The Collaborative International Dictionary of English v.0.48:

Agriculturist \Ag`ri*cul"tur*ist\, n.
   One engaged or skilled in agriculture; a husbandman.
   [1913 Webster]

         The farmer is always a practitioner, the agriculturist
         may be a mere theorist.                  --Crabb.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "agriculturist":
   Bauer, agriculturalist, agrologist, agronomist, coffee-planter,
   collective farm worker, crofter, cropper, cultivator, dirt farmer,
   dry farmer, farm laborer, farmer, farmhand, gentleman farmer,
   granger, grower, harvester, harvestman, haymaker, husbandman,
   kibbutznik, kolkhoznik, kulak, muzhik, peasant, peasant holder,
   picker, planter, plowboy, plowman, raiser, rancher, ranchman,
   reaper, rustic, sharecropper, sower, tea-planter, tenant farmer,
   tiller, tree farmer, truck farmer, yeoman