Guide to Growing Cabbages
Cabbages do well in well drained, sandy loam soils with high organic matter, with a PH range of 6.5 to 7.0. They are normally grown from seed. Cabbages are a temperate vegetable which do best under cool climates where there is a significant difference between day and night temperatures.
The land, which should have access to plenty of sun and be well drained, must be prepared well in advance – preferably some weeks before planting the seedlings.
Cabbage seedlings are first raised in the nursery bed in raised or sunken beds about one meter wide fertilized with organic manure. The seeds are sowed along the drills 10cm apart and covered lightly with soil. Shade the nursery and water once or twice a day. 100 to 120g of the seeds is enough for one acre. The seedlings will be ready for transplanting four to six weeks after sowing.
Plough the land and harrow it to a fine tilth. While transplanting, select vigorously growing and healthy seedlings. Transplant them in the evening to reduce seedling mortality.
Space the crop at 60cm by 60cm. Spread farm yard manure at the rate of eight to 10 tons per acre before final sowing to mix well. The recommended planting fertilizer is DAP at 75kg/acre. However, avoid using DAP in acidic soils with PH levels of below seven.
Water the crop at least once in a week, applying 11/2 inches into the soil to enable the head form.
Top dress the cabbages four weeks after transplanting with Calcium Ammonium Nitrate (CAN) at the rate of 75kg/acre. A 50kg bag of CAN retails at an average of Sh1600 in agro vets across Kenya.
Cabbage plants need 6-8 hours sunlight per day. Most varieties take some 45-100 days to harvest after planting. Larger cabbage head varieties take longer to mature. Temperatures averaging between 60-70 degrees celsius are ideal for the crop, though an established crop can endure temperatures dipping into freezing levels at night.
Fertilizing and watering
Cabbage is a heavy feeder crop and requires a lot of water and fertilizer. Lack of food would stunt their growth leading to undersized heads. Water is used by cabbage to absorb nutrients from the soil. Since cabbage is mainly made up of water, without enough watering its head would dry out and become bitter.
If the area is not receiving sufficient rains the cabbages should be treated to a once a week heavy watering, which sinks deep into the soil as cabbage roots run deep.
Water pressure should be kept low when watering to avoid eroding away the soil. Avoid watering the top of the cabbage head as it can encourage pests and diseases. Early morning watering is advisable and it should be re-emphasized that cabbage is a thirsty plant which needs a lot of water.
Since cabbage is a heavy feeder it is recommended that plants are treated to doses of fertilizer throughout the growing season. Fertilizer can be added to the soil just before transplanting cabbage seedlings and sprinkle another dosage on the area where the seedlings are to be planted. Work it well into the soil.
When the plants are some 6 inches tall the farmer should fertilize the cabbage again with water soluble fertilizer, since granular fertilizer will burn the cabbage plant if it comes into direct contact with the leaves.
Another dose of water soluble fertilizer should be applied when the seedling starts developing a cabbage head. The fertilizer will energize the plants to produce large and well formed heads.
Before harvesting the farmer should test the ripeness of the cabbage by squeezing it firmly. When ripe the cabbage head will be firm and not give in much to the applied pressure.
A sharp knife should be used to cut off the cabbage head from its stem. The cutting should be just below the cabbage head and the stem must remain in its position. If the weather is favourable another cabbage head can develop on the stem as a bonus to the farmer. After harvesting the plants can be pulled up and turned into compost.
PESTS AND DISEASES
Cabbage aphids appear as masses of soft, pale green insects covered by mealy powder. They feed in clusters on the underside of the leaves and occasionally on stems. In this, infested leaves become yellow as a result of the feeding. They can be controlled by spraying insecticide chemicals at the rate recommended by the manufacturer.
Diamond back moth is another pest that affects cabbage in all growth stages; the seedling stage, vegetative growing stage, flowering stage and fruiting stage. It attacks the growing points, inflorescence, leaves and stems. Under heavy infestations the entire plants may become riddled with holes. Cabbages develop deformed heads which encourages soft rots.
The larvae feed on leaves from the underside and leave tiny “windows”. The caterpillars first attack the outer leaves of the young plants and subsequently attack the developing plant leaving entry points for pathogens. They are controlled by destroying infected crop residues and crop rotation. Also spray insecticide chemicals at the rate recommended by the manufacturer.
Black rot is a bacterial disease in cabbage that causes up to 100 per cent yield losses in infected crops. The disease attacks cabbages at any stage of growth. Farmers can spot signs of the disease though presence yellow v-shaped or u-shaped areas extending inwards from the margins of the leaf. As the disease progress, the yellow areas turn brown and the leaf dies. One plant can produce enough infectious materials to destroy a whole field. Early removal of infected plants and foliage from the fields can assist in reducing black rot damage.