General Information and Agronomic Aspects

Brassicas constitute the majority of cultivated Cruciferae in eastern and southern Africa. The main brassicas grown in the region include:

• Cabbage (Brassica oleracea L. var. capitata)
• Kale (sukumawiki) or choumolea (B.o. acephala)
• Chinese cabbage(B. campestris chinensis/pekinensis)
• Cauliflower (B.o. botrytis)
• Rape B. carinata (indigenous), and B. napus, (exotic type).

Cauliflower (Brassica oleracea var. botrytis)

Ⓒ Pankaj Oudhia (Courtesy of EcoPort, www.ecoport.org)

 

Other brassicas grown in the region are broccoli, Brussels sprouts, kohlrabi, savoy and turnip.Also grown in the region are radish (Raphanus sativus L. var. hortensis) and horseradish (Armoracia rusicana Gaertn.)

 

These vegetables are grown mainly for the local market. They are valuable as sources of vitamins and minerals, as well as a source of cash for smallscale farmers in rural and peri-urban areas. However, production is often constrained by damage caused by a range of pests (insects, diseases, nematodes and weeds).The range of pests attacking the different brassicas is similar, but the relative importance of individual pest species varies between the different crops. Cabbage is mainly sold fresh or as processed canned product. Processed products include those that are treated in vinegar, or fermented such as sauerkraut or kimchi. Fresh cut or lightly processed products include coleslaw and ready-to-eat salad mixes that contain shredded cabbage. Consumers generally prefer fresh green cabbage, when available, to stored cabbage. Much of the stored cabbage is grown for processing.

 

Nutritive Value per 100 g of edible Portion

Raw or Cooked Cabbage/Kale /Brassica

Food Energy (Calories / %Daily Value*)

Carbohydrates (g / %DV)

Fat (g / %DV)

Protein (g / %DV)

Calcium (g / %DV)

Phosphorus (mg / %DV)

Iron (mg / %DV)

Potassium (mg / %DV)

Vitamin A (I.U)

Vitamin C (I.U)

Vitamin B 6 (I.U)

Vitamin B 12 (I.U)

Thiamine (mg / %DV)

Riboflavin (mg / %DV)

Ash (g / %DV)

