There are many reasons: 1. The flowering climate is not good, too dry, high temperature, low temperature and even rainy days are easy to cause poor pollination and fertilization, resulting in large and small grains.

2. Lack of trace elements, mainly boron and zinc.

3. Unreasonable use of fertilizer and excessive nitrogen fertilizer lead to vigorous growth of the ear and relatively insufficient nutrition.

4. Improper pruning leads to disharmony between vegetative growth and reproductive growth, and the nutrition in the ear is relatively insufficient.

5. Improper use of regulators can easily lead to poor pollination of some flower buds and the formation of large and small grains.

Solution: 1 Strengthen the management of fertilizer and water, pay attention to the application of long-acting base fertilizer such as organic fertilizer, and ensure the supply of nutrients needed for flowering and fruit setting.

2. Spray liquid boron and zinc sugar alcohol on 2-3 leaves before flowering.

3. Choose reasonable pruning, combine with variety characteristics, scientifically core, and carry out secondary shoot treatment.

4. Scientific and rational use of regulators and correct use of regulators can reduce flower drop, fruit drop and grain size.

5. Pruning before flowering will not cause the fruit to be too dense and different in size after sitting on it.