You have the option to select suppliers for requisitions and have the option to select the same supplier for all items or a different supplier for each item:
*Please note: There is a branch profile option to allow users to select a supplier on requisitions that will need to be enabled.
The following three options will then be offered:
-Supplier is optional
-Supplier is mandatory on external items
-Supplier is mandatory on database items
-Supplier is mandatory on all items