Behind the tractor rolled the shining disks, cutting the earth with blades – not plowing but surgery, pushing the cut earth to the right where the second row of disks cut it and pushed it to the left; slicing blades shining, polished by the cut earth.
– John Steinbeck
The Grapes of Wrath, Chapter 5. The use of the word "surgery" creates a negative tone towards the invading tractor. It paints an image of an invasive process and the earth suffering.