Imperative has, as its primary sense according to Collins (and I think that this is the sense we must accept here):
- extremely urgent or important; essential
Essential (/ crucial / of vital importance / imperative [in this sense] ) are absolute (in the semantic sense) adjectives (or, in the case of the phrase, adjectivals), and hence are non-gradable.
Correct alternatives are:
The drought we have suffered this year makes it all the more / even more important to wisely use the stock of food we have.
The drought we have suffered this year makes it imperative to wisely use the stock of food we have.
If emphasis is deemed necessary (people being selectively deaf to instructions they don't like),
The drought we have suffered this year makes it IMPERATIVE to wisely use the stock of food we have.
And if my family is threatened by others' greed or complacency, I might even endorse the ungrammatical
The drought we have suffered this year makes it ABSOLUTELY IMPERATIVE to wisely use the stock of food we have.