Reasons and control measures of lettuce twitch

Lettuce has been cultivated in many places. However, the cultivation of plants are often prone to leaf lobule, thin stems in detail, tender shoots long sticky rod-like convulsions phenomenon, affecting the yield and reduce quality. Summarizing the production experience in recent years, the reasons for the high convulsions and the effective control measures for lettuce tender stems are as follows:
(1) Improper selection of species. There are many varieties of lettuce, and their adaptability and sensitivity to light and temperature are not the same. Often early-maturing varieties are more resistant to low temperature than middle-late-maturing varieties and have lower temperature tolerance, and are more sensitive to high temperatures and long days, so they should be based on the cultivation season. Use suitable varieties. For example, lettuce grown in spring and summer harvests and summer harvests are grown under high-temperature and long-day conditions. Therefore, mid- and late-maturing varieties that are resistant to high temperatures and unresponsive to long-day sunlight should be selected. If early-maturing varieties are used, they can be easily convulsed. Early-maturing varieties planted early in the spring, the market is early, high yield, good efficiency, if late planting, due to the late growth temperature, long sunshine and easy to high twitching, and low yield, poor efficiency.
(2) Sowing period is not suitable. Spring lettuce cultivation, if the early autumn seedling nursery, long growth period before the winter, seedlings are too large, early flower bud differentiation, winter is vulnerable to frost damage, early in the following year is also easy to convulsions; if sowing too late, the short growth period before winter, the seedlings Small, low accumulation of nutrients, wintering is also vulnerable to freeze damage, and the market is late for the following year. Late summer lettuce sowing or autumn lettuce sowing too early, high temperature during the nursery period, long sunshine, prone to grow seedlings. Therefore, lettuce cultivation should pay attention to grasp the appropriate sowing date, general spring lettuce sowing ground in early October, protective land in the late next year in January next year, summer lettuce shoots in early April, autumn lettuce planted in early August, winter lettuce in late August Sowing is appropriate.
(3) Poor management at seedling stage. Seeding volume is too large, seedlings are too dense, and seedlings are not susceptible to squeezing seedlings in time; seedbeds are treated with nitrogenous fertilizers, excessive watering, and shading when seedlings are covered with shades, or removal is not timely, etc., which can cause seedlings to become leggy. Therefore, seedling management should be aimed at controlling legacies and cultivating short-sturdy seedlings. Specific measures include: seedbed base fertilizer with organic fertilizer, can be applied with appropriate amount of compound fertilizer; appropriate dilute sowing, and time seedlings, control of watering, to see the bed see dry see wet is appropriate, shade seedlings should gradually after the whole seedlings Covering the cover as soon as possible, it is no longer shaded after 3 leaves; summer, autumn Lettuce seedlings can be sprayed 1 to 2 times 500 mg / kg of chlormequat solution, can effectively prevent leggy.
(4) Planting is not timely. Implantation is not timely, the seedlings tend to grow too fast, the hypocotyl elongation is in a state of leggy, and it is difficult to obtain the hypertrophic shoots after planting. Generally, seedlings of 5 to 6 leaves are planted in a timely manner. The seedling age for autumn sowing shall be about 40 days (days), the seedling age for spring sowing or summer sowing shall be about 25 days (days), and the seedling age for autumn sowing should be 30. ~ 35d (days) is appropriate.
(5) Cultivation is too dense. The density of colonization was too large and the ridges had been sealed before the rosette leaves were formed. This resulted in crowded plants and insufficient illumination. Under normal circumstances, the spring harvest lettuce can be moderately densely planted for early benefits, planting 8,000 acres; summer harvest lettuce due to high temperatures, long days easy to grow, should be sparse planting, 5000 acres planted is good; late harvest late lettuce temperature is appropriate, per acre 7000 strains can be planted with good commercial quality and high yield.
(6) There is less cultivator loose soil. After planting fertilization, watering and rainfall can cause soil compaction, high humidity, and poor ventilation. If the soil is not ploughed in time, it will affect the growth of the root system and the absorption of water and fertilizer, so that the leaves do not get enough water and fertilizer, and plants that are not robust and have a weak stem are easy to emerge. Therefore, timely cultivating after culturing the vegetative seedlings should be carried out in a timely manner, and the medlar should be deeply immersed in order to facilitate seedling growth and promote the development of the root system so that the rosette leaves grow and the tender stems grow robustly.
(7) Improper watering. After lettuce is planted, if excessive watering or rainwater is not removed in a timely manner due to lack of fertility, the soil moisture is too large, and the tender stems are easy to grow long and “squeaky”, and under the condition of soil drought and high temperature, the growth of tender stems is weak. It is also easy to "drought." Therefore, lettuce cultivation watering should be appropriate, not only to prevent "squeak" but also to prevent "drought." Before the formation of rosette leaves and the ridges of the plants, appropriate watering should be controlled to make it easier to see and see wet. After the ridges are enclosed, the water supply is increased to keep the surface wet, so as to ensure the rapid growth and expansion of the tender stems.
(8) Insufficient fertility or partial application of nitrogen fertilizer. Insufficient base fertilizer or topdressing is not timely, soil fertility is low, plant nutrient growth is inhibited, will accelerate reproductive growth, but also prone to immature convulsions. Partial application of nitrogen fertilizer, can easily lead to plant leaves too long, less accumulation of nutrients, often young stems will not develop as long as pulling up the long, so the basic fertilizer to apply enough, can be applied to the decomposed manure 4,000 kg, compound fertilizer 25 kg, so that organic fertilizer Combined with compound fertilizer. In addition, it is also timely to apply slow-release Miaofei, Tuanjiefei, reminder of bamboo shoot fertilizer, topdressing each application of ammonium sulfate or urea 15 to 20 kilograms or the top two times each topdressing 50% of the diluted manure water 1000 kilograms.
(9) Weather conditions are not suitable. During the late growth of lettuce or summer and autumn, due to high temperature and long daylight conditions, the leaves tend to be less differentiated, flower buds differentiate earlier, floral development is faster, and management is slightly careless, easily causing convulsions and affecting quality and yield. To this end, in addition to strengthening water and fertilizer management, the regular application of chlormequat is an effective measure to control the convulsions of cultivated lettuce during the high temperature season. The spraying of chlormeine can delay the growth of lettuce twitches, promote leaf growth, increase plant nutrient area, and thicken tender stems. Spraying is usually started at the beginning of the rosette period, 7 days to 10 days (days), and sprayed 2 or 3 times in total at a concentration of 350 mg/kg.
(10) Harvesting is not timely. Lettuce harvesting takes the time of "flat mouth" between heart and outer leaves. In particular, late spring bamboo shoots, summer bamboo shoots, and autumn bamboo shoots that grow during the hot season tend to form buds before harvesting. If harvesting is not timely, the tender stems will quickly grow high. If the supply is delayed for harvesting, S. acuminata can effectively control the high stem pods of the tender shoots, that is, timely picking up the top growth spots or buds of the lettuce in sunny days during the “flat mouth” period. After the top of the plant can inhibit the growth of the top, increase the backflow of nutrients in stems, prevent hollow stems, promote bamboo shoot stem hypertrophy, can be late 5 ~ 7d (days), increase production by 10% to 20%.

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