After the Start of Spring, vegetable management enters its busiest period
The Start of Spring (Lichun) marks the beginning of the year's solar terms. At this time the climate in the Beijing area is still cold, with low temperatures, continued snowfall, and occasional windy weather, but temperatures begin to rise day by day and the number of daylight hours gradually lengthens. Therefore, in the Beijing area the Lichun solar term can be called the prelude to spring; meteorologically it still belongs to winter, and spring has not officially begun. As the saying goes, "The whole year's work depends on a good start in spring" - this is precisely the busiest time for raising seedlings, preparing the soil, and transplanting spring-season vegetables in protected facilities, as well as for managing overwintering fruit and melon vegetables in solar greenhouses.
?Cultivating strong seedlings
Most spring-season facility vegetables and some open-field vegetables begin to be raised as seedlings. The farming proverb "With seedlings you get half a harvest; with strong seedlings you get half a harvest more" speaks to the importance of cultivating strong seedlings. Seedling-raising sites are chosen in solar greenhouses or small arch sheds; if the ground temperature is below 15°C, geothermal heating cables and temperature controllers should be installed to raise the ground temperature.
◆Melon family vegetables: Cucumber, zucchini, pumpkin, winter melon, watermelon, melon and other cucurbit crops grown under double-layer coverage in large sheds and small arch sheds are sown and raised as seedlings in early to mid-February and transplanted in late March. Use 32-cell or 50-cell plug trays or 8×8 cm nutrition pots for seedling raising, with peat and vermiculite as the substrate. For cucumber, it is advisable to choose excellent varieties such as "Zhongnong 12" and "Beinong Jiaxiu", which are early-maturing, good in quality and strongly disease-resistant.
◆Legume vegetables: Early spring-season bush beans and cowpeas in solar greenhouses are sown and raised as seedlings in early February, using 50-cell plastic plug trays or 6×6 cm nutrition pots, sowing 2-3 seeds per cell. The seedling age is 15 days; they are transplanted in mid to late February and harvesting begins successively in late April.
◆Celery and lettuce: Open-field spring-season celery and lettuce are sown and raised as seedlings in early February; lettuce is transplanted in late March and celery in early to mid-April. Use 128-cell plastic plug trays, or ordinary seedbeds. Choose early-maturing, good-quality varieties such as "Ventura". Sun the seeds for one day in advance, soak them for 24 hours, then rub off with your hands the substances on the seeds that inhibit germination before sowing; after watering the seedbed thoroughly, sow evenly.
◆Management of seedlings that have emerged
·Prick out seedlings in time: Eggplant-family and melon-family vegetable seedlings raised in ordinary seedbeds should be pricked out at the 2-leaf-1-heart stage. Pricking the seedlings out into nutrition pots is beneficial to root growth; after pricking out, raise the room temperature by 3°C-5°C.
·Adjust to a suitable temperature: Do a good job of cold protection and heat preservation, and maintaining ground temperature is especially important. Especially when extremely cold weather occurs, keep the night temperature no lower than 13°C; this is particularly important for tomato and cabbage seedlings. Tomato seedlings enter the flower bud differentiation stage after the 2-leaf-1-heart stage, and under low-temperature conditions below 13°C they easily produce deformed fruit; cabbage is prone to early bolting when it encounters low temperatures at the 6-leaf stage. Temporary heating measures such as installing bathroom heater bulbs, electric heaters, and heating combustion blocks should be taken to ensure the seedlings are not frozen. Also, warm-loving crops such as tomato and cucumber should be placed separately from cold-tolerant crops such as lettuce and celery in different temperature zones, and the positions of the seedling trays should be swapped about once a week so that the seedlings grow evenly.
·Increase light: After the seedlings emerge, ensure as far as possible that the seedlings receive strong light and are exposed to plenty of it. Install supplemental lighting to provide artificial light, which is conducive to cultivating strong seedlings; turn it on for 4-5 hours after the straw mats are put down on sunny days, and for 12 hours on cloudy days.
·Timely watering, topdressing and pest and disease control: After the seedlings reach the 2-leaf-1-heart stage, water and topdress in time; focus on preventing damping-off, especially under continuous cloudy days and low-temperature, high-humidity conditions.
