Why do leeks have yellow leaves?

Why do leeks have yellow leaves? How to solve the yellow leaves of leek has the following possibilities: first, lack of trace elements. Leeks with yellow leaves are generally not sprayed or sprayed with trace elements such as iron, copper and zinc, and yellow leaves are formed due to the lack of such elements. Second, partial application of nitrogen fertilizer, the imbalance of nitrogen, phosphorus and potassium, thus inhibiting the absorption and utilization of trace elements, the formation of yellow leaves. Third, excessive application of fertilizer containing humic acid changes soil physical and chemical properties and presents acidification, which is not conducive to root development and growth, poor absorption and transformation of nutrients, and leaf yellowing due to malnutrition. Fourth, only pay attention to the application of chemical fertilizer, ignore organic fertilizer, reduce soil porosity, poor permeability, poor root respiration, resulting in malnutrition and yellow leaves. Fifth, blind watering, excessive humidity in the field, affecting root respiration and nutrient absorption, resulting in yellow leaves. Sixth, the damage of diseases and insect pests, especially after the damage of leek maggots, the absorptive capacity of roots decreased, the nutrient supply of leaves was insufficient, and in serious cases, it dried up and died. Leek after the emergence of yellow leaves to distinguish different situations, targeted prevention in advance, generally can take the following measures: 1, increase the application of organic fertilizer, reasonable use of nitrogen, phosphorus and potassium fertilizer, supplement trace elements to ensure a balanced and adequate supply of nutrition. 2. According to the fertilizer characteristics of leek, pay attention to the application of phosphorus, potassium and trace elements during the stubble period, 50 kg of Chuxing potassium sulfate compound fertilizer per mu and 10 kg of medium and 15 kg of trace element fertilizer can be applied per mu from the middle and last ten days of September to the first and middle of October, or before the plastic shed, and foliar fertilizers such as chlorophyllin and Shibao are sprayed 2 times during the growing period. 2. Timely and reasonable watering. In the case of ensuring the wetness of the soil in the field, the amount of water and times of watering are reduced, the interval of sandy soil is shorter, the interval of clayey soil is longer, and the soil moisture is loosened by ploughing after watering, and the soil permeability is increased. 3. Control diseases and insect pests and use insecticides with high efficiency and low toxicity to reduce the harm of leek maggots. It can be irrigated once in the middle and second ten days of August to the first and middle of September, and three to five days after the shed is fastened. Generally, it is possible to irrigate phoxim with 1000kg / mu or 1000g / mu, or when the leek is 5cm high, 1500g / mu and 2000g / mu. Click for more leek planting techniques click to see more vegetable planting techniques