Environmental requirements and cultivation techniques of Western lettuce

Environmental requirements and cultivation techniques of Western lettuce

Western lettuce is introduced from the West, hence the name Western lettuce, which belongs to lettuce and Compositae. Leaf lettuce is fed with fresh young leaves, and its export is mainly based on heading. Western lettuce has straight root system, shallow distribution and weak ability to absorb water and fertilizer. The ball of heading lettuce is round, flat, conical, cylindrical and tender, which is the main edible part.

1 characteristics of western lettuce

Western lettuce belongs to straight root system, the ability to absorb water and fertilizer is weak, the soil is deeper during direct seeding, the lateral root is less, and the stem is short and shrinking, which extends and thickens slowly with the exuberant growth of plants. Flower buds continue to extend after differentiation, thickening to form flower stems, leaves for root tips, mutual growth on short stems, as the main edible part [Jishan Huayao].

2 requirements for the environment

2.1 temperature

Western lettuce is a semi-cold vegetable, the lowest temperature of seed germination is 4 ℃, the optimum temperature is 15-25 ℃, and the germination is damaged when it exceeds 30 ℃.

2.2 Lighting

Western lettuce requires medium light temperature, light is too strong, the temperature is too high, not easy to ball, poor quality. Lack of light, mutual shade, affecting leaf growth and photosynthesis.

2.3 moisture

Western lettuce has more leaves, tender tissue, large evaporation, high water consumption, and is not resistant to drought. Seedlings should keep the soil moist, not too dry and too wet, so as to avoid seedling aging or overgrowth, properly control moisture at the heading stage and promote the growth of rosette leaves. during the heading period, there should be adequate water supply, insufficient water and bad pilling, resulting in bitterness. Pay attention to water control in the later stage, too much water is easy to crack ball, rot root, and lead to disease.

2.4 soil nutrition

The root distribution of western lettuce is shallow, the root system has a high demand for oxygen, and it grows poorly in the clayey and barren land. Therefore, it is required to have a good structure, and it is better to have soil or sandy loam with rich organic matter and strong water and fertility conservation, and pay attention to crop rotation. Western lettuce likes slightly acidic soil, the pH value is about 6, the pH value is above 7, the growth is poor, and the yield is the lowest when the pH value is less than 5. There is a high demand for nitrogen fertilizer, nitrogen deficiency inhibits the growth and area increase of seedlings, and phosphorus and potassium fertilizer is also indispensable. Phosphorus deficiency in seedlings resulted in not only fewer leaves, but also small plants, low yield and poor quality, while potassium deficiency affected leaf growth and weight, as well as nitrogen uptake, N ∶ P2O5 ∶ K2O=2 ∶ 1 ∶ 4 [3].

3 cultivation techniques

3.1 sowing and raising seedlings

The average altitude of Anning City is 1800m, and the annual average temperature is 14.7℃, which can be sown almost all the year round. However, the quality is better and the yield is higher from October to April of the following year. It is suitable for direct seeding in spring and summer, and seedlings and transplanting in autumn and winter. The soil should be kept moist after sowing to before seedling emergence, and the seedlings should be watered in the morning and evening when the temperature is high. There are 2 or 3 leaves in 10-15 days after seedling emergence, so that the seedlings can maintain a certain nutritional area. Western lettuce is sensitive to phosphate fertilizer and a certain amount of phosphate fertilizer should be added to topdressing to promote the growth of seedlings. In order to prevent the harm of downy mildew at seedling stage, 75% chlorothalonil 600 times or 70% methyl topiramate 1500 times can be sprayed twice. The seedlings can be fixed when there are 4-5 leaves in direct seeding, and it is better to choose strong seedlings with good growth and no disease when fixing seedlings.

3.2 colonization

Dig deep into the sun immediately after harvest, apply sufficient base fertilizer before planting, apply 45 t/hm2 of farm manure, 450 kg/hm2 of common calcium, 150 kg/hm2 of potassium sulfate, 225 kg/hm2 of urea, and mix well into the soil. When the seedling is about 30 days old and has 4-5 leaves, it can be planted with more soil and less root damage. The planting specification is 30 cm plant spacing and 35 cm row spacing, the suitable planting depth is not burying the heart, and the planting density is about 60 000 plants / hm2.

3.3 Field management

3.3.1 Irrigation. Root water was poured immediately after planting to facilitate the survival of slow seedlings. In the early stage of seedling growth, the seedlings were kept wet and watered every 5 to 7 days to promote the growth of roots and rosette leaves. In the middle and later stage (sufficient water in the heading period) irrigation should be uniform, pay attention to drainage in rainy days, keep rosette leaves green, dry and wet uneven easy to produce crack ball, hollow, core is not tight. Stop irrigation in the late stage of heading to prevent cracked balls. Pay attention to the control of moisture before harvest so as not to affect the quality and harvest transportation.

3.3.2 topdressing. Western lettuce needs more nitrogen fertilizer, and it is skillful to apply topdressing by stages under the condition of sufficient base fertilizer. Generally, topdressing is required for 3-4 times, and 0.3% urea water is irrigated for the first time 3-5 days after planting slow seedlings, and then topdressing every 7-10 days, with urea 75 kg/hm2+ and 15 kg/hm2 each time. The principle of "promoting ahead, controlling in the middle and attacking after attack" should be adopted, early application of nitrogen fertilizer to promote growth, middle control and prevention of apprentice growth, late application of topdressing to attack leaf balls, and topdressing should be combined with watering.

3.3.3 weeding by ploughing. Weeding and ploughing for 2 to 3 times at seedling stage, and stop ploughing after closing the row [4].

3.4 Disease and pest control

The common diseases of western lettuce are Botrytis cinerea and downy mildew, and the main insect pests are aphids, Liriomyza huidobrensis and so on. Spraying medicine in time at the initial stage of the onset of Botrytis cinerea can choose 70% methyl topiramate wettable powder 1 500 × 2 000 times and 50% Sukeling wettable powder 3000 times, once every 7 times 10 days, 2 times 3 times successively, and stop using the medicine 15 days before harvest. To control downy mildew, spray 75% methyl topiramate 1 500 times twice at the seedling stage; spray 1 000 times 25% Ruidui wettable powder and 500% 600 times 75% chlorothalonil wettable powder in the early stage of the disease, spray every 10 days, spray 2 times 3 times, and stop spraying 15 days before harvest. Aphids were sprayed with 2000 times of 20% fenvalerate EC, and the drug was stopped 10 days before harvest. Liriomyza huidobrensis was sprayed with 800 times of green vegetable treasure EC and 2.5% of chlorhexidine EC 1 200 to 1 500 times for 2 or 3 times in a row, and the drug was stopped 7 days before harvest.

3.5 harvesting

After 50-60 days of planting, the leaf bulbs grow fully and should be harvested in time. The mature period of western lettuce is not very consistent and should be harvested in stages and timely. When harvesting, the plants with tight leaf balls are selected to cut off the external old leaves from the ground, and the water vapor on the knife edge is needed to dry when harvesting. Handle it gently during harvest to avoid squeezing and crushing the leaves, pack it in time, cold it to the cold storage, classify, pack and sell it.