Key techniques for overwintering storage of sweet potato

Sweet potato as a natural green food, its unique health function is gradually recognized by people, and the planting area of sweet potato is also increasing. Therefore, fresh sweet potatoes are safely stored over the winter, and the economic benefits brought to potato farmers in the wrong season are also considerable. Sweet potato is different from other grains, the root contains a lot of water, reasonable measures can be stored for more than 8 months, the intact rate is up to 96%, while poor preservation will rot in about 20 days. In order to prevent fresh sweet potato from rotten cellar, prolong the storage life of sweet potato and increase its value, we must do a good job in the following aspects. The main results are as follows: 1. The way of disinfecting sweet potato cellar is different in different places, and the most commonly used method is cellar storage. There are many kinds of cellars for storing sweet potatoes, such as well cellar, shed cellar, buried cellar and so on, but the management measures are about the same. Before entering the cellar, sweet potatoes should be disinfected in the cellar. Half a month before harvest, open the cellar door for ventilation, and then remove a layer of old soil from the walls and floor of the cellar. Then use 0.5 kg of formalin plus 25 kg of water to spray around, the ground and the top of the pit or fumigate with sulfur twice to eliminate pathogens such as black spot and soft rot. 2. Timely harvest according to the growth law of sweet potato, when the air temperature is lower than 18 ℃, the stem and leaf stop growing, and the soil temperature of 10 cm is lower than 20 ℃, the root weight decreases. There is a proverb in North China that "Cold Dew is early, the Beginning of Winter is late, and it is timely before frost", that is, the harvest of sweet potatoes must be finished at a temperature of more than 10 ℃ before Frosts Descent, so as to ensure that sweet potatoes will not be harmed by cold in the fields. 3, harvest, selection, timely cellar harvest choose a windless sunny day, so that the harvest on the same day, enter the cellar on the same day, do not let potato pieces spend the night in the field. To achieve careful collection and selection, it can be summarized as "four light, five no". Not only light planing, light loading, light transportation, light handling, reducing the chance of damage and disease infection of potato pieces; do not want those suffering from frost, those with disease spots, those who are seriously broken, do not soak potato blocks, and do not put them in the open field for too long after harvest. The cellar should not be too full, usually only 1/2, no more than 2/3 at most, in order to facilitate ventilation. In addition, 50% compound carbendazim was diluted into 500 times liquid spray to disinfect and sterilize potato pieces, and the storage effect would be better. 4. Management of potato cellar the storage environment of sweet potato requires high humidity and strict control of temperature change. It is easy to sprout when it is higher than 18 ℃ and rot when it is lower than 10 ℃. During the whole storage period, the pit temperature should be controlled at 10-14 ℃, and the most suitable temperature should be between 11-13 ℃. Too low humidity is easy to make potato chips dry and shrink, while too high humidity can easily lead to the reproduction and spread of bacteria and cause pathological changes and rot. The optimum humidity for sweet potato storage is 80% Murray 95%. When the relative humidity in the pit is less than 80%, it will cause water loss and wilting of sweet potato, and the edible quality will decline; when the relative humidity is more than 95%, the respiration will decrease, but the microbial activity is exuberant and is vulnerable to diseases. The initial 20 days of entering the cellar is the sweating period, the fresh potato breathes vigorously, releases a large amount of water and heat, the temperature in the cellar is high, and the humidity is high. During this period, pay attention to ventilation, cooling and dampness, and use exhaust fans to cool down if necessary. The middle period is from 20 days after entering the cellar to the beginning of February of the following year, when the temperature is low and vulnerable to cold injury, so we should pay attention to heat preservation so as to maintain a suitable temperature in the cellar. When the temperature rises after the Beginning of Spring, the temperature should be ventilated timely according to the weather changes, so that the highest temperature in the cellar should not exceed 18 ℃. In a word, sweet potato storage management is a very complex work, which is highly technical and requires managers to have a strong sense of responsibility and be careful about their work. In the whole process of storage, we should do a good job in every link, check frequently, remove rotten potatoes in time, and solve problems in time to ensure safe storage of fresh potatoes over the winter.