Even though the zombie horde inflicted some damage to the farmland, it wasn't significant—it was just a few wheat stalks trampled inadvertently, as zombies generally show no interest in a vegetarian diet.
Yet this time was different. The goal of the zombie horde was laid bare: the crops in the farmland! The reason was simple: this zombie horde was human-controlled, and this "human" knew how to maximize the damage to Cloud Gorge Base.