Autumn lettuce is typically sown during the hot summer and early autumn seasons, when high temperatures make seed germination challenging. To ensure successful growth, special care must be taken to produce healthy and vigorous seedlings. The ideal germination temperature for lettuce seeds ranges between 15°C and 18°C, with a maximum of 28°C, and light is essential for proper development. Therefore, it's important to implement low-temperature germination techniques before planting in the summer or autumn.
There are several effective methods to promote germination under these conditions:
1. **Well Water Hanging Method**: Soak the seeds in fresh well water (around 15°C) or cold water for 5 to 6 hours. Rinse them 2 to 3 times to remove mucus and impurities, then dry them slightly. Place them in a damp cloth bag and hang it about 10 to 30 cm below the surface of the well, where the temperature remains around 15°C. Rinse the seeds with well water once or twice daily for 3 to 4 days to maintain moisture and encourage germination.
2. **Refrigeration Method**: Soak the seeds for 24 hours, then rinse and wrap them in gauze. Place them in a refrigerator or freezer at 3°C to 5°C for 24 hours. After that, move them to a cool, well-ventilated area. Germination will occur slowly. When the sprouts turn white, spread them out in a shaded, well-ventilated place with indirect light. Mist them regularly to keep them moist. After 2 to 3 days, when the shoots appear pale green, they are ready to be sown. These germinated seeds grow uniformly and show strong resistance to environmental stress.
3. **Sand Mixing Method**: Soak the seeds for 1 to 2 hours, then mix them with moist sand. Place the mixture on an air-raid shelter or near a water tank, keeping it cool and moist. Germination usually takes 3 to 4 days. This method helps maintain consistent moisture and temperature, which supports better seedling development.
4. **Irrigation Covering Method**: After preparing the seedbed, level and finely till the soil. Sow the dry seeds and cover them with a thick layer of straw. Use straw or bricks to hold the straw in place. Every evening, water the seedbed thoroughly. The seeds will begin to germinate within 2 to 3 days, thanks to the cooling effect of the straw and the regular watering.
5. **Growth Regulator Method**: In high-temperature conditions (30°C to 40°C), you can soak the seeds in a solution of gibberellic acid (5 mg/L) for approximately 8 hours. Afterward, rinse them with tap water and sow them. This technique can increase the germination rate to as high as 80%. Once sown, use a shade net, cloud cover, or plant them under a melon stand to provide protection from excessive heat. Alternatively, you can intercrop them with un-harvested cabbage to create a more favorable microclimate.
By using these methods, farmers can successfully cultivate autumn lettuce even in hot weather, ensuring strong, healthy seedlings and higher yields. Each technique has its own advantages, so choosing the right one depends on local conditions and available resources. With careful management, the challenges of summer and autumn lettuce cultivation can be effectively overcome.
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