Also, non-farmers still provided a portion of their own foodstuffs. Preachers and Doctors had gardens, henyards, milk cows and maybe even orchards. Breweries operated dairies, feeding the exhausted mash to the cattle. The White House had extensive greenhouses. Modern farming is horizonally integrated.
Some farmers grow corn or soybeans or wheat or potatos, which they sell.
Some farmers raise chickens or pigs or cattle, which they sell. Dairy products and butchering are done by specialists for wages. The seed is purchased from agribusiness. Chemical fertilizers, herbicides and pesticides are used if not required. The chicks are purchased from an agribusiness.