Broccoli cooked

35 / 2%

7.2 / 2%

0.4 / 1%

2.4 / 5%

40.0 / 4%

67.0 / 7%

0.7 / 4%

293 / 8%

1548 IU / 31%

64.9 / 108%

0.2 / 10%

0.0 / 0%

0.1 / 4%

0.1 / 7%

0.8

Brussel Sprouts cooked

36.0 / 2%

7.1 / 2%

0.5 / 1%

2.5 / 5%

36.0 / 4%

56.0 / 6%

1.2 / 7%

317 / 9%

775 IU / 15%

62.0 / 103%

0.2 / 9%

0.0 / 0%

0.1 / 7%

0.1 / 5%

0.9

White Cabbage cooked

23.0 / 1%

5.5 / 2%

0.1 / 0%

1.3 / 3%

48.0 / 5%

33.0 / 3%

0.2 / 1%

196 / 6%

80.0 IU / 2%

37.5 / 62%

0.1 / 6%

0.0 / 0%

0.1 / 4%

0.0 / 0%

0.6

Red Cabbage cooked

29.0 / 1%

6.9 / 2%

0.1 / 0%

1.5 / 3%

42.0 / 4%

33.0 / 3%

0.7 / 4%

262 / 7%

33.0 IU / 1%

34.4 / 57%

0.2 / 11%

0.0 / 0%

0.1 / 5%

0.1 / 4%

0.6

Savoy Cabbage cooked

24.0 / 1%

5.4 / 2%

0.1 / 0%

1.8 / 4%

30.0 / 3%

33.0 / 3%

0.4 / 2%

184 / 5%

889 IU / 18%

17.0 / 28 %

0.2 / 8%

0.0 / 0%

0.1 / 3%

0.0 / 1%

0.7

Chinese Cabbage cooked

14.0 / 1%

2.4 / 1%

0.2 / 0%

1.5 / 3%

32.0 / 3%

39.0 / 4%

0.3 / 2%

225 / 6%

967 IU / 19%

15.8 / 26%

0.2 / 9%

0.0 / 0%

0.0 / 3%

0.0 / 3%

0.7

Cauliflower cooked

23.0 / 1%

4.4 / 1%

0.5 / 1%

1.8 / 4%

16.0 / 2%

32.0 / 3%

0.3 / 2%

142 / 4%

12 IU / 0%

44.3 / 74%

0.2 / 9%

0.0 / 0%

0.0 / 3%

0.1 / 3%

0.6

Kale cooked

28.0 / 1%

5.6 / 2%

0.4 / 1%

1.9 / 4%

72.0 / 7%

28.0 / 3%

0.9 / 5%

228 / 7%

13623 IU / 272%

41.0 / 68%

0.1 / 7%

0.0 / 0%

0.1 / 4%

0.1 / 4%

0.9

Kohlrabi cooked

29.0 / 1%

6.7 / 2%

0.1 / 0%

1.8 / 4%

25.0 / 2%

45.0 / 4%

0.4 / 2%

340 / 10%

35.0 / 1%

54.0 / 90%

0.2 / 8%

0.0 / 0 %

0.0 / 3%

0.0 / 1%

1.1

Radish raw

16.0 / 1%

3.5 / 1%

0.1 / 0%

0.7 / 1%

25.0 / 2%

20.0 / 2%

0.3 / 2%

233 / 7%

7.0 IU / 0%

14.8 / 25%

0.1 / 4%

0.0 / 0%

0.0 / 4%

0.0 / 0%

0.5

Turnip Greens cooked

20.0 / 1%

4.4 / 1%

0.2 / 0%

1.1 / 2%

137 / 14%

29.0 / 3%

0.8 / 4%

203 / 6%

7626 IU / 153%

27.4 / 46%

0.2 / 9%

0.0 / 0%

0.0 / 3%

0.1 / 4%

1.1

Turnip Roots cooked

22.0 / 1%

5.1 / 2%

0.1 / 0%

0.7 / 1%

33.0 / 3%

26.0 / 3%

0.2 / 1%

177 / 5 %

0.0 IU / 0%

11.6 / 19%

0.1 / 3%

0.0 / 0%

0.0 / 2%

0.0 / 1%

0.5

*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.

 

Climate conditions, soil and water management 

Cabbage is a biennial plant that grows best under full sunlight. The optimum mean temperature for growth and quality head development is 15-18degC, with a minimum temperature of 4degC and a maximum 24degC. Generally, young plants are more tolerant to heat and cold than plants nearing maturity. For seed production cabbage plants need to pass through vernalisation: continuous days with temperatures at 1.7-10 degC before they start bolting. Broccoli and cauliflower produce seed without vernalisation. Cabbage grows well on a wide range of soils with adequate moisture and fertility. Soil pH in the range of 6.0-6.5 is preferred, but cabbage will tolerate a soil pH range of 5.5 to 6.8. Cabbage is a heavy feeder, so to get good yields, proper fertilisation is necessary. To maintain growth, cabbage requires a consistent supply of moisture, and should as a general rule receive a minimum of 2.5 cm of water per week. Larger quantities may be required when cabbage is grown on sandy soils or when evapotranspiration is high.  

 

Nutrient deficiencies 

Growing healthy plants is the best way of avoiding problems. Healthy plants grow on a healthy and well nourished soil with a good texture. Good compost is the best and most balanced soil and plant feed available to farmers. Regardless of soil type, excessive N (nitrogen) can promote second growth and split heads. A high level of nitrogen will also shorten storage life of cabbage and promote pungent odour (strong smells) during cooking. Combined with high temperatures, excess N (nitrogen) can promote such rapid growth that plants show symptoms of tip burn in susceptible cultivars. Depressed yields, delayed maturity, reduced keeping quality and strong or objectionable flavours are indicative of N deficiency. Like most cruciferous crops, cabbage has a high requirement for boron and molybdenum. Boron deficiency causes yellowing or chlorosis of the youngest leaves and stems, which often starts from the base and extends to the tip, hollow and discoloured inside stems of broccoli and cauliflower, and hollow and/or shrunken roots of turnips. Rosetting or even death of terminal shoots or buds occurs in extreme cases. The common symptoms of molybdenum deficiency in cabbage include a general yellowing, marginal and interveinal chlorosis, marginal necrosis, rolling, scorching and downward curling of margins usually on older leaves. Compost and well rotted animal manures are good sources of most micronutrients including boron and molybdenum. 

