HEAD CABBAGE

pH: 6-7.2
Plant spacing: 60-80 cm (4-8 plants/m2)
Germination time and temperature: 4-7 days; 8-29 °C
Growth time: 45-70 days from transplanting (depending on varieties and season) Ideal temperature: 15-20 °C (growth stops at > 25 °C)
Light exposure: full sun
Plant height and width: 30-60 cm; 30-60 cm

Recommended aquaponic method: media beds (not suitable for newly established aquaponic units)

Growing cabbage in aquaponic units: Cabbage is a highly nutritious winter crop. The plants grow best in media beds because they reach significant dimensions at harvest and may be too large and heavy for rafts or grow pipes. Cabbage is a nutrient-demanding plant, which makes it unsuitable for newly established units (less than four months old). Nevertheless, owing to the large space required, cabbage crops take up fewer

nutrients per square metre than other winter leafy vegetables (lettuce, spinach, rocket, etc.). Although cabbage can tolerate temperatures as low as 5 °C, the low temperatures may not be suitable for culturing fish.
Growing conditions: Cabbage is a winter crop with ideal growing temperatures of 15-20 °C; Cabbage grows best when the heads mature in cooler temperatures, so plan to harvest before daytime temperatures reach 23-25 °C. High concentrations of phosphorus and potassium are essential when the heads begin to grow. Integration with organic fertilizers delivered either on leaves or substrates may be necessary in order to supply plants with adequate levels of nutrients.
Growing instructions: Transplant seedlings at 4-6 leaves and a height of 15 cm. Position seedlings with an optimal planting density according to the chosen variety. In the event of day temperatures > 25 °C, use a shading net of 20 percent light shading to prevent the plant from bolting (growing to produce seeds). Given the high incidence of cabbage worms and other pests such as aphids, root maggots and cabbage loopers, it is important to carry out careful monitoring and use organic (aquaponic safe) pesticides when necessary.
Harvesting: Start harvesting when cabbage heads are firm with a diameter of about 10-15 cm (depending on variety grown). Cut the head from the stem with a sharp knife, and place the outer leaves into the compost bin. If cabbage heads tend to break, it indicates they are over-ripe and should have been harvested earlier.