Main cultivation technical points for purple sweet potato planting

1. Land selection

Most purple sweet potatoes belong to mid-to-late maturing varieties, with tuber rapid expansion and yield formation occurring relatively late. The plot to be planted not only requires relatively high soil fertility, but the soil texture should be light loam or sandy loam, and the land levelness and drainage and irrigation conditions should be good. Purple sweet potato has relatively good adaptability, but in continuous cropping land with a history of nematode and black spot disease occurrence, diseases may occur, causing reduced yield, so attention should be paid to soil disinfection and insecticidal treatment.

2. Variety selection

At present, there are many purple sweet potato varieties in China, and varieties should be selected or introduced according to local soil conditions and planting purposes. For health care and fresh eating, Jingshu No. 6, Ji No. 18, Xu 22-5, etc. can be selected; for dry powder processing, Xu Zi No. 1, Guaizi, Shanchuanzi, etc., which have a high dry matter rate, can be selected; for soil with high fertility, Jingshu No. 6, Ji No. 18, and Xu Zi No. 1, which have large yield increase potential, can be selected; for soil with low fertility, Shanchuanzi, Guaizi, etc., which have strong adaptability, can be selected. 

3. Cultivation techniques 

In the suburbs of Beijing, purple sweet potato is best planted by ridging with film mulching or flat planting. For spring sweet potato, the ridge spacing is 75-80 cm, for summer sweet potato 70-75 cm, the ridge top width is 15-20 cm, the ridge height is 25 cm, and the entire ridge is covered with 800×0.008 mm black or transparent polyethylene film. Before ridging, apply base fertilizer per mu (N:P:K=8:7:10) compound fertilizer 50 kg, and 5 kg of poison bait mixed evenly with 0.2% phoxim liquid pesticide, broadcast applied, and applied into the ground as the soil is turned and loosened. When using organic fertilizer as base fertilizer, it must be fully decomposed, and according to conditions, 2-3 cubic meters per mu. Purchased or self-raised sweet potato seedlings should be properly graded before planting, and those with consistent performance should be planted together to ensure uniform and balanced growth in the field. Purple sweet potato seedlings are relatively robust, and before planting, the part that has already produced adventitious roots should also be cut off, which can not only promote rapid concentrated adventitious root formation at the lower nodes, making tuber formation neat and concentrated, but also reduce seedling height and promote earlier seedling recovery. Seedlings are planted in the central part of the ridge top. Use the thumb and index finger to pinch the middle of the seedling, and the middle finger to pierce downward through the plastic film, while opening a concave hole with a diameter of 5-6 cm and a depth of 4-5 cm. The root of the sweet potato seedling is fixed at the bottom of the hole with soil, and 3-5 leaves are exposed above ground. Plant spacing is determined by ridge spacing. The total number of seedlings planted per mu is 3200-3400 plants for spring sweet potato and 3500-3700 plants for summer sweet potato. Water each seedling hole twice, with a total amount of 500-600 milliliters, then cover the concave hole evenly, and seal and press the film opening tightly.