Lettuce

The cultivation of lettuce

Lettuce (Lactuca sativa L) is an annual, herbaceous rosette, native to Western Asia and belonging to the botanical family of Compositae. The part consumed is the sheet or the apple constituted by the leaves and stem reduced. The vegetable is rich in vitamin A. In Morocco, there are lettuce all over the country, in small areas.

Pedoclimatic preferences:

The plant is cold season. The optimum temperature is 20-23 ° C during the day and 7 ° C at night (growth begins at 4 ° C and continuing at 24 ° C). At 15 ° C, seed germination is rapid (2-3 days). The seed has 4 types of dormancy: (1) post-harvest dormancy (it takes some time between harvest and germination; this time depends on the varieties). (2) a second dormancy induced by high temperatures (above 18 ° C, seeds should be exposed to low temperatures). (3) another dormancy induced by the infrared (seeds should be exposed to visible light for a few days before planting). (4) a fourth dormancy induced by long days (there is risk of bolting under long days of summer and high temperature). Culture to be held in cool period (fall, winter and spring. It is possible in summer in coastal regions). The soil requirements are low: we find salads on all soil types. The optimum pH of the soil is of 6 to 6.8. The culture tolerates excess boron and magnesium deficiency. It is sensitive to salinity. She responds well to a contribution in Cu, Mo and Mn.

Varieties, tillage and seeding:

The main varieties used in Morocco belong to three main types of lettuce: type in or cut leafy salad, green leaf (varieties Secalina, Royal Green) or red leaves (Prizehead, Vulcan, Western red). The headed guy (variety capitata, Iceberg, May Queen, Wonder 4 seasons). The Roman-type (variety Romana Lam, Paris Island Cos, Pic Bos Capri, Balon, Blonde maraichère). The spread is sexual. The number of seeds per gram of seed is from 450-900. For the winter crop, sowing is done from November to February in warm layers. For the summer crop, sowing is carried out from May to September in the fresh coastal areas in the nursery. For the fall crop, sowing takes place between October and April on coastal in potting soil. For the cultivation of spring sowing is done between March and August in the nursery. This should be sunny to expose the seeds to light at least at planting. There should be about 400,000 seeds per ha. Seeds are sold in two forms: free or pelleted. The pellets offer ease-till precision. If nursery, planting should not be deep. The collar must stay above ground. The seedlings remain in the nursery for about twenty days. The time between the planting and harvesting definitive place is nearly a month and a half. The arrangement between plants in the field is as follows: 0.5 m between troughs of 1 m and 5 rows x 15- 20 cm between plants in the row with the type of lettuce (15 cm for leafy salads; 20- 25 cm for lettuce salads and 30 cm for the Roman type). The plant population density of 150,000 to 200,000 plants / ha depending on the variety.

Irrigation:

The water requirement of culture is 350- 400 mm per crop cycle. Most producers use to start sprinkling of culture (germination - emergence) and the gravity thereafter. Over 80% of water supplies are provided during the last month of culture. A few days before harvest, reduce water inputs to improve the quality of apples and avoid soft apples.

Fertilization:

The base dressing may consist of 5-10 T / ha of manure 20 kg + 50 kg N + P2O5 + K2O 100 kg / ha. On the cover, you can bring 30 kg N / ha + 30 kg P2O5 / ha at 20-25 days after planting.

Main enemies of culture and Controls:

The fight against weeds is essential (using herbicides before planting or after emergence; it is necessary to inquire with the houses of specialized plant protection products on specific herbicides to use). The most fearsome insect for growing lettuce are worms, aphids, leaf miner and white fly. The most dreaded diseases are basal rot (Rhizoctonia solani) and the melting of seedlings (Sclerotinia minor). Viruses (LBVa or Big Vein Virus, or LMV mosaïc virus BWY or beet Western Yellows, TuMV or Turnip mosaïc) are generally controlled by a good selection of healthy seed and a good crop rotation. The melting of seedlings can be overcome by effective fungicides (mancozeb and maneb) and crop rotation. Downy mildew (Bremia lactucae) is a dangerous disease since the genetic variability of the pathogen does not allow effective chemical control. Bacterial blight and fusarium wilt are also dangerous. We must not grow lettuce on infested plot.

Harvesting and product handling:

The cutting is done as and sales in order not to exaggerate the offer on the market. Iceberg type can be coated in thin plastic and packed in cartons 2 layer (2 x 3x 4, or 24 apples per box). These cartons can be cooled by chilled water or in a vacuum cooler (cooler vacum) before being shipped long distances. The sorting is done on the field, without the need of a packaging station: Workers clean the head of lettuce and throw to the ground the outer leaves sick or injured.

Conditions for safe storage or transport:

  The product is perishable. This must be pre-cooled in a cooler Vacuum before transporting it by refrigerated truck or store it in a ventilated area to 1- 2 ° C and 95% RH. Under these conditions the retention time may be of the order of 2-3 weeks. Avoid ethylene in the cold storage, if spots appear on the leaves, with gradual expansion of browning.

Agronomic and Veterinary Institute Hassan II