More scene setting. They pass "the fields of […] grain" and "the setting sun." When she describes the grain as "gazing" maybe she thinks the thicker tops of the grain resemble heads, or perhaps that the grain seems to stand still and just look at the carriage as it passes.
The sun and field are much more general descriptions of the scene than the previous lines, yet might even have symbolic significance. The setting sun, for example, signifies the end of the day, but might also stand for the end of life. Ever heard of old people being in their twilight years?
We should also notice the repeated phrase, "We passed" (in poetry-speak, a repeated word or phrase throughout a poem is called anaphora). Here it works to mimic the slow progression of the carriage. You can almost hear the echo of clomping horse hooves in the repeated phrase. So instead of feeling like this poem is at a standstill, we're aware that it's moving forward. It almost allows us to be a part of their journey, not just outside observers.