Kale, scientifically known as Brassica oleraceae var acephala and commonly referred to as Sukumawiki, is a type of vegetable that thrives in cooler seasons. It belongs to the family of Brassicas. The nutrient-rich leaves of kale are frequently used either on their own or combined with other vegetables, pulses, or meat in various dishes.
With its versatility and abundance throughout the year, kale possesses the capacity to help alleviate poverty levels.
Benefits of Kale
Kale is in high demand due to its numerous health benefits, which include the following:
- It is an excellent source of iron, essential for vital functions such as the formation of haemoglobin and enzymes, cell growth, and proper liver function.
- Kale is rich in vitamin K, which not only protects the body against different types of cancer but also plays a crucial role in various bodily functions.
- It is high in fiber, low in calories, and contains no fat.
- The anti-inflammatory properties of kale contribute to its effectiveness in combating conditions like asthma, arthritis, and autoimmune disorders.
- Kale is packed with antioxidants such as flavonoids and carotenoids, which shield the body against various forms of cancer.
- It is a rich source of vitamins A and C.
- Kale serves as a good calcium source, aiding in the prevention of osteoporosis, bone loss, and maintenance of a healthy metabolism.
- The presence of zeaxanthin and lutein in kale makes it a potent nutrient for protecting the eyes.
Ecological Requirements of Kale
Kale can be cultivated successfully across a wide range of climatic conditions, as long as water is available. Here are some factors to consider:
- Soil: Kale thrives in well-drained soils that are rich in organic matter, with a pH level ranging from 5.5 to 7.5.
- Altitude: This crop performs well at altitudes between 800 and 2200 meters above sea level.
- Temperature: Kale requires an optimal temperature range of 16 to 21 degrees Celsius.
- Rainfall: Sufficient moisture throughout the growing season is essential for kale. Ideally, a well-distributed rainfall between 30 and 500mm would promote optimum yield. In cases of inadequate rainfall, irrigation is recommended.
Tips!
- Kale exhibits tolerance to slightly alkaline soil and frost.
- It requires a minimum of 6 hours of direct sunlight each day and prefers consistent moisture.
- Some kale varieties have drought-tolerant characteristics.
Kale seed selection
Here are some commonly cultivated kale varieties and their characteristics:
- Thousand Headed: This variety has smaller leaves compared to Collard and has a slower growth rate. It requires frequent pruning due to its long harvesting time and produces multiple heads.
- Collards Southern Georgia: Drought-tolerant and compact, this variety produces large, tender, bluish-green leaves that spread widely.
- Sukuma Siku Hybrid: Known for its curled leaves with a soft texture, this variety exhibits good tolerance to the Diamond Back Moth.
- Collard Mfalme F1: As a hybrid variety, it features short internodes and many tender leaves per internode, resulting in higher yield per unit area. It also demonstrates tolerance to a wide range of diseases.
- Marrow Stem: This variety thrives in cool climates with moderate to fairly heavy and evenly distributed rainfall. It produces dark green leaves.
These are just a few examples of the kale varieties commonly grown.
FIELD OPERATIONS
Kale is propagated exclusively through seeds. Initially, the seeds are sown in a nursery and later transplanted into the main field for cultivation.
When growing kale, it is advisable to choose a location where other plants from the same family as kale have not been grown for at least one year.
Land preparation
It is advisable to prepare the land early when cultivating kale to expose pests to sunlight and attract birds for pest control.
To eliminate broadleaf and grass weeds before ploughing, it is recommended to apply CATAPULT® 480SL weedkiller at a rate of 200ml per 20 liters of water. This weedkiller is a systemic, non-selective herbicide.
Ploughing should be carried out 2 to 3 weeks prior to planting, reaching a depth of approximately 7-9 inches. After ploughing, harrowing should be done 2 to 3 weeks later, followed by soil preparation to achieve a fine tilth.
Incorporating crop residue into the soil can significantly increase the organic content and improve soil quality.
Raising Kale seedlings
Procedure:
- Prepare a nursery bed with a width of approximately 1 meter, according to the required length.
- Apply a soil drench mixture of LOYALTY® 700WDG (10g), PYRAMID® 700WP (100g), and OPTIMIZER® (20ml) in 20 liters of water. This mixture helps control soil pests and diseases, provides nutrients, breaks seed dormancy, and promotes uniform germination.
