Nutritive Value: Knol khol is another member of the Cole crop family that forms edible and bulbous stems above the ground. Knol khol contains 93 percent water, 3.8 percent carbohydrates, 1.1 percent proteins and is rich in vitamins A and C, and potassium, phosphorus, calcium and iron.
Soil and Climate: Knol khol requires medium to light well drained soil. It cannot survive in heavy, loamy and poorly drained soils. It is basically a cool climate crop, which originated from the European region, and can grow well in the temperature range of 10 to 20°C.
Important Varieties: White Vienna and Purple Vienna are the popular varieties of knol khol grown on a wide scale in various parts of South India.
Planting and Irrigation: In the plains of South India, knol khol seeds are sown in September-October to grow seedlings. However, direct seeding in the field has also shown results similar to those of seedling transplanting. About 5 g of seeds are sufficient to raise seedling on an area of 10 m 2 . Sowing on a raised bed can be done by keeping a distance of 20 cm between two rows. The seedlings are ready for transplanting in 1.0 to 1.5 months after sowing. Manuring and irrigation can be done as in the case of cultivating cabbage and cauliflowers.
Plant Protection: Knol khol crop is mostly attacked by aphids, leaf miner and leafeating caterpillars that can be controlled initially by spraying systemic insecticides and, at later stages, when the crop grows towards maturity by using botanical insecticides can be used to protect it from insect infestation.
Harvesting: Tender leaves of knol khol are nutritive and can be cooked as a leafy vegetable. Tender, succulent and bulbous knobs are uprooted and used for vegetables. If harvesting is delayed by 15 days, fibrous tissues develop inside the bulb and the quality of the vegetable is reduced considerably.