MRP controller field in PR w/o material code

Hello Experts,

Is it possible to fill in the MRP controller field in PR with no material code? OR Does MRP controller field exists w/o material code?

Actually, I created a PR from project builder itself, I wanted to enter in the field of MRP controller but that is non-editable. So,is there any way to populate date in this field with the above combination of 'N' and no material code?

Regards