Now, To the Fields of Battle! is the 172nd chapter of Shokugeki no Soma.
The first years arrive in Hokkaido, where the promotion exam called "Tour du Nord" will be held.
Seven days before their arrival, Hisako explains to the Polar Star Dorm group how the promotion exam works. Students start at the southernmost portion of the island and move further north with each trial passed. The goal is to pass 6 trials ending up at a lone island near Hokkaido. If they fail any stage of the exam, they will be taken back to Tokyo where they are assessed of expulsion.
Afterwards for the remaining days until their departure, Erina lectures the group about potatoes as well as plants, fish, meat and wild game that are unique to the island.