SALADS

SALADS

Lettuces are annual plants that belong to the family of the Composites or Asteraceae. The different species have been used by man since ancient times. Known by the Egyptians and consumed by the Greeks; in Roman times, they were widely cultivated throughout the Empire. The Romans, in particular, ate lettuce not only as a vegetable, but also as a medicinal plant for its calming properties. In fact, besides being in the name of the plant itself (lattuga), lactucarium, the latex of the lettuce that flows copiously at the rupture of the tissues, is a complex substance that exerts an analgesic and sedative action and it is believed that, if copiously consumed during dinner, induces sleepiness and promotes digestion. Its caloric value is very low: about 15 kcal/100g and is therefore recommended in low-calorie diets. Like all leafy vegetables, it is a good source of vitamin A, calcium, potassium, and iron. Dietary consumption of lettuce goes well with protein (dairy, fish, or meat) or starchy foods (pasta, bread, rice, or potatoes). It contains pectin, lactucin, and many vitamins (A, E, C, B1, B2, and B3) and minerals (calcium, magnesium, potassium, sodium, and a good concentration of iron). Lastly, lettuce is high in fiber which very useful for constipation. The varieties of lettuces on the market today can be divided into three categories according to their morphology: lettuce with a tight tuft (cappucce, Roman, and iceberg), lettuce without a tuft (Gentilina, oak leaf, and lollo) and leaf lettuces.

CULTIVATION

Lettuces do not have high thermal requirements, although the temperature of the soil should remain above 9 ° C for good growth. On the other hand, the optimal temperature of the air should not exceed 22 ° C. Any thermal drops, with temperatures close to 0 ° C, may block the plant's development but, for many varieties, they are not lethal. Lettuce plants grow very fast and their cycle, from transplanting to harvest, ranges from 45 to 70 days. During this period of time, however, they produce a large green mass that can reach and exceed 3 kg / sqm. In order to have such a rapid development, they require well-drained, fertile soils with a good supply of water. The presence of organic substances that allow the plant to maintain proper humidity, good availability of nutrients, and low salinity is of utmost importance. The removal of major nutrients is in the ratio of 1:04:2,3 (N: P: K). To cope with a production of about 3Kg/smq, a good fertilizer should include 4-6 kg / sqm of organic compost, to which one should add about 10 g / sqm of phosphorus and 20g/smq of potassium that, using mineral fertilizers, may be made ??from about 50 g /sqm of superphosphate and 40 g /sqm of potassium sulphate. On top of the soil, and before the plants have covered the ground, one must evenly distribute 40 g /sqm of calcium nitrate or of guano. The planting density depends on the variety, but the distances are usually about 25-30 cm on the row and 25-30 cm between rows, equal to 11-16 plants/ sqm. Transplantation, where possible, should be always done on the high soil placed in prose (strip of land between two furrows) to avoid very dangerous waterlogging under the plant.

ADVERSITIES

The main diseases that can affect lettuce are soil parasites and foliar parasites. Attacks by fungi present in the substrate, such as sclerotinia and Botrytis, which infect the roots or the collar in a short time causing the collapse of the entire plant, are very dangerous. The only way to fight against these pathogens (outside of chemical recourse) is by taking preventive measures: not planting in infected soil or stagnant water, rotating crops on different plots, and using resistant varieties. There may always be attacks on the plant's rootage by mole crickets and Elateridae, against which one can fight with poisoned baits or natural pyrethroids. The foliage is rather undermined by Bremia (downy mildew of lettuce), powdery mildew, and Alternaria. Against these fungi, one can perform preventive care with copper and sulfur based treatments, always respecting the timeframe of preharvest interval listed on the packaging. Given the extremely short cycles of these vegetables, one should only intervene in the early stages of cultivation. Among the non-parasitic diseases of lettuce, there can occur browning of the leaf margins, which are due to water imbalances or excessive soil salinity.