How to improve the fruit setting rate of Shatian pomelo

First, replanting or high grafting of pollinated trees. The proportion of pollinated trees in the whole garden reached about 10-15%, and pomelo varieties with strong pollen quantity, strong pollen vitality and similar flowering period to Shatian pomelo were selected. At present, sour pomelo is often used as the pollination variety of Shatian pomelo. Second, carry out artificial pollination. Artificial pollination can significantly increase the fruit setting rate of Shatian pomelo. The method of artificial pollination is that when the petals of most flowers of Shatian pomelo tree are cross-shaped, choose sunny weather, pick off the blooming flowers of Shatian pomelo tree, remove petals and pistils, pollinate Shatian pomelo flowers directly, or collect pollen in glass dishes or paper bags, and then choose well-developed Shatian pomelo flowers from 8 am to 10:00 or 3 to 4 pm that day. Place the pollen gently on the stigma of the Shatian pomelo flower with a brush and be careful not to damage the flower. The mixed pollen liquid can also be used for pollination by pollinating tree pollen 0.5%, borax 0.1%, urea 0.2%, yellow sugar 0.3%, honey 0.2%, water 98%, and then spraying the stigma of Shatian pomelo flower with a small sprayer for 2 times in a row. The number of pollination per plant should be determined according to the age and strength of Shatian pomelo trees. Trees with large crowns can be pollinated more than those with large crowns. Usually, the number of pollinated flowers is 4 times more than that of fruit trees to be kept. Pollen had better be collected and taught as soon as possible. If the pollen can not be used up for a while, it can be spread out and preserved on the paper under dry conditions. It cannot be sealed and the time cannot be too long, so as to maintain a high germination rate of pollen. Third, spraying trace elements at the last flowering stage or young fruit stage. When the magnesium content in the leaves of pomelo is less than 0.2%, there will be symptoms of magnesium deficiency, which will cause leaf yellowing and affect the ability of spring shoot leaves to turn green and photosynthesis, and turn yellow and fall off due to poor nutrition supply during the period of young fruit growth and expansion, which is disadvantageous to fruit protection. In low boron soil, boron deficiency occurred in pomelo orchard leaves when boron content was less than 20ppm, brown or dark spots appeared in young fruit pericarp, white spots in mesocarp and accumulation of yellowish-brown colloid, small tumor-like protuberances appeared on fruit surface, fruit shape was abnormal, young fruit was hard, and could not grow and develop normally. For this reason, trace elements must be supplemented at the last flowering stage or young fruit stage. Pomelo leaves can be sprayed twice with 0.1 Mel 0.2% boric acid or borax, 0.1 Mel 0.2% magnesium sulfate and 0.2% KH 2PO 4 to supplement an appropriate amount of trace elements, which is beneficial to fruit preservation. Fourth, release bees in the pomelo garden during the flowering period to promote pollination and improve the fruit setting rate. Shatian pomelo must be pollinated and fertilized by different strains of pollen in order to have a higher fruit setting rate, and a lot of seeds can be produced after fertilization. in the process of seed formation, a large amount of gibberellin is produced to keep the young fruit green, thus reducing fruit drop, especially in the second physiological fruit drop period. Therefore, during the flowering period of Shatian pomelo orchard, honeybees should be released, pesticides harmful to honeybees should be stopped, and honeybees should be protected, which is beneficial for bees to spread pollen of different varieties and lines, promote pollination and fertilization of Shatian pomelo, increase fruit setting rate and increase yield. Fifth, use plant growth regulators. At present, plant hormones have been widely used in pomelo orchard to protect flowers and fruits, and the effect is remarkable. The commonly used plant hormones are paclobutrazol, cytokinin, gibberellin, 2mai 4mer D and so on. Paclobutrazol has the effects of controlling winter shoots, promoting flowers, inhibiting spring shoot growth, increasing fruit setting rate and increasing yield, especially for young trees. From late November to early December, Huaguoling produced by Guangdong Academy of Agricultural Sciences was sprayed once every 20 days (a compound shoot control and flower promotion agent made of paclobutrazol as the main ingredient and mixed with potassium, phosphorus, nitrogen, zinc and other nutrients). It can effectively reduce the occurrence of winter shoots, significantly inhibit the growth of spring shoots in the following year, shorten the distance between spring tips, thicken leaves, make leaves dark green, petioles and fruit stalks thick and short. It is very beneficial to the growth of fruit setting and young fruit, and the fruit setting rate is increased. The effect of mixed use of cytokinin (BA), gibberellin (GA) and 2mem4murD was better than that of single use respectively. High concentration of BA + GA and BA + 2mae 4rel D mixed solution sprayed fruit surface or coated fruit surface, the fruit setting rate was high, but both were easy to produce abnormal fruit. If the mixed hormone solution was used to coat the fruit stalk, the effect was significant and the abnormal fruit was avoided. 