Recently, many vegetable farmers have reported that the tomato seedlings and cucumber seedlings that have not been planted for a long time frequently wilt and die. However, when these seedlings were first sent from the seedling factory, the leaves were dark green and growing vigorously. So what are the reasons? What about the occurrence of dead seedlings?
Cause Analysis
Excessive watering The temperature of retting roots in summer is high, vegetable plants grow fast and require a large amount of water. Vegetable farmers generally water more frequently, but excessive watering is very unfavorable to the growth of seedlings. On the one hand, excessive watering will cause the root layer of the seedlings to be relatively shallow, and the root system will hover on the surface without deep penetration, weak resistance and vulnerable to pests and diseases, and the phenomenon of weak and dead seedlings will appear; on the other hand, severe excessive watering will cause soil The reduction of oxygen in the medium can cause retting of roots and dead trees, especially for greenhouses with poor soil stickiness and water seepage.
The seedlings that have just been planted by high temperature burns are generally tender before the slow seedlings, with high summer temperatures and strong sunlight. Under the high temperature and strong light environment, the transpiration of the seedling leaves is strengthened, and it is easy to wilt, which will lead to dead trees. At the same time, the high temperature environment is not conducive to the growth of the root system, and the root system has poor water absorption capacity, resulting in insufficient water supply. In addition, high temperature and strong light environments such as air-dried blades are prone to burns.
Root and stem diseases Root and stem diseases are the main cause of vegetable deaths, especially for sheds that have been planted for a long time. The soil environment is getting worse and worse. Even if the soil is sterilized before planting, it is sometimes difficult to avoid the roots. The occurrence of disease. In addition, the greenhouse environment with high temperature and high humidity in summer is very conducive to the occurrence of *** disease, such as damping-off, wilt disease, stem base rot, etc., which cause the epidermis at the base of the plant stem to rot, which is what vegetable farmers say The "bad neck roots".
1. Damping-off disease: The damping-off disease occurs at the roots or the base of the seedling stems on the soil, which turns brown in a water-soaked state, the diseased part shrinks and loses support ability, the seedling falls to the ground and quickly wilts.
2. Stem base rot: mostly occurs after seedlings are planted. Dark brown irregular lesions occurred at the base of the stem, which expanded to the left and right, causing the cortex at the base of the stem to become necrotic, constricted and thinner, and the above-ground leaves wilted and turned yellow, and the whole plant died. The reason for this is that the soil is moist, the continuous cropping causes the accumulation of pathogens, and the wounds at the base of the agricultural operations cause the invasion of pathogens.
3. Blight: Mainly damage the base of seedling stems or underground roots, initially oval or irregular dark brown spots, the diseased part gradually sinks, overflowing and shrinking, when the disease spot expands around the stem for a week, it withers and dies, but does not fall down. Lightly diseased plants only saw brown sunken spots but did not die. When the seedbed humidity was high, the diseased part could see light brown spider filamentous mold.
Immature manure and chemical fertilizers burned roots. Before planting seedlings, incompletely decomposed manure was applied in the base fertilizer, or excessive chemical fertilizers were applied, which caused the burned roots to die.
Responses
First of all, rationally fertilize and reduce the amount of base fertilizer used in the summer. In order to prevent the manure from incompletely decomposing and causing burning of roots, use commercial organic fertilizers or bio-organic fertilizers; at the same time, use less chemical fertilizers or use controlled-release chemicals Fertilizer, reduce the damage of fertilizer to root system.
Secondly, the medicament dipping dish is very important. Now, the dipping dish has become an indispensable measure for vegetable planting. The effect of dipping pan is mainly manifested in three aspects: first, it can control or reduce the damage of root diseases at the seedling stage of crops; second, it can control or reduce the damage of underground pests to seedlings; third, it can promote root development and shorten the slow seedling time.
Commonly used root dipping formulas are: hymexazol 1000 times liquid, Pulique 500 times liquid, 2% emamectin benzoate 1500 times, intelligent compound chitin 400 times liquid, or 963 root nutrient 300 times liquid, and soak in the solution. Seedling plate.
Third, water frequently in the early stage and water control in the later stage. After cultivating strong seedlings and planting, water in time before slow seedlings. The planting water should be thoroughly watered. According to the weather and soil conditions, see dry watering to avoid high soil temperature causing seedling burns. Slow seedling water should be irrigated in the morning, and the amount of water should not be too large. Generally, the water should flow to the front end of the planting row. In order to prevent root diseases, it can be flushed together with microbial agents, such as Mumei Tuligenbao. After planting the seedlings for about 10 days, the water should be properly controlled and hoeed in time to promote the rooting of the root system and cooperate with the rooting agent to raise the roots.
Finally, promptly irrigate the roots for disease prevention and planting about 7 days after planting, you can spray the base of the stems with hymexazol, Pulique and rooting agent or chitin, and do not water within 1 day before and after the roots are irrigated.
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