Newly spawned farmer villagers will not farm unless they already have seeds.

When a new village is generated, the farms are a crucial component to them, as they serve as a means for the village to repopulate naturally. However, the farmer villagers that spawn next to the village composters will not farm without player intervention, thus severely crippling the village. To get them to begin farming, they must first have a seed (or potato/carrot) in their inventory to plant; otherwise, they will only work at their workstations and wander around like every other profession.