boron fertiliser vs boron fertilizer

boron fertiliser and boron fertilizer both are nouns.

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

As nouns, boron fertiliser and boron fertilizer are synonyms defined as:

boron fertiliser and boron fertilizer: a plant fertilizer which formula contains boron.

boron fertiliser (noun)	boron fertilizer (noun)
a plant fertilizer which formula contains boron.	a plant fertilizer which formula contains boron.