The Latest Technical Methods and Tutorial for Efficient Vegetable Seedling Raising

Vegetable seedling raising is a major feature of vegetable production, and is an important measure for seizing the farming season, increasing the number of cropping cycles, giving full play to capacity, achieving earlier maturity, extending the supply period, reducing pests, diseases and natural disasters, and increasing yield. Seedling raising can also save on seed use and facilitate centralized management and the cultivation of strong, healthy seedlings. Seedling raising is usually carried out earlier than the suitable period for sowing or transplanting in the open field, whether in the severe cold of the depths of winter and early spring, or in the hot, rainy midsummer and early autumn. That is, during periods when climatic conditions are unsuitable for vegetable growth, protective facilities are used to create a suitable environment for cultivating seedlings of the right age and vigor. Once climatic conditions are suitable, they are transplanted into the open field.

Types of Seedling Beds

1. Cold bed: The cold bed, also called a sun-facing bed, is a protective facility that relies on sunlight for heating. It consists of three parts: the bed frame, the glass cover (or film), and the straw curtain. The site for a cold bed should be chosen in a place that is sheltered from the wind and faces the sun, with high, dry terrain, good drainage, close to a water source, convenient transportation, near the vegetable plot and near the dormitory for easy management. The cold bed should be oriented facing south with a slight deviation of 15° to the west, to increase light exposure and raise the bed temperature. The bed frame structure can be built with cement and red bricks, or made of mud and straw, but the former is more durable, does not require annual maintenance, and is more convenient to use. Generally, the north frame is 50cm high and the south frame is 15cm high. The glass window can both let in light and retain heat. The straw curtain is generally laid over the glass window on cold nights to enhance the insulation effect. Agricultural film can also be used instead of glass windows, but on rainy or snowy days, care must be strengthened to ensure smooth drainage and timely clearing of snow.

2. Small plastic arch shed: The small plastic arch shed is made by bending bamboo strips into an arched frame and covering it with plastic film. The frame is 50cm high, and a 2m-wide film is laid over it. One side of the film is compacted with soil to retain heat and block wind; the other side is weighted down with bricks so that the film can be lifted at any time for ventilation. Small arch sheds are often used in early spring for sowing seeds of melons and beans, or for placing nutrient pots with eggplant-family and melon-family seedlings. They can also serve as a temporary planting bed. Small arch sheds are generally 1-2m wide and 20-30m long.

3. Plastic tunnel: The plastic tunnel is made by constructing an arched framework from bamboo, wood, reinforced concrete pieces or steel pipes, and covering it with plastic film. At present, the provinces in the Yangtze River basin mostly use plastic tunnels that are 30cm long and 6m wide, or 20m long and 4m wide. In winter, plastic tunnels are mainly used for raising seedlings of the eggplant family (Figure 1-2); small plastic arch sheds are set up inside the tunnel, and electric heating wires are laid inside the small arch sheds for raising pepper, eggplant and tomato seedlings. As a seedling-raising facility, the plastic tunnel is more convenient to manage than cold beds, hot beds and small plastic arch sheds, and gives better results.

Preparation of Seedbed Potting Soil

1. Conditions the potting soil should have: The bed soil used for vegetable seedling raising is also called potting soil. The quality of the potting soil has a great bearing on the growth and development of the seedlings. In order to cultivate strong seedlings, the potting soil is required to be fertile, loose, slightly acidic or neutral, with good water retention and drainage performance, and free of pathogens, insect eggs and weed seeds. To give the potting soil the above excellent traits, it must go through scientific blending, composting and fermentation, and chemical disinfection.

2. Proportions of potting soil and preparation of raw materials: Garden soil is the main component of potting soil and should generally account for 30-50%. When selecting garden soil, care must be taken to prevent the introduction of soil-borne diseases such as damping-off, seedling blight, early blight and cottony leak of the Solanaceae, and fusarium wilt and anthracnose of the cucurbits. Generally, do not use garden soil from vegetables of the same family. Soil that has been used to grow eggplant-family or cucurbit crops should not be used; soil that has grown beans or allium crops is better. This is because bean plots contain rhizobia, which have a certain nitrogen-fixing effect and can increase soil fertility; allium plots contain large amounts of sulfides such as allicin, which help to inhibit or kill pathogens in the soil. If the above garden soil is truly unavailable, the topsoil must be removed and the subsoil dug out. Garden soil is best dug out during the high temperatures of August, fully baked in the sun, then crushed and sieved. The sieved garden soil should be stored indoors or covered with film, kept dry for later use. Organic fertilizers, such as human and animal manure and urine, other barnyard manure or compost, edible mushroom residues, and garbage, are the main nutrient sources and should account for 20-30% of the potting soil. These organic fertilizers must be fully fermented and decomposed before use. Undecomposed organic fertilizer adsorbs more pathogens and easily harms seedlings. Therefore, pig manure residue and other barnyard manure or compost must first be piled to decompose before use. Alternatively, mix and pile it with garden soil and use it after it is completely decomposed. Chemical fertilizers: add about 1kg of urea, 0.5kg of potassium chloride, and 2kg of superphosphate or calcium magnesium phosphate to about 1000kg of potting soil. Carbonized rice husk or plant ash can increase potassium; it makes the soil loose and air-permeable, darkens the color, absorbs more solar heat, and raises soil temperature. It can account for 20%-30% of the potting soil. When carbonizing rice husk, the appropriate degree should be controlled; generally the rice husk should be completely carbonized but still basically retain its original shape. If rice husk is lacking, waste cottonseed hulls left after growing edible mushrooms can be used instead, piled and fermented together with garden soil and barnyard manure.

