What are the reasons for garlic yellow leaves? How to prevent it?
In the yellow leaf plot of garlic, the garlic is reduced by 40%-50%, and the garlic is reduced by 30%-40%, which becomes a major obstacle to the increase of garlic. So what are the reasons for garlic yellow leaves? How to prevent it?
Occurrence characteristics and symptoms:
Continuously planting garlic for more than 10-20 years, only chemical fertilizer is applied, and plots where organic fertilizer is not applied are heavy; winter temperatures are high, and years with less precipitation occur early and heavy, and early spring and spring cold increase. Generally, symptoms appear at the end of February and early March. The initial yellow leaf spots occur. After 2 to 3 years of heavy planting, the area gradually expands, and finally the whole plot shows yellow leaves. First, the tip of the leaf turns purple-red, and gradually develops along the leaf vein to the leaf sheath, which is chlorotic and yellowish. In severe cases, the whole blade is dry and dead.
Root dysplasia, the death roots are 3 to 5 times higher than the normal plants, the plants are obviously dwarfed, the garlic stalks are short, the serious plants can not be convulsions, and the diameter of the garlic is about 5cm.
Yellow leaf reasons:
1. Fertilization
The application of chemical fertilizers in large quantities, while neglecting the application of micro-fertilizers and organic fertilizers, combined with the long planting time, lead to serious imbalance of nutrients in the soil, especially the serious lack of some trace elements necessary for the growth of garlic (such as calcium deficiency, magnesium deficiency can be directly Leading to the dryness of garlic yellow leaves, premature aging, can not meet the normal growth of garlic, due to the failure to rational fertilization caused by the yellow leaves accounted for 50% of the proportion of yellow leaves.
2, many years of heavy
The planted land has been planted for 15 years, and the number of pests in the field is high, and the pests and diseases are increasing year by year. The leaf blight of the yellow leaf block occurs early and is harmful. The average disease rate of leaf blight of the yellow leaf block is 65%, the diseased leaf rate is 14.2%, and the onset period is about 15 days earlier than normal. The hazards of cockroaches and root mites also increase the yellow leaves of garlic. According to the investigation and analysis, the yellow leaves accounted for 30% of the yellow leaves caused by pests and diseases, especially the garlic leaf blight can directly cause yellow leaves.
3. Environmental factors
According to many years of systematic investigations, in the years when winter temperatures are high and precipitation is low, garlic yellow leaves occur early, soil moisture is poor, affecting the normal growth of garlic roots and nutrient and water absorption. Three large cold currents at the end of March Garlic freeze damage, cold damage, so that its resistance to stress is reduced, which is also conducive to the occurrence of yellow leaves, causing garlic yellow leaves to occur earlier than normal, large area, and serious damage.
4, soil compaction
The front of the garlic is planted with corn. After the corn is harvested, the straw is not fermented and returned to the field. Instead, it is burned in the field, causing a large number of beneficial microorganisms to be burnt to death, destroying the surface structure of the soil, causing soil compaction and alkalization, which is not conducive to garlic. The normal growth of the roots represents yellow leaves.
Governance measures:
1, rotation
It is best to plant 2 to 3 years of garlic for 1 year of wheat or other crops. The maximum planting rate for a year cannot exceed 5 years.
2. Adding bio-organic fertilizer
Combining fertilization and fertility to cultivate land and land, generally 667m2 high-quality soil fertilizer 4000kg, cake fertilizer 50kg, decomposed straw more than 200kg, can effectively supplement the medium and trace elements necessary for the normal growth of garlic, and also loose the soil and promote the root system. development.
3. Biological control
(1) Treat soil during autumn seeding. Use 3-5 kg ​​of Yifuyuan soil per acre to improve your body, plow the soil after spraying, smash the head after ploughing, resist heavy mites, increase the beneficial microorganisms and beneficial organisms in the soil, improve the soil, and reduce the source of pests and diseases. Control the damage of garlic roots and cockroaches years ago.
(2) Control the damage of garlic leaf blight, stem rot, root lice and cockroaches in early spring, and combine the disease prevention and spraying of Yifuyuan garlic to increase the production of treasure, improve the leaf nutrition of garlic, and play the role of disease resistance and yield increase.
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