Which preposition to use with fosterings

of Occurrences 20%

But with the conclusion of peace he resumed the original scale of his benefactions, and the last four years of his life were, perhaps, the most fruitful of all in sterling good achieved in the fostering of the Renaissance.

by Occurrences 1%

So ended his fostering by the desert and by Hailima.

Which preposition to use with  fosterings