 

Land preparation and management

• Prepare land well before transplanting.
• Avoid field operations when it is wet. This will help to prevent inadvertent spread of diseases from plant to plant and movement of infested soil within and outside the field.
• Keep fields free of weeds. Especially weeds of the brassica family are potential alternative hosts of insect pests and diseases and are nutrient competitors.
• Ensure optimal fertilisation. Cabbage has a very shallow root system and is particularly responsive to phosphorus. Where the soil has a low phosphorus content the application of 'Mijingu Rock Phosphate' is recommended.

Propagation and planting Seedlings:

• Practise crop rotation: site seedbeds on land not previously under crucifers, and preferably away from old crucifer fields.
• Use clean wooden trays to raise seedlings, use mixture of compost and top soil or forest soil for raising seedlings.
• Heat soil in the seedbed: place plenty of crop trash or straw and burn for at least 30 min, and after cooling, mix the soil with compost in equal proportions.
• Use certified disease free seed of resistant/tolerant cultivars.
• Mulch seedlings in the seedbed, if possible.
• Do not over water seedlings in the seedbed: water seedlings early in the morning and thin out seedlings to avoid plant congestion in the seedbed. Excessive watering is conducive to damping-off diseases, and extended wetness of seedlings favours development of foliar diseases.

A smallholder farmer watering a kale nursery bed

(c) A. A. Seif

Seeds:

Treating own seed in hot water to prevent seed-borne diseases such as black rot, black leg, black spot and ring spot is recommended where these diseases have previously appeared Hot water treatment of seeds helps reduce the seed-borne pathogens. However, the specified temperature and time interval should be strictly followed in order to maintain seed viability. Use a good thermometer or better ask for assistance from qualified personnel from your local agriculturist office. Recommended temperature and time for hot water treatment for broccoli, cabbage, cauliflower, kale kohlrabi and turnip is 50degC (122 F) for 30 minutes.

For more details on Hot water treatment click here

Husbandry

• Cabbage is often planted on raised beds that are shaped from bare soil after ploughing and disking. This technique is popular on level soils where furrow irrigation is also used. Bed culture is also used in other areas to improve soil drainage or when plastic mulch is used. The trend has been toward increased use of conservation tillage, particularly on steeply-sloping soils prone to erosion. Producing cabbage using conservation tillage reduces the number of field passes by farm equipment, thus reducing compaction, preserving equipment and conserving fuel.
• Conservation tillage systems cause minimum disturbance to the soil after the previous crop has been harvested. Crop residues are left in the field to reduce soil erosion, conserve moisture, inhibit weed growth, and act as green manure. There are several types of conservation tillage in use, as well as combinations of conservation and conventional tillage. However, in disease management, crop residues must be either removed from the field and destroyed or deeply ploughed to reduce sources of disease infection and spread.
• Advantages of conservation tillage for cabbage production include less machinery, labour and fuel, as well as reduced soil erosion and compaction. Disadvantages of conservation tillage include lower soil temperatures, slower germination and emergence when direct sowing is used, slower early growth, delayed competition with weeds, higher incidence of root diseases, heavier crop residue, the possibility of more difficult planter operation, weed spectrum changes, and potential increase of soil insect pests or insects that spend part of their life cycle in the soil (e.g. cutworms, thrips, leafmining flies, grubs). Cultivation exposes these pests to desiccation by the sun heat and to predation by natural enemies

