Onion Allium cepa scientific name L, is a high-vegetable products, which are used for processing the food that most of the world are used. Currently onions for our country is still a fresh vegetable commodities exported to Western countries and the countries in the region.
The major onion-growing areas in the country including Phan Rang, Da Lat, Vinh Phu, Ha Bac, Ha Noi .... has drawn a lot of experience in intensive production to achieve high performance, full quality assurance standards for export.
- Characteristics of biology: onion sunshine all day long, day light length is 12-14 right now, especially in the formative stages and root development. Onions do not tolerate waterlogged soil, but if drought reduces yield and quality of tubers. Needed moisture for the seedling stage and tubers growing around 80-85%, while the old bulbs are about 70%. Due to poor root development so soil should onion porous, sandy, nutrient-rich, pH of 6-6.5.
- The current major cultivars include: Granex, Grano, Red Creole.
- Planting season: 9-10 months for the planting and harvesting January January 2 Department against sowing late March, early April, harvested in 8-9 months.
- Technical nurseries: nursery land to a high place, open drainage. Land used for technical, raised bed, beds 1.2-1.5 m wide. 3-4 grams per square meter sowing seeds. Need 2,5-3kg use seeds to plant a hectare.
After planting is complete, use chopped straw and sprinkled soaked, germinated seeds after 7-12 days, at which irrigated daily with sufficient permeability. When plants 3-5 cm high, peel away layer of straw mulch. Pruning trees removing weak, bad crops.
Experience distinguish seedlings good or bad is based on a special stage of development called "bending the knee" before tree upright. If the bad seeds grow upright phase without phase "bending the knee" we need the trees removed, this phase usually at 15-20 days old seedlings.
- Planting techniques and care: to export onions, celeriac required to have, sure, beautiful exterior, long shelf, one of the conditions of cultivation is the right age to seedlings . When plants reach 50-60 days of age, when there are 5-6 true leaves, new planting should spit. If planted early, early customers quickly take root and tuber harvest but plenty of water (90% water content, root perishable, non-preservation is long, should not be exported). To bed 1.2m, 0.3m trench. Growing 4 vertical rows, each row spacing 20cm, 15cm plant spacing, planting density ideal from 150-170 thousand plants / ha.
- Fertilize:
Intensive fertilizer for onions to create high yield, good quality for export requirements, need fertilizers as follows:
Manure + (or other organic fertilizers): 20-30 tons / ha.
+ Urea: 140-200 kg / ha.
+ Super Phosphate: 400-500 kg / ha.
+ Potassium Sulfate: 200-260 kg / ha.
+ If you need liming acid soils from 250-350 kg / ha. Notice must reach 6-6.5 pH.
How to apply phosphorous fertilizers, manure, lime fertilizer entire liner, the third nitrogen and potassium. The remaining amount split evenly distributed, fertilizer 3-4 times on the stage of development stems, leaves, root formation and development. Depending on soil fertilizer can increase potassium, phosphorus, manure without increasing the amount of pure protein exceeding 100 kg (ie, does not exceed 220 kg urea) will cause nitrate accumulation in large onion, reduce the quality even , act quickly rot ... the quality control will not achieve the export standard.
- Pest prevention: Notes 2 diseases that often occur and affect the yield and quality of onions.
+ Downy (Pernospora Sp) occurs at high air humidity above 90%, a low temperature below 20OC. So when he saw on the weather prevented by spraying 1% Bordeaux spray solution periodically 4-7 days / times.
+ Onions rot: This is a common disease of concern growers, because it is easy to see appear on the field out. Bacterial disease Ervinia Sp, or harmful fungus Botrytis species from the harvested tubers to make and store.
The cause of the disease is caused by damp weather and more fertilizer nitrogen imbalance.
Prevention is by seed treatment with Granosan 3 g / 1 kg of seeds, or Benomyl 2 g / 1 kg seed.