Production practices of KnolKhol is almost similar other Brassica vegetables such as cauliflower, cabbage and broccoli. Propagation is by seeds.

Seed rate of 500 -750 grams is required to raise seedlings for one hectare area. Seedlings may be raised on nursery beds. If direct sowing is practiced, more seeds are required@ 1- 2 kg/hectare.

Seed treatment is essential to prevent seed-borne diseases and pest infestations. Hot water treatment (50°C) of seeds for half an hour is effective against black rot disease.

Seedlings are raised in the nursery beds. 60cm wide and 2.5m long raised nursery beds are prepared with 30cm channel along with the nursery. On light and drought sensitive soils, sunken nursery beds are preferred. For one square meter nursery area, 100 grams of fertilizer mixture is applied.

Fertilizer mixture is prepared by mixing 15 grams each of N, P, K and 5 kg of FYM or compost. After preparing the nursery beds, these nursery beds should be treated with formalin (40% formaldehyde diluted in 5–6 parts of water) for disinfestation purposes.

Seeds are sown in rows at a distance of 5–6 cm. Sowing depth of 1.5–2cm is optimum. The nursery bed is then covered with a mulch to conserve moisture. Irrigation is done as and when required. Mulch is removed just before the seed germination.

Sowing time in tropical plains is September-October (Asia) and in tropical hills is March to November (Europe).

Transplanting is done when seedlings have 7–9 true leaves, that is, 30–40 days after sowing.

Land is prepared by 2–3 ploughings followed by pulverizing and levelling of land; then field beds and irrigation channels are prepared. Transplanting is done in the evening and/or on cloudy days. A light irrigation is given after transplanting. Dead plants should be replaced and gaps should be filled 5–6 days after transplanting.

A spacing of 25cm × 30cm, or 25cm × 40cm or 30cm × 45cm is recommended depending on climatic conditions and fertility of the soil.

100,000–120,000 plants/ha is recommended in case of transplanting. In case of direct sowing, plant population is thinned to a density of up to 300,000 plants per ha.

KnolKhol is a heavy feeder just like any other Cole crop and hence responds well to fertilization. However caution is required not to over fertilize or under nourish the plants as excess nitrogen enhances vegetative growth but delays crop maturity. In the same manner, deficiency of trace elements such as Boron and Molybdenum induces physiological disorders such as browning, whiptail and buttoning. Recommended NPK dose is 200kg of N; 100kg P and 100kg K for one hectare area in tropical countries.

An illustration of fertilizer application is as given below:

  • Before transplanting and at the time of land preparation-FYM or compost 25 tons/hectare
  • At the time of transplanting-Half of N along with full quantity of P and K
  • Follow up N- application-The remaining half N is applied in 2 equal split doses, 3 weeks after transplanting and the other at the knob development stage
  • To correct N-deficiency-Foliar application of urea (1–2%)
  • To correct the general micronutrient deficiencies-Multiplex (0.2–0.3%) as foliar spray
  • To correct boron deficiency-10–15kg/ha of borax as soil application or 2 sprays of 0.3% borax on the crop
  • To correct Mo deficiency-By liming or soil application of ammonium molybdate @ 200–300g/ha at concentration of 0.01–0.1%

Regular hoeing and weeding is recommended until plants grow well and leaves cover the soil surface. Thereafter hoeing and weeding must be stopped. 2–3 hoeing and weeding are recommended. Manual weeding is generally recommended. If weed menace is very severe chemical weed control may be practiced.

KnolKhol requires a continuous supply of water for its healthy growth. First irrigation is done immediately after transplanting subsequent irrigations are done at 15 days interval or as and when needed, depending on soil and weather conditions. At the time of maturity of knobs, irrigation is detrimental and should be stopped.

Diseases and Pests are same as that of other Brassica vegetables. IPM and IDM may be practiced for effective control of diseases and pests.

Stem tuber or knob as it is called, attains maturity after 60 days of sowing. Thereafter harvesting can be completed within a month as knobs have good standing ability for up to 30 days after maturity.

When the harvesting stage approaches, the knobs will be globular-round, light green, smooth, and tender. Spring-sown crops are picked when the knobs reach 5–6 cm in diameter. Those of autumn grown are harvested when the knobs reach 10–12 cm in diameter.

Harvesting is done either manually or by using mechanical harvesting methods. The knobs are harvested by cutting the stem just below it by a sharp knife or sickle before they are fully grown and knobs are still very tender.

KnolKhol tubers have good keeping qualities; they can be stored at room temperature for 2-3 days and for about 3 weeks at 0–1°C and a relative humidity of 98%.

The knobs of early varieties may have an average weight of 150–200 grams while those of late varieties weigh up to 1 kg. Generally, the yield ranges from 25–35 tons/ha.

Major quality indices are size of the knob, its colour, and texture. The demand is fairly high for knobs of smaller size of about 5–8 cm diameter. Mostly green knobs with white flesh are preferred by the consumers. Texture of the knobs should be very tender. Avoid woody, cracked and fibrous knobs by all means as they are not marketable.

Post Harvest Management

Pre-Cooling: There are four pre- cooling methods. These are vacuum cooling, hydro cooling, top icing and forced air cooling. Vacuum-cooling is the most effective cooling method. In hydro-cooling, products are rapidly cooled from 20 °C (68 °F) to 2 °C (35.6 °F) in about 15 minutes. Package or top-icing is used if storage or transport conditions cannot maintain recommended temperature or RH (relative humidity). In forced-air cooling, packaging is adequately vented to permit good air contact with the products.

Optimum Storage Conditions: Temperature at 0 °C (32 °F) and relative humidity (RH) at 95 to 100% provides maximum shelf life i.e. up to 5 weeks.

Physiological Disorders: Cracking of knobs which is caused by moisture stress and physical injury which is due to the rough handling at harvest are major physiological disorders.

Pathological Disorders: Bacterial soft rots caused by Erwinia spp. and Pseudomonas spp.; bacterial leaf spot caused by Pseudomonas syringae pv. Maculicola; black or gray leaf spot caused by Alternaria spp. and grey mold caused by Botrytis cinerea pers are some major pathological disorders that are found in KnolKhol.

Packaging: The root portion or the portion below the knob is removed and the products are tied in bundles along with the associated leaves. Sometimes leaves are also removed and the knobs are packed alone without the leaves. Europe is a major export market for Knol-khol tubers.

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