• (n.) An agriculturist (which is the preferred form.)
An agriculturalist was a man involved in introducing new techniques and developments into farming, during the Agricultural revolution.
Ag`ri·cul'tur·al·ist noun An agriculturist (which is the preferred form.) 
agriculturalist Someone who is engaged in the science, art, and business of cultivating soil, producing crops, and raising livestock; farming. Whoever could make two ears of corn . . . grow upon a spot of ground where only one grew before, would deserve better of mankind . . . than the whole race of politicians put together. —Jonathan Swift (16...