There answer is simple: No. Some people (also the Census of Agriculture) use
it to mean the part of the food and (natural) fiber production process that
happens on farms. Others use it to mean the entire production process,
both post-farm industries (e.g., grain handlers, food processors,
distributors) and those supplying farmers with production inputs (e.g.,
fertilizer manufacturers). People who use this broader definition, when they
want to confine themselves to the on-farm part, call it "production
agriculture." Conversely, people who use "agriculture" to mean only on-farm
production typically refer to the larger version as the "food system", or
something like that.
As long both of these widely divergent definitions are in common use, there
may not be much point in trying to refine the definition any further. But
each has some vagueness and inconsistency. For example, while the broader
definition includes food processing, it does not include the manufacture of
cotton shirts, although it definitely includes cotton growing.
"Production agriculture" has definitional difficulties too, such as whether
it includes farm-related activities like agritourism, woodlot management, or
on-farm value added processing. It's sometimes hard to decide where
agricultural production ends and something else begins, when the latter also
takes place on a farm.
And, as in so many cases, there are definitional disagreements that at bottom
are really political, i.e., modes of production that some people exclude from
agriculture because they don't like them. It's sometimes hard to confine
oneself to purely lexical matters, but it would be helpful if "What is
agriculture?" could be discussed separately from "What is desirable
agriculture?"
Willie Lockeretz
Tufts University