Please tell me which is the subject and which is the predicate in the following sentence:
Farmers usually work long hours.
I am told that "Farmers usually" is the subject and the rest of the sentence is the predicate, simply because the verb, "work", comes after the word "usually", but this makes no sense to me. I always thought that the predicate was the "action" or verb part of the sentence - and "usually" is an adverb. Why not make "Farmers" the subject and the rest of the sentence the predicate?
You understand it very well. Farmers is the subject, everything else is the predicate. Usually modifies the verb work, therefore it must be part of the verb phrase (predicate).
The subject could be longer: The farmers I've seen or The farmers who live on this side of the river or any description imaginable. Farmers and any other words that describe them is the subject of the sentence.