Breath—the last sweet scent of cane, (5)
In this line, death and life meet. The sweet smell of the sugarcane from the fields nearby seems wildly out of place as the victim is tortured to death. This smell also reminds us of America's troubled history with slavery and how the farming of crops like sugarcane and tobacco fueled slavery and the slave trade.
And her slim body, white as the ash of black flesh after flame. (6-7)
Violence has rendered the black male victim's body into a feminine and white body. Or at least, that's one way to read it. You could also read it the other way around—that this white woman can't help but be described in violent terms because her status in society depends on violence toward black people.