6. fertilizer and water management at flowering and young fruit stage. Shatian pomelo goes through the long-term low temperature and dry season in winter, when the temperature gradually rises, the root system begins to return to normal growth. at this time, it must be mainly fully mature farm manure, diluted into thin water and fertilizer, and must not be applied with too high concentration. cause root damage and affect the germination of new roots. At the same time, the application of available nitrogen fertilizer must be strictly controlled, especially young fruiting trees or overgrowing trees, and do not apply available nitrogen fertilizer or only use available nitrogen fertilizer as extra-root topdressing. If too much available nitrogen fertilizer is applied at flowering and flowering stage, it is easy to cause excessive growth of flower branches and nutritious spring shoots, resulting in serious contradiction between shoot and fruit, which is not conducive to flower and fruit protection. Attention should be paid to the drainage of pomelo garden during flowering and young fruit growth period. Stagnant water in the garden is easy to cause grapefruit root rot, affect the growth of new roots, and cause a large number of falling flowers and fruits, which is not conducive to flower and fruit protection. In case of severe spring drought or summer drought, timely irrigation and moisturizing are required. Seventh, ring cutting and ring ligation to protect fruit. Ring cutting and ring ligation can make the nutrition can not be transported to the root through the phloem sieve tube, so that the nutrition accumulates on the branches, leaves, flowers and fruits, which ensures that the young fruits have sufficient nutrients to expand rapidly, and it is not easy to turn yellow and fall off, so as to improve the fruit setting rate. When using the method of ring cutting or ring ligation to protect flowers and fruits, the time of ring cutting or ring binding must be chosen according to the different methods used, the growth strength of the tree, and the number of flowers. The object of ring cutting to protect fruit is the young fruiting tree with vigorous vegetative growth and less flowers, so it must be cut in the full flowering period, that is, the first ten days of April. The trees with more flowers can postpone the time appropriately, and the effect is good only if they are cut in the middle and last ten days of April. The method of ring ligation is adopted, because the channel of the phloem sieve tube can not be cut off immediately, so it must be earlier than the time of ring cutting in order to have an effect. Generally, it is chosen to loop in the trunk or main branch when the bud is white in the middle and last ten days of March, and the iron wire should be untied from late May to early June after setting the fruit, otherwise the normal growth of the tree will be affected because the ring is too deep. Eighth, strengthen the prevention and control of diseases and insect pests and reduce the harm to flowers or young fruits. The prevention and control of bud maggots and beetles should be strengthened before flowering. Flower bud maggots harm the flower buds of Shatian pomelo with larvae, make the buds white, expand and shorten ahead of time, and can not open normally, like lanterns, also known as lanterns, seriously affecting the flowering and fruit setting of Shatian pomelo. The prevention and control method is that when the flower buds just show white, after loosening the soil around the tree plate, immediately sprinkle on the ground and spray on the tree crown, carbaryl powder or phoxim can be used, and pyrethroid pesticides can be used for crown spraying. It can also be covered with plastic film before the adults are unearthed, so that the adults of bud maggots can not fly out of the ground and die in the ground. Ploughing in winter and spring can also kill some larvae. Artificial removal of injured "lantern flowers" in full bloom is also an effective method. The beetle endangers the flowering period of Shatian pomelo. In the flowering period of Shatian pomelo, the flowers secrete honey and fragrance substances, which often cause harm to the beetles. In a serious orchard, there are more than 3 beetles on a flower that harm the flower or young fruit, cause damage to the stigma live young fruit, produce abnormal fruit, or cause the young fruit to fall off. Beetles can be caught manually by spraying before flowering or during flowering.