Shen Qingling (Huzhu County Seed Management Station) The promotion and application of virus-free seed potato is one of the important measures for increasing potato production. The quality of seed potatoes directly affects the level of field production. Therefore, how to maintain the superior seed-species of virus-free seed potatoes, prevent virus infection and degeneration of varieties is an important link in the breeding of excellent virus-free seed potatoes. 1 preparation of the original species Select high-purity, detoxified seed potatoes that are specialized in the production of virus-free seed plants as seed breeding species. Size of 20 ~ 30g, choose no insects, no breakage, no germination, smooth skin, uniform and consistent potato chips, prepared for 90 ~ 120 kg per mu. Whole potatoes must be sown and it is forbidden to use mulching techniques. 2 Select plots Breeding areas should be selected from the cold, humid, windy and easily accessible, semi-shallow hemispheres without locusts, and brain regions, surrounded by no cruciferous crops or with natural barrier isolation conditions around them. The plots should be fertile, loose, and fertile. The terrain should be open and flat, and no other non-virus-free varieties or multi-generation virus-free varieties should be planted to prevent reinfection. 3 deep ploughing Deep plowing can loosen the soil, promote the decomposition of organic matter, store water, and improve soil physical properties. In general, when the soil water content reaches 40% to 60%, it is deeply turned and the depth is 20 to 30 cm. This is combined with the treatment of soil chemicals. When the basal fertilizer is applied, it is turned over once and then turned over. 4 formula fertilization Potatoes are high-yielding and fertile crops and organic fertilizers should be added. Organic manure must not have fallen leaves of solanaceous plants such as potatoes. Virus-free seed potatoes have strong growth potential and fast seedlings. They need to use enough base fertilizer to apply seed fertilizers. General Mushi quality organic fertilizer 5000kg, with chemical fertilizer pure nitrogen 23kg, phosphorus pentoxide 4.6kg, potassium oxide 26kg. Generally before the flowering period combined with cultivating top-dressing soil, Mu topdressing ternary compound fertilizer 5 ~ 10kg or with 0.3% potassium dihydrogen phosphate solution foliar spray. 5 sowing 5.1 Reasonable close planting: Generally, 4,500 to 5,500 plants are planted in Mu, with a spacing of 50-65 cm and a plant spacing of 25-35 cm. 5.2 Sowing Date and Depth: Usually sowing in the soil lOcm depth, ground temperature 7 ~ 8 °C. Qinghai Province is generally suitable for sowing from late April to early May, with a depth of 8-12 cm. 6 Field Management 6.1 Loose soil, earth-cultivation and weed control: Virus-free seed potatoes grow faster and should be managed as soon as possible. In the Miao Qi, artificial weeding can be used to increase the soil temperature and strengthen roots. The seedlings grow to about 20cm in height and they are suitable for fertilizing soil, and the second soil is planted before planting ridges. 6.2 Remove miscellaneous and contaminated: In the seedling stage, budding stage, full flowering stage and 20 to 25 days afterwards, conduct inspections and remove diseased plants, miscellaneous strains or premature decayed plants. When harvesting, the plants of the diseased plants, miscellaneous strains, and fragility and cracking of the potato blocks were strictly eliminated, and the rest of the plants were mixed. 6.3 Pest Control: The use of pesticides to prevent earthworms, beetles and other underground pests. In the epidemic year of potato late blight, if the diseased plants were found in the field, spraying was used to control the disease. 7 Harvesting and Storage Seed harvesting should be preceded by field crops. Pay attention to antifreeze, prevent mechanical damage, and cool for a day or two in the air and light. When entering the pit, it must be done lightly, lightly, and gently, so as to avoid colliding tubers with each other and improving the quality of storage. After the tuber enters the pit, the temperature and humidity in the pit are adjusted. The most suitable storage temperature is 2 to 4°C and the relative humidity is 80%. Ventilate well and keep fresh air flowing to allow the potato in the cellar to breathe normally to prevent atrophy and germination of seed potatoes. Different varieties of seed potatoes and edible potatoes should be stored in the cellar. The storage pit should be thoroughly cleaned one month before harvest and then formalined and fumigated. During storage, pay attention to anti-freeze, heat release, moisture prevention, prevent the mixture of varieties, and ensure the quality of seed potatoes. 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