The lettuce (lactuca sativa) is considered synonymous with salad in several regions of the world. The consumption per capita Brazilian weight is around 41kg/year. It consists, on average, of 95% water, which is why it is a vegetable highly recommended in diets. Each 100g of fresh product provides, on average, 42g of calcium, 23g of phosphorus, 1,2g of iron, 8g of sodium, 242g of potassium, 1.340 IU of vitamin A, 14g of vitamin C and 0,6g of fiber.
Recently, mini-sized lettuce cultivars with leaves of varying color and shape have been introduced. These products are considered to be differentiated not only by size and color, but also by the consistency and flavor of their leaves.
Lettuce is a species native to the Mediterranean. Due to its center of origin, in Brazil, it was originally cultivated in autumn-winter due to the early bolting that occurs under long days and high temperatures. However, with genetic improvement, lettuce cultivars were developed that allow cultivation throughout the year.
Seed germination occurs at an optimum temperature between 18ºC and 21ºC, and above 26ºC it can be inhibited, in an effect known as thermodormancy. The development of the lettuce plant is favored when the daytime temperature is between 18ºC and 25ºC and the nighttime temperature is between 10ºC and 15ºC.
Lettuce is grown in a wide range of soil types, however, the crop grows best in fertile soils with a pH between 6,5 and 7,2.
Seedling production
The seedlings are produced in expanded polystyrene or polypropylene trays, normally with 288 cells, filled with an organic substrate generally based on coconut fiber. Care must be taken when choosing the substrate in relation to EC (electrical conductivity), as lettuce seedlings produced in substrate with high EC (> 1,5mS/cm) may present burning of the leaves.
In summer, care must be taken with high temperatures (> 34ºC), as disorders known as blindness (death of the apical meristem), double heart (double heart) and tip burn (burning of young leaf maples).
When the seedlings have approximately four definitive leaves (20-30 days) they are ready to be transplanted to their final location.
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