The first is the lack of trace elements. Yellow leeks are generally not applied or sprayed with trace elements such as iron, copper, and zinc. Yellow leaves are formed due to the lack of such elements.
Second, partial application of nitrogen fertilizer, NPK imbalance, thereby inhibiting the absorption and utilization of trace elements, the formation of yellow leaves.
Third, over-application of fertilizers containing humic acid, changes in soil physical and chemical properties, showing acidification, is not conducive to the development and growth of roots, nutrient absorption and conversion is poor, due to malnutrition and leaves yellow.
Fourth, only pay attention to the application of chemical fertilizers, ignoring organic fertilizer, soil porosity decreased, poor permeability, poor root breathing, leading to malnutrition yellow leaves.
The fifth is blind watering, and the humidity in the field is too large, which affects root respiration and nutrient absorption, resulting in yellow leaves.
Sixth, pests and diseases, especially the earthworms, have reduced root absorption capacity, insufficient leaf nutrient supply, and severe dry death.
After the yellow leaves appear in the leek, it is necessary to distinguish between different situations and to prevent them in a targeted manner. Generally, the following measures can be taken:
1, increase the application of organic fertilizer, a reasonable use of NPK fertilizers, trace elements, to ensure a balanced and adequate supply of nutrition. According to the characteristics of leeks and demand for fertilizer, during the raising season, the application of phosphorus and potassium fertilizers and trace elements should be emphasized. From mid-to late September to mid-October, or before the shed, 50-75 kg of Chuxing potassium sulfate compound fertilizer should be applied per mu. The application of trace element fertilizer 10 ~ 15 kg; growing season foliar spray 2 to 3 times chlorophyll, spray Bao and other foliar fertilizer.
2, timely and reasonable watering. In order to ensure the soil moisture in the field to reduce the amount of watering and the number of times, the sand interval is generally shorter, the clay soil interval is appropriate longer, after watering, cultivating loose soil wet, increase soil permeability.
3, control pests and diseases, the use of high-efficiency and low-toxicity pesticides to reduce the harm of earthworms. In the middle and late August to mid-September, after the shed, 3 to 5 days after the shed, one dose of water can be applied. Generally, 1000 to 1500 g of Nendot or 1000 to 1500 g of Nongpo can be used per mu, or 5 to 5 kg of leek. Phoxim is watered at a height of 10 cm and is 1500-2000 g per mu.
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