25℃ is usually the standard temperature for asparagus cultivation and ventilation in greenhouse. Generally, the film is uncovered in the morning and covered at night on sunny days. When the average outdoor temperature is below 5℃, cover it with straw cover at night to keep warm. When the outside air temperature is at least 5℃, plastic film shall not be covered at night. Due to daily ventilation, the water in the shed loses quickly, and the soil is dry, which makes it vulnerable to freezing injury at night. At this time, a small amount of water should be poured frequently to improve the insulation effect. Several points should be paid attention to in asparagus greenhouse cultivation, otherwise the yield will be reduced. The elongation of asparagus stems needs high temperature, so the early temperature is low and the yield will increase slowly. But the product is of high quality, tight head and high sugar content. When the temperature reaches a certain range, the harvest peak appears. After the temperature rises, under the influence of high temperature, the head of asparagus is easy to loosen and the flavor is weak. In order to improve the quality, it is necessary to strengthen the management of ventilation and cooling, and increase the number of harvesting and cutting every day. The harvesting method of asparagus in greenhouse is the same as that in open field. At the same time, bad asparagus stems such as excessive fineness and frostbite, as well as side buds on stubble, should be removed as soon as possible.

Early irrigation of asparagus in watering greenhouse requires only a small amount of water to prevent frost. In the middle and late harvest period, the temperature rises, and the greenhouse should be ventilated frequently to cool down, so the soil water loss is fast, and because the young stems grow faster and faster, the water demand is increasing, so it is necessary to increase the number and frequency of watering, usually once every 5 to 7 days. Watering asparagus in greenhouse should be finished before noon after harvest. Immediately after watering, close the greenhouse film to increase the temperature. After picking and cutting asparagus tender stems in surface greenhouse, topdressing once. Apply 10 kg urea per mu each time, combined with irrigation. At the end of the harvest period, asparagus cultivated in greenhouse began to harvest more than one month earlier than that cultivated in open field, and the peak harvest period appeared earlier, and the end harvest period was obviously earlier. The harvest period is often different every year. The main index that determines the harvest time is the change of yield and quality. Generally, the young stems that meet the first grade (stem diameter 0.96 cm) are below 15%, and the young stems spread early, so harvesting should be stopped; Otherwise, it will not be conducive to the restoration of plant clusters.

Greenhouse preparation Plastic greenhouses can be covered with bamboo frames, wooden frames or steel frames, supported by arches and covered with double layers. The temperature in the greenhouse can be controlled by straw curtains and cotton. Generally, after clearing the garden, the shed will be built in 1 month and demolished from the end of April to the beginning of May. The shed can be 3.8 meters wide, 1.65 meters high and 66 meters long, depending on the terrain and the scale of farming. It is best to build a shed on both sides of the shed to avoid high temperature in the middle and low temperature on both sides, so that the temperature in the whole shed can reach a balance, which is conducive to the orderly excavation of bamboo shoots. The shed covered in the shed can also be used for asparagus seedling raising, and a nursery bed can be built, with a width of1.2m, a thickness of 30-33cm and a general length of10-15m. At the bottom of the hotbed, first lay 2-3 cm thick insulation materials such as broken rice straw, rice husk and wheat straw, and then lay an electric hotline. The electric heating linear density 10 square meter is 600~700 watts, and the covering soil is 7~8 cm. In addition, after planting asparagus, manure such as horse manure can be covered on the seedbed as brewing heat instead of electric heating wire. The thickness of the brewing material changes with the increase of temperature, and the temperature around the bubble tray should reach 15~ 18℃, with a general thickness of 20~30 cm.

The method of planting asparagus in greenhouse is to arrange the plant clusters on a hotbed covered with fine soil according to the plant density of about 20 asparagus plants per square meter, and then cover 7~8 cm with fine soil. For example, the cultivated white asparagus needs to be covered with soil for about 20 cm, then irrigated with water and infiltrated with fine water to make the root system closely connected with the soil. If the bed surface is uneven after water seepage, it should be paved in time to keep the bed surface loose and fine soil 2~5 cm to protect soil moisture and prevent soil hardening and cracking. Post-planting management of asparagus in greenhouse 1. Meet dormancy requirements: If asparagus plants are not lower than 5℃ before planting, and cannot be heated immediately due to low temperature dormancy for more than 20 days, the low temperature required for dormancy should be met first. Heating and temperature control: after the hotbed is fully watered, the temperature in the greenhouse will gradually increase from 5~ 10℃ to 18~20℃ for 7~ 10 days, and then keep the temperature relatively stable. When the temperature rises above 25℃ at noon on sunny days, the film should be uncovered for ventilation and cooling, and the film and straw curtain should be tightly covered at night to prevent cooling and freezing. After 10~ 15 days, the scaly buds germinated and the tender stems extended to about 25 cm.