A Detailed Tutorial on the Latest Asparagus Cultivation Techniques and Methods

Asparagus is also known as shidiaobai and longxucai (dragon-whisker vegetable); it belongs to the genus Asparagus in the lily family and is a perennial herbaceous plant with a persistent root system. Asparagus is eaten for its young shoots; it is nutritious, crisp and tender in texture, and delicately fragrant and tasty. It can be eaten fresh or processed and canned. It is a premium delicate vegetable and one of the world's top ten famous vegetables. It is rich in vitamins and minerals, and also contains asparagine and aspartic acid, as well as rutin, folic acid, nucleic acids and other substances. Regular consumption of asparagus has a certain therapeutic effect on heart disease, high blood pressure, cystitis, diabetes and leukemia, and can inhibit the development of cancer cells, so it is called an anti-cancer health vegetable.

Botanical Characteristics

Although asparagus is a perennial, its above-ground stems and leaves die back each winter when low temperatures and frost arrive, overwintering and going dormant as underground rhizomes. When temperatures rise again the following March to April, new stems sprout from underground; the newly emerged young shoots are the asparagus spears. With good management, the harvest period can last more than 10 years.

Requirements for Environmental Conditions

1. Temperature

Asparagus has a relatively wide temperature tolerance. The suitable temperature for seed germination is 25-30°C, and the optimal temperature for vegetative growth is 20-30°C. Below 15°C growth is slow and few young shoots are produced; above 30°C the outer skin of the young shoots tends to become fibrous and the shoot tips easily splay open, resulting in poor quality; above 35°C growth stops.

2. Light

Asparagus is a light-loving plant and requires strong light. With sufficient sunlight it grows luxuriant branches and leaves, and photosynthesis is closely related to temperature. High-temperature seasons are unfavorable for asparagus growth, and prolonged rainy weather also affects asparagus yield.

3. Soil

Asparagus is a deep-rooted crop, and its young shoots also need hilling with soil for shading, so a sandy loam with deep soil layer, loose and fertile texture, and rich organic matter should be chosen. A pH of 5.8-6.5 is optimal.

Cultivation Techniques

1. Sowing and Raising Seedlings

(1) Sowing period: spring, March to April; autumn, August to September.

(2) Seed treatment

Place the seeds in a 400-fold solution of 50% carbendazim or 70% thiophanate-methyl, keeping the water temperature at 25-30%, and disinfect for 24 hours. Then rinse clean with clear water and soak the seeds in warm water at about 30°C for 2-3 days. After the seeds have fully absorbed water, wrap them in gauze or a towel and place them in an incubator or a warm place to promote germination. During this period, spray or rinse them frequently with water. Once the seeds crack and show white after 2-3 days, they can be sown.

(3) Seedbed preparation

The seedbed should preferably be a loam or sandy loam with good drainage and loose, breathable texture. For base fertilizer, apply per mu of seedbed 1500-200 kg of high-quality farmyard manure, 10 kg of urea, 7 kg of ordinary calcium superphosphate, and 6 kg of potassium sulfate, spread evenly, then turn them into the soil layer and mix with the soil.

(4) Sowing method

For broadcast sowing, about 10 kg of seed is used per mu; for dibbling and drilling, about 1 kg of seed is needed per mu. After sowing, cover the bed surface with rice straw or pine needles, then water thoroughly and evenly with a watering can. Seedlings begin to emerge 15-20 days after sowing.

(5) Seedbed management

Once 80% of the seeds have emerged, the covering can be removed gradually. Pay attention to watering lightly, weeding, and topdressing, and control underground pests promptly when found.

(6) Seedling separation and temporary planting   This is done when the seedlings are about 10 cm tall.

2. Field planting

(1) Site selection and trench digging

The planting site should be a loam or sandy loam that is sheltered from wind and faces the sun, with a low groundwater table and convenient irrigation and drainage. Dig and turn the soil to dry and weather it, maturing the soil, then dig planting trenches at a row spacing of 1.5 m, with a trench depth of 50 cm, a top width of 40 cm and a bottom width of 50 cm. Asparagus should be given heavy base fertilizer: first fill the trench with about 10 cm of topsoil, then apply per mu 4000-5000 kg of organic fertilizer, 150-200 kg of compound fertilizer or 100-150 kg of oil cake, 50 kg of ordinary calcium superphosphate, 15 kg of potassium sulfate, and 2 kg of carbofuran to prevent underground pests, mix them evenly, then backfill about 20 cm of topsoil, mix and tread firm. Finally, backfill the trench with topsoil, but the trench surface should still remain about 10 cm lower than the bed surface.

(2) Planting time and density

Spring-sown seedlings are planted in May to June, and autumn-sown seedlings are planted in March to April of the following year. For white asparagus, the row spacing is 1.6-1.8 m and the plant spacing is 30-35 cm, with 1000-1200 plants per mu; for green asparagus, the row spacing is 1.4-1.5 m and the plant spacing is 20-25 cm.

(3) Cut off part of the stems and leaves of the selected asparagus seedlings, leaving 20 cm. According to the set plant spacing, spread the root mass apart so that it extends obliquely downward in all directions. Do not cover with soil too deep at one time; after the plants survive, cover with soil two more times in combination with intertillage and weeding, so that the root crown is buried 10-15 cm below the soil surface.

3. Field management

(1) Management of newly planted seedlings

Topdressing can begin one month after field planting, mainly with dilute manure water; thereafter apply once every two months, and the concentration can be appropriately increased. Carry out intertillage, loosening of the soil and weeding, and combine with intertillage to hill up the soil shallowly 1-2 times to prevent roots from being exposed. All young shoots grown in the planting year should be retained.

(2) Removing flowers and fruits of female plants

Because female plants consume a large amount of nutrients for flowering and fruiting, affecting the yield of the current year and the next year, they should be removed as early as possible.

(3) Irrigation and topdressing

During the shoot-harvesting period, irrigation must be guaranteed and the plants must not suffer drought; generally irrigate once every 7-10 days. The highest yield occurs after the 3rd-4th year. Each year, heavy application of organic-fertilizer-based autumn-development fertilizer and winter fertilizer is also needed. Avoid partial application of N fertilizer; N, P and K should be rationally combined.

4. Main diseases and pests

There are relatively many diseases and pests damaging asparagus, among which the most damaging is stem blight; in addition there are brown spot, rust, root rot and so on. The main insect pests are the tobacco cutworm, the black cutworm, and white grubs.

5. Harvesting

A small amount of harvesting can begin in the second year. Every morning or evening, when the young shoots are 15-20 cm tall, cut them off with a sharp knife 1-2 cm above the soil surface, and wrap them in a wet towel. At each harvest, all young shoots, regardless of size, must be fully harvested.