Key points of Seedling raising techniques of seed Sweet Potato in Cold bed

Sweet potato is rich in starch, protein, fat and a variety of vitamins, which has become a very popular health food. At the same time, it is also a very important chemical raw material, and its development prospect is very broad. Sweet potato has the characteristics of wide adaptability, strong stress resistance, drought tolerance, barren tolerance and less diseases and insect pests, especially the soil types and climatic conditions of Huang-Huai-Hai Plain in the central and southern part of our province are very suitable for planting sweet potato. In recent years, in some places, planting sweet potato has become a good way for farmers to adjust their planting structure and increase their income. Now, it is the season of raising sweet potato seedlings again. The following introduces a method of raising seedlings with plastic film, which is often used by farmers in the plain area of our province. This method has the characteristics of low cost, easy management and strong potato seedlings.

First, select a site and build a bed. To choose the leeward to the sun, fertile soil, high dryness, good drainage, close to the water source, convenient management of the place to build the bed, containing saline and alkali and continuous cropping sweet potato land is not suitable to build the bed. Generally, seedlings are raised in the middle and late March. According to the quantity and management requirements of seed potatoes, the trend of the seedling bed is along the east-west direction, digging soil, with a width of 2 meters, a length of 6 meters and a depth of 0.4 meters. After the seedling bed is dug out, the walls at the bottom of the bed and on all sides should be flattened to facilitate the manipulation of seed potatoes.

Second, select seed potatoes and put them to bed. At present, the high-quality sweet potato varieties popularized in our province are Hebei 351, Jishu 98, Jishu 99, Beijing 553, Xinong 431, Xushu 18 and other dual-purpose or special-purpose varieties, according to the market demand and production and processing objectives, flexibly select the right varieties. Seed potato for seedling cultivation should pay attention to single harvest and storage, which can be calculated according to the need to reserve 70 kilograms of seed potato for planting one mu of field. To select potato with the characteristics of the original variety, potato shape is correct, bright and smooth, free from cold, freezing, waterlogging, injury and disease, the single piece size is about 150Mel 250g. In recent years, black spot, soft rot, dry rot and nematode disease are rampant in the old sweet potato planting areas. Chemical treatment of seed potato can have a good preventive effect before raising seedlings. The selected seed potato was treated by soaking the seeds for 10 minutes with 50% ammonium benzoate in the solution of 300 / 400 times of water. After soaking seeds, you should immediately put the potato to bed. When arranging the potato, the head of the seed potato should be upward, the principle of uneven upper and lower should be mastered, and the oblique method should be adopted. The potato head is pressed on the potato tail and the seedling emerges more and faster. Generally, 25 kilograms of seed potato per square meter is appropriate.

After arranging the seed potato, fill the gap between the seed potato with sand, then pour the bed soil thoroughly with well warm water, and so on, gently press the seed potato with flat wood plate, and then cover the sand soil about 3 cm, which should not be too thick, otherwise it is not conducive to the rise of soil temperature, but also easy to lead to weak potato seedlings, and easy to spread diseases. Immediately after the seed potato goes to bed, cover it with plastic film and straw to increase the temperature.

Third, seedbed management. Strengthening the management of seedling bed is the key to more seedling emergence and cultivation of strong seedlings. Before emergence should be in line with high temperature sprouting, do a good job in warming and heat preservation measures, appropriate moisture, and strive to early emergence, more seedlings, not bad bed. After emergence, it is necessary to cool down properly, grow smoothly, and pay attention to watering and ventilation to prevent sprouting. Low temperature seedling refining should be carried out before rice seedling collection, and attention should be paid to topdressing fertilizer after seedling collection.

