Establishing healthy cabbage seedlings is only the first step towards a successful harvest. As the crop develops, growers must provide the right nutrients and water while managing weeds, pests and diseases. In this second part of the series, we examine the management practices that help cabbage reach its full production potential.
By combining sound fertilisation and irrigation practices with regular scouting and integrated pest and disease management, farmers can produce healthy, high-quality cabbages that meet market requirements while maintaining long-term soil and crop health.
Start weeding once the plants are established and continue until the leaves cover the ground. Take care not to damage the roots when weeding mechanically.
Also read: Cultivating cabbage (Part 1): Building the foundation for a high-yield crop
Fertilisation
Cabbage is regarded as a heavy feeder and responds well to manure, compost and organic fertilisers. A fertiliser recommendation should always be based on a soil analysis.
The following serves as a general guideline:
- Before planting, dig in 2:3:4 (27) fertiliser at 600–900 kg/ha (60–90 g/m2). This should be regarded as the minimum required to give the plants a good start. An application of about 1 200 kg/ha (120 g/m2) is considered optimal.
- The crop also responds well to top dressings of LAN nitrogen-based fertiliser at two, four and six weeks after transplanting. Apply 4 g per plant initially, increasing to 10 g per plant later in the season. Spread the fertiliser about 20 cm away from the plants.
- Avoid applying nitrogen once the cabbage heads have started forming, as this can cause splitting or excessive leaf growth, resulting in loose, poorly formed heads.
Also read: How to grow top-quality carrots (Part 1): Build the foundation for a successful crop
Irrigation
It is crucial to supply sufficient water at critical times, such as immediately after sowing or transplanting. Young plants need adequate moisture to support vegetative growth before head formation. The larger the plant at this stage, the larger the eventual head is likely to be.
About 35 mm of water per week is considered optimal. Consider using mulch to conserve soil moisture.
Once heads have formed, excessive watering may cause them to crack. Cracking can also result from inconsistent watering, for example, alternating between heavy and light watering. Drip irrigation is recommended to conserve water.
Harvesting
Harvesting usually takes place 90 to 110 days after transplanting. Harvest when the heads are firm by cutting them with a sharp knife. Harvesting can continue selectively over several weeks and should preferably be done early in the morning.
Do not leave harvested heads in the sun, as they will wilt. Store harvested cabbages in a cool, shaded place. Leave two or three outer leaves attached to protect the heads during transport.
After harvest, incorporate crop residues into the soil.
Also read: Cultivating onions | From soil requirements to transplanting
Pests and diseases
Cabbage is susceptible to a range of pests and diseases that can cause significant economic losses. The best approach is an integrated pest management programme that combines regular scouting, crop rotation, good crop management, and appropriate mechanical and chemical control measures.
Always use only pesticides registered for cabbage and follow the label instructions carefully. Updated information on registered products is available from the Department of Agriculture.
Also read: Growing beetroot successfully | Fertilisation, irrigation and crop protection
Pest management
Inspect seedlings and growing plants regularly for signs of infestation. Consult an agricultural co-op or crop adviser about suitable registered control products.
Aphids suck sap from the leaves, weakening plants and reducing growth.
The bagrada bug sucks sap from the leaves and can damage the growing points of seedlings, causing plants to produce several small, unmarketable heads.
Diamondback moth larvae are small, pale-green caterpillars that feed on the leaves, creating characteristic window-like patches. They may also damage the growing points, leading to severe crop losses.
Disease management
Good disease management begins with prevention. Practise a three- to four-year crop rotation, irrigate early in the day so that foliage dries before nightfall, and avoid working among plants when they are wet. Use only disease-free transplants, remove and destroy infected plants promptly, and apply only registered crop protection products when necessary.
Black rot, caused by the bacterium Xanthomonas campestris pv. campestris, is characterised by yellow-brown V-shaped lesions along the leaf margins, blackened veins, and black discolouration of the vascular tissue, visible when stems are cut open.
Control: Once plants are infected, there is no effective treatment. Remove and destroy infected plants immediately. Plant disease-free seed, rotate crops, maintain good field sanitation and grow resistant cultivars where available.
Downy mildew is caused by the fungus Hyaloperonospora brassicae, which can survive in the soil and infect the next crop. Pepper spot lesions develop on the upper leaf surface, and white fungal growth appears underneath the leaves.
Control: Plant disease-free seedlings, avoid over-irrigation and use a registered fungicide where necessary.
Clubroot is caused by the soilborne organism Plasmodiophora brassicae. Affected plants become stunted and yellow, with large swollen roots.
Control: Plant disease-free seedlings, practise long crop rotations (at least seven years), apply lime to acidic soils where recommended, control weeds and use registered chemical treatments where available.
White rot is caused by the fungus Sclerotinia sclerotiorum. White fluffy growth develops on leaves and stems, causing rot and wilting.
Control: Plant healthy, disease-free seed or seedlings, control weeds, practise crop rotation and avoid over-irrigation. Although chemical products are available in some countries, no product is currently registered for this disease in South Africa.
Blackleg, caused by the fungus Leptosphaeria maculans, is characterised by large brown lesions on stems and leaves, with small black fruiting bodies visible within the lesions.
Control: Plant only treated seed or buy seedlings from a reputable nursery. Practise crop rotation and plant in well-drained soils.
This information was first published in the Agricultural Research Council’s “Production Guide for Winter Vegetables”.
Also read:
Practical solutions for rural household food production
Growing beetroot successfully | Establishing a high-yielding crop
How to grow top-quality carrots (Part 2): From irrigation to harvest and storage
No more imported rice? ARC’s upland rice trials show promising results
