Detailed Explanation of Greenhouse Cultivation Techniques for Green Asparagus Seedlings

Asparagus, also known as “shidiaobai”. It is one of the world's top ten famous vegetables and enjoys the reputation of “king of vegetables” on the international market. Asparagus is rich in various amino acids, proteins and vitamins, all of which are present in higher amounts than in ordinary fruits and vegetables. It is a new type of medicinal and health-care vegetable with anti-cancer, disease-preventing and anti-aging effects. Below is an introduction to greenhouse cultivation techniques for green asparagus seedlings.

I. Establish a high-standard greenhouse

Choose a site sheltered from the wind and facing the sun, with flat terrain, fertile soil, a thick plow layer, convenient drainage and irrigation, and good aeration in sandy soil to build the greenhouse. For the greenhouse orientation, facing south with a 5-degree deviation toward the sun gives the best lighting effect. The greenhouse is 50 m long from east to west, with a span of 8.2 m, a rear wall 2 m high, a wall thickness of 1.2 m at the bottom and 0.9 m at the top, and a ridge height of 3 m. The rear slope uses double films with 20 cm thick corn stalks or wheat straw sandwiched between them, with 45 cm of soil covering the film. The front slope is covered with polyethylene non-drip film. A 70 cm*70 cm cold-proof trench is dug in front of the greenhouse and filled with corn stalks or wheat straw.

II. Summary of greenhouse cultivation techniques

1. Variety selection

For green asparagus, choose hybrid varieties that are cold-resistant, disease-resistant, have tightly clasped scales, and produce green, relatively thick and uniform tender spears.

2. Soaking seeds in warm water

Before sowing, soak the seeds in warm water at 45-50°C for 30 minutes, then replace with clean well water and soak for another 24 hours, then drain. Rinse once with warm water at 30°C and place at 25-30°C to promote germination. Rinse once each morning and evening with warm water at 30°C, then wash off the secretions on the seed surface to prevent mildew and rot. When the seed germination rate reaches 15%, sowing can begin.

3. Sowing

In early March, raise seedlings in a small arch shed. For each mu of greenhouse, use two seedbeds of 1.5 m*10 m. Apply 2.5 kg of diammonium phosphate and 1.5 kg of potassium chloride to each seedbed, then plow the soil 20 cm deep and level and refine the seedbed. First open furrows at a row spacing of 10 cm and a furrow depth of 5 cm, then sow by spot seeding at a plant spacing of 10 cm, with 1 seed per hole, cover with about 3 cm of soil, and scatter 1605 mixed with wheat bran poison bait on the seedbed surface to eliminate underground pests. Then cover the small arch shed with a layer of plastic film, cover it tightly and seal it well, and generally do not ventilate before emergence.

4. Seedbed management

Because asparagus seeds can only germinate above 10°C, with the optimum temperature being 25-30°C, and the temperature is still low when sowing in small sheds, straw mats should be covered over the shed at night. When 60% of the seedlings have emerged through the soil, the plastic film should be removed promptly. After the seedlings have all emerged, ventilation should begin. Ventilation should be carried out after 11 a.m. and closed at 2 p.m., with the ventilation opening increasing from small to large. As the asparagus seedlings grow, finally remove all the shed film. During the seedling stage, the daytime temperature is best controlled at 20-25°C, and at night it is appropriate to maintain around 18°C.

5. Field planting

In early June, when the seedlings are 50 cm tall, have 3-6 root systems and 3 tender spears, they can be planted out. The asparagus seedlings to be planted should be graded by size and planted separately. When transplanting, make the sprouting surface of the asparagus root crown face south. Before planting, clear away the residual branches and fallen leaves of the previous crop to prevent pests and diseases in the greenhouse. Apply sufficient base fertilizer; generally apply more than 7500 kg of farmyard manure per mu, 50-70 kg of ternary compound fertilizer, 20 kg of urea, and 30 kg of potassium chloride. Plow the soil 20 cm deep and level it. From one side of the greenhouse, open furrows in a north-south direction, with a furrow depth of 10 cm. Apply 3 kg each of dichongjing and dijunJing in the furrow, mix the soil and pesticide evenly, and then plant at a row spacing of 90 cm*30 cm. After planting, the first soil covering should be 3-5 cm. After 7-8 days, when the seedlings have recovered, the second soil covering should preferably be to the same depth as the original seedling soil. After the first soil covering, water thoroughly.

6. Management after field planting

Within 1 month after planting, inspect and replant seedlings promptly. When dead seedlings are found, replant them promptly, and the replanted seedlings should be larger than the original ones. After the young seedlings are planted, tender spears emerge in 7-8 days. Because the seedlings are tender and delicate, their resistance to pests and diseases and their regeneration ability are very poor, so timely inspection is necessary. If stem blight is found, spray 800 times 50% carbendazim promptly; if pests are found, spray pesticide promptly for control. One month after planting, the young tender spears have grown to 4-5 cm high. To promote their growth and development, sufficient water and nutrients must be provided. At this time, quick-acting chemical fertilizer can be applied as a top dressing, with 10-15 kg of urea per mu, or 15-20 kg of ternary compound fertilizer. Around August 25, asparagus enters the autumn growth stage. Open furrows again and apply 3000-4000 kg of farmyard manure, 10 kg of diammonium phosphate, 15 kg of potassium chloride, and 40 kg of ternary compound fertilizer. Around October 25, cut off the asparagus stalks and clear away all residual branches and fallen leaves completely, take them outside the greenhouse, and burn them in a centralized manner. Then carry out intertillage and loosen the soil, open furrows and apply 40-50 kg of ternary compound fertilizer and 20 kg of urea. In mid-November, water once. Combined with intertillage and soil loosening, apply 4 kg each of dichongjing and dijunJing, shape the ridge into a fish-back shape, and cover with plastic film. In mid-December, cover with straw mats at night so that the temperature inside the greenhouse is 20-28°C during the day and 18-20°C at night.

7. Harvesting

When the tender spears push through the soil, break the film promptly to release the seedlings. When the tender spears grow to 20 cm high, cut them off at ground level with a sharp asparagus harvesting knife. Put the harvested asparagus into the harvesting box immediately. After harvesting, sort the tender spears, tie them in bundles by grade, box them, cover them with a damp cloth and sell them. They can be temporarily placed in a cool place, but must never be soaked in water to avoid rot and deterioration.

III. Precautions

During greenhouse cultivation, because the temperature is suitable for the growth of pathogens, preparations for pest and disease prevention must be made. After harvesting asparagus, sort the tender spears, tie them in bundles by grade, box them, cover them with a damp cloth and sell them. They can be temporarily placed in a cool place, but must never be soaked in water to avoid rot and deterioration.