The Collaborative International Dictionary of English v.0.48:

Agriculturalist \Ag`ri*cul"tur*al*ist\, n.
   An agriculturist (which is the preferred form.)
   [1913 Webster]

WordNet (r) 3.0 (2006):

agriculturalist
    n 1: someone concerned with the science or art or business of
         cultivating the soil [syn: agriculturist,
         agriculturalist, cultivator, grower, raiser]