1. Temperature management. In order to meet the requirements of high temperature sprouting and disease prevention before emergence, the work of increasing temperature and heat preservation must be done well. Keeping the temperature of potato layer at about 35 ℃ within 3 days after seed potato went to bed was beneficial to promote sprouting and wound healing, and could produce sweet potato ketone, which could inhibit black spot. Under normal circumstances, on a sunny day, the sun film will be heated in the morning, and the grass will be covered at three or 04:00 in the afternoon to keep warm. Before emergence, the bed temperature should be kept at 30 ℃ 32 ℃, and after emergence, it gradually decreased to about 25 ℃ with the growth of seedlings. The seedling should be refined at low temperature before collecting seedlings, and the bed temperature should be reduced to 20 ℃ and 22 min. It is necessary to increase the temperature and keep warm within one or two days after collecting seedlings, so as to facilitate the germination of new buds to promote the rapid growth of small seedlings. After that, the seedlings are refined at low temperature, and the seedlings are generally collected once every five or six days.

2. Water management. Seedling bed watering is one of the important measures to cultivate strong seedlings. The amount and frequency of water watering should be determined according to the dry humidity of the bed soil, the growth of potato seedlings and the bed temperature, and coordinate the water, temperature and gas to promote the growth of potato seedlings. On the basis of fully watering seed potato in bed, seed potato is generally not watered before emergence to facilitate high temperature germination, disease prevention and seedling emergence. If the seedling bed is too dry, spray water on the seedling bed with a sprayer. After coming out of the seedlings, the seedlings were watered once before refining and the next day after collecting seedlings. Between the two floods, small water can be watered gently and evenly according to the growth of potato seedlings and the moisture of the bed soil. Watering time, in line with the "early afternoon, late afternoon" principle. Early spring temperature is low, watering in the morning, covering the film at noon to raise the temperature, the temperature can rise in the afternoon to prevent the bed temperature from being too low at night. The temperature is higher in the later stage, so it is appropriate to water it in the afternoon to prevent the temperature at night from being too high and the potato seedlings grow fast and tender.

3. Refining seedlings. Seedling refining is an important measure to cultivate strong seedlings. In order to make potato seedlings grow healthily and improve the survival rate, measures such as ventilation and cooling of seedling bed, uncovering film and drying must be carried out before planting. After the potato seedlings come out, choose sunny weather and begin to ventilate the bed temperature gradually, so as to facilitate the steady growth of the seedlings and prevent the emergence of thin and tall seedlings. When the seedling grows to 12ml 15cm, the temperature is stable and it can be ventilated day and night. 3 days before seedling collection, the grass and film can be removed completely, so that the seedlings can be refined day and night to adapt to the external field environment. In this way, the seedlings will be returned quickly after planting, and the survival rate is high.

4. Topdressing. In order to increase the number of seedlings and meet the nutrient needs of potato seedlings, topdressing was carried out after each seedling collection combined with watering. Topdressing should be based on quick-acting nitrogen fertilizer, such as urea (avoid using ammonium bicarbonate to prevent burning young seedlings), and the effect of phosphorus and potassium fertilizer is better. Generally 10 square meters of urea 0.5 kilograms of potassium dihydrogen phosphate 50 grams, the two fertilizers will be mixed evenly spread on the seedbed, immediately after sprinkling the chemical fertilizer on the seedling leaves gently, and then water rinse.

Fourth, collecting rice seedlings. When the seedlings grow to 20 centimeters, should be harvested in time, picking seedlings too late, potato seedlings crowded, will cover the lower part of the seedlings, affecting the number of seedlings in the next crop. There are two methods of collecting seedlings: cutting seedlings and pulling seedlings. Generally, the method of cutting seedlings is often used. The advantage is that it is not easy to spread diseases and move seed potatoes, and make the next crop of small seedlings grow faster and emerge more. Especially in places where sweet potato black spot occurs seriously, it is recommended to cut seedlings high and leave stubble more than 3 cm in order to prevent the disease. Generally speaking, it is best to pick seedlings in the early morning, and the cut seedlings had better be planted on the same day to facilitate survival. If they cannot be planted in time, they can be placed in a cool and ventilated place (not suitable for sprinkling water) to strive for early planting in the future. After cutting seedlings, cover with plastic film to raise temperature during the day, cover grass grass at night, and water and fertilize the next day.