Inquiries: I am a farmer in Liangzhou District. Why does the greenhouse leek I plant always have yellow tips, but there are no spots and mildew on the leaves, and the field is not contagious?
Answer: The peasant said that the yellowed leaves are free from lesions and mildew, and the field is not contagious. It should be a physiological disease, that is, caused by unreasonable environmental conditions. There are three reasons. First, the temperature inside the shed is too high. Viola is a cold-tolerant crop, the optimum temperature for growth is 12°C~24°C, and over 24°C, the plants grow slowly and the quality deteriorates. Cultivation in the greenhouse, the temperature is high, sometimes even above 30 °C, in case of soil moisture can not keep up, there will be yellow tips; Second, soil moisture can not keep up. Chives are semi-humbic vegetables, and the leaves are drought-tolerant, while the roots are hi wet and require strict water requirements. In the autumn, during the period of vigorous growth, assimilation strengthens, growth increases, and water shortage is not possible. If the soil moisture does not keep up, not only the growth is slow, but also the quality is reduced. The third is lack of fertilizer, especially nitrogen deficiency. Amaranth is a hi-fertilizer crop and has a high requirement for soil nutrients. Its main edible parts are leaves and leaf sheaths. Therefore, more nitrogen fertilizer is needed. In greenhouse production, strong growth in autumn and winter is also the period when most fertilizers are needed. If nitrogen fertilizers cannot keep up, there will be a large area of ​​yellow tips. Therefore, it is recommended to control the temperature during greenhouse planting. The daytime temperature should not be higher than 25°C, and pay attention to topdressing nitrogen and potash fertilizers and water them properly. Yellow tip has emerged, and it can be poured with shallow water once to recover nitrogen and potassium fertilizers with water, and spray 0.2%~0.3% of potassium dihydrogen phosphate or 1% urea on the leaves to help them regreen.
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