The crop usage icon shows how much crop you have available and how much you are using. As with all resources, crop is stored in individual villages. Each village's granary can hold a certain amount of crop (depending on its level). Each village's crop fields produce a certain amount of crop per hour (depending on their levels), and the buildings and troops in the village consume a certain amount of crop per hour. In the image above, the granary statistics are circled in green. The granary in this village can store a maximum of 45700 units of crop, and currently contains 3219 units.