- Sow the seeds evenly across the bed, at a depth of around 2cm, and lightly cover them with soil.
- Place a thin layer of dry grass (mulch) over the nursery bed, which should be removed after seed germination.
- Water the nursery bed.
Tips:
- Germination of the seeds typically occurs within 5-8 days.
- Soaking the seeds in a solution of OPTIMIZER (20ml) per 1 liter of water for at least 30 minutes can enhance faster and more uniform germination.
- Once the seedlings have germinated, thin them out, leaving a spacing of approximately 2-3cm between each seedling. This helps reduce competition for space and nutrients, as well as prevent damping-off disease.
- Regular watering is important for the seedlings’ growth.
- Providing proper nutrition to the seedlings promotes the development of strong and healthy plants, resulting in a healthy crop after transplanting.
- To mitigate transplanting shock, spray the seedlings with OPTIMIZER (10ml) per 20 liters of water prior to transplanting.
- It is recommended to irrigate the nursery bed before lifting the seedlings.
Transplanting
The kale seedlings are suitable for transplantation within 4-6 weeks, once they have developed 3-4 leaves. However, the specific timing may vary depending on regional ecological factors, such as temperature. To prepare the kale seedlings for transplantation, it is recommended to reduce the irrigation rate approximately one week prior to transplanting. This process helps to harden the seedlings and prepare them for the transition to the main field.
Procedure:
- Create raised or sunken beds on the prepared land, with a preference for raised beds due to their better drainage and root development.
- Mix the soil with manure and DAP (Di-ammonium phosphate). For improved nutrient uptake, stimulation of root development, and other benefits, mix 1kg of HUMIPOWER® with 50kg of DAP and/or 1 ton of manure.
- Irrigate the beds to ensure suitable planting conditions.
- Plant the seedlings in the beds at the same depth they were growing in the nursery.
Tips:
- It is recommended to carry out transplanting early in the morning, in the evening, or on a cloudy day when the sun is not intense.
- Select only healthy and robust seedlings for transplanting.
- Prior to transplanting, apply a selective herbicide called COMMANDER® 240EC at a rate of 50ml per 20 liters. This herbicide effectively eliminates both grass and broadleaf weeds.
Spacing:
- The spacing between kale plants varies depending on the variety being grown. For example, large-headed varieties should be spaced at 60x60cm, medium-sized varieties at 60x45cm, and small-headed varieties at 30x30cm.
Mulching:
- Mulching is highly recommended for kale cultivation as it serves multiple purposes. It helps conserve soil moisture, prevents soil erosion, increases organic matter in the soil through decomposition, and suppresses the splashing of rain or irrigation water, as well as the spread of diseases. Mulching is particularly important during dry seasons.
Weeding:
- It is crucial to keep the kale field free of weeds since kale does not compete well with them. Weeds can cause significant losses by competing for growth factors like nutrients and water. Additionally, weeds can harbor pathogens that could attack the crop.
Tips:
- Effective weed control can be achieved by using CATAPULT 480SL at a rate of 200ml per 20 liters during land preparation, as well as applying COMMANDER® 240EC at a rate of 50ml per 20 liters prior to transplanting. These measures significantly reduce weed development throughout the growing season.
- When cultivating the soil, it is important to perform shallow cultivation to avoid injuring the roots of the kale plants.
Irrigation:
- Adequate water supply is crucial for optimal production of the kale crop.
Crop rotation:
- It is beneficial to rotate kale with non-family crops such as spinach, onions, maize, carrots, and potatoes. This practice helps improve soil fertility and aids in the management of pests and diseases by breaking their development cycles.
Fertilizer application:
- Proper fertilizer application is essential to ensure optimal production of the crop. The kale plants should receive sufficient nutrients throughout the growing season.
During transplanting:
- Apply 50kg of DAP TSP (Diammonium phosphate Triple Superphosphate) per acre. This fertilizer is rich in phosphorus, which is highly required during the early developmental stages of the crop.
Two weeks after transplanting:
- Spray the young plants with LAVENDER SUPER STARTER® at a rate of 20ml per 20 liters of water or GOLDCHANCE SUPER START® at a rate of 50g per 20 liters. This promotes rapid root development, balanced crop growth, and increased resistance to infections and weather stress. Additionally, applying 10ml of ZINC GOLD per 20 liters of water enhances root development and stimulates growth.
