Detailed explanation of the latest purple sweet potato planting techniques and methods

Purple sweet potato likes a warm climate environment. The suitable growth temperature for stems and leaves is 18-25°C, and growth stops when the temperature is below 15°C. The optimum soil temperature for storage root growth is 22-24°C, and root enlargement stops when the soil temperature is below 20°C. Purple sweet potato is a short-day crop and needs sufficient light and high intensity. During the growth period of purple sweet potato, the suitable soil moisture is 60%-80% of the maximum field water-holding capacity.

Variety selection

Purple sweet potatoes can be divided by use into fresh-eating types and processing types. When selecting varieties, choose specifically according to the purpose of cultivation. For fresh-eating types, choose varieties with good taste, moderate pigment content, good disease resistance and attractive root shape; for processing types, choose varieties with high pigment content, good disease resistance and high dry matter rate.

Seedling raising techniques

Raising seedlings early and cultivating enough strong seedlings, forming adventitious roots that are both early and thick, is the foundation for fast seedling survival, early and numerous root formation, and high yield. In order to prevent diseases such as black spot of purple sweet potato, strict control must be exercised before raising seedlings. Choose seed tubers without wounds or disease spots. They can be soaked for about 5 minutes in a 1000-fold solution of 70% thiophanate-methyl at a temperature of 51-54°C or a 500-fold solution of 25% carbendazim.

1. Prepare the seedbed

Seedling raising is generally carried out on sunny days in mid-to-late March. Choose a seedbed in a leeward, sunny place with high and dry terrain, good soil permeability, rich organic matter, and easy management, using sandy soil or sandy loam. The seedbed is 1.2 m wide, 20-30 cm deep, and the length depends on the garden plot. Apply 10-15 loads of decomposed human manure and urine per mu, and after the soil has absorbed and dried thoroughly, arrange the tubers.

2. Arrange the seed tubers well

When the temperature reaches about 15 degrees, place the purple sweet potato seed tubers on the seedbed. Generally, about 18 kg of seed tubers are used per square meter, with the back facing up, the head slightly higher, the tail touching the mud, and the head and tail in the same direction. Then apply 10-15 loads of decomposed barn manure per mu, evenly covering the seed tubers, cover with 1.5-2 cm of fine soil, then cover with plastic film and press the edges firmly with fine soil.

3. Seedbed management

Seedbed management mainly focuses on measures such as heat preservation, moisture retention, and ventilation, with temperature as the main factor. Before emergence, cover with straw curtains at night and maintain the bed temperature at 25-35°C. After emergence, control the temperature at 20-25°C and prevent high-temperature damage to the seedlings. If the temperature inside the film exceeds 30°C, ventilate and dissipate heat in time to prevent seedling scorching. When a cold wave comes, do a good job of heat preservation. Before the seed tubers emerge, generally do not water, so as to facilitate high-temperature sprouting, disease prevention and emergence. If the seedbed is too dry, use a sprayer to spray clear water on the seedbed. After emergence, pay attention to the humidity of the seedbed. When the seedbed turns white, water in time, moisten the bed soil and sprinkle dilute human manure and urine to promote the growth of sweet potato seedlings. Fertilize after the seed tubers germinate. At the first “red bud” stage, generally use dilute human manure and urine; when the seedlings are 10-13 cm high, carry out a second topdressing with human manure and urine or urea. After each fertilization, splash clear water to wash the seedlings to prevent fertilizer from adhering to the seedlings and causing seedling scorching. Soil cultivation can be carried out 2-3 times. When the seedlings are about 10 cm high, the first soil cultivation can be carried out, and the second after an interval of one week, with a total soil cultivation of 3-5 cm. For soil cultivation, it is best to use fertile, loose fine soil mixed with burnt mud ash or decomposed compost, and evenly scatter it into the seedbed. Soil cultivation can be combined with applying liquid fertilizer, doing soil cultivation first and fertilization afterward, so that the soil and the base of the seedlings are closely combined, so as to facilitate early and abundant new root development.

Land preparation and ridging

1. Soil treatment

Purple sweet potato has wide adaptability to soil. To achieve high yield, it is generally advisable to choose loose, fertile sandy soil with relatively high organic matter. Because purple sweet potato storage roots have strong elongation, root enlargement requires deep, loose soil. To obtain high yield, after the spring thaw, deep plow, harrow and level the soil to preserve moisture. Before transplanting, pick out stubble, break up clods, combine fertilization and insect prevention (soil treatment), and complete ridging in one operation. For every 667 sq m, use 0.25-0.5 kg of 47% chlorpyrifos made into a 1000-fold solution and spray it on the ground, then plow deeply to prevent underground pests.

2. Deep plowing and ridging

Sweet potato can be planted in two ways: flat planting and ridge planting, with ridge planting being better. The advantages of ridge planting are: thickening the soil layer, expanding the range of root activity, loosening the soil, expanding the contact area between topsoil and air and sunlight, facilitating gas exchange and increasing soil temperature, increasing the diurnal temperature difference, and also facilitating drainage and irrigation. Ridging should be carried out on sunny days when the soil is moderately dry and wet, preferably with deep furrows and large ridges, achieving deep plowing, fine soil, and straight ridges, so as to facilitate drainage and irrigation. The ridge surface should be flat and smooth to facilitate digging holes and planting seedlings. The size of the ridges should be determined according to local conditions such as field type, soil quality, planting season, planting method, growth period and variety. For clay soil with strong water retention, ridges should be high and narrow; for sandy soil with poor water retention, ridges should be wide and slightly lower. Ridging methods include single ridge single row (ridge spacing 60-70 cm including furrow, plant spacing 20-25 cm), single ridge double row (ridge spacing 120 cm including furrow, plant spacing 25-30 cm), etc.