3. Composting and fermentation of potting soil: After the raw materials are prepared, composting and fermentation should be carried out 40-50d before sowing and seedling raising. Generally, choose a high, dry, well-drained flat ground close to the seedling-raising site to compost the potting soil. The pile width is 1-1.5m, and the pile length depends on the amount of potting soil; the pile is in the shape of a long trapezoid. Specific method: first spread a 20cm-thick layer of garden soil on the ground, then drench it thoroughly with manure water, then spread a 10-13cm-thick layer of barnyard manure and other miscellaneous fertilizers, and again sprinkle a layer of manure water. Then continue to build up the fertilizer pile in the above order, generally to a height of 1.5m, and then cover with plastic film to protect from rain.

Setting Up an Electric Heating Hotbed

1. Performance and models of electric heating wires: The electric heating hotbed mainly relies on electric heating wires to raise the seedbed temperature. The electric heating wire is essentially a device for electrical-to-thermal conversion, a specially made wire with a certain resistivity. Its exterior is wrapped with a highly heat-resistant vinyl resin as an insulating layer. It is buried in a soil layer at a certain depth; after the power is turned on, the current passes through the high-resistance conductor and generates a certain amount of heat, converting electrical energy into thermal energy and thereby raising the soil temperature. The heat generated by electric heating is transmitted horizontally outward layer by layer, with a transmission distance of about 25cm, and the most heat is within 15cm. The closer to the electric heating wire, the higher the soil temperature; the farther away, the lower. Therefore, to distribute the heat evenly in the seedbed soil, the distance between wires should not exceed 30cm.

2. Laying procedure for the electric heating hotbed

① Level the bed bottom: In a PS—4 type tunnel, make the bed to a standard of 10m or 20m long and 1m wide, shovel out the excess soil in the bed, and level the bed bottom.

② Lay the insulation layer: Lay a 5cm-thick insulation layer on the bed bottom and rake it level.

③ Lay the heating wires: Before laying the wires, prepare several small bamboo skewers. When laying the wires, insert the small bamboo skewers directly at both ends of the seedbed according to the wire spacing, then use 3 people to lay the wires, with two people pulling the wire at both ends and pulling each strand tight one by one. Before laying the wires, it must be considered that the two lead-out wires of the electric heating wire are at the same end of the seedbed, so as to connect to the power supply. A (10×1) m2 seedbed uses 1 DV20810-type electric heating wire, which makes exactly 5 round trips; a (20×1) m2 seedbed needs 2 DV20012-type electric heating wires, which make exactly 6 round trips. This ensures that the lead-out wires are all at the same end of the seedbed. When laying the wires, note: First, the wires must not overlap or cross, and certainly must not be twisted together, to prevent burning out when the power is turned on. Second, the heating wires must not be arbitrarily lengthened or shortened, because their resistance and power are rated; otherwise they will burn out. Third, when 2 or more electric heating wires are laid in the same bed, they can only be connected in parallel, not in series.

④ Power-on test: After the wires are laid, connect the power supply, close the knife switch, and energize for 1-2min. If the heating wire becomes soft and generates heat, it indicates normal operation, and the bed soil can be covered; if the heating wire does not generate heat, it indicates the circuit is not connected, and the circuit should be checked and the fault eliminated.

⑤ Cover with bed soil: After the power-on test, cover the electric heating wires with 8-10cm-thick bed soil, that is, cover 100-125kg of bed soil per m2. When covering with soil, note that part of the bed soil should first be used to press down the electric heating wires section by section, to avoid displacement when filling soil, and the bed soil should be spread along the direction in which the electric heating wires extend. After the bed soil is covered, scrape the bed surface flat with a wooden board to facilitate sowing.