Lack of corn ear fill can stem from a variety of causes. Hot, dry weather can result in poor pollination. Periods of heavy rain when pollen is shedding can also be a problem, as can planting a very small patch or a single row of corn. In these situations, the corn cannot pollinate adequately. Certain nutrient imbalances, particularly high nitrogen or low potassium, also can cause ears of corn to fill out improperly.