In the wintering cultivation of cucumber, "yellow ring leaf" generally occurs, which seriously affects the yield and economic benefits. This phenomenon is not caused by infectious diseases and is generally a physiological disease. First, the symptoms of cucumber in the lower part of the occurrence of more leaves. At the beginning, the edge of the blade is yellow, and the back edge develops along the edge of the blade toward the inside of the blade. There is a greenback phenomenon of 2 to 3 centimeters in width, followed by a yellow-green color, and it surrounds the blade one week. It is called "yellow ring leaf." In severe cases, the yellow ring scorch and the leaves die. Second, the occurrence of conditions and laws of the disease caused by the lack of potassium plants. Severe at low temperatures. This is due to the low ground temperature and the reduced ability of microorganisms in the soil to cause the imbalance of ammonium nitrogen and nitrate nitrogen in the soil and inhibit the absorption of potassium. Therefore, despite the lack of potassium in the soil, cucumbers still show symptoms of potassium deficiency. The soil is too sandy, organic fertilizer is insufficient, and when potassium is lacking, it is heavier. In the greenhouse, too low ground temperature can also produce cucumber yellow ring. Third, prevention and control methods (a) increase the temperature in the greenhouse. Improve the structure of solar greenhouses, such as thickening walls, digging cold trenches, increasing the height of greenhouses, increasing the angle of incidence of sunlight, increasing the incidence of sunlight, and using plastic films and grasshoppers with better insulation performance for double coverage, northern greenhouses Side hanging reflective screen. (B) increase the application of organic fertilizer, moderate application of ammonium nitrogen fertilizer. When using chemical fertilizers, pay attention to the proper combination of nitrogen, phosphorus and potassium. (C) During the growing period of winter, spraying Shuofeng 481 solution once can promote photosynthesis and root growth. (4) When the temperature is low, spray 0.2% potassium dihydrogen phosphate once every 3 to 5 days to supplement the potassium supply of the plant. At the same time, enhance the plant's ability to resist cold.
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