How to cultivate lettuce for high yield in summer

Lettuce is the most common vegetable in our life, which can be seen everywhere in vegetable markets and supermarkets. Xiaobian also likes to eat it very much. Eating more of this green vegetable in daily life is very helpful to human health. Therefore, vegetables must be eaten by every household.

What is lettuce?

Lettuce, also known as lettuce, Asteraceae lettuce species can form a variety of fleshy tender stems, herbaceous plants in 2012. Alias stem lettuce, lettuce bamboo shoots, green shoots, lettuce. Delivery period: from January to April. It is native to Central or North China. The aboveground stem is edible, the stem skin is white-green, the stem is crisp and tender, the young stem is emerald green, and turns white-green after maturity. Mainly edible fleshy tender stems, which can be eaten raw, salad, fried, dried or pickled, and tender leaves can also be eaten.

Growth and propagation of lettuce

1. Germination period: it takes 8-10 days from sowing to the exposure of true leaves. Effects of temperature and light on seed germination of lettuce.

2. Seedling stage: the true leaves are exposed to the first leaf order 5 or 8 leaves spread out, commonly known as "Tuanzhu". It takes 17-27 days for direct seeding, more than 30 days for seedling growth, 12-20 ℃ for growth, and can withstand the low temperature of-5 ℃, 6 ℃.

3. Rosette stage: from "Tuanzhu" to the third leaf, the heart leaf is flush with the outer leaf, which takes 20-30 days, the leaf area expands rapidly, and the tender stem begins to elongate and thicken.

4. succulent stem formation stage: the stem expands rapidly and the leaf area expands rapidly, which takes about 30 days. The suitable temperature for growth is 18-22 ℃ in daytime and 12-15 ℃ at night, freezing below zero. At this stage, the tip of the seedling differentiated the flower bud, and the flower stem began to elongate and thicken, becoming a part of the fleshy stem.

5. Flowering and fruiting stage: from bolting to achene maturity, the growth temperature is the same as that of lettuce. Lettuce belongs to high temperature sensitive type, and flower bud differentiation is greatly affected by daily average temperature. When the daily average temperature is above 23 ℃, the flower buds differentiate rapidly. Others think that flower bud differentiation is related to the accumulated temperature of more than 5 ℃. For varieties with different sensitivity to high temperature, the accumulated temperature needed for flower bud differentiation is different when sowing in different periods. Plants with larger stems are more sensitive to high temperature than plants with smaller stems. Long-day sunshine promoted bolting and flowering. Under 24-hour sunshine, bolting and flowering could be achieved early no matter 15 ℃ or 35 ℃. Long days at high temperature are more favorable for bolting and flowering than those at low temperature.

How to cultivate lettuce for high yield in summer

In order to regulate the off-season supply of vegetables, in recent years, some places have explored a set of new techniques for planting lettuce in summer. The yield can reach 1200 kg per 667m 2, and the economic benefit is remarkable. The specific practices are as follows.

1. Budding at low temperature

The growing season of summer lettuce is in the high temperature season, so heat-resistant varieties must be selected. Before sowing, soak the seeds in cold water for 8-12 hours, wrap the seeds with wet gauze when the water absorption reaches 70% to 80%, place them in the refrigerator freezer or hang them 10 cm above the water surface of the well, keep them at a low temperature of 4-5 ℃, after 24-28 hours of treatment, keep them moisturized and germinate under the appropriate temperature of 15-20 ℃ (the germination rate can be increased without drying the seeds during the dormant period), and sow most of the seeds after 2-3 days of exposure.

2. Shading and raising seedlings

When sowing summer lettuce at the end of June and early July, it is best to mix seeds with an appropriate amount of dry and fine soil before sowing, sowing 1.2 meters per gram of seeds, watering in case of drought, sowing soil moisture after sowing, shading and raising seedlings with grass curtains, covering early in sunny days and uncovering late in sunny days, open all day in cloudy days, in order to cool and moisturize. Dilute water dung was applied for 2-3 times in combination with watering at seedling stage, and it could be transplanted when there were 4-5 true leaves at the age of 25 days.

3. Transplanting method

Before planting, 3000 kg of rotten barnyard manure and 2000 kg of human and animal manure were applied every 667m, and ditches were dug and leveled. The border was 1.5-2m wide, 25cm wide and 15-20cm deep. In the evening of sunny day in late July, seedlings were planted with soil after seedling bed watering. The plant spacing was 25 cm and the row spacing was 35 cm. There were 700-800 plants per 667 m. After planting, pour enough fixed root water, and then pour dilute water dung every 2-3 days. You'd better build a shed to shade before you live.

4. Fertilizing and watering

Summer lettuce has shallow roots, weak absorptive capacity, rapid growth in summer and needs more fertilizer and water, so special attention should be paid to heavy fertilizer and water management. After the seedlings are alive, dilute water dung is applied every 3 to 5 days combined with drought resistance. Frequently irrigate fertilizer and water when the stem begins to expand (stop watering 10 days before harvest), and spray 0.3% potassium dihydrogen phosphate on the leaf once or twice. If downy mildew is found, spray metalaxyl at the initial stage of the disease. Where there are conditions, when the lettuce is ridged and the stem begins to enlarge, spraying thalidomide regulator for 2 to 3 times can effectively increase the stem weight.

5. Harvest in batches

If the summer lettuce is harvested too late, the fleshy stem can form buds, consume nutrients, form a hollow, and cannot be eaten. Harvesting early will reduce the yield. Generally, when the stem is enlarged and the tip of the stem is as high as the tip of the outer leaf, it can be harvested in batches after transplanting for about a month.

For those who grow lettuce, it is very important to improve its yield. in this process, in addition to understanding its growth habits, it is also very important to understand its fertilization, watering, transplanting and so on. only a comprehensive understanding of some of its characteristics can better improve its yield.