Hand weeding in a cabbage plot

Ⓒ A.A. Seif

Intercropping

• Intercrop brassica crops with trap crops or repellent plants, to reduce pest infestation. Tomato reportedly repels diamondback moth and Indian mustard acts as a trap crop. Intercropping brassicas with spinach, beans or dill reportedly reduces aphid infestation.
• Tomatoes when planted 14 days before cabbage reduce the incidence of and damage by diamondback moth. Cabbage intercropped with tomato, coriander or garlic, combined with the application of neem seed kernel extract protects plants from diamondback moth in the field. Indian mustard, Chinese cabbage, and radish are good trap crops for controlling cabbage webworm, flea hopper, and mustard aphid when planted in every 15 rows of cabbage. The mustard row is either in the outermost or in the middle row to avoid caterpillars being blown by wind into the cabbage plants. To control cabbage head caterpillar, Indian mustard should be planted 12 days before transplanting cabbage. Do not plant cabbage where members of the cabbage family have been grown for 3 consecutive years to avoid serious problems of pests and diseases (especially soil borne diseases).

Monitoring

Scouting on a kale nursery by icipe trainees

Ⓒ A.A. Seif

Kale . Small scale farmers inspecting a kale crop.

Ⓒ Monique Hunziker, Biovision

It entails regular field observation during the crop production cycle for pests, diseases, weeds and general aspects of crop health like nutrition and water requirements. Field monitoring methods are virtually the same, but most importantly, in the process is problem recognition. Thus it is very important to be able to identify pests and diseases and to differentiate a pest from a beneficial insect, a pest damage from disease damage, and a pest or disease damage from nutritional problems or physiological disorders.

• Monitor fields regularly for pest and disease occurrence. Early detection of pests and diseases is important as outbreaks are easier controlled in the initial stages. Cutworms and other insects can do a lot of damage in just 1 or 2 days.
• Scout for caterpillar presence: feeding damage and caterpillar excrement give an indication of their activity. Scouting can be done by walking in a zigzag pattern through the field.
• Check for aphids and whether parasitised aphids (mummies) and natural enemies such as ladybird beetles and lacewings are present. Since aphid populations are often clustered, all portions of the field should be checked. For more information on Natural enemies click here.
• Scout for the major brassica diseases (refer to major diseases below).

Harvesting

Cabbage is often hand-harvested when heads are firm to the touch but before cracking begins. With hand harvesting, a given field is harvested two to four times to obtain heads of uniform size and maturity. Only one to three harvests of hybrid cultivars are required because of their greater uniformity. Use of uniform transplants and consistent growing conditions also helps reduce the number of harvests. Yields will vary with the season of production, cultivar, and production system used. With proper management, cabbage can produce 10-12 tons per acre. Generally, most fresh markets prefer heads that weigh on average 1-2,5 kg. For processing into coleslaw or sauerkraut, or for long-term storage, larger-headed cultivars are used.

Field sanitation

Remove crop residues immediately after harvest and also remove volunteer plants from the field.

Oxalis weed in kale nursery

Ⓒ A.A. Seif

Nut grass(Cyperus rotundus ) in kale nursery seedbed

Ⓒ A.A. Seif, icipe

Varieties grown in Kenya

Cabbage varieties  

"Globe Master F1 Hybrid"

"Gloria F1 Hybrid"

"Blue Dynasty F1":

"Victoria F1"

"Oxylus F1"

"Green Coronet F1 Hybrid"

"Riana F1 Hybrid"

"Super Master F1"

"Santar F1"

"Field Winner F1 Hybrid"

"CPI"

"Pruktor F1 Hybrid"

"Hero F1 (Sokoni)"

"Chihili"

"Red Dynasty F1"

"Ruby Perfection F1 Hybrid"

"Copenhagen Market"

"Glory of Enkhuizen"

Glory of Enkuizen cabbge planted in strips

Ⓒ A.A. Seif

"Prize Drumhead"

"Sugar Loaf"

Broccoli varieties  

"Calabrese"

"Heritage F1"

"Dandy Early No. 32 F1"

"Early Green F1"

Cauliflower varieties  

"Snowball"

"Snow Crown F1 Hybrid"

"Extra Early Six Weeks"

"Kibo Giant"

"Fremont F1"

"Italian Giant"

"Wallaby"

Kale varieties  

"Thousand Headed"

"Southern Georgia"

"Marrow Stem"