Lettuce is the stem lettuce, is a biennial herb crop of Asteraceae. In my county vegetable planting area has extensive planting, can be cultivated throughout the year, but the optimal temperature for growth is 10C to 25C, the most suitable for winter and spring cultivation.
The most common problem affecting yield and quality in lettuce cultivation is the “seedlings†and cracking of lettuce.
"Pick seedlings" refers to the phenomenon of convulsions in advance, that is, the phenomenon that the fleshy stems are slender and the internodes are elongated, the leaves are thin and small, the skin is thick and the meat is small, the food value is not high, and the phenomenon of easy convulsions and flowering occurs. During the growth of the shoots and leaves of the lettuce, if it encounters high temperatures above 22 to 24°C and long days of 12 hours or more, it will cause premature convulsions. In the autumn, asparagus lettuce is cultivated, and the seedling stage is in high temperature season. The temperature difference between day and night is relatively small, the respiratory rate is heavy at night, the stems are easy to grow long, and the flower buds can be easily differentiated, resulting in the autumn lettuce “sowing seedlingsâ€. In addition, planting seedling age is too large or in the growth period of stems and leaves if there is insufficient supply of water and fertilizer or too much water to cause poor vegetative growth can easily cause seedlings and cracks.
The fissure refers to the period when the meaty stem of the lettuce is enlarged. The fleshy stem is split longitudinally and reaches the middle of the stem deeply. The cracked part is yellow-brown and perishable. Causes of cracks: First, related to varieties; Second, it is related to uneven supply of water and fertilizer, and it is related to sudden drought, especially when the fleshy stems are mature, the skin has been lignified. At this time a lot of watering, sudden enlargement of the fleshy stem, epidermis Can't swell with it.
To solve these two problems, we should first select the light green leaves and lettuce varieties that are insensitive to the sunshine response, and arrange their growth period in the appropriate temperature season (about 20°C). Seeds are treated with low temperatures to promote germination. After more than half of the germination can be sown. Shade nursery to keep the seedbed moist. When seedlings grow 2 to 3 true leaves, they are planted with 5-6 cm of seedlings and seedlings. When there are 5 to 6 true leaves, colonization begins, and the time for planting should be in the afternoon. It is advisable to plant 6,000 or so per acre.
The second is to strengthen the management of fertilizer and water after planting: control water seedlings between 2-3 leaf rings after planting to promote root development and rosette leaf development. Be careful when the leaves are flush with the rosette leaves when the stems begin to hypertrophy, which should be watered and applied quickly. Nitrogen fertilizer and potash fertilizer are promptly transferred from "control" to "promotion." This water and fertilizer must be timely and prematurely affect the growth of the fleshy stems. After starting watering, the stem's hypertrophy speeds up, water and fertilizer are increased, the ground is slightly dry, and the watering is even, the water should be moderate, and flooding should be strictly prevented. When the land can enter people, shallow loose soil is broken and combined with watering, and then top dressing 1-2 times, applying urea 15 kg per 667 square meters, and appropriate amount of quick-acting potash fertilizer, fertilizer amount should not be too large to prevent stems Part of the gap.
The third is the use of plant growth regulators to inhibit seizures: Spraying 800-1000ppm of Qingxinsu or 6,000-times longer than the growth of lettuce during the late growth stage has a good effect on increasing yield and inhibiting seizures, but it should be noted that it is not possible to spray at the seedling stage. Plant growth regulators, otherwise it will accelerate seizures.
The fourth is the timely harvest: When the lettuce leaves and the outer leaves are flush when the harvest is appropriate, at this time the fleshy stem has fully expanded, the quality of crisp. Harvested in stages can be removed at the top of the growth point to prevent the "cockroach" seedlings or cavity aging. However, the interval should not be too long. In addition, when it is found that the lettuce has a slight crack, it must be harvested earlier.
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