Wenzhou tangerine, also known as seedless tangerine, is deeply loved by consumers because of its thin skin, sweet and sour taste, convenient eating and containing zeaxanthin, an effective anticancer ingredient. However, in production, extensive management such as over-dense planting, neglect of pruning and indiscriminate application of chemical fertilizers lead to poor fruit quality, which can not give full play to the advantages of varieties themselves and reduce market competitiveness. High sugar is the central link of citrus quality. In recent years, we have accumulated some experience in the practice of high sugar cultivation of mandarin oranges. The relevant situation is briefly introduced as follows. 1 Physiological basis of fruit sugar accumulation The input of photosynthetic products in leaves is the basis of fruit sugar accumulation. Leaves use carbon dioxide absorbed by stomata and water transported by roots as raw materials to synthesize starch through photosynthesis. Photosynthesis is the strongest at 30 ~ 33℃, and net photosynthetic products are the most at 27 ~ 28℃. In order to produce high-sugar citrus fruit, it is required to have many leaves on the tree, strong leaves, good light conditions and strong photosynthetic efficiency. Starch produced in leaves is first decomposed into sucrose, which is transported to other parts through the sieve tube of phloem, but the transportation and distribution are uneven, and it accumulates in fruits, thick branches, roots and trunks, and then is converted into starch for storage. Sucrose is combined with phosphoric acid during transportation, and there is more phosphoric acid in fruit than in other organs. If phosphorus is lacking and the fluidity of sugar is poor, it is difficult to bear high-sugar fruits. However, the sugar content in trees is low, and even if a large amount of phosphate fertilizer is applied, high sugar cannot be produced. Excessive phosphorus easily leads to copper deficiency. The substance that regulates sugar accumulation in fruits is auxin. Embryos in seeds synthesize a lot of auxin when they start to divide after fertilization, and the growing point contains high auxin. During the growth and development of seeds, auxin synthesized in leaves accumulates in seeds, which promotes the differentiation and growth of embryos and the expansion of fruits, and makes sugar transport and accumulate in fruits. Citrus fruit has no seeds, but its auxin content is high. Another study shows that it is soil drying that inhibits the growth of roots, reduces the transport of sugar synthesized by leaves to roots, and increases the sugar moving to fruits, which are storage places closer to the ground. Therefore, in the period of fruit quality formation, dry soil trees are under mild water stress and the fruit sugar content is high. 2. The conditions and tree shapes of producing high-sugar satsuma were observed and compared, and the basic conditions and tree shapes of producing high-sugar satsuma were summarized. 3. High-sugar cultivation method of tangerine 3. 1 pier cultivation keeps the root system dry to improve the sugar content of the fruit. Before planting seedlings, a conical or cylindrical mound should be built. In a flat orange orchard, ditches should be dug first and then mounds should be built. The height of the mound is 45 ~ 50 cm, and plastic sheets should be placed under it to prevent the roots from falling. In the year of unusually rainy autumn, although pier cultivation has good drainage effect, it still can't achieve the purpose of increasing sugar. 3.2 Plastic film mulching cultivation In early September, plastic film should be covered after 3-5 days of fine weather to prevent rainwater from entering the garden soil. When covering, it is required to seal the film and the trunk with adhesive tape and compact it with clods or stones. The water in the flat orange orchard is easy to penetrate into the soil, so the furrow should be dug before the plastic film mulching, and the rainwater can be discharged out of the orchard in time after the rain. The above two methods are to control the water content of soil, so that the growth of roots is hindered by water stress and the accumulation of sugar in fruits is improved. The basis of this method is soil improvement, looseness and air permeability, and strong water and fertilizer conservation ability. Then the capillary roots of orange trees are many and dense, which can withstand the dry soil environment. The key is to master the degree of water control. If the water control is insufficient, the soil water content is too high to increase the sugar in the fruit; Too dry, leading to tree decline or even death, contrary to expectations. It is appropriate for the leaves to curl slightly, but they can be leveled again the next morning. If you can't recover, there are fallen leaves, which means it is too dry. Therefore, timely and appropriate irrigation is required. When the temperature is low in the morning or evening, the leaves should be sprayed (if the leaves are yellow and have symptoms of fertilizer deficiency, 0.3% urea +0.2% potassium dihydrogen phosphate can be sprayed) to alleviate the water stress of trees and restore their vigor. 3.3 Bagging to complete the cultivation. Put the fruits in paper bags and hang them on trees for the winter, and then harvest them when they are fully ripe. Miyagawa Satsuma Citrus is the best variety, and the bagging object is small fruit with an inner chamber diameter less than 55㎜. During the normal harvest period (65438+1mid-October), this kind of fruit has green surface and high acid content, and it is not easy to peel after bagging, and the fruit surface turns orange-red and the sugar content is obviously improved. The number of bagged fruits per plant should be controlled below 30% of the fruit hanging amount. The harvest period is from the end of February to the end of 10. 4. Wenzhou mandarin 4. 1 Key points of high-sugar cultivation technology management: Choose suitable varieties, and choose high-sugar varieties such as Qingdao and Dajin No.4 in areas with no freezing injury in winter (minimum temperature above -5℃) and high annual accumulated temperature, and choose early-maturing varieties such as Miyagawa, Xingjin and Guimei in other areas. 4.2 Appropriate planting density is required, with 55-73 plants per 666.7m2 in mountain orange orchards and 465,438+0-55 plants per 666.7m2 in flat orange orchards. If planted too closely, adjacent branches will cross easily, resulting in canopy. Reasonable shaping and pruning, leaving 3 ~ 4 main branches, auxiliary main branches and horizontal line 15 ~ 20? Angle, so that the crown is large and small, the height of the tree is 2 ~ 2.5 m, pruning or shortening the big branches will disturb the tree potential and form a well-ventilated transparent tree. 4, 3 Before high-sugar cultivation, the soil should be deeply ploughed to improve the soil structure. High-sugar cultivation and fertilization need to control nitrogen, increase phosphorus and potassium. Rapeseed cake, compost, manure and other organic fertilizers are the main body to promote a large number of capillary roots and leaves. 4. Moderate results, the output per 666.7m2 is 2,000 ~ 2,500, and the range of results in two years is controlled within 10%. 4, 5 to prevent extreme drought, less fertilizer, excessive fertilization, excessive pruning. In particular, urea, ammonium bicarbonate and other nitrogen fertilizers and pigsty fertilizers with more nitrogen should not be used too much, otherwise the high-sugar cultivation techniques will not achieve the desired results. 5 Selection method of high-sugar satsuma fruit The appearance characteristics of satsuma with high sugar content and good flavor are: flat fruit shape, thin fruit stalk, thin skin, smooth fruit surface, small and dense oil cells in the skin, orange-yellow or orange-red peel color, moderate size, good elasticity, unique citrus aroma, soft and slag-melting entrance, sweet and juicy, fragrant and delicious. Mainly observe the shape, smell the fragrance and touch it. High ursolic acid; Fruits with a transverse diameter greater than 65mm, with thick stems and rough skins, are tasteless and have little juice; Soft fruit tastes bad. In addition, generally cultivated small fruits taste sour.