Commercial inorganic fertilizers primarily contain nitrogen sources such as ammonium nitrate, which is recognized for its rich nitrogen supply. Urea, while a nitrogen source, is classified as an organic substance and thus does not fall under the category of inorganic fertilizers. The discussion highlights the role of bacterial flora in processing these nitrogen compounds to synthesize necessary nitrogenous compounds. Additionally, it references the urea cycle from biochemistry, noting the production of fumaric acid, which is also involved in the Krebs cycle, illustrating the interconnectedness of nitrogenous compounds with other physiologically active substances.
