harvest

Answer: crop

Explanation: To harvest means to gather agricultural produce; the primary thing that is harvested is a crop.

• crop — Correct. Harvesting is the process of collecting crops or produce from the field.

• autumn — Incorrect. Autumn is a season when many crops are harvested in some areas, but harvesting can occur in other seasons depending on the crop and location.

• stockpile — Incorrect. Stockpiling is storing or accumulating goods after they are harvested; it is not the act of harvesting or the thing being harvested.

• tractor — Incorrect. A tractor is equipment that may assist with harvesting, but it is not the crop itself and is not required to harvest by hand.

Summary: Harvest refers to collecting agricultural produce (the crop); the other words refer to a season, a storage action, or farming equipment.