The phenomenon of rapeseed is more common, mainly characterized by yellowing and redness of leaves, curling of heart leaves, growth basically stopped, and even dead roots, resulting in insufficient winter hair, thin seedlings, and reduced rapeseed yield. In the production, corresponding prevention measures should be taken for different situations of the dead seedlings. So what are the causes of rapeseed?
1. Preventing seedling aging and causing dead seedlings
Over the age of the seedbed, it is prone to high seedlings, the roots are poorly viable, and the new roots are not planted in the field, and the new leaves are not long. The leaves are reddened because the roots are unable to absorb or seldom absorb nitrogen and phosphorus. Therefore, rapeseed should be transplanted at the appropriate age, and it is usually transplanted in time for 30 to 35 days. The density should be appropriately advanced, and the nutrient conditions of the seedbed should be deteriorated to form an "old seedling". In order to transplant rapeseed in a timely manner, late rice should be harvested in due course. If you use Bantian no-till transplanting, you can transplant rapeseed 3 to 5 days earlier.
2. Protection against waterlogging or drought
Some low-lying paddy fields and rice fields under the Kutang do not prematurely drain the ditch, the groundwater level is high, the soil is deficient in oxygen; or the paddy fields that continue to fall in autumn and have not been ditched and have serious water accumulation are prone to lack of oxygen. Waterlogging caused by hypoxia caused the decay of rapeseed roots, resulting in dead seedlings. If the rapeseed is transplanted, the surface layer of the soil will be hardened and the roots will not grow. The water and nitrogen and phosphorus required for the plant will not be satisfied, and the leaves will be red and stiff.
Therefore, the rapeseed field should be opened with three ditches, and the narrow ditch should be implemented. At the same time, it is necessary to pay attention to clearing the ditch. In case of drought, it can be ditched, but avoid the large water tank, so as to avoid soil water and oxygen deficiency.
3. Prevention of boron deficiency causes dead seedlings
Rape is sensitive to boron, and for rapeseed, most soils are deficient in boron. When the soil is insufficiently boric, the rapeseed is characterized by growth stagnation, rotten roots and heart, and the roots must be swollen. Therefore, the application of boron fertilizer in rape can prevent the dead seed caused by boron deficiency. According to the test, 0.1%～0.2% borax solution was used as the root water and drenched into the crotch. After 7 days, the survival rate of rapeseed plants in the boron application area was 96.7%, and the growth potential was good. The survival rate of the non-boron plant was only 79.1. %.
When transplanting, if there is much rain, do not need to apply root water, mix borax with organic fertilizer and use it as base fertilizer, and apply rapeseed root to 0.1%~0.2% borax solution.
4. Prevention of pests and diseases caused by dead plants
The main pests and diseases of rapeseed are aphids, viral diseases and cabbage caterpillars. The mites are harmful, the leaves are curled, and the growth point is not long. The virus disease causes the leaves to shrink, hard and brittle, and the growth is stagnant. The cabbage worm harms the nick. Their serious harm can cause deadlocks. Viral diseases are transmitted by mites, and they can prevent diseases. When it is found that individual plants have aphid damage, it is necessary to control the whole hill rapeseed. Generally, 10% of the acres are cleaned (one pass net, big hero, imidacloprid) or 2.5% enemy killing.
5. Anti-soil knots cause dead seedlings
The rapeseed field with heavy soil, soil compaction, poor permeability, delayed growth after rapeseed planting. Therefore, rapeseed should be combined with topdressing and cultivating loose soil before winter to facilitate ventilation and protection.
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