Freezing damage Once the vegetables are subjected to freezing injury, the growth is inhibited. If the temperature of the strawberry in the greenhouse is lower than 6°C, the growth will stop; if it is heavy, the plants will be partially necrotic or the whole plant will die. The main measures for preventing freezing Remove snow: In case of snow and ice disasters, remove snow from the shed and prevent the shed from being collapsed. Multi-layer covering: In the large shed, a small arch shed is added. In the evening, multiple layers cover the cold insulation. In the day, the covering is removed to increase the light. Moderate ventilation: due to long-term closed management, low temperature, high humidity, and no sunshine in the shed, after the snow or sunny days, it should be timely, moderately shaded and gradually uncovered to prevent the plants from “sweeping†due to sudden water loss. Control watering: control watering or filming on the ground, reduce air humidity in the shed, maintain and increase ground temperature, and improve the light transmission conditions of the shed film. Rational fertilization: Appropriate control of nitrogen fertilizer, organic fertilizer, and phosphorus and potassium fertilizers. For unvictimized or lightly damaged vegetables, spray 0.2 to 3% of potassium dihydrogen phosphate solution for 2 to 3 times as appropriate, yellowing and nitrogen deficiency. Plants can also be sprayed with 2-3 times 0.3% urea solution. Fat damage Excessive application of nitrogen fertilizers, compound fertilizers containing high amounts of nitrogen, and organic fertilizers that are not decomposed in the enclosed vegetable greenhouses are most likely to occur with ammonia or nitrous acid gases when they are neither covered with soil or covered with soil, nor ventilated in time. Poisoning. After being smoked by ammonia, water-stained patches or spots appeared in the lower leaves of the plants, which turned yellow-brown till it died. In the flowering period, tomatoes, etc., fell after the damage, fruit drop or flower buds died. Under acidic or low-temperature conditions, nitrite accumulation in the soil is likely to produce nitrous acid gas poisoning. The main symptoms of the victim crops are water-stained spots between leaf margins or veins. The rapid chlorosis becomes yellow-brown or yellow-white. Only the leaf veins are green and even whole leaves die. According to the causes of fertilizer damage, take appropriate measures: Rational fertilization: Reasonable fertilization based on soil characteristics and crop needs is the fundamental measure for prevention and control of various types of fertilizer damage, especially for nitrogen fertilizers. The amount of one-time fertilization should not be too large. After the basal fertilizer is applied, it must be timely covered with soil or fully mixed with the soil; the topdressing fertilizer must be deeