Kale (Brassica oleraceae var acephala), commonly known as Sukumawiki, is a cool season crop that belongs to the Brassicas family. Its leaves, which are rich in vitamins and essential mineral elements are widely utilized alone or mixed with other vegetables, pulses or meat.
Kale is an all-year crop and has the potential to reduce poverty levels.
Benefits of Kale
The demand for kale is usually very high because of their benefits, which include the following;
- High in iron which is essential for good health, e.g. in formation of haemoglobin and enzymes, cell growth, proper functioning of the liver, among others.
- Rich in vitamin K which helps in protecting the body against various cancers and is also necessary for a wide range of bodily functions.
- High in fibre, low in calorie and zero fat
- Has anti-inflammatory properties which helps in fighting against asthma, arthritis and autoimmune disorders
- Rich in antioxidants, e.g. flavonoids and carotenoids which protect the body against various cancers.
- Rich in vitamin A and C
- Good source of calcium which helps in preventing osteoporosis, bone loss and maintaining a healthy metabolism.
- Rich in zeaxanthin and lutein which are powerful nutrients which protect the eyes
Ecological Requirements of Kale
Kale is grown in a wide range of climatic conditions provided water is available.
- Soils- performs best in well drained soils which are rich in organic matter with a pH of 5.5-7.5.
- Altitude- does well at altitudes of 800-2200M above sea level
- Temperature- requires an optimum temperature range of 16-21o
- Rainfall- the crop requires sufficient amounts of moisture throughout the season. A well distributed rainfall of 30-500mm is ideal for optimum yield. Irrigation is recommended if rainfall is inadequate.
- Kale can tolerate slightly alkaline soil and frost.
- Kae requires at least 6 hours of direct sunlight daily and prefers plentiful, consistent moisture.
- Some kale varieties are drought tolerant.
Kale seed selection
Some of the commonly grown varieties include the following;
- Thousand headed – has smaller leaves than Collard and is slow growing compared to other varieties. It has long harvesting time and produces many heads thus requires frequent pruning.
- Collards southern Georgia– it is a drought tolerant short variety that produces large, tender, bluish green leaves which spread widely.
- Sukuma Siku Hybrid – produces curled leaves with soft texture and has good tolerance to Diamond Back Moth.
- Collard Mfalme F1 – it is a hybrid variety with short internodes and many tender leaves per internode hence more yield per unit area. It is tolerant to a wide range of diseases.
- Marrow stem – Produces dark green leaves and prefers cool climate with moderate to fairly heavy and well-distributed rainfall.
Propagation of kale is solely by seeds. It is first raised in a nursery before transplanting into the main field.
Kale should be grown in a place where crops in the same family as kale have not been cultivated for about 1 year.
Early land preparation for kale production is recommended in order to expose pests to sunlight and birds.
To get rid of broadleaf and grass weeds before ploughing, spray them with CATAPULT® 480SL 200ml/20L which is a systemic non-selective weedkiller.
Ploughing should be done 2 to 3 weeks in advance at about 7-9 inches deep, followed by harrowing, 2 to 3 weeks after ploughing then preparation of the soil to a fine tilth.
Crop residue can significantly increase the organic content if incorporated into the soil.
Raising Kale seedlings
- Prepare the nursery bed, about 1 metre wide against the required length.
- Drench the soil with a mixture of LOYALTY® 700WDG 10g + PYRAMID® 700WP 100g + OPTIMIZER® 20ml in 20 litres of water. The mixture controls soil pests and diseases, provides nutrients, breaks seed dormancy and promotes uniform germination.
- Drill seeds across the bed at a depth of about 2cm and cover them lightly with soil
- Cover nursery bed with a thin layer of dry grass (mulch), which should be removed after seed germination.
- Water the nursery bed.
- Seeds germinate after 5-8 days.
- Seeds soaked in OPTIMIZER 20ml/1L for at least 30minutes germinate faster and uniformly.
- After germination, seedlings should be thinned out to about 2-3cm apart in order to reduce competition for space and nutrients, as well as preventing the development of damping off disease.
- Seedlings should be watered regularly.
- Proper nutrition promotes production of strong and healthy seedlings hence a healthy crop when transplanted.
- To overcome transplanting shock, spray seedlings with OPTIMIZER 10ml/20L prior to transplanting.
- Irrigate the nursery bed before lifting the seedlings.
The kale seedlings are ready for transplanting after 4-6 weeks, after attaining 3-4 leaves. This however depends on the ecological factors in the region, e.g. temperature. To harden the kale seedlings, the rate of irrigation should be reduced, a week before transplanting.
