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Sunflowers are cross-pollinated crops. There are 1000 to 3,000 sturdy flowers in the disk. The phenomenon of empty shells of sunflowers in dry areas is more common. Generally, the empty shell rate is 20% to 35%, and the highest is more than 50%. Even the flower discs are all glutinous grains. Empty shells are an important factor affecting sunflower yield. The empty shell of sunflower has the largest number of empty granules in the center of the disk. The outer shell is mainly caused by poor pollination; the empty shell in the center is mainly caused by insufficient fertilizer and water and lack of nutrition. Therefore, the prevention of sunflower shells is first to ensure adequate fertilizer and water conditions, followed by artificial assisted pollination.
First, strengthen water and fertilizer management Sunflower is a crop that likes fertilizer water. The advantages and disadvantages of water and fertilizer conditions have a close relationship with reducing the empty shell rate of sunflower and increasing yield. Tests have shown that the shell rate of sunflower with sufficient fertilizer is only 3.5% to 5%.
1. Rational use of natural precipitation is an effective way to reduce the rate of empty shells. Sunflower has strong adaptability to drought resistance, but it is still a crop with more water demand from the perspective of growth period. The transpiration coefficient is larger, which is 2 to 3 times that of cereal crops. When the water absorbed by the seed is about equal to 56% of its own weight, it can germinate. Moreover, in the 25 to 30 days from the formation of the sunflower to the final flowering period, the water needs most, accounting for more than 2/3 of a lifetime. The lack of water during this period will severely reduce production and increase the number of empty shells. Tests have shown that in dry areas, irrigation is reduced by 1 to 1.5 times than without irrigation.
However, in semi-arid areas where irrigation is lacking, natural rainfall is used to meet the water requirements of the sunflower growing season. Here, there is a problem of how to make the bud flowering and filling period with more water demand coincide with the peak of natural rainfall. Choosing the right type of variety and determining the optimal sowing date is the core to resolve this contradiction. For example, Jianping County has a rainfall of 300-500 mm, and 70% of the rainfall is concentrated in June-August. Spring drought and autumn drought often occur. According to the characteristics of water demand in the early and late period of sunflower, water demand in the medium term and local rainfall, it is advisable to choose medium-early or mid-maturing varieties to be sown on May 10-15, and early-maturing varieties to be sown on May 20-25. As long as you catch the spring seedlings, drought and less rain will benefit the seedlings and make the seedlings strong. The water requirement accounts for 60% to 70% of the life of the flower disc formation, flowering, and filling period is the peak of the rainy season from June to August, which is conducive to the development of the flower disk, the formation of flower organs, and the reduction of empty grains. However, too much rain will also affect the powder and increase the spread of the disease.
2. Scientific fertilization is an effective measure to reduce empty shells. Sunflower is a fertile crop. The plant is tall and requires a lot of fertilizer. Each 100 kg of grain needs to consume 4.4 to 6.5 kg of pure nitrogen, 1.5 to 2.5 kg of pure phosphorus, and 6 to 18 kg of pure potassium, which is 1 to 2 more than cereal crops. Times. Moreover, the intake of fertilizer particles is uneven at each stage of growth, and more fertilizer is required from emergence to flowering. Insufficient fertilizer is not only unfavorable to plant development, but also has a direct impact on the formation and development of floral organs. In particular, the empty granules in the center of the disk are increased, and the empty shell rate is as high as 40.1%.
Sunflowers require a large amount of fertilizer from emergence to flowering. The amount of nitrogen, phosphorus and potassium required accounted for 67%, 54% and 66% of the lifetime, respectively. Therefore, on the basis of the application of the base fertilizer, the seed fertilizer should be re-applied to ensure sufficient nutrient supply, laying the foundation for reducing the open rate. Generally, 4000 to 5000 kilograms of organic fertilizer per mu is used as base fertilizer, 20 kilograms of diammonium phosphate, 10 kilograms of urea, and 10 kilograms of potassium nitrate are used as seed fertilizers, combined with treading and planting. When the leaves are unfolded 8 to 10 pieces, that is, when the original body of the disk begins to differentiate, 20 kg of urea is applied per acre, 20 kg of superphosphate and 5 kg of potassium nitrate. The experiment proves that at this time, top dressing can ensure the demand for nutrients in the early growth stage, promote the differentiation of small flowers, increase the number of small flowers by 19% to 44%, increase the yield by 25% to 44.4%, and reduce the empty shell rate.
3, manual snoring is a good way to reduce nutrient dispersion. Sunflowers have the characteristics of branching, especially the edible varieties are more obvious, each leaf axillary can grow branches and open into a flower disk. Branches consume nutrients. Seeds of small seeds, at the same time, make the main stem disk smaller, empty granules increase, yield decreased. In order to avoid nutrient consumption, ensure that the main stem disk production should be promptly hit in the outcrop of the branching buds. Tests have shown that the rate of artificial snoring is below 8%, compared to 41% without snoring.
Second, strengthen insect pollination
Sunflower is an insect-borne pollen crop, and the effect of bee pollination is extremely significant. Tests conducted by the former Soviet Union on insect pollination showed that the shells of pollinated plants with bees and other insects were 14.8%; the shells with only a few insects pollinating were 59.8%; and the shells without natural pollination of insects and insects were empty. It is 85.8%. From this point of view, the development of beekeeping industry, the use of bee pollination is a great advantage to increase sunflower yield and reduce the shell rate. Tests have shown that a box of bees is placed every 5 acres of sunflower field, the seed setting rate is above 95%, and the yield is increased by 10% to 20%.
Third, artificial assisted pollination
In the case of insects and bees, artificial assisted pollination is an effective way to increase the seed setting rate. After the sunflower is flowering, the viability of the pollen and the energy of the stigma without pollination can be maintained for 10 days. The pollen is most energetic during the first 2 to 3 days of flowering. Therefore, the first artificially assisted pollination should be carried out 2 to 3 days after the sunflower enters the flowering stage (70% of the whole plant is flowering).
It will be given once every 3 to 4 days, and pollinated 2 to 3 times. Pollination time is best done after the morning dew falls and ends at 11 o'clock in the afternoon. If it is not done in the morning, it can be done after 3 pm. There is dew in the morning, pollen forming a group affects the pollination effect; at noon, the heat is weak, and the pollen is weak and the effect is not good.
For artificially assisted pollination, it is best to use a 10 cm diameter round paper or wooden board, which is covered with a layer of cotton, covered with gauze, and tied diagonally on the back to make a "puff" similar in size to the disk. When pollinating, hold the sunflower flower pan neck in one hand, and gently touch the flower pan on the front of the other hand with a puff. Do not use too much force to avoid damage to the stigma of the pistil, so that the pollen grains of the stamens stick to the puff, and then the puff is treated in the same way. Pollination was carried out in contact with another faceplate. When pollinating, be careful to give fresh pollen to the flowering florets. The more pollination plants, the more mixed pollen on the puff, the more chances of pollination, and the better the pollination effect. According to the test, the artificial shelling rate of sunflower is only 37%, and the shell rate of artificially assisted pollination is as high as 61%. The original Soviet test proved that artificially assisted pollination increased by 8.6% compared with no artificially assisted pollination. In areas where there are no bees, the effect of artificially assisted pollination is most pronounced.
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