Main Difference
The main difference between Farmer and Agriculturist is that the Farmer is a person that undertakes agriculture and Agriculturist is a profession concerned with studying and publicising agricultural methods.
Farmer
A farmer (also called an agriculturer) is a person engaged in agriculture, raising living organisms for food or raw materials. The term usually applies to people who do some combination of raising field crops, orchards, vineyards, poultry, or other livestock. A farmer might own the farmed land or might work as a laborer on land owned by others, but in advanced economies, a farmer is usually a farm owner, while employees of the farm are known as farm workers, or farmhands. However, in the not so distant past, a farmer was a person who promotes or improves the growth of (a plant, crop, etc.) by labor and attention, land or crops or raises animals (as livestock or fish).
Farmer (noun)
A person who works the land and/or who keeps livestock, especially on a farm.
Farmer (noun)
Agent noun of farms.
Farmer (noun)
One who takes taxes, customs, excise, or other duties, to collect for a certain rate per cent.
“a farmer of the revenues”
Farmer (noun)
The lord of the field, or one who farms the lot and cope of the crown.
Agriculturist (noun)
One who practices agriculture, a farmer, a gardener.
Agriculturist (adjective)
Of or pertaining to agriculture or agriculturists.
Farmer (noun)
a person who owns or manages a farm.
Farmer (noun)
a person to whom the collection of taxes was contracted for a fee.