Butterhead lettuce "Merkurion"

* Cultivation of lettuce in protected and open ground.
In greenhouses, as a rule, head lettuce varieties are grown in seedlings. The culture is carried out in two periods: winter-spring (2 turns) and autumn (1-2 turns).
In the conditions of Estonia, the autumn culture of head lettuce with planting seedlings in the phase of 3-4 leaves in a permanent place is quite justified.
The optimal sowing time is August 3-10 with planting seedlings in the first decade of September. For the III light zone, the earliest sowing date in the winter period is December 5, while the seedlings must be illuminated for 10-15 days. However, planting seedlings early may not be economical. Without additional lighting, seedlings can be grown from the third decade of January (25-30 days), while the crop arrives in late February - early March.
Seedlings are grown in two ways: through the picking of seedlings and sowing with a pneumatic seeder into peat cubes of pelleted seeds. The second method is less laborious and provides a higher and earlier yield. In the spring, pots of 5x5 cm are used, and in winter, when using additional illumination, the size of the cubes is reduced.
A mixture for making cubes is prepared from peat with the addition of small sawdust up to 20% by volume: if riding peat is used, sawdust is not added. Until the emergence of shoots, the air temperature is maintained at +18 ... 20 ° С. When shoots appear, the temperature is reduced to + 8 ... 12 ° C during the day and + 6 ... 10 ° C at night.
Seedlings dive in the phase of deployed cotyledons. After picking, the air temperature in sunny weather is maintained at +18...20°С, in cloudy weather - +15...17°С during the day and +10...12°С at night.
Seedlings are planted in the phase of three or four leaves. When planting seedlings immediately in a permanent place, the number of diseased plants decreases by 8-18% and, most importantly, the cost of growing seedlings is almost halved.
With the main dressing of the soil for salad, they are as follows: nitrogen - 60-80, phosphorus - 8-10, potassium - 80-100, magnesium - 20-30 mg / l. On the eve of planting seedlings, the soil is abundantly moistened (20-25 l / m2). Humidity is maintained at 65-80% to avoid leaf burns.
The density of planting plants depends on the time of year and variety. Small-headed varieties of the "Böttner" type are planted according to the scheme 20x20 cm, for a medium-sized variety of the "Berliner" type, planting is 25x25 cm and for large varieties of the "Batavia" type - 30x30 ... 25 cm.
With an early sowing time (spring), plants are planted less often - 16-20 pcs / m2, and with an autumn culture, it is thicker, up to 25-30 pcs / m2. Watering is carried out in good weather in the morning in several steps to achieve uniform absorption of moisture. After watering, active ventilation is required to remove excess air humidity.
At the beginning of head formation, ventilation is increased, and the air temperature is reduced: + 14 ... 18 ° C during the day and + 8 ... 12 ° C at night.
Studies conducted in Canada, the Netherlands and the UK have shown that with a difference in day and night temperatures from + 25 ... 28 ° C to + 6 ... 7 ° C, the heads become loose. In order to prolong the arrival of the head lettuce crop in the distribution network, the temperature in the head formation phase is reduced to +8...10°С during the day and +4...8°С at night.
Growing lettuce as a compactor is generally not recommended as the main crop will quickly begin to shade it.
To expand the period of consumption of lettuce from open ground, different sowing dates and varieties that differ in early maturity are used. The earliest production is obtained during the winter sowing of seeds, for which the soil is especially carefully prepared. Well-levelled areas with a slight southern slope are best suited, quickly warming up in the spring. Sowing dates are chosen to take into account the average long-term data when stable frosts occur.
In Estonia, usually at the end of October - the first decade of November before the snow cover. The soil prepared for sowing should be loose, without lumps on its surface. Light loams or sandy loamy soils are best suited; ridges are cut immediately before sowing. Sowing is carried out in grooves with a depth of 1-1.5 cm. The sowing scheme for leaf lettuce is five-, seven-, ten-line or solid. For head varieties, sowing is single-row 60x20 or double-row 50+20x20...30 cm, followed by mulching and rolling the soil. Sowing is carried out by vegetable seeders SON-2.8; SKON-4.2; SKOSSh - 2.8 with the simultaneous introduction of granular mineral fertilizers. When sowing lettuce on ridges in the zone of excessive moisture, a bed maker is used - a seeder GS-1.4.
Lettuce is placed on the fields of intensive crop rotations and areas of early vegetable growing after tilled crops, under which high doses of organic fertilizers are applied.
Mineral fertilizers are used at the rate of 150-300 kg/ha of ammonium nitrate, 300-500 kg/ha of superphosphate and 150-200 kg/ha of potassium salt. Two-thirds of the dose of superphosphate and potassium salt is used under fall or in the spring for its plowing, and the rest of the superphosphate and potassium salt and all ammonium nitrate are used for spring cultivation. The introduction of 40-50 t/ha of rotted manure or compost under the fallow land significantly increases the yield.
Lettuce gives low yields on acidic soils, so such lands must be periodically limed.
Early-ripening leaf varieties are sown earlier - from the beginning of April to May in several terms, mid-season and late - from April to mid-June. The period of cultivation of leaf lettuce is short: in fertile areas, the crop is ready for harvest in 30-40 days from the moment of germination.
Romaine lettuce is sown from early July to late August for autumn consumption. The seeding rate of head varieties with one breakthrough is up to 2 kg/ha, with two - 2.5-3.0 kg/ha. With a seedless method of cultivation, a double thinning is carried out. The seeding rate of leafy varieties with continuous sowing is 4-7 kg/ha. The seedling method of cultivation is used to obtain an early harvest. First, seedlings are grown, which are then dived into pots or peat-muck cups ranging in size from 3x3 to 6x6 cm, depending on the period of seedling preparation. To obtain seedlings, seeds are sown 30 ... 35 days before planting in the field. 0.5 g of seeds are sown in one box (20 ... 25x40 cm). At a temperature of +20...22°C shoots appear in 2-3 days, after which the temperature is reduced to +10...12°C. In the real leaf phase, the seedlings dive into cubes or pots, pre-watered abundantly. You can sow seeds directly into cubes using the IGT-10 machine.
The planting of finished seedlings is carried out with conventional transplanters, one-line, with a row spacing of 70 cm or two-line according to the scheme 50 + 20x30 cm. When planting, the cube is deepened by no more than two-thirds of the height.
Care of crops consists in the shallow loosening of row-spacings, weeding and watering in dry weather. The irrigation regime affects the concentration of nitrate ions in plants, especially at high temperatures. During the formation of heads, watering is carried out only along the furrows.
Harvesting is carried out in the evening or early in the morning when the plants are cooled and therefore better retain their fresh presentation.
Leaf varieties are harvested at a time, pulling out of the soil along with the roots.
Head lettuce is harvested by cutting the plants below the head, selectively, determining the readiness of heads for harvesting by pressing the head with the back of the hand. Cut it near the surface of the soil, remove diseased and yellowed leaves.