This poem takes place out in the country. In fact, the setting is so important to the poet that he announces it in the title, just to be sure that you don't miss it! Why would the country make more sense for the setting of this poem? Well, country folks are generally seen as simpler than their city counterparts. Since they're farmers, they're more in tune with the earth and with nature, and more in touch with the things that really matter, according to the speaker—things like the cycles of life and death.
Line 2: If the title of the poem didn't tip you off right away that we're hanging out in the country, and not in the city, maybe the mooing herd of cows that appears in line 2 will convince you. Guys: this is NOT a city poem. Cows!
Line 3: The speaker uses alliteration when he repeats the Pl- sound of "plowman plods" and the W sound of "weary way." The repetition of those consonant sounds might help to emphasize how tired the farmer is—he's "plodding" along. It also might emphasize that the farmers do this every single day. Plod, plod, plod.
Line 25: The speaker personifies the harvest when he says that it "yields" to the farmer's sickle, the way a beaten warrior would "yield" or surrender to a superior force. (A sickle is a sharp, curved farm tool used to cut grain. They've been used for so many centuries and millennia that they often get associated with our ancient, primitive ancestors. Here's what a sickle looks like.)
Line 29: The speaker personifies "Ambition" when he says that we shouldn't let the desire to get ahead and get rich keep us from appreciating the useful work of the farmers.
Lines 101-104: The poet uses alliteration to describe the laziness of stretching out under a tree near a stream. The repetition of the L sounds ("listless length") and of the B sounds ("brook that babbles by") sort of imitates the sound of the wind in the tree overhead and the sound of the flowing stream.