Detailed Explanation of Key Techniques for Greenhouse Cultivation of A-choy (Taiwan lettuce) in Autumn and Winter
A-choy, also known as youmai cai, and also called bitter vegetable or lettuce, belongs to the Asteraceae family and the Lactuca genus. It is a pointed-leaf leaf lettuce whose product is tender shoots and tender leaves. The leaves are long and lanceolate, pale green in color, crisp and tender in texture, and the taste is extremely fresh and tender, delicately fragrant, with a unique flavor. It contains large amounts of vitamin A, vitamin B1, vitamin B2, and abundant calcium, iron, and other nutrients. It is a premium choice among vegetables eaten raw and is known as the “phoenix tail”.
Morphological Characteristics of A-choy
A-choy belongs to the Asteraceae family. It is a pointed-leaf leaf lettuce whose product is tender shoots and tender leaves. The leaves are long and lanceolate. Its appearance is somewhat like the “head” of celtuce, with slender, flat-spreading leaves and a thin, short stem. In terms of genetic relationship, A-choy belongs to a variety of leaf lettuce——long-leaf lettuce, and is close to the familiar lettuce, so it is also called niuli lettuce. It is pale green in color and vigorous in growth. It has strong disease resistance and adaptability, a crisp and tender texture, and an extremely fresh, tender, and delicately fragrant taste, and is known as the “phoenix tail”. A-choy has effects such as lowering cholesterol, treating neurasthenia, clearing dryness and moistening the lungs, and resolving phlegm and relieving cough. It is a low-calorie, high-nutrition vegetable.
Nutritional Value of A-choy
A-choy contains large amounts of vitamins, calcium, iron, protein, fat, and various other nutrients, and can supplement the various nutrients needed by the human body. The main characteristic of A-choy is that it is very rich in minerals. For example, the calcium in A-choy is 1.9 times higher than in lettuce and 2 times higher than in celtuce. Its protein content is 40% higher, carotene is 1.4 times higher, calcium is 2 times higher, iron is 33% higher, and selenium is 1.8 times higher.
Key Points for Greenhouse Cultivation of A-choy in Autumn and Winter
1. Seed Treatment, Seed Soaking, and Germination Promotion
First wrap the seeds in gauze and soak them in cool water for about 1 hour, then take them out and place them at 15-20°C. Alternatively, place them in the refrigerator compartment of a home refrigerator for 2-3 days. Once the seeds show white sprouts, they can be sown. The seeding rate is 20-25 grams per mu.
2. Seedbed Preparation
Select a seedbed plot with high, dry terrain and strong water- and fertilizer-retention capacity, apply more organic fertilizer, and use 15-20 sq m of seedbed per mu of cultivation field.
3. Sowing
Generally sow in mid-to-late September. When sowing, mix an appropriate amount of fine sand with the seeds, separate the seeds, and then broadcast them for seedling raising. Be careful not to sow too densely, to prevent the seedlings from becoming leggy. Cover the seeds with 0.5 cm of medicinal soil mixed with phoxim, and at the same time set up a shed for sun protection and rain protection.
4. Seedling Stage Management
When the seedlings grow 2 true leaves, thin them out, with a transplanting density of 6 cm×6 cm. Keep the seedbed moist, and provide shade at noon. Pay attention to pest and disease control during the seedling stage.
5. Land Preparation and Field Planting
About 25 days after sowing A-choy, when 5-6 true leaves have grown, plant them in the greenhouse in a timely manner. Before planting, apply 3500-4000 kg of decomposed organic fertilizer, 20-25 kg of phosphate fertilizer, 40-50 kg of nitrogen fertilizer, and 10-15 kg of potassium fertilizer per mu. After broadcasting, prepare the land and make beds. The bed width is 1-1.5 m, the plant and row spacing is 10 cm×10-15 cm, and 40,000-50,000 plants are planted per mu. After transplanting, water thoroughly to settle the plants.
6. Management After Field Planting
1) Management before closing the greenhouse. After planting and seedling recovery, apply 1-2 small amounts of quick-acting nitrogen fertilizer along with watering, generally 5 kg of urea or ammonium sulfate per mu, to promote plant growth and development. After that, keep the soil moist frequently and cultivate and weed in a timely manner.
2) Management after closing the greenhouse. A-choy is a fast-growing leafy vegetable. Its suitable growth temperature is 18-25°C. Close the greenhouse when the nighttime temperature is below 12°C. After closing the greenhouse, promptly adjust the greenhouse temperature and relative humidity inside the greenhouse. Generally, the relative temperature inside the greenhouse should be less than 90%. During cultivation management, keep things clean and hygienic, and it is forbidden to use diluted manure as a topdressing. In the early and middle stages of A-choy growth, spray the leaves 3-4 times with 0.3% potassium dihydrogen phosphate and urea solution. During the entire growth period, topdress 2-3 times, applying 5-10 kg of urea or 10 kg of ammonium sulfate per mu, applied along with irrigation water.
3) Pest and disease control. The main pest is aphids, which can be sprayed with 800-fold dilution of 40% dimethoate emulsifiable concentrate; the main diseases are downy mildew and soft rot, which can be controlled by spraying with 300-500-fold dilution of 70% mancozeb wettable powder and 0.02% agricultural streptomycin solution, respectively.
7. Harvesting
A-choy is mainly eaten for its tender leaves. From late October to early January of the following year, when the number of leaves reaches 30-34, the plant height is 45-48 cm, and the spread is 60-69 cm, harvest all at once at 2-3 cm above the ground. Remove old leaves and diseased leaves, and supply the winter market in a timely manner.