Top dressing:
- Apply 50kg of CAN (Calcium ammonium nitrate) per acre two weeks after transplanting, and repeat after four weeks. Alternatively, other nitrogen-rich fertilizers like N.P.K 23.23.0 can be used.
Crop spraying:
- Spray the crop with GOLDCHANCE SUPER GROWTH® at a rate of 50g per 20 liters of water or LAVENDER SUPER GROWTH® at a rate of 20ml per 20 liters. This promotes faster vegetative growth, increases resistance to infections and weather stress, and ensures balanced crop growth.
Tips:
- Conduct soil analysis to determine the specific nutrient requirements.
- Mix all basal fertilizers with HUMIPOWER® at a rate of 1kg of HUMIPOWER® per 50kg of fertilizer.
- OPTIMIZER® is an organic biostimulant that aids in plant growth and stress management. It can be applied at any growth and development stage of the crop.
- Application of manure is recommended, especially for soils with low organic matter content. It improves soil structure and gradually provides additional nutrients.
Major Kale Pests and Diseases
Pests
Cutworms:
- Cutworms are caterpillars with smooth, soft bodies, usually brown to black in color. They cut seedlings or young plants near the soil level, particularly during morning and evening hours. When disturbed, they curl up tightly. Heavy infestations can cause significant crop loss.
To control cutworms, drench the soil with one of the following solutions:
- PROFILE® 440EC at a rate of 60ml per 20 liters of water,
- PENTAGON® 50EC at a rate of 20ml per 20 liters of water, or
- LOYALTY® 700WDG at a rate of 10g per 20 liters of water.
Diamondback Moth (DBM):
- The larvae of the diamondback moth are green caterpillars that feed on leaf tissue, except for the veins. If not controlled, they can cause significant crop losses.
To control diamondback moth, spray the crop with one of the following solutions:
- ESCORT® 19EC at a rate of 10ml per 20 liters of water,
- BACIGUARD® 16WDG at a rate of 15g per 20 liters of water,
- LEXUS® 247SC at a rate of 8ml per 20 liters of water, or
- OCCASION STAR® 200SC at a rate of 3ml per 20 liters of water.
Aphids:
- Aphids are small, soft-bodied sap-sucking insects that are typically black or green in color. They can be found on the undersides of leaves or stems and cause damage by sucking sap, leading to leaf curling, distortion, and wilting in severe cases. They also produce honeydew, a sticky substance that promotes the growth of sooty mold.
To control aphids, spray the crop with one of the following solutions:
- KINGCODE ELITE® 50EC at a rate of 10ml per 20 liters of water,
- PENTAGON® 50EC at a rate of 10ml per 20 liters of water, or
- LEXUS® 247SC at a rate of 8ml per 20 liters of water.
To remove sooty mold, spray the crop with JAMBO CLEAN® at a rate of 100ml per 20 liters of water.
Sawfly:
- Sawfly larvae feed on leaves, creating small, regular holes and leading to the production of poor-quality leaves.
To control sawflies, spray the crop with one of the following solutions:
- ESCORT® 19EC at a rate of 10ml per 20 liters of water,
- BACIGUARD® 16WDG at a rate of 15g per 20 liters of water,
- LEXUS® 247SC at a rate of 8ml per 20 liters of water,
- OCCASION STAR® 200SC at a rate of 3ml per 20 liters of water, or
- KINGCODE ELITE® 50EC at a rate of 10ml per 20 liters of water.
Thrips:
- Thrips are small, slender sap-sucking insects with fringed wings. They cause damage to the crop by feeding on leaves, resulting in leaf distortion, stunted growth, and sunken tissues on the undersides of the leaves.
To control thrips, spray the crop with one of the following solutions:
- ALONZE® 50EC at a rate of 5ml per 20 liters of water,
- BAZOOKA® 18EC at a rate of 10ml per 20 liters of water, or
- DEFENDER® 25EC at a rate of 40ml per 20 liters of water.
Whiteflies:
- Whiteflies are small white insects that suck plant sap and excrete honeydew, which can lead to the growth of molds and affect plant vigor. Their feeding causes damage to the crop and reduces its overall health.
To control whiteflies, spray the crop with one of the following solutions:
- TAURUS® 500SP at a rate of 10g per 20 liters of water,
- LEXUS® 247SC at a rate of 8ml per 20 liters of water, or
- KINGCODE ELITE® 50EC at a rate of 10ml per 20 liters of water.
