ANS:A - All the nitrogenous fertilisers are not soluble in water.

The wrong statement is: "Calcium cyanamide is used as a weed killer in onion fields." While calcium cyanamide can indeed be used as a fertilizer, it is primarily used for its fertilizing properties rather than as a weed killer. Calcium cyanamide is a nitrogenous fertilizer that also provides a herbicidal effect by releasing ammonia when it reacts with water. This ammonia can act as a herbicide, but it is not commonly used solely for weed control in onion fields. Instead, it is more commonly used as a nitrogen fertilizer to supply plants with nutrients.