Detailed Explanation of Potato Harvesting, Storage and Processing Techniques
I. Timely harvesting. Potatoes intended for storage are best harvested when dry matter accumulation is at its maximum and the tubers are fully mature. Spring potatoes should be harvested in early to mid-June, while autumn potatoes should be harvested in early November and must not be exposed to frost. Whether spring or autumn potatoes, if rain occurs before harvest, harvesting should wait until the soil has dried appropriately. Freshly dug tubers have tender skins and should be left on the ground to air for 1-2 hours, then collected after the potato skin surface has dried slightly. However, they must not be sun-dried for long periods in summer; after harvest they should be promptly stored in a cool, shaded place. During storage, strict selection should be carried out, removing tubers that are diseased, damaged, insect-bitten, rain-soaked, frost-damaged, cracked, undersized, or with speckled skin.
II. Pre-storage treatment. Within 2-4 weeks before potato harvest, spray the foliage with 0.2% maleic hydrazide, which can inhibit sprouting of the tubers during storage. If rain occurs within 48-72 hours after spraying, the spray should be reapplied.
III. Storage conditions. (1) Temperature: During the initial 10-15 days of storage, a relatively high temperature of 15-20°C should be maintained. After the tuber skin forms a suberized protective layer, the temperature should be controlled at 3-5°C for storage. (2) Humidity: The suitable relative humidity for storage is about 90%.
IV. Storage methods
1. Indoor heap storage: Choose a well-ventilated warehouse with a dry floor. Generally, tubers are placed in baskets and stacked indoors for storage; in some places, tubers are directly piled on indoor bamboo floors or floorboards; others put tubers into bags and stack them or hang them on floorboards. These methods are simple and easy to carry out, but sprouting is difficult to control. If combined with chemical treatment, the storage effect can be improved. Sprouting can also be inhibited by covering to block light; this method is relatively ideal for storing potatoes harvested during the rainy season. Place several bamboo ventilation tubes in the potato heap to facilitate ventilation and heat dissipation. To improve space utilization, it is best to use nylon woven bags for rack storage indoors, or use baskets, boxes, or woven bags for stacking and storage.
2. Cellar storage: In the warm regions of the south, choose a light-proof, cool, well-ventilated, dry indoor or outdoor area under a shed, and build a rectangular storage pit with bricks. Leave holes in the pit walls in a decorative wall pattern to facilitate ventilation and heat dissipation. Cover with 10-15 cm of fine sandy soil and lightly compact it. In the northwest region, well cellars or cave cellars are mostly used for storage. These two types of cellars can hold 3000-4000 kg. Since only the cellar opening is used for ventilation to regulate temperature, the insulation effect is relatively good. However, it is not easy to lower the temperature in the early stage after entering the cellar, so attention should be paid to pre-cooling before entering the cellar.
Whether heap storage or cellar storage is used, attention should be paid to strengthening ventilation in the early stage. Ventilate mainly when temperatures are lower in the morning and evening, and exhaust fans can also be used for ventilation. After several weeks, excessive ventilation is no longer necessary; ventilate appropriately according to the temperature conditions within the potato heap, so that the temperature inside the heap approaches the lowest outdoor temperature, but not below 0°C. In the early stage after potatoes enter the storage facility, they should be checked once about every 2 weeks, removing rotten and deteriorated tubers. After that, check once about every 1 month.