nitro-chalk vs plant food

nitro-chalk and plant food both are nouns.

Word	Noun	Adjective	Verb	Adverb
nitro-chalk	Yes	No	No	No
plant food	Yes	No	No	No

As nouns, plant food is a hypernym of nitro-chalk; that is, plant food is a word with a broader meaning than nitro-chalk:

nitro-chalk: a chemical fertilizer containing calcium carbonate and ammonium nitrate.
plant food: any substance such as manure or a mixture of nitrates used to make soil more fertile

Other hypernyms of nitro-chalk include fertiliser, fertilizer.

nitro-chalk (noun)	plant food (noun)
a chemical fertilizer containing calcium carbonate and ammonium nitrate.	any substance such as manure or a mixture of nitrates used to make soil more fertile