Key Field Management Techniques for Growing Vegetable Sweet Potato
1. Checking seedlings and filling gaps: 5-7 days after planting, check the survival of the sweet potato vines and promptly replant strong seedlings in spots where plants are missing.
2. Topdressing: For spring sweet potatoes, 30-40 days after planting, after the vines spread and before the rows close; for summer sweet potatoes, 20-25 days after planting, open holes below the side of the ridge and apply topdressing, using 30 kg per mu of compound fertilizer (N:P:K=10:7:8); combine topdressing with loosening the soil between ridges and hoeing weeds.
3. Drought resistance and waterlogging prevention: Spring sweet potatoes enter the row-closing stage around the wheat harvest period in mid-June and are prone to drought. If wilting is found in the middle and upper leaves, water promptly to resist drought. The watering method is alternate-row furrow irrigation or sprinkler irrigation, using about 30 cubic meters of water per mu. After the rainy season begins, prevent water from accumulating in the furrows and drain it at any time.
4. Pest and disease control: Purple sweet potato has good adaptability. If planted on fresh land, severe pests and diseases generally will not occur. Before and after the beginning of autumn, various leaf-eating pests are likely to occur, and they should be promptly controlled with high-efficiency, low-toxicity pyrethroid biological pesticides.
5. Harvest: As daylight hours shorten and temperatures drop after the beginning of autumn, sweet potato storage roots expand rapidly. In order to achieve a higher yield, purple sweet potato (except that rushed to market early) should be harvested as late as appropriate, delaying until around National Day when the soil temperature is 13-15 degrees C, and then harvested promptly, and transported and stored as it is harvested. Cultivation of vegetable sweet potato. Vegetable sweet potato generally refers to the fresh tender stems and leaves about 12 cm long below the growing point used as a vegetable. Tender sweet potato stems and leaves, like the storage roots, are rich in vitamin C, dietary fiber, crude protein, various minerals and some special nutrients. According to testing by the Chinese Academy of Preventive Medicine, when sweet potato leaves were compared with 14 vegetables including spinach, sweet potato leaves ranked first in 13 nutritional components including protein, calcium, phosphorus, iron, carotene and vitamin C. In recent years, the National Cancer Prevention Research Institute of Japan analyzed anti-cancer components in more than 40 vegetables and conducted anti-cancer experiments showing that leaf-vegetable sweet potato ranks first in anti-cancer properties; American scientists found that sweet potato contains an active substance called “dehydroepiandrosterone”, which can prevent colon cancer and breast cancer, and can delay intellectual decline and increase human immunity. Developed countries regard sweet potato as “health food” and “space food”.
At present, domestic and foreign varieties include Taiwan, China's Tainong 71, Japan's Kanto 109, and others. Our country started this research work somewhat late, and in the late 1980s selected dual-purpose leaf and root varieties such as Lu Shu No. 7, Beijing 553, Shi 20 and others. In the 1990s, after more than ten years of effort, Fujian Province successfully bred the country's first leaf-vegetable special-type new sweet potato variety approved at the provincial level, Fushu 7-6. With deeper understanding of the edible value of sweet potato stems and leaves, and the successful breeding of excellent leaf-vegetable type sweet potato varieties, eating tender sweet potato stems and leaves as a vegetable has quietly become fashionable. In the vegetable markets of Japan, Southeast Asia and other countries and of Taiwan, China, Hong Kong, China, the tender tips and leaves of sweet potato stems are best-selling nutritious and health-care vegetables and are highly favored. In the Hong Kong, China market, the price per kilogram of tender sweet potato leaves and tender shoots reaches about 100 Hong Kong dollars. In recent years, the consumption of vegetable-use tender sweet potato stems and leaves in our province has grown rapidly, with an average annual growth rate of about 230%. Tender sweet potato stems and leaves have commonly entered mid- to high-grade hotels and have gradually reached ordinary people's dining tables. The application and promotion area of leaf-vegetable sweet potato has expanded rapidly.
At present, the cultivation of vegetable sweet potato in China is still in the initial stage. Because the rainy season in the south is long and rainfall is heavy, high-ridge cultivation is used: on ridges 15 cm high and 1-1.2 m wide, 6 rows of vegetable sweet potato are planted, and the 25-30 cm space between ridges is used for drainage and harvesting operations. 15,000-20,000 plants per mu, planted once and growing year-round, can produce about 3000 kg of commercial vegetables per mu, with an output value of more than 4000 yuan. Since the trial introduction in this city in 2004, the results show that leaf-vegetable sweet potato can be planted in open fields with flat planting and plastic film mulching in the suburbs of Beijing, can grow for 150-160 days, with a harvesting period of 120-130 days, and a yield of 2000-2500 kg per mu; in protected greenhouse cultivation it can grow year-round, with a yield reaching 3000-4000 kg.
The main cultivation techniques are as follows: 1. Land and ridge selection: Vegetable sweet potato is mainly grown to harvest stems and leaves, while also taking into account the characteristics of sweet potato, so fertile light loam soil should be selected. Soil fertility should be high, and the previous crop should be one that has not grown sweet potato within three years (watermelon, vegetables, corn or wheat fields are best). According to the climate characteristics of the north, the ridge specification is 15 cm high and 60-80 cm wide, with a 30 cm watering operation strip in the middle. Before making the ridges, 2000-2500 kg per mu of decomposed organic fertilizer and 50 kg of poisoned grain mixed with 0.2% phoxim liquid are broadcast, and turned into the soil as the soil is loosened and ridges are made. The ridge surface is fully covered with 0.015 m thick plastic film and pressed firmly on both sides.
2. Planting: Sweet potato seedlings are planted on top of the ridge, with a row spacing of 20 cm and a plant spacing of 12-15 cm, planting 14,000-16,000 plants per mu. The seedlings are planted vertically or inserted at an angle, with a planting depth of 4-6 cm. After planting, use a watering can to spot-water, and cover the film cracks well.
3. Harvesting and pruning: After the sweet potato vines recover from transplanting, immediately pinch off the growing tips to promote axillary buds to form side branches. About 30 days after planting, the 12 cm portion of the tips of new side branches can be picked, packaged and sold. After that, harvest once every 7-8 days according to growth, until the vines stop growing at the first frost. Each harvest should leave about 2 nodes at the base of the branch to ensure regeneration of new buds. While harvesting, the mother stems must also be trimmed, removing deformed small buds sprouting from the old stems at the bottom, to ensure ventilation and light penetration of the population and concentrated supply of nutrients.
4. Topdressing and management: To ensure the yield and quality of stems and leaves, after harvesting twice, water and apply topdressing once. Use nitrogen-phosphorus-potassium compound fertilizer or special water-flush fertilizer 10-15 kg, with about 25 tons of water per mu, poured along the harvesting operation strip and seeping into the ridge from the side. After watering, loosen the soil and pull out weeds on the ridge surface or in the middle at any time. Vegetable sweet potato has good adaptability, and diseases rarely occur on fresh land. If leaf-eating pests occur, high-efficiency, low-toxicity biological pesticides should be applied as early as possible.
5. Seed potato propagation: Because storage roots cannot expand in sweet potato fields where stems and leaves are harvested, seed preservation must be planted separately. The requirements for growing vegetable sweet potato for seed are consistent with those for ordinary sweet potato cultivation.