Sweet potatoes are a versatile crop, and the variety selected should align with the export purpose. For processing into vermicelli and other starch-based products, high-starch varieties such as Yushu No. 7, Sushu No. 7, Meiying No. 1, and Shanglu SL-19 are ideal choices. For baking or fresh consumption, varieties like Xushu 34, Purple Sweet Potato from the United States, black sweet potato, and Japanese Chuanshan purple—such as Gaodeng 14—are preferred.
The quality of seedlings plays a crucial role in both yield and overall plant health. Strong seedlings grow faster, develop roots earlier, and have better resistance to environmental stress. In contrast, weak or old seedlings tend to lag in growth, resulting in weaker stems and leaves, and lower resilience to pests and diseases. Therefore, cultivating robust seedlings is a key factor in achieving high yields.
Deep plowing and proper fertilization are essential for optimal growth. It is recommended to apply 4,000 kg of well-decomposed organic fertilizer per mu (667 square meters), along with 40 kg of ammonium bicarbonate, 60 kg of superphosphate, and 20 kg of potassium sulfate. Plow to a depth of over 25 cm, and create ridges that are 30 cm high, 40–50 cm wide at the top, and 90 cm wide at the base. The furrow should be 30 cm wide. Plant two rows of seedlings on each ridge to maximize space and productivity.
In moderately fertile fields, strong seedlings can increase yield by 26.5%, while in highly fertile areas, the increase is around 9.6%. This highlights the importance of nurturing healthy seedlings. Choose a nursery bed that is sunny, elevated, well-drained, and easy to manage. Two common methods are film-covered and buried seedling techniques. The bed width should be 1.2–1.3 meters, and the length can vary based on need. Approximately 150 kg of seed potatoes are used per bed. Each 10 kg of seed can produce about 0.5 million seedlings. Proper management includes maintaining temperature, moisture, ventilation, hardening off, and cutting back excess growth.
Early planting is vital for maximizing yield. Sweet potatoes are a long-season crop, so extending the growing period under suitable temperatures increases production. In spring, mulching allows for earlier planting—about 10–15 days ahead of traditional methods. Once the risk of frost has passed, seedlings are transplanted. This method can boost yield by more than 30% compared to non-mulched cultivation. For open-field planting, use strong seedlings that are about 25 cm tall. Plant two rows per ridge, with 3,500–4,000 plants per mu for spring crops and 4,000–5,000 for summer crops. Plant shallowly, leaving 5 cm above ground, and bury the rest 5–8 cm deep. Water thoroughly after planting, cover with fine soil, and leave 3–4 leaves exposed. Apply 80–100 g of trifluralin mixed with 60 kg of water to prevent weeds. Check seedlings within five days of planting.
Watering and fertilization are critical throughout the growth cycle. Ensure sufficient water after planting. If drought occurs after 20 days, water along the furrows. During rainy seasons, ensure proper drainage to avoid waterlogging.
Sweet potatoes require substantial nutrients and should be fertilized using the "four principles": enough, appropriate, heavy, and skillful. Base fertilizer should account for 40–50% of total application, including organic and mineral sources. A side dressing of 5–7 kg of urea or 1,000–1,200 kg of diluted manure is applied 10–15 days after planting. A second dose, accounting for about 40% of total fertilizer, should be applied before the vines spread out. In the late growth stage, when cracks appear on the soil surface, apply 1,500 kg of urea (or 10 kg per hectare) with water. Foliar sprays of 0.2% "sweet potato expansion agent" or potassium dihydrogen phosphate can also promote tuber development.
Weed control is important before the vines cover the field. Perform 2–3 cultivations to keep the ridges clean and maintain their shape. After rain or when the soil is moist, many roots develop near the surface. Prune the vines and spray 15% paclobutrazol at a concentration of 230 g per 60 kg of water to regulate vine growth and encourage tuber formation.
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