Producing lettuce hydroponically, in a controlled environment, produces a clean, uniform and superior quality crop throughout the year.
- Lettuce is rich in calcium, iron and vitamin A, and the nutrient value is high, because it is eaten uncooked.
- Lettuce has a shallow root system, and lends itself to nutrient film production systems.
- In South Africa the gravel flow technique (GFT) is the most widely used system for its cultivation.
CLIMATIC REQUIREMENTS
- Lettuce is a cool-weather crop and, if grown under shade net and in tunnels, is not generally affected by winter cold and frost.
- The only exception is fully matured crisphead lettuce, which sometimes suffers frost damage if not harvested in time.
- If the heads start to decay, the plants must be removed as soon as possible to avoid spreading diseases to other plants.
- The optimum temperatures are 17°C to 27°C (daytime) and 3°C to 12°C (night).
- If the night temperature falls below 3°C, the growth rate will be retarded.
- If temperatures of 28°C and higher prevail, most of the cultivars will form small, inferior, loose heads, and bolt (form seed stalks).
- They will have a bitter taste.
- High temperatures can also cause a high incidence of tip burn, a physiological disorder.