jQuery Grid Plugin - jqGrid

I am using Form Editting...

When the form for EDIT opens, there is one field on the form I want to show, but not be edittable. It is the key field of the row.

BUT

When the form for ADD opens, this same field, the key field, needs to be enterable.

How to do this?

If I add editoptions to the colmodel like readonly: "readonly"

It does make the field readonly, but does so for both EDIT and ADD operations.