Northeast Sweet Potato Maturity Time and Planting Techniques Explained in Detail

Sweet potato is a high-yielding and highly adaptable food crop, closely tied to industrial and agricultural production and people's daily life. The harvest time of sweet potatoes differs slightly between northern and southern China. So, when do sweet potatoes mature in Northeast China? Planting techniques explained in detail!

1. When do sweet potatoes mature in Northeast China?

Sweet potatoes in Northeast China generally begin to be harvested in mid-October, with the latest harvest period before frost, and harvesting is prohibited on rainy days. When harvesting, dig, load, transport and unload gently to prevent the skin and tubers from being bruised. Storage requires a temperature of 10-15°C and relative air humidity of 85%-90%. The storage site should be clean and hygienic, with good rat-proofing and pest-proofing measures. At the same time, insulation measures should be taken to prevent freezing injury and compression, and attention should be paid to ventilation and heat dissipation.

2. Sweet Potato Planting Techniques

1. Raising seedlings

Early-maturing varieties are best raised with three-layer insulation: a large greenhouse + small arch tunnel + plastic film, and after early emergence they are cultivated under plastic film mulch to supply the market earlier; conventional cultivation can use two-layer insulation with a small arch tunnel + plastic film. The seedbed should be about 1.0 m wide and 15-20 cm deep; spread a layer of organic fertilizer on the bed bottom, then water and cover with soil.

Seed potatoes selected should have the typical characteristics of the variety, be free of pests and diseases, and weigh 100-250 g. The sowing density is about 3 cm between tubers. After the seed potatoes are arranged, cover with soil 2-3 cm thick, not exceeding 5 cm, so as not to affect emergence. When 60% of the tubers have sprouted, remove the plastic film. On sunny days when the temperature is above 20°C, open both ends of the arch tunnel film and greenhouse film for ventilation to prevent high-temperature damage to the seedlings, maintain a bed temperature of 25-30°C, and keep humidity such that the bed soil is alternately dry and moist. When the sweet potato seedlings are 20-25 cm long and have 6-8 complete leaves, they can be cut and planted in the field.

2. Cutting and planting

When the average temperature is above 15°C, seedlings can be cut and planted in the field. Because the early temperature is relatively low (late April to mid-May), plastic film mulch cultivation can be used. When planting, insert 4 nodes horizontally or obliquely into the soil; in dry conditions, leave two leaves and one heart above the ground and bury the remaining leaves in the soil, so as to help the seedlings survive and make tuber formation evenly distributed, improving the marketable rate and yield. The planting density is 4000 plants/667 sq m, with a plant spacing of 20 cm.

3. Land preparation and fertilization,

Land preparation should be carried out on sunny days, and the soil should be broken up and finely worked. After leveling, fertilizer is applied in bands at the bottom of the ridges, with a ridge spacing of 80 cm and a ridge height of about 20 cm. Special organic compound fertilizer can be used. For larger planting areas, soil n, p, k and organic matter should be tested, and in the south the soil pH value should also be tested. The use of ordinary compound fertilizer is not recommended.

4. Pruning and topping

For sweet potato fields with many branches and vigorous growth, two or three branches can be cut off with scissors; this allows nutrients to flow back and gives the tubers more nutrients. Topping can regulate nutrient movement and promote the transport of nutrients to the roots. When the seedlings grow to 40-60 cm, remove the tender tips; when branch growth is excessive, also remove the tender tips.

5. Timely topdressing

For seedling-promoting fertilizer, about 15 days after planting, together with the first intertillage, apply 750-1000 kg of dilute human and livestock manure or 2.5 kg of urea per 667 sq m. For tuber-setting fertilizer, apply during the branching and tuber-setting stage, generally within one month after planting together with the second intertillage, mainly nitrogen fertilizer combined with phosphorus and potassium fertilizer. For crack fertilizer, after the stems and leaves close the rows, when the tuberous roots grow faster and cracks appear in the ground, apply topdressing. Per 667 sq m, apply 1.5 kg of urea, 10 kg of superphosphate extract, and 3 kg of potassium sulfate mixed with 150-200 kg of water to make a nutrient solution, and pour it along the cracks on a cloudy day or in the afternoon of a sunny day, requiring even topdressing.

6. Pest and disease control

Diseases mainly include viral disease, black spot disease, and violet root rot. Control methods: select disease-free seed potatoes, soak them in a 2000-fold dilution of 80% 402 agent for 5 minutes before sowing in the seedbed, and for cuttings soak in a 1500-fold dilution of 25% carbendazim or a 2000-fold dilution of 50% thiophanate for 10 minutes.

Pests mainly include the tobacco cutworm and the sweet potato leaf beetle. For the tobacco cutworm, in late June spray a 1000-fold dilution of 10% chlorfenapyr, an 800-1000-fold dilution of 5% tebufenozide, or a 1000-fold dilution of 48% chlorpyrifos. For the sweet potato leaf beetle, 30 d after cutting and planting the seedlings, spray a 600-fold dilution of 20% triazophos emulsifiable concentrate or a 4000-fold dilution of 2.5% deltamethrin.

Whether sweet potato yield is good or not, seed selection is key. Choose ones that are appropriate in size, uniform, free from pest and disease attack, and free from wounds as seed.