In the greenhouse production of the current Langfang area, most of the tomatoes are in the seedling stage, and earlier ones have already flowered and set fruit. In flowering and fruit setting period, tomato often shows a large number of fruit and fruit shedding, which seriously affects the increase of tomato yield. What are the reasons for falling tomatoes? 1, low temperature, rain and sunshine. This phenomenon occurs mostly in deep winter seasons. The optimum temperature for tomato flowering is 25-28°C. When the temperature drops below 15°C, the pollen germinates poorly, and when it drops below 10°C, pollen cannot grow and germinate. Poor fertilization, flower growth hormone deficiency and a large number of flowers. At the same time, the lack of sunshine at low temperatures and cloudy days sometimes leads to long-term glare, organic matter cannot be produced through normal photosynthesis, and flower development is impaired. On the other hand, the humidity of the air in the greenhouse at low temperature, rain, and snow is relatively high, and the pollen grains expand excessively and burst, and pollinating ability is lost and the flowers fall. 2, high temperature and drought. Occurred in the spring and summer. During the fruiting period of tomato flowering, water is particularly needed, and the soil is too dry, especially if it is wet and dry or the plant loses too much water in a short period of time, the growth is poor, and the pollen loses water and infertility causes flowering and fruit drop. On the other hand, when the relative humidity of the air is too low, the stigma and pollen of the flower will shrink and shrink quickly, and the pollen cannot grow on the stigma and fall. In early summer, hot weather will occur. If the greenhouse does not release air quickly, the temperature at noon will be as high as 35-40°C, or even more than 40°C, causing high-temperature burns, pollen abortion, and flowers falling and falling. 3, plant growth malnutrition. After the tomato enters the flower and fruit stage, the demand for various nutrients such as flowering, bud formation, fruit set and fruit growth and development reaches a peak period. If there is insufficient supply of nutrients at this time, there will be a drop in fruit. Malnutrition can also affect the normal development of flower organs and fruits. If pollen is small and the style is uneven, it cannot be normally pollinated and fall off. According to many years of experience of technicians of the Vegetable Management Bureau of Yongqing County, the following measures were taken to prevent tomato drop and fruit drop: 1. Breeding seedlings to enhance plant resistance. 2. Scientifically regulate the temperature and humidity conditions of tomato growing environment. Anti-low temperature in winter and spring, anti-high temperature and drought in summer, timely irrigation and drainage, keep the ground dry, high temperature when the spray mist spray to protect the flowers and protect the fruit. Sunshade nets can also be used to prevent high temperature hazards. 3, timely and rational fertilization after the flower and fruit period to ensure a balanced supply of various nutrients. The use of formula fertilization technology to prevent partial application of nitrogen fertilizer; watering to a small water pouring, to avoid flooding or stagnant water, to ensure the coordination of water, gas, fertilizer, and temperature. It is better to use foliar spray fertilizer, such as spraying 0.2%-0.3% of potassium dihydrogen phosphate during fruit setting. 4, timely chemical regulation. The currently more effective agents are Tomato Spirit and 2.4-D. Tomato Spirit is used at a concentration of 20-40ppm, generally 25-30ppm for spray, dip flower, 30-35ppm for peduncle, 35-40ppm for spring against low temperature and 25ppm for summer against high temperature. The concentration of 2.4-D is 10-20ppm. When the temperature is high, the dip or spray concentration is slightly lower, and vice versa, but it should be prevented.
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