Onion Planting Techniques

Choose high-yielding and disease-resistant varieties, such as Red Boy and Purple Crown. Purple Crown is a conventional variety for open-field onion cultivation, classified as a medium to long-day purple-skinned onion. Red Boy is the latest hybrid variety, with a long-day type, extremely early maturity, and a deep purplish-red color with a glossy finish. It is high and flat or spherical, measuring 7-9 cm in length and 8-10 cm in width. Each bulb weighs about 350 grams, with the largest reaching 760 grams. It has a mild spiciness, high dry matter content, making it ideal for fresh sales. The variety is disease-resistant, cold-tolerant, resistant to bolting, and can be propagated and stored easily. From planting to harvest, it takes about 120 days, making it suitable for spring planting in long-day regions. With proper management, the yield can reach up to 8,500 kilograms per mu.

sow seeds

In the Beijing area of China, onion cultivation in open fields takes place from March 15 to 30. Therefore, seedling cultivation begins in mid to late December of the previous year. Seedlings can be grown using a 200-cell tray or directly on the soil ridge surface by laying the substrate. The substrate mixture should be prepared with a volume ratio of peat, vermiculite, and perlite at 1:1:1, and the ridge should be 1.8 meters wide, with a substrate thickness of 7 centimeters. A 200-cell seedling seeder is used for sowing, with a seeding rate of about 600,000 seeds per mu. Before sowing, the substrate should be disinfected using a 3000-fold dilution of 50% chlorobromophenol formal or drip irrigation, and it is advisable to thoroughly water the 20-centimeter-thick seedbed soil.

Temperature management: Onion seeds require a minimum temperature of 4℃ and a maximum temperature of 33℃ during the germination process, with an optimal temperature range of 15-25℃. After germination, the minimum, maximum, and optimal temperatures for young root growth are 4℃,38℃, and 30℃, respectively. For the growth of above-ground young shoots, the minimum, maximum, and optimal temperatures are 6℃,38℃, and 30℃, respectively. Soil moisture is closely related to seed germination; when the soil moisture content is between 10-18%, the germination rate can reach 90%. Onion seeds do not require light to germinate, but exposed seeds can also germinate after sowing. The germination of onion seeds does not require high levels of oxygen.

Water and fertilizer management: In the middle and late stages of seedling cultivation, spray 2% compound fertilizer solution (N-P-K content of 16-16-16) 2-3 times. During seedling cultivation, water the seedbed substrate once a day at 10:00 to ensure that the substrate is saturated without dripping water.

Pest and Disease Management: To prevent pests and diseases, it is essential to disinfect the soil during onion seedling cultivation. Hartzman can be used to control diseases caused by pathogens such as Rhizoctonia solani and Fusarium oxysporum. Apply 3 kg of Hartzman powder (with at least 1 billion live bacteria per gram) diluted in water to a 300-fold dilution and flood irrigate; apply 10 kg of 3% phoxim granules and 100 times diluted solution of Pseudomonas lilacina (with at least 2.1 billion live bacteria per gram) for flood irrigation to control underground pests. During the mid-to-late stages of seedling cultivation, based on pest conditions, spray 30% thiamethoxam at 1000 times dilution plus 3% carbendazim at 500 times dilution or 30% bifenthrin and clothianidin at 2000 times dilution 2-3 times to control thrips.

Seedling standards: 60 days old, plant height 15-25 cm, 4-5 true leaves, stem diameter 0.6-0.7 cm, short internodes, robust stems, large leaves; well-developed fibrous roots, soil clumps can be easily pulled out without breaking, leaves are thick and not overgrown, free of pests and diseases.

Onions have poor flood resistance and weak root development, which limits their ability to absorb nutrients from the soil. It is recommended to plant on fertile, loose soil that retains water and nutrients. After the land thaws in early March, apply 1000 kilograms of organic fertilizer (NPK content of at least 4.0%, organic matter content of at least 30%) per mu, 50 kilograms of compound fertilizer (N-P-K ratio of 17-17-17), and 10 kilograms of 3% phoxim granules. After application, till the soil. Deep plow the soil to a depth of 30 centimeters, then level it to improve its looseness and aeration. Use a fertilizer covering machine to cover the ridges, with 2 drip irrigation tapes per ridge, and select 1-meter-wide white mulch film to help increase soil temperature in early spring.

The planting time is from March 15 to 30, with 17,000 to 20,000 plants per mu. Each ridge has 4 rows, with a ridge surface width of 55-60 cm and a ridge height of 15-20 cm. The length of the ridges is determined by the land length, with a ridge spacing of 1.0-1.2 meters, row spacing of 15.5 cm, and plant spacing of 14 cm. Install drip irrigation equipment for integrated water and fertilizer management to save water and reduce fertilizer use.

field management

After transplanting, cover the soil around the seedling holes with soil to retain moisture and prevent weed growth. Water immediately after transplanting, using a light watering to ensure the soil is moist and water seeps through the ridges, which helps restore ground temperature. After 10 days, water again, applying 5 kg of high-nitrogen compound fertilizer (30-5-15) per mu (about 0.167 acres); then water every 7 days, and apply 5-10 kg of compound fertilizer (17-17-17) every 15 days; in the later stages, use high-potassium compound fertilizer (16-6-24),5-10 kg each time; control watering and fertilizing 15 days before harvest.

Onion cultivation in the open field is susceptible to thrips and diseases such as soft rot and anthracnose. After planting, it is important to focus on pest and disease control. After watering, apply a 250-fold dilution of dimethoate to control weeds; after the second watering, spray a 1000-fold dilution of 30% thiamethoxam or thiamethoxam to control thrips; apply 3.3 kg of Hartzmyces powder (with at least 1 billion live bacteria per gram) to control fungal diseases; subsequently, spray a 1200-fold dilution of 2.5% carbendazim or a 1500-fold dilution of 5% abamectin every 15 days to control pests and diseases.

Onions in Beijing are generally harvested from late June to early July before the hot and rainy season to prevent high temperature scorching and flood rot. The grading standard for harvest is 8 cm in diameter and 375 g per fruit, with higher grades being superior.

The bulbs are spherical or flat and range in color from purple to pink. They have a strong spicy taste. They are high-yielding and slightly less resistant to storage, and are mostly medium to late maturing varieties

The bulbs are flat, round, or oval-shaped, with a copper-yellow or light yellow outer skin and brown longitudinal stripes. The flesh is slightly yellow, sweet and spicy, and of high quality. The scales contain little water, have a long dormant period, and are highly storable. The yield is relatively low, and most varieties are mid-to late-maturing.