The kiwifruit is so happy that it is afraid of embarrassment, hi light and fear of exposure. It naturally grows in places where it avoids yin and dampness, and it is almost absent in sunny areas and dry areas. Zhouzhi County has more than 20 years of kiwifruit cultivation history. Each summer's hot weather has a very large impact on kiwifruit. Correctly understanding the adverse effects of high temperature on kiwifruit production and taking corresponding preventive measures are of great significance to the development of the monkeyfruit industry.
First, the impact of high temperature on kiwifruit
1. Influence on the leaves During the months of June and July of each year, when the temperature reached above 35°C, the leaves of the kiwifruit were exposed to strong light for 5 hours, which meant that the leaf margin was chlorotic, and it turned brown and black. If this high temperature lasts for more than two days, the kiwifruit will show a blackening of the leaf margin and a fiery appearance. When it burns severely, it can cause early defoliation and even dead trees.
2, the impact on the fruit temperature continued to occur, can make the part of the fruit surface contact with sunlight dark brown, peel cell keratinization, thereby limiting the growth of the fruit. Mild day-burning fruit ripening results are smaller and the fruit surface is unclean, losing the value of the goods it deserves. In severe cases, the fruit is soft rot or even ulcerated.
Second, the law of high-temperature sunburn
The daily heat caused by high temperature mainly occurs in the orchard where the tree vigor is weak. According to the survey, under the same conditions, the incidence of daily burning in orchards from 3 to 5 years can reach 15% to 30%; in adult gardens aged over 5 years, the incidence is only 2% to 3%. Among the same age trees, the number of new shoots is more than 20, the incidence is 50%-8%, and the number of new shoots is less than 10, and the incidence rate can reach 20%-30% or even higher. It can be seen that the orchard leaf surface coefficient is the key to affect the extent of the occurrence of sunburn. In addition, the ground management of orchards is also an important factor in the occurrence of solar flares. Under the same conditions, the overgrown orchards are much lighter than the ploughed orchards. Parks that have grass and more than 60% coverage are generally not burned. Even in the same orchard, the growth of a robust tree with the daily burning of individual weak trees is intact.
Third, the cause of high temperature burning
1. The kiwifruit leaf is related to the special structure of the leaf blade. To a certain extent, the leaf blade can play the role of shading, but the physiological structure of the kiwifruit leaf is rather special. Because its leaf hole does not have two guard cells, it cannot Body water transpiration is effectively controlled. When the temperature is too high, and the water absorbed by the roots does not meet the transpiration requirements, the water in the tree loses its balance. The first part that expresses water loss is the leaf margin with the most distribution of leaf holes.
2. It is related to climate and phenology period Since Zhouzhi is located in the Loess Plateau and the climate is relatively dry, a continuous high temperature of 35°C or more begins to occur in June each year. This period is the peak of kiwifruit fruit growth. Fruit development and new shoot growth require large amounts of nutrients and water. At this time, the leaves are tender and the peel is thin. If the nutrients and water are not sufficient, the tree will be relatively weak and resistant. Reduced power. Therefore, in June and July, the peak period of solar flares occurred. In August, the trees grew more leafy, the maturity of leaves and fruits increased, and the daily burning decreased.
Fourth, the relationship between high temperature and other diseases
1. The symptoms of burning with brown spot and burning with brown spot are very similar. In production, the masses often misunderstand the day burning as brown spot and spray control. The result is often due to excessive temperature caused by phytotoxicity. In fact, as long as careful observation, the two can still be distinguished:
(1), brown spot symptoms. The disease is a fungal disease. From the symptomatic point of view, although the brown spot can also cause the leaves to become dark, the disease firstly produces dark spots along the side of the veins, and gradually expands later. Zhouzhi areas often begin to develop in August.
(2), daily burning symptoms. Ricin is a physiological disease and pathogen free. In terms of time, it mainly happened in June-July. The disease has a rapid onset. Within one day, the leaf margin can be darkened, but the color is lighter than that of brown spot; if the leaf margin is dark, but the leaf margin is still green, except for phytotoxicity and fertilizer damage. Day burn.
2. High temperature and root rot Root rot is a devastating disease of kiwifruit. The pathogens are mainly fungi and bacteria. Because the diseased area is in the ground, the tree often shows symptoms when the disease is severe, and the symptoms on the tree are mainly due to damage to the roots, limiting the absorption and transportation of nutrients and moisture, causing the tree to show symptoms of wilting and even death. . High temperature can aggravate the transpiration of kiwifruit, thus intensifying the contradiction between supply and demand of water, making the tree repetitively appear wilting day and night, and finally died.
Fifth, take measures to prevent high temperature hazards
Taking grass system is one of the effective ways to prevent high temperature hazards. According to a comparative survey conducted between Qingqinyuan and Shengcaoyuan, when the temperature in the natural world reaches 35°C, the temperature in the Qingnong Park can reach 45-48°C. The reason that the temperature in the garden is higher than the natural temperature is that the orchard is affected by direct sunlight and reflected light from the ground, and the air humidity in the park is also about 5% lower than the natural humidity. In recent years, Zhouzhi has promoted the system of weeding and promoted and guided fruit growers to plant hairy pods in the orchards. The incidence of sunburn has been greatly reduced. The reason is mainly to reduce the reflected light in the garden, reduce the temperature, and increase the air humidity in the park. After measuring the orchard that had been growing grass for more than two years, the air humidity in the garden was 15%-18% higher than the natural humidity, and the moisture in the air compensated for the partial moisture in the transpiration. In addition, the cultivation of robust trees, reasonable branches, and scientific summer cuts are also a good way to prevent heat hazards.
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