Detailed Explanation of Key Points for Pollution-Free Cultivation Techniques of Mini Sweet Potato

Mini sweet potato refers to small, vegetable-type sweet potatoes with individual tuberous roots weighing 50-150 g, a fine texture and a rich flavor. Mini sweet potatoes are suitable for microwave baking or whole steaming in modern small households, and for eating as a combination of coarse and refined grains. In supermarkets in Hangzhou, Shanghai and other places, their price is 4 times higher than that of ordinary sweet potatoes, and they are deeply loved by consumers, with their planting area showing a rapidly rising trend.
1. Environment selection: Select the planting site according to the environmental conditions standard for pollution-free food - vegetable production areas. At the same time, the soil is required to be loose newly opened red or yellow soil, or sandy land under paddy-upland rotation, and the soil should be acidic.
2. Variety selection:
Jinyu (formerly named Zhe 1257). Bred by the Zhejiang Academy of Agricultural Sciences. The skin color is pink, the flesh color is pure yellow, the tuberous roots are short and round, the skin is smooth, the taste is mealy, sweet and glutinous, the texture is fine, with no coarse fiber (strings), and the flavor is fragrant and rich. The drying rate is 30%-32%, with 5-7 tuberous roots per plant, and the tuberous roots are uniform in size. It has good early maturity and can be harvested in about 110 days. It is suitable for planting in different seasons, and the marketable tuber rate can reach 85%. Small tubers below 50 g also have distinctive features and are suitable for consumption in guesthouses and restaurants. This variety sprouts well, has average drought tolerance, and its main disadvantage is susceptibility to vine-cutting disease. Effective disease avoidance measures are selecting disease-free seed tubers, high cutting of seedlings, and avoiding continuous cropping, with paddy-upland rotation giving better control results.
Liangyuan (formerly named AIS). An introduced variety from abroad. The skin color is golden yellow, the flesh color is red, the tuberous roots are round, the skin is relatively smooth, the taste is soft, sweet and glutinous, the quality is excellent, and the flavor is fragrant and rich; the drying rate is 25%-26%, suitable for steaming or baking, with 5-6 tuberous roots per plant, and the tuberous roots are uniform in size. It sprouts well and is mid-maturing, with a growth period of about 130 days.
Xinxiang. A new variety bred by the Zhejiang Academy of Agricultural Sciences. Purple-red skin and yellow flesh, elliptical tuberous roots, relatively smooth skin, relatively mealy taste, fine texture, relatively sweet, drying rate 27%-29%. The underground tuberous roots are shallow and concentrated, suitable for mechanized harvesting, with 6-7 tuberous roots per plant, and the tuberous roots are uniform in size. This variety has good early maturity and high yield. When cultivated with plastic film mulching from late April to early May, it can be harvested in 90 days. Its yield and maturity are comparable to the high-yielding variety Sushu No. 8, and it can be planted for two seasons a year in Zhejiang Province.
Zheshu 6025. Purple-red skin and orange-red flesh, elliptical tuberous roots, relatively smooth skin. When freshly harvested, the taste is mealy; after storage (November), the starch continuously degrades, and the taste becomes relatively soft, glutinous and sweet, with good flavor. It is better to supply it to the market starting in November. There is a small amount of coarse fiber at both ends, and the drying rate is 28%-32%. It has 5-7 tuberous roots per plant, sprouts well, the aboveground part is semi-erect, with vigorous growth, dark green leaves, medium vines, and mid-maturity, with a growth period of more than 120 days. Planting in early to mid-June is better.
Zheshu 78. Red skin and orange-red flesh, round tuberous roots, relatively smooth skin, soft, sweet and glutinous taste, with a small amount of coarse fiber at both ends, relatively good flavor, drying rate 25%-26%, good early maturity, suitable for early planting and early harvest. If harvested after October, the quality declines.
3. Seedling raising: Early-maturing varieties should use three-layer heat-preservation seedling raising with a large shed + small arched shed + plastic film. After early sprouting, use plastic film mulching cultivation to supply the market early; for conventional cultivation, two-layer heat-preservation seedling raising with a small arched shed + plastic film can be used. The seedbed is about 1.0 m wide and 15-20 cm deep. Spread a layer of organic fertilizer on the bottom of the bed, then water and cover with soil. Select seed tubers that have the typical characteristics of the variety, are free of pests and diseases, and weigh 100-250 g. The sowing density is with tuberous roots spaced about 3 cm apart. After the seed tubers are arranged, cover with soil to a thickness of 2-3 cm, and it must not exceed 5 cm, so as not to affect sprouting. When 60% of the tuberous roots 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 large shed film for ventilation to prevent high-temperature burning of seedlings, maintain the bed temperature at 25-30°C, and keep the humidity based on the bed soil being dry and then wet. When the sweet potato seedlings are 20-25 cm long and have 6-8 complete leaves, the seedlings can be cut and planted in the field.
4. Land preparation and fertilization: Land preparation should be carried out on sunny days, and the soil should be broken up and made fine. After leveling, fertilizer should be applied in bands at the bottom of the ridge, 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, it is required to test soil N, P, K and organic matter. In the south, soil pH should also be tested. The soil fertility levels are hydrolyzable nitrogen 40-60 mg/kg, available phosphorus 20 mg/kg, available potassium 100 mg/kg, organic matter 1%, and pH 5.0-6.5. According to the soil fertility level and the fertilizer requirements of sweet potato, prepare N, P, K and organic fertilizer. The use of ordinary compound fertilizer is not advocated.
5. Planting: When the average temperature is above 10°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 facilitate the survival of the seedlings and the uniform distribution of tuberous roots, and improve the marketable rate and yield. The planting density is 4000 plants/667 sq m, with a plant spacing of 20 cm.
6. Field management: Sweet potato diseases mainly include black spot disease and soft rot; underground pests mainly include white grubs and wireworms. Selecting loose newly opened red or yellow soil or implementing paddy-upland rotation can effectively avoid diseases and underground pests. Aboveground pests mainly include Spodoptera litura and sweet potato leaf folder, which cause damage from July to September. At the 1st-2nd instar stage of the pests, spray the leaves with 5% Yitaibao or 5% Kasike at 1000-1500 times dilution for control. After planting, use acetochlor for chemical weed control; in the middle stage of sweet potato growth, carry out manual weeding 1-2 times, and there is no need to turn the vines.
7. Harvest: Sweet potato has no obvious maturity period. The harvest time should be determined by field sampling, continuously digging 10 plants and measuring yield and marketable tuber rate. When the marketable rate reaches 65%-70%, it can be harvested. Xinxiang can be harvested 90 days after planting, and the earliest harvest period is late July. All localities can determine the harvest period according to local climatic characteristics and market demand. Harvest must be completed at the latest before frost.
It should be noted that sweet potatoes must not be harvested on rainy days, so as to avoid too much soil on the tuberous roots, which affects the marketable appearance; when harvesting, dig, load, transport and unload gently to prevent the skin and tuberous roots from being bruised, and harvest and store separately by variety. If the temperature reaches 32°C during harvesting, the sweet potatoes should be brought indoors within 2 hours to avoid sunburn of the skin, which affects appearance and storability.
8. Transportation and storage: Use plastic turnover boxes to transport them into the warehouse. Short-distance transportation should prevent sunlight and rain, and long-distance transportation should prevent freezing and keep warm or cool down. The optimum storage temperature for sweet potato is 10-15°C, with relative humidity 85%-90%. Pay attention to preventing low-temperature freezing injury and reducing water evaporation, pay attention to ventilation and heat dissipation, prevent contamination by toxic and harmful substances, and prevent damage caused by squeezing.