fertiliser vs fertilizer

fertiliser and fertilizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
fertiliser	Yes	No	No	No
fertilizer	Yes	No	No	No

As nouns, fertiliser and fertilizer are synonyms defined as:

fertiliser and fertilizer: any substance such as manure or a mixture of nitrates used to make soil more fertile

Other synonyms of fertiliser include plant food.

fertiliser (noun)	fertilizer (noun)
any substance such as manure or a mixture of nitrates used to make soil more fertile	any substance such as manure or a mixture of nitrates used to make soil more fertile