- Make raised or sunken beds on the prepared land. Raised beds are preferred for proper drainage and root development.
- Mix soil with manure and DAP. For efficient and improved nutrient uptake and stimulation of root development, among other benefits, mix 1kg HUMIPOWER® with 50kg DAP and /or 1 ton of manure.
- Irrigate the beds to allow for easy planting.
- Plant the seedlings in the beds at the same depth they were previously growing at while in the nursery.
- Transplanting is best done early in the morning, evenings or on a cloudy day, when the sun is cool.
- Transplant only the healthy and strong seedlings.
- Before transplanting, spray COMMANDER® 240EC 50ml/20L, a selective herbicide which kills both grass and broadleaf weeds
Spacing: this varies with the type of variety grown. For instance, 60x60cm for large headed varieties, 60x45cm for medium-sized varieties and 30x30cm for small headed varieties.
Mulching: this is recommended because it helps in conservation of soil moisture, prevents soil erosion, increases organic matter into the soil after decomposition and suppresses splashing of rain or irrigation water and spread of diseases. It is very important during the dry seasons.
Weeding: kale does not compete well with weeds and therefore the field should be kept weed-free. Weeds cause significant losses as they compete for growth factors like nutrients and water and harbour pathogens which could attack the crop.
- Proper weed control with CATAPULT 480SL 200ml/20L during land preparation and application of COMMANDER® 240EC 50ml/20L prior to transplanting significantly reduces weed development throughout the season.
- Shallow cultivation should be done in order to avoid root injury.
Irrigation: the crop requires adequate water supply for optimal production.
Crop rotation: rotate kales with non-family crops like spinach, onion, maize, carrots, potatoes, etc. this improves soil fertility and helps in management of pests and diseases t by breaking their development cycles.
Fertilizer application: this is essential in ensuring optimal production. The crop should be supplied with sufficient nutrients throughout its season.
During transplanting; apply 50kg of DAP TSP in one acre. These are rich in phosphorous which is highly needed at early developmental stages of the crop.
After 2 weeks, spray the young plants with LAVENDER SUPER STARTER® 20ml/20L or GOLDCHANCE SUPER START® 50g/20L to promote rapid root development, ensure balanced crop growth and increase the crops’ resistivity to infections and weather stress. Application of ZINC GOLD 10ml/20L, also enhances root development and stimulates growth.
Top dressing; apply 50kg of CAN in one acre, two weeks after transplanting and after 4 weeks, at rate of 50kg per acre. It can also be done using other nitrogen-rich fertilizers like N.P.K 23.23.0.
Spray the crop with GOLDCHANCE SUPER GROWTH® 50g/20L or LAVENDER SUPER GROWTH® 20ml/20L, which promotes a faster vegetative growth, increases crop resistance to infections and weather stress and ensures a balanced growth of the crop.
- Soil analysis is recommended.
- All basal fertilizers should be mixed with HUMIPOWER® at a rate of 1kg of HUMIPOWER® into 50Kg of fertilizer.
- OPTIMIZER® is an organic biostimulant which is essential for plant growth and stress management and should be applied at all or any growth and development stage of the crop.
- Manure should be applied especially for soils with little or no organic matter. It improves soil structure and slowly provides extra nutrients.
Major Kale Pests and Diseases
Cutworms– these are soft bodied, smooth caterpillars, brown to black in colour, which cut seedlings or young plants near the soil level mainly during morning and evening hours. When disturbed, they curl up tightly. Heavy infestations cause significant crop loss.
Drench soil with PROFILE® 440EC 60ml/20L or PENTAGON® 50EC 20ml/20L or LOYALTY® 700WDG 10g/20L
Diamondback moth (DBM) – the larva is a green caterpillar which feeds on the leaf tissue except the veins. Infestation causes significant losses if the pest is not controlled.
Spray ESCORT® 19EC 10ml/20L or BACIGUARD® 16WDG 15g/20L or LEXUS® 247SC 8ml/20L or OCCASION STAR® 200SC 3ml/20L
Aphids– these are tiny black and green soft –bodied sap sucking insects usually on the undersides of the leaves or stems. They cause damage by sucking sap from leaves and stems of plants causing leaf curling and distortion. In severe cases of infestation, wilting of the crop occurs. They also excrete a sticky sugary substance called honeydew, which encourages the growth of sooty mold.
Spray KINGCODE ELITE® 50EC 10ml/20L or PENTAGON® 50EC 10ml/20L or LEXUS® 247SC 8ml/20L
To get rid of the sooty mold, spray JAMBO CLEAN® 100ml/20L.
