Solutions to common problems of seedling cracking affecting the yield of lettuce

Lettuce, that is, lettuce for stem, can be planted widely in four seasons, but the optimum temperature for growth is 10 ℃-25 ℃, which is the best in winter and spring. The most common problems affecting the yield and quality of lettuce in lettuce planting are the "fleeing" and cracking of lettuce.

Lettuce sprouting

"channeling seedling" refers to the early bolting of lettuce, in the middle growth stage, the fleshy stem is slender, the leaf internodes are elongated, the leaf is thin and small, the outer skin is thick and less meat, the edible value is low, and it is easy to bolt and blossom. Lettuce stems and leaves are easy to bolting if they are exposed to high temperature of more than 22 ℃ and sunshine of more than 12 hours during the growing period. When lettuce is cultivated in autumn, the seedling stage is in high temperature, the temperature difference between day and night is small, the respiration consumption at night is large, the stem is easy to grow, and the disease rapidly differentiates the flower bud, which leads to the "fleeing" of autumn lettuce. In addition, the seedling age is too old or in the stem and leaf growth period, if the supply of water and fertilizer is insufficient or too much watering leads to poor vegetative growth, it is also easy to cause seedling channeling and cracks.

Lettuce cracking

Fissure refers to the late expansion of the succulent stem of lettuce, the fleshy stem split longitudinally, deep into the middle of the stem, and the split part is yellowish brown and perishable. The reason: first, it is related to the variety; second, it is related to the uneven supply of water and fertilizer, drought and waterlogging, especially when the succulent stem is mature, the skin has been lignified, and when it is heavily watered, the fleshy stem suddenly expands, but the skin cannot expand and crack.

Solution: the green leaf lettuce varieties with middle and late maturity and relatively light cracks which are not sensitive to sunlight were selected, and the peak growth period was arranged in the suitable temperature season of about 20 ℃. When sowing, the seeds are treated with low temperature to promote germination. After more than half of the seeds germinate, they can be sown. Raise seedlings under shade and keep the seedbed moist. 5~6cm between seedlings and seedling spacing was carried out when the seedlings grew 2-3 true leaves. The planting began when there were 5 to 6 true leaves, and in the afternoon, 6000 plants were planted per mu.

Secondly, strengthen the fertilizer and water management after lettuce planting: squatting seedlings under water control between the three leaf rings of lettuce after planting, promoting the development of root system and rosette leaves of lettuce. When the leaves and rosette leaves are flush and the stem begins to become hypertrophic, we should water and apply available nitrogen and potassium fertilizer. Timely from "control" to "promote". Water and fertilizer should be timely, too early and too late are disadvantageous. After the beginning of watering, the speed of stem hypertrophy is accelerated, the amount of water and fertilizer is increased, the ground is slightly dry, watering should be uniform, the amount of water should be moderate, and flood irrigation should be strictly prevented. When the land can enter people, the soil should be loosened and broken, combined with watering, and then topdressing 1 Mel twice, applying about 15 kg urea per mu, and an appropriate amount of quick-acting potash fertilizer, not too much fertilizer to prevent stem cracks.

The third is to use plant growth regulators to inhibit bolting: spraying 800~1000ppm at the later stage of lettuce growth or 6000 times for a long time can increase the yield and inhibit bolting, but it should be noted that lettuce seedlings should not be sprayed with plant growth regulators, otherwise bolting will be accelerated.

The fourth is timely harvest: when the heart leaf of lettuce is flush with the outer leaf, the fleshy stem has been fully expanded and the quality is crisp and tender. If harvested by stages, the top growing point of lettuce can be removed to prevent "channeling" seedlings or cavity aging. However, the interval period should not be long, and lettuce should be harvested early when it is found that there are slight cracks in lettuce.