humpherson-Jones, F.M. et al.: Control of clubroot using calcium cyanamide - a review.
Brighton Crop Protection conference - Pests and diseases - 9B-4, pp 1147-1154, 1992
4.
Minuto, A., A. Pomè and M. L. Gullino: Le Alternative al bromuro di metile.
Le Alternative al Bromuro di Metile, Supplemento a Colture Protette, n.4, pp. 26-36, 1999
5.
Koc, K. and A. Eskalen: Untersuchungen über die Wirkung von PERLKA (Kalkstickstoff) auf den
Krankheitsbefall von Phytophthora capsici beim Paprika.
University of Adana, trial report, 1996
6.
Mattusch, P.: Elimination of the apothecia of Sclerotinia sclerotiorum under field and glasshouse conditions. Acta
horticulturae 152, pp. 49-56, 1984
7.
Müller, H.: Untersuchungen über die Wirkung des Cyanamids im Kalkstickstoff auf pathogene und
nichtpathogene Mikroorganismen im Boden.
Archiv für Mikrobiologie, 22, 3, pp 285-306, 1955
8.
Pallumbo, A.D. et al.: La solarizzazione nell‘orticoltura di pieno campo della Piana del Sele.
L‘Informatore Agrario, 4/99, pp. 97- 102, 1999
9.
Verona, O.: Der Einfluß des Kalkstickstoffs auf einige Gruppen von niederen Pilzen (The effect of calcium
cyanamide on some groups of lower fungi).
Landwirtschaftliche Forschung, 23, pp. 36-52, 1970
10. Walker, J.T.: J. Nematology, 3, 43-49, 1971