When to Plant Sweet Potatoes in Northeast China? High-Yield Cultivation Techniques Included

Sweet potato is a coarse grain food with complete and rich nutrition. Its starch has a wide range of uses: it can be mixed with various meats to make food balls, mixed with flour and steamed into cold noodles, or used alone to make pancakes, stir up jelly, and so on. It is widely cultivated in both northern and southern regions of China. So, when to plant sweet potatoes in Northeast China? High-yield cultivation techniques included!

I. When to plant sweet potatoes in Northeast China?

In Northeast China, when the average temperature reaches above 15°C, the seedlings grown from the nursery can be cut and transplanted into the field. Spring sweet potatoes can generally be planted from late April to mid-May; autumn planting is best done from late August to late September.

II. High-Yield Cultivation Techniques for Sweet Potato

1. Seed selection and seedling raising

The selected seed potatoes should have the typical characteristics of the variety, be free of pests and diseases, and weigh 100-250 grams per tuber. The arrangement density should leave about 3 cm between tubers. After the seed potatoes are arranged, cover them with soil to a thickness of 2-3 cm, not exceeding 5 cm, so as not to affect sprouting. 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 arched shed film and the greenhouse film for ventilation to prevent high-temperature seedling damage, maintain a bed temperature of 25-30°C, and keep humidity such that the bed soil alternates between dry and moist. When the sweet potato seedlings grow to 20-25 cm and have 6-8 complete leaves, they can be cut and planted in the field.

2. Land selection and soil preparation

Sweet potato has a well-developed root system and strong fertilizer absorption capacity, so it is best to choose plots with deep soil layers, loose soil, good soil quality, and strong irrigation and drainage capacity. Before planting, first plow the land deeply. Fertilizer can be applied first and then the land prepared, or the land can be prepared first and then fertilizer applied in holes or bands. Soil preparation should be carried out on sunny days, and the soil should be broken up and finely crushed. After leveling, apply fertilizer in bands at the bottom of the ridges, with a ridge spacing of 80 cm and a ridge height of about 20 cm.

3. 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 mulching 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 distribute the tubers evenly, improving the commercial rate and yield. The planting density is 4000 plants/667 sq m, with a plant spacing of 20 cm.

4. Soil preparation and fertilization

Soil preparation should be carried out on sunny days, and the soil should be broken up and finely crushed. After leveling, apply fertilizer 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. When the planting area is relatively large, soil n, p, k and organic matter should be tested; in the south, soil pH should also be tested. The use of ordinary compound fertilizer is not recommended.

5. Pruning and topping

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

6. Timely topdressing

For seedling-promoting fertilizer, about 15 days after planting, together with the first cultivation, 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 topdressing during the branching and tuber-setting stage, generally within one month after planting together with the second cultivation, mainly nitrogen fertilizer supplemented 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 on the ground, apply topdressing. Apply 1.5 kg urea, 10 kg superphosphate extract, and 3 kg potassium sulfate per 667 sq m, mixed with 150-200 kg water to make a nutrient solution, and pour it along the cracks on a cloudy day or in the afternoon of a sunny day. Topdressing should be uniform.

7. Pest and disease control

The main diseases include viral disease, black spot disease, and purple felt disease. Control methods: select disease-free seed potatoes; before arranging seed potatoes for seedling raising, soak them in 2000-fold dilution of 80% 402 chemical for 5 minutes; cuttings can be soaked in 1500-fold dilution of 25% carbendazim or 2000-fold dilution of 50% thiophanate-methyl for 10 minutes.

The main insect pests include tobacco cutworm and sweet potato leaf beetle. Tobacco cutworm can be sprayed in late June with 1000-fold dilution of 10% chlorfenapyr, 800-1000-fold dilution of 5% chlorfluazuron, or 1000-fold dilution of 48% chlorpyrifos. Sweet potato leaf beetle can be sprayed 30 d after sweet potato seedling cuttings with 600-fold dilution of 20% triazophos emulsifiable concentrate or 4000-fold dilution of 2.5% deltamethrin.

When harvesting sweet potatoes, 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 sanitary, with good rat-proofing and anti-toxicity measures. At the same time, insulation measures should be taken to prevent frost damage and compression, and attention should be paid to ventilation and heat dissipation.