It causes mal rouge (definition below) because of its strong antabuse type effect when mixed with alcohol it is often blended with citric acid & used to treat alcoholism. I wouldn't go near it myself when there are so many natural alternatives for use as fertiliser.
m. rouge (rōōzh) [Fr. “red sickness”] a syndrome occurring after inhalation or ingestion of calcium cyanamide followed by drinking an alcoholic beverage, marked by intense flushing, rapid pulse and pounding heart, panting respiration, and perception of the taste and smell of acetaldehyde in the exhaled breath, which may be followed by nausea, vomiting, and a precipitous fall in blood pressure; the extent and severity of the symptoms depend on the amount of calcium cyanamide and alcohol in the system. The reactions are due to the inhibition by calcium cyanamide of one or more of the enzymes required for oxidation of acetaldehyde formed from alcohol, resulting in the accumulation of acetaldehyde and the altered vascular reaction to it. A similar syndrome, also due to accumulation of acetaldehyde, occurs on ingestion of disulfiram followed by drinking an alcoholic beverage, but in addition there are impaired taste, unpleasant breath and perspiration, and lessened sexual potency.
