Not much is happening on the surface here. The speaker is in a field. His presence is "the absence of field." Wait. What? Think of it this way: when you're standing in a field, you're occupying the particular space that your body takes up, no more, no less. And where your body is, the field can't be, since two things can't occupy the same space at the same time. You know, physics and such.
Then our guy walks. And when he walks, the air fills in where he was previously standing. Makes sense, given what we learned in stanza 1.
Then, he declares that he moves to "keep things whole." So when he moves through the field and the air fills in behind him, the air is becoming whole again—it's piecing itself back together after he interrupted it so rudely with his standing there.
Hey, we never said this one was a blockbuster.