"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 i disk cut it" which word or words most creates a negative tone towards the tractor?

The word that most creates a negative tone towards the tractor is surgery.

Explanation:

This excerpt describes a regular process that doesn't have any kind of negative connotation in the general basis, then when the word surgery is added, we have the inclusion of an invasive process applied to the land, and the object that is doing it is this tractor, this can make the reader have some negative reaction toward it.

there purpose is to entertain