acts_as_ferret:: "field-restricted search" possible?

Can we tell acts_as_ferret - to take up multiple search terms from a form, then - use each term only on a specific column in the table to search?

I.e.: - Model: User - Attributes: firstname, lastname, location, favoritecolor - Form fields: firstname, lastname, location, favoritecolor

-> Then let ferret search only in the "firstname column" using only "firstname form field (entry)" -> Do this for every form field entry -> Compose the final search result list ?

Wikipedia seems to call that "Field-restricted search": " Some search engines enable users to limit free text searches to a particular field within a stored data record, such as "Title" or "Author." "

As far as I have understood, acts_as_ferret takes multiple search terms and uses them to search the *entire* created index (meaning all columns specified in the model).

Is a "field-restricted search" possible (to speed up the query)? If yes, what exactly would I have to do?

Thanks for your help!