Sweet Potato Protected Cultivation Experience and Key Technical Points

Using large and medium shed facilities for early-maturing sweet potato cultivation can not only improve the utilization rate of limited land resources and light-heat resources and increase the yield and benefits of sweet potato production, but also enable double-season sweet potato cultivation in the Beijing suburbs, promoting reform of the cropping system. 

1. Site selection and shed construction 

For protected cultivation of sweet potato, land that has been out of sweet potato for a rotation period of more than three years should generally be selected, and sandy loam soil is ideal. Because sweet potato fields with more than two consecutive years of cropping are prone to the spread of soil-borne diseases such as sweet potato nematode disease and black spot disease and to imbalance of soil nutrient elements, soil disinfection and balanced fertilization with increased organic fertilizer application should be used for treatment. The previous crop on the land is best as wheat, corn, melons or vegetables, and there should be good drainage and irrigation conditions. The construction specifications and orientation of the shed should be determined according to the terrain and topography, and generally aligning with the wind direction is better, which can not only reduce the impact of wind damage but also improve work efficiency. Large sheds can be built according to the standard specifications for melon and vegetable large sheds, while medium sheds generally have a span of 4 meters and a height of 1.2-1.5 m. Along the length, support one bamboo slat keel every 1-1.2 m, with the plastic film closely attached to the keel and stretched tight, and both sides pressed into the ground about 15 cm. Bury them well and tamp them firmly, tie the keels tightly with wire or nylon rope, and whether to cover the film with straw curtains depends on the local climate and the planting period. Large sheds should be built and covered with film before sweet potato planting, while medium sheds should have supports and film installed after sweet potato planting. 

2. Variety selection and land preparation 

In order to give play to the effect of protected facilities on the use of light and temperature resources, early-maturing and high-yielding varieties should generally be selected, such as Yushu 10 (also called Red Heart King) and Jingshu 2. Land preparation is generally carried out before covering the shed film, and leveling and deep plowing are carried out together with the application of base fertilizer. On the basis of applying 2000 kg of high-quality organic fertilizer per mu, apply 40-50 kg of sweet potato special fertilizer (10:7:8). After broadcast application, plow it into the ground; for plots that need disinfection and pest control, apply the disinfectant and insecticidal bait together. The flatness of the land in the same shed should be sufficient to ensure smooth watering, drainage and ridging with film covering. The ridge spacing is 75 cm, the ridge height is 25 cm, the top is flat, and the width is 20-25 cm. Cover the ridges with plastic mulch, covering the entire ridge tightly and stretching it taut. 

3. Planting 

1. The planting time of seedlings is determined according to the harvest period and seedling raising conditions. General experience holds that large-shed sweet potatoes are suitable in early to mid-April, and medium-shed sweet potatoes in mid to late April. 2. Seedlings taken from the seedbed can be planted directly or first heeled in. According to the soil temperature of the production field and the grading of the seedlings, first transplant the seedlings into a warm seedbed sheltered from the wind and facing the sun, water appropriately, and cover with film in the morning and evening. Through adaptive training and root promotion, the standard for suitable planting can generally be reached in 3-7 days. Seedlings after heeling in can not only increase the survival rate but also recover quickly after transplanting. 3. Sweet potatoes in protected facilities generally use oblique planting or vertical planting to help ensure density. The planting density per mu is determined according to variety characteristics and the planned harvest period, and is generally about 10% higher than in ordinary open fields. Plant the seedlings in the middle part of the ridge top, break the film, and plant them 4-5 cm into the soil. After watering twice, press soil to close the holes and firmly press the broken edges of the plastic mulch. 

4. Management and harvest 

Management of sweet potatoes in protected facilities is relatively simple, and the key is to keep warmth and moisture in the early stage to promote seedling recovery. In order to promote early recovery of sweet potato seedlings, within 3-5 days after planting the temperature inside the shed should not be higher than 35 degrees Celsius, and ventilation is generally not carried out so as to maintain internal humidity. Below 13 degrees Celsius, the shed should be kept sealed or artificially heated; above 35 degrees Celsius, side-wind ventilation should be carried out to prevent cold wind from blowing straight in. In combination with ventilation, loosen the soil in the inter-row furrows to raise temperature and conserve moisture. After the late frost and late spring cold have completely passed, gradually increase the ventilation openings as the outside temperature rises; after the vines spread and close the rows, open all the side openings, and when the temperature reaches about 30 degrees Celsius, the shed film can be removed. According to the seedling growth and soil fertility, after the sweet potato vines spread and before the rows close, open holes on the side of the ridges and apply topdressing, applying 30-40 kg of special compound fertilizer per mu, and water according to soil moisture. This promotes fertilizer dissolution and prevents drought. Under protected conditions, early-maturing varieties can be harvested after 65-70 days from planting according to market information, and promptly harvested, packaged and rushed to market fresh. Also promptly carry out land preparation and soil treatment for second-crop planting. Main technical points for summer-planted sweet potato. Summer-planted sweet potato is commonly called wheat-stubble sweet potato in the Beijing suburbs. It mainly refers to sweet potato planted in succession after the harvest of summer-harvested crops such as wheat, using cuttings of stems and vines taken from early-spring-planted sweet potato as seedlings, and its main difference from spring sweet potato is in the form of seedlings; spring sweet potato seedlings are taken from seed potatoes. Due to differences in light and heat resource conditions among regions and differences in the growth of summer-harvested crops, the seedling insertion periods of late-planted spring sweet potato and early-planted summer sweet potato are sometimes very close. 

Sweet potato originated in the tropical regions of South America, and in production it mainly relies on vegetative propagation. Summer-planted sweet potato has a short growth period, and its growth and development differ greatly from spring sweet potato, but its economic benefits are very obvious. According to surveys, the per-unit yield of summer sweet potato in the Beijing suburbs can reach 2000 kg, with an output value of more than 400-1000 yuan, so the scale of summer sweet potato planting continues to expand in agricultural structural adjustment.