Sawfly– the larvae feed on the leaves creating small regular holes and this leads to production of poor quality leaves.
Spray ESCORT® 19EC 10ml/20L or BACIGUARD® 16WDG 15g/20L or LEXUS® 247SC 8ml/20L or OCCASION STAR® 200SC 3ml/20L or KINGCODE ELITE® 50EC 10ml/20L
Thrips– these are small, slender sap sucking insects with fringed wings. As they feed, they damage the crop, causing distortion of leaves, stunted growth and sunken tissues on the undersides of the leaves.
Spray ALONZE® 50EC 5ml/20L or BAZOOKA® 18EC 10ml/20L or DEFENDER® 25EC 40ml/20L
Whiteflies–These are small white insects which suck plant sap and excrete honeydew where molds grow, affecting plant’s growth and vigour. Their feeding causes crop damages and reduces the crop’s vigour.
Spray TAURUS® 500SP 10g/20L or LEXUS® 247SC 8ml/20L or KINGCODE ELITE® 50EC 10ml/20L
Spray the crop with JAMBO CLEAN® 100ml/20L to clean the sooty mold.
Root knot nematodes– these are microscopic parasites found in the soil and whose infestation leads to formation of galls/swellings on the roots, which reduces plant vigour thus causing stunting of the crop and eventual death.
Drench soil with ALONZE® 50EC 10ml/20L or mix basal fertilizer, 50kg with 2kg of ADVENTURE® 0.5GR.
Damping-off– this is a soilborne disease caused by Pythium spp, Rhizoctonia spp, and Fusarium spp which frequently occurs in the nurseries. The diseased seeds do not germinate while the emerged seedlings rot and eventually die. White cottony growth is seen on the roots of the infected seedlings.
Drench the soil with PYRAMID® 700WP 100g/20L and spray the crop with DOMAIN® 250EC 10ml/20L or GEARLOCK TURBO® 250WP 25g/20L
Black rot– this is a bacterial disease whose symptoms are seen as v-shaped yellow to brown lesions which start forming from the leaf margin. In severe cases of infection, leaves drop and subsequently the crop dies.
Spray GREENCOP® 500WP 50g/20L, a copper-based products which suppress the activity of the pathogen.
Leaf spots – infection leads to development of small dark spots on leaves which enlarge forming brown lesions, become brittle and eventually the necrotic centres crack. The lesions can also develop on stems and petioles.
Spray RANSOM® 600WP 15g/20L or CHARIOT® 500SC 20ml/20L or ABSOLUTE® 375SC 10ml/20L
Powdery mildew -symptoms first develop as whitish talcum like powdery growth on upper leaf surface and as infection progresses, the stems also get infected. Severely infected plant parts become chlorotic and eventually wilt. Infection also causes stunted growth.
Spray RANSOM® 600WP 15g/20L or DOMAIN® 250EC 10ml/20L or ABSOLUTE® 375SC 10ml/20L
Downy mildew– infection leads to formation of yellow patches on the underside of the leaf. These patches turn light brown and eventually fall off as disease progresses. Stunted growth occurs.
Spray GEARLOCK TURBO® 250WP 25g/20L or FORTRESS GOLD® 720WP 40g/20L or TOWER® 720WP 50g/20L
- In all foliar sprays, mix the chemical with INTEGRA 3ml/20L, which is a sticker, spreader and penetrant that increases the efficacy of the product.
- Use CADILAC® 800WP 50g/20L, which is a preventative fungicide against fungal diseases.
- Alternate different chemicals (insecticides and fungicides) during the crop’s season in order to prevent resistance build-up.
HARVESTING & POST-HARVESTING HANDLING OF KALE
Most kale varieties are ready for harvesting within 4 weeks after transplanting. However, harvesting can start as soon as the crop begins growing leaves.
Harvesting is done through hand picking the leaves.
The time frame for harvesting is usually a personal decision, based on various preferences. For instance, if one requires a lighter side to kale’s taste, younger leaves are best, while for those who like the more pungent and bold flavor of kale, the matured leaves are preferable.
The younger leaves are a tasty addition to some salads while the more mature ones become more flavorful as they grow.
The harvested leaves should be handled with care in order to avoid bruises.
If refrigerated, fresh harvested kale leaves can be stored for up to approximately 7-10days while once cooked, they can be frozen and stored for a longer period.
- For a continuous growth cycle, outer and older leaves should be removed.
- The demand for kales in the market is very high. Some of the market opportunities for the produce include institutions like schools and hospitals, supermarkets and open-air markets, among others.