1, caused by drought: Sunflower is a drought-resistant adaptable crops. However, the maximum amount of water is required in the formation of the flower disk to the final flowering period, which accounts for about 60% of the water requirement in the whole growth period. The lack of water during this period will increase the number of empty shell grains, resulting in a serious reduction in production. Drought-stressed supplemental irrigation, which lacks water, is an important factor leading to an increase in empty space.
2. Ambient temperature is too high: Sunflower is highly adaptable to temperature, and it is both thermophilic and drought-tolerant. It has stronger resistance to low temperature at seed germination to seedling stage. Seeds can germinate at 4°C, they can emerge at 5°C, and 8~10°C can meet the needs of normal emergence. The suitable temperature for germination is 31~37°C, and the maximum temperature is 38~44°C. Due to improper sowing date in the production, unfavorable temperature after sowing hindered the development of sunflower, which affected the coordinated development of vegetative growth and reproductive growth.
3, caused by insufficient light: Sunflower is a short-day crop, its young leaves, leaves and disk have a strong phototropism. Adequate sunshine, strong seedling growth, mid-fertility can promote vigorous growth of stems and leaves, normal flowering and pollination, increase seed setting rate; late growth can promote full and full kernels. However, due to climatic factors in production, the light intensity is affected, resulting in poor flowering and pollination and an increase in the empty rate.
4. Continuous cropping: Repeated planting of sunflowers on the same plot resulted in reduced yields due to pest and weed damage and imbalance in soil nutrient composition.
5, planting too dense caused by: Sunflower due to different types of species, the density requirements are very different. Generally, the edible varieties are tall and planted, and the oil-using varieties are short and should be planted densely. In order to pursue high yields, people in production have blindly increased their density, resulting in an irrational group structure, prominent conflicts in competing for water and competing for light, and reduced utilization of light energy. As a result, sunflower hollow grains have increased, production has declined, and quality has declined.
6, caused by low fertilization: Sunflower is hi fertilizer crops, cultivation must be enough base fertilizer, timely fertilizer. According to reports, for every 100 kilograms of sunflower seeds produced, 4.4 to 6.5 kilograms of pure nitrogen, 1.5 to 2.5 kilograms of pure phosphorus, and 6 to 18 kilograms of pure potassium are consumed, which is 1 to 2 times more than cereal crops.
7, caused by poor pollination: sunflower is cross-pollination crops. There are 1000~3000 small flowers in the flower disk. The self-pollination rate is very low, and the rate of cross-pollination is high. And the normal fertilization process is determined by the appropriate temperature, light, atmospheric humidity, insect activity, and wind power. The high temperature and dry weather from June to July tended to weaken pollen viability, affect the activities of bees and other insects, and affect normal fertilization, resulting in poor seed setting rate of sunflower due to poor pollination, and an increase in the rate of open space.
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