Taller seedlings are among the most common and easily formed abnormal seedlings in rapeseed fields. The primary cause of this issue is excessive seeding density, overuse of fertilizer and water, and extended seedling age. As a result, the main stem becomes elongated while still in the seedbed, especially in early and mid-season varieties. These tall seedlings are prone to lodging after transplanting, have exposed stems, and are more vulnerable to cold damage. In severe cases, their stems may freeze and crack, leading to poor branching and reduced yields. To avoid this, it's important to manage planting timing and apply growth regulators. At the 3-leaf stage, spraying 15% paclobutrazol at a rate of 50 grams per acre with 40–50 kg of water can effectively prevent tall seedlings from forming.
Sowing too early or too late can also lead to problems. If sown too early, higher temperatures accelerate leaf growth, making seedlings weak and more susceptible to frost damage during winter. On the other hand, sowing too late results in slower growth due to lower temperatures, which hinders the development of strong autumn and winter growth.
Leggy seedlings often occur when there is an excess of available nitrogen, combined with high temperature and humidity. This leads to excessive vegetative growth, resulting in weak, thin stems and tender tissue that lacks resilience. After transplanting, these seedlings often wilt, take longer to green up, and are more likely to suffer from frost damage, which negatively affects their ability to survive the winter and thrive in spring. To prevent this, proper sowing timing and controlled fertilization are essential. For seedlings showing signs of excessive growth, applying chlorothalonil at a concentration of 50–100 ppm at the 4-leaf stage can help regulate their growth.
Thin and weak seedlings, often referred to as "shady foot seedlings," typically develop when seedlings are crowded and lack sufficient light. This causes them to grow weak, with low chlorophyll levels. To prevent this, it's crucial to prepare enough seedbeds—generally about 20% of the total planting area—with well-drained, fertile soil. After emergence, timely thinning and adequate watering and fertilizing are necessary. At the 3-leaf stage, any weak or non-emerged seedlings should be removed, and each remaining plant should receive a dose of nutrients to promote healthy growth.
Stiff or dwarf seedlings, also known as short seedlings, usually result from poor seedbed conditions, such as infertile soil, insufficient water and nutrients, or prolonged waterlogging. These conditions lead to poor root development and stunted growth. Additionally, late sowing and exposure to cold waves can contribute to this problem. Affected seedlings have short stems, thin roots, and small, pale leaves with low chlorophyll content. Their photosynthesis is weak, and they grow slowly, often failing to recover after transplanting. To prevent this, it's important to maintain proper seedling age (around 35–40 days for early and mid-maturing varieties) and ensure consistent water and nutrient supply. During periods of shortage, foliar sprays or top-dressing can help compensate for deficiencies and encourage robust growth.
Vaccine For Prevention Of Rabies
Rabies vaccine is used in two ways. Rabies vaccine is given to persons who have been exposed (eg, by a bite, scratch, or lick) to an animal that is known, or thought, to have rabies. This is called post-exposure prophylaxis. Rabies vaccine may also be given ahead of time to persons who have a high risk of getting infected with rabies virus. These persons include veterinarians, animal handlers, or travelers who will spend more than 1 month in countries having a high rate of rabies infection, and persons who live, work, or take vacations in wild areas of the country where they are likely to come into contact with wild animals
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