Which one of the following is not a nitrogenous fertilizer?

Nitrogenous fertilizers are substances that supply nitrogen to plants to enhance growth [1]. Common examples include Urea (CO(NH2)2), which contains 46% nitrogen, and Ammonium Nitrate (NH4NO3), which provides nitrogen in both ammonium and nitrate forms [1]. Calcium Cyanamide (CaCN2), commercially known as nitrolime, is also a well-known nitrogenous fertilizer used as a defoliant and herbicide [2]. In contrast, Calcium Cyanide (Ca(CN)2) is a highly toxic chemical compound primarily used as a fumigant or pesticide and in gold mining processes [2]. While CaCN2 is used to manufacture Ca(CN)2, the latter is not used as a fertilizer due to its extreme toxicity and lack of agricultural nutrient value [2]. Therefore, Ca(CN)2 is the correct answer as it is not a nitrogenous fertilizer.

Sources

1. [1] Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > FERTILISERS > p. 302
2. [2] https://agritech.tnau.ac.in/agriculture/agri_nutrientmgt_fertilizers.html