This is the 8916th most frequent Polish word.
sieradzkiej
"Sieradzkiej" means "of or pertaining to Sieradz," a town in Poland.
In this sentence, "sieradzkiej" is an adjective describing the noun "okolicy" and indicates that the vicinity pertains to the region of Sieradz.
Mieszkam w okolicy sieradzkiej.
I live in the Sieradz area.
Here, "sieradzkiej" functions as an adjective describing the noun "społeczności", signifying that the community is associated with Sieradz.
Kultura sieradzkiej społeczności jest bardzo bogata.
The culture of the Sieradz community is very rich.
In this usage, "sieradzkiej" modifies "ziemi", characterizing the traditions as belonging to the land of Sieradz.