?Fertilizing and soil preparation in the solar greenhouse
The early spring-season warm-loving crops are about to be transplanted, so fertilize and prepare the soil 15 days in advance. First, clean up the field to reduce sources of pests and diseases: promptly remove the residual stubble, rotten leaves and plastic film from the previous crop and transport them to a designated location for harmless treatment such as ozone disinfection or high-temperature composting. Apply 5000 kg per mu of decomposed, finely crushed high-quality organic fertilizer or 3000 kg of bio-organic fertilizer, and plow to a depth of 25-30 cm. Level and refine the soil until it meets the standard of level ground, level beds and no visible or hidden clods; lay drip irrigation pipes, cover with silver-gray plastic film, and wait for a suitable time to transplant.
?Transplanting warm-loving crops
Early spring-season warm-loving crops such as cucumber, tomato, eggplant, pepper and zucchini in solar greenhouses begin to be transplanted successively in early to mid-February. Generally, transplanting can be done once the 10 cm ground temperature stabilizes above 15°C. Improve the quality of soil preparation and apply sufficient organic fertilizer as base fertilizer in advance. Choose the "end of cold, start of warm" period for transplanting.
?Sowing and transplanting of cold-tolerant fast-growing vegetables in the greenhouse
For fast-growing vegetables grown in solar greenhouses, such as bok choy, garland chrysanthemum, spinach, lettuce, baby bok choy and cherry radish, this is exactly the suitable season for sowing and transplanting. According to sales conditions, a planting method of sowing in batches and harvesting successively can be adopted. Apply 3000 kg per mu of fully decomposed, finely crushed high-quality organic fertilizer or 2000 kg of bio-organic fertilizer, and prepare the soil finely so that the ground is level, the beds are level and the ridges are straight, with loose surface soil and no visible or hidden clods. Garland chrysanthemum, spinach, cherry radish and baby bok choy are best grown by direct sowing; after watering the seedbed thoroughly, sow evenly, cover with soil of uniform thickness, then cover with a layer of plastic film to keep warm and retain moisture, and remove it promptly when 50% of the seedlings have emerged. Bok choy, lettuce and celery are grown by transplanting.
?Critical period for managing overwintering vegetables in the greenhouse
Do a good job of heat preservation and cold protection: pay attention to weather changes at all times to prevent strong cold waves and continuous cloudy weather from harming the crops, and take temporary heating measures such as bathroom heaters, heating combustion blocks or electric hot-air furnaces when necessary. Frequently wipe and wash the greenhouse film to enhance light transmission.
Plant and fruit management: Prune and remove side shoots and lower the vines in time, and remove old and yellow lower leaves; assist pollination, and thin out excess flower buds, fruit and deformed fruit.
Scientific watering and topdressing: For topdressing, it is advisable to apply instant fertilizers with comprehensive nutrition and a reasonable ratio, such as "Christmas Tree", through drip irrigation, or apply organic liquid fertilizers rich in alginate or humic acid with a full content of nitrogen, phosphorus and potassium along with the water; set up a water storage tank, jar or barrel in the greenhouse, and water only after the water temperature rises to about 18°C. Also note to water frequently in small amounts; vegetables in the greenhouse should avoid flood irrigation.
Timely harvesting: Harvest at the optimal commercial stage. Around the Spring Festival is exactly the season with large market demand and high prices. The produce that has formed in the Beijing market over many years must not only be fresh and tender but also look good and uniform, so the quality of trimming and sorting should be improved to increase commercial value.
Pest and disease control: The Lichun solar term still belongs to low-temperature, low-light weather, and the low-temperature, high-humidity growing environment in the shed makes it prone to infection by pests and diseases such as gray mold, sclerotinia, downy mildew, late blight and root-knot nematodes. First, adjust the growing environment conditions appropriately; warming and supplemental lighting are especially important. On cloudy days, also ventilate briefly at noon to remove moisture, and spread a layer of dry sawdust or dry straw between the rows to absorb excess air humidity in the shed; promptly remove diseased leaves and fruit and place them at a designated location for harmless treatment to reduce sources of spread; at the early stage of disease onset, promptly use low-toxicity, low-residue pesticides for control; dust formulations and smoke fumigation should be used as much as possible to control pests and diseases, and conventional spraying should be avoided as far as possible to reduce humidity in the shed. Strictly observe the specified safety interval before harvest after pesticide application to ensure the safety of the product. Cao Hua