Rashi, on Gen 41:48

“And all the abundance of grain was laid up in every city.”

“אכל שדה העיר אשר סביבתיה נתן בתוכה THE FOOD OF THE FIELD WHICH WAS ROUND ABOUT EVERY CITY LAID HE UP IN THE SAME — for every district preserves its own produce; and for this people always put amongst the grain some of the earth of the place in which it grows and this prevents it decaying (Genesis Rabbah 90:5).”

Imported from an open dataset — not yet checked against the printed edition.