The use of greenhouses to cover plastic film to grow vegetables is to artificially create a suitable ecological environment, adjust the season for vegetable production, regulate market demand, and promote the high quality and high yield of vegetables. This is one of the effective measures to increase farmers' income. From the survey of farmers in most greenhouses, the benefits are obvious. However, some farmers have grown greenhouse vegetables. The results are not satisfactory. Except for vegetable varieties, the “four hazards†constraint is often an important factor causing losses. The so-called “four hazards†are the harms of fertilizers, medicines, droughts, and obstacles.
First, fertilizer damage is actually a hazard of salt accumulation, mainly due to partial application of chemical fertilizers or excessive fertilization to cause soil salinization. After the occurrence of fertilizer damage, the first problem is to inhibit the development of vegetable roots, weakening the absorption of water and fertilizers; second, the concentration of soil solution is too large, the vegetable plant body reverse osmosis phenomenon, leading to physiological wilting or leaf margin Jiao Jiao; Is the introduction of toxic gas hazards; Fourth, causing vegetable deficiencies.
Second, phytotoxicity has obvious phytotoxicity and symptoms are obvious. There are hidden phytotoxicity, symptoms lurking or extending to squat vegetables. The reasons for the occurrence of phytotoxicity are: first, the selection of pesticide species is not the right way or the misuse of herbicides; second, the application concentration is too large; third, the use of inferior pesticides; and (4) the application of high temperature seasons is not avoided. After the occurrence of phytotoxicity, some vegetable leaves soon become chlorogenic; some produce focal spots and perforations; some have fallen leaves, fallen flowers, fallen fruits, or are deformed; the most severe whole plants wither.
Third, drought damage is one of the most critical factors restricting the development of greenhouse vegetables. The reasons for this are the improper location of vegetable greenhouses and the lack of water resources in the local area. Second, there is water, but the water quality is poor. Third, the amount of water is more than enough, and the ditch, canal, irrigation and drainage facilities are not matched, and water is difficult to attract. Drought damage not only affects the timely sowing of vegetables and seedlings, but also affects the normal growth of vegetables. At the same time, it brings great difficulties to the management of vegetables such as fertilization and pesticide application. The effects of droughts sometimes exceed those of fertilizer and phytotoxicity.
Fourthly, the obstacles to success are that in the same greenhouse, the same category or the same kind of vegetables are used year after year or season, and the output and product quality decline year by year. The reasons for the obstacles are: First, the same or similar vegetables prefer a certain kind of nutrient elements; the supplementation of such elements is not timely prone to deficiency of the disease; second, the accumulation of soil pathogens causes disease caused by dead seedlings, such as wilt disease and yellow wilt; Third, the secretion of root vegetables in the same vegetable can easily lead to loss of balance in the soil microbial community structure and cause soil degradation.
Therefore, in order to enable plastic greenhouses to produce more high-quality vegetables, lessons should be learned during the selection and production of the site, and effective response measures should be taken in a timely manner.
First of all, we must choose the site of the site and improve the water system. Before determining the shed, should we check whether there is sufficient water in the shed and whether the water source is polluted? With sufficient water sources, it is necessary to open channels and canals to facilitate water diversion and drainage. Where conditions permit, one tap should be installed in each shed. Standard high should also be equipped with irrigation facilities.
Second, it is necessary to balance fertilization and promote the steady growth of vegetables. First, it is necessary to use organic farmhouse fertilizers that are fully decomposed year-round; the second is to apply refined organic fertilizers, high-energy organic fertilizers, such as Ye Meifeng, Guo Meifeng, etc.; third is to apply nitrogen and phosphorus to reduce nitrogen, stabilize phosphorus, and increase potassium. Fertilizer with fertilizer; Fourth, it is appropriate to fertilize fertilizer in divided doses; Fifth, there is fertilizer damage on one day, spraying a variety of active liquid fertilizers to mitigate the hazards.
Again, science should be used to ensure the safety of vegetables. First, there is a slight phytotoxicity that can be used to strengthen the management of fertilizers and water to restore the normal reproductive function of vegetables; Second, it is necessary to select the right counterpart pesticides, especially herbicides should be used cautiously; the third is to put the pesticide dose, concentration closed, while avoiding Repeated use of a pesticide; four is not allowed to mix pesticides; five is to avoid high temperature application; six is ​​applied herbicide must be cleaned before reuse.
Fourth, we must change crop rotations and adjust the vegetable cultivation environment. First, vegetables susceptible to eggplant, tomatoes, and melons must be planted in different seasons or seasons to grow other vegetable varieties. Second, greenhouses that are prone to successive obstacles must be increased with organic fertilizers to improve the soil. Third, use soil retting agents. Suppression of pathogens; Fourth, the lack of nutrients in the soil, timely supplement of the lack of nutrients.
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