I. Physiological characteristics of storage period
Sweet potatoes are harvested from tuberous roots. Fresh potatoes are large in size, high in water content, tender in tissue and crisp in skin, and vulnerable to chilling injury and diseases.
Sweet potato still has a strong respiratory function during storage, and its respiratory intensity is ten to dozens times higher than that of cereal seeds. When o2 is sufficient, sweet potato carries out aerobic respiration, inhales more o2, and releases more co2 and heat. When o2 is insufficient, sweet potato breathes anaerobically, producing alcohol, co2 and a small amount of heat. Alcohol is toxic to potato pieces, which easily leads to pit rot.
Second, the environmental requirements for safe storage
Length temperature: The optimum temperature for sweet potato storage is l0℃-l4℃, and there is little difference in respiration in this range. When the temperature rises to 20℃, the respiration is enhanced, more nutrients are consumed, chaff heart is caused, and the occurrence of black spot disease and soft rot is accelerated. When the temperature is lower than 9℃, it is vulnerable to cold damage, which makes the inside of potato pieces brown and black, hard and not rotten, and easy to rot in the later stage.
2. Humidity: The optimum humidity for sweet potato storage is 80%-95%. When the relative humidity in the cellar is lower than 80%, the sweet potato loses water and wilts, and the edible quality decreases. When the relative humidity is greater than 95%, although the respiration is reduced, the microbial activity is vigorous and easy to get sick.
3. Air composition: According to the determination, when o2 and co2 in the air are 15% and 5% respectively, it can inhibit breathing, reduce the consumption of organic nutrients and increase the storage time of sweet potatoes. When o2 is less than 5%, sweet potato will rot due to anaerobic respiration.
Third, preparation before storage.
The harvest time of sweet potato is closely related to safe storage. Sweet potato is a vegetative body, with infinite growth characteristics, low yield when harvested too early, and vulnerable to chilling injury and storage resistance when harvested too late. The harvest begins at 65438 08℃, and the best harvest is at the temperature above l0℃. When harvesting, we should dig, transport and release lightly. Take out the diseased, insect-bitten, damaged and flooded potato pieces, dry them in the sweet potato storage area for 3-4 days, and then enter the cellar.
If an old cellar is used, it should be cleaned before entering the cellar. Sick old pits should be fumigated with sulfur, or the pit wall soil should be stripped 2 cm. Generally, it is advisable to store sweet potatoes in the cellar, occupying 2/3 of the cellar space.
Fourth, the storage method
L shed cellar storage method: the cellar pool is dug outdoors, with a depth of 2m, a width of 1.5m and a length depending on the storage capacity. Put 1 wood column on the top of the cellar every 80cm, and lay 20cm thick corn straw, rice straw or wheat straw. The overlying soil is about 0.5m, leaving an exit in the south.
2. Pit storage method: this method can be used in cold areas in the north. The excavation depth is 3-5m, the diameter of the upper wellhead is about 1m, and the diameter of the lower wellhead is1.5m. Water storage holes are dug on both sides of the bottom hole, and the bottom hole needs to be padded with yellow sand.
Verb (abbreviation of verb) management measures
We should master three principles: ventilation and cooling in the early stage, heat preservation and cold prevention in the middle stage, and stable cellar temperature in the later stage.
Pre-storage: sweet potatoes often sweat due to high temperature and humidity within 20 days after entering the cellar, resulting in wet loss of potato pieces on the pile surface, and a layer of hay can be covered on the potato pile. Also be careful not to seal the pit prematurely.
Medium storage period: the medium storage period is from 20 days after into the pit to early February of the following year. At this time, the temperature is low and vulnerable to cold, so the pit mouth should be closed. In addition, covering potatoes with grass can also prevent frostbite.
Late storage: The physiological function of sweet potato decreases after long-term storage. At this time, when the temperature rises, the pit mouth should be opened for ventilation in time to reduce the temperature and humidity in the pit.
In the process of storage, we should pay attention to two points: first, check regularly and remove rotten potatoes in time; Second, it must be tested with lights before entering the cellar. If the fire doesn't go out, you can enter the cellar.