To remove sooty mold, spray the crop with JAMBO CLEAN® at a rate of 100ml per 20 liters of water.
Root Knot Nematodes:
- Root knot nematodes are microscopic parasites found in the soil. Their infestation leads to the formation of galls or swellings on the roots, which reduces plant vigor, causes stunting, and eventually leads to crop death.
To control root knot nematodes, drench the soil with one of the following solutions:
- ALONZE® 50EC at a rate of 10ml per 20 liters of water, or
- Mix 2kg of ADVENTURE® 0.5GR with 50kg of basal fertilizer.
Diseases
Damping-off:
- Damping-off is a soilborne disease caused by Pythium spp, Rhizoctonia spp, and Fusarium spp, commonly observed in nurseries. It prevents germination of infected seeds, while emerged seedlings rot and eventually die. Infected seedlings exhibit white cottony growth on their roots.
To control damping-off, drench the soil with PYRAMID® 700WP at a rate of 100g per 20 liters of water. Additionally, spray the crop with DOMAIN® 250EC at a rate of 10ml per 20 liters of water or GEARLOCK TURBO® 250WP at a rate of 25g per 20 liters of water.
Black rot:
- Black rot is a bacterial disease characterized by v-shaped yellow to brown lesions that start forming from the leaf margin. In severe cases, leaves may drop, leading to the eventual death of the crop.
To suppress the activity of the pathogen causing black rot, spray the crop with GREENCOP® 500WP at a rate of 50g per 20 liters. GREENCOP® 500WP is a copper-based product effective against the pathogen.
Leaf spots:
- Leaf spots result in the development of small, dark spots on the leaves, which enlarge and form brown lesions. These lesions become brittle, and the necrotic centers may crack. Infections can also occur on stems and petioles.
To control leaf spots, spray the crop with RANSOM® 600WP at a rate of 15g per 20 liters of water, or CHARIOT® 500SC at a rate of 20ml per 20 liters of water, or ABSOLUTE® 375SC at a rate of 10ml per 20 liters of water.
Powdery mildew:
- Powdery mildew manifests as whitish, talcum-like powdery growth on the upper leaf surface, and as the infection progresses, it may spread to the stems. Severely infected parts become chlorotic and eventually wilt. Stunted growth can also occur.
To control powdery mildew, spray the crop with RANSOM® 600WP at a rate of 15g per 20 liters of water, or DOMAIN® 250EC at a rate of 10ml per 20 liters of water, or ABSOLUTE® 375SC at a rate of 10ml per 20 liters of water.
Downy mildew:
- Downy mildew causes the formation of yellow patches on the undersides of leaves, which turn light brown and eventually fall off as the disease progresses. Stunted growth may occur.
To control downy mildew, spray the crop with GEARLOCK TURBO® 250WP at a rate of 25g per 20 liters of water, or FORTRESS GOLD® 720WP at a rate of 40g per 20 liters of water, or TOWER® 720WP at a rate of 50g per 20 liters of water.
Tips:
- For all foliar sprays, mix the chemical with INTEGRA at a rate of 3ml per 20 liters. INTEGRA acts as a sticker, spreader, and penetrant, increasing the efficacy of the product.
- Consider using CADILAC® 800WP at a rate of 50g per 20 liters, as it is a preventative fungicide effective against fungal diseases.
- Alternate between different chemicals (insecticides and fungicides) throughout the crop’s season to prevent the development of resistance.
HARVESTING & POST-HARVESTING HANDLING OF KALE
Most kale varieties can be harvested within approximately 4 weeks after transplanting. However, harvesting can commence as soon as the crop starts producing leaves.
Harvesting is typically done by hand-picking the leaves.
The timing of harvesting is a personal decision influenced by individual preferences. For a lighter taste, younger leaves are preferred, while those who enjoy the stronger and bolder flavor of kale may opt for more mature leaves.
Younger kale leaves can be a delicious addition to salads, while the flavor of the leaves becomes more pronounced as they mature.
It is important to handle the harvested leaves with care to prevent bruising.
Freshly harvested kale leaves can be refrigerated and stored for approximately 7-10 days. Cooked kale can be frozen and stored for a longer period.
Tips:
- To maintain a continuous growth cycle, regularly remove the outer and older leaves.
- The market demand for kale is generally high. Some potential market opportunities for kale include institutions such as schools and hospitals, supermarkets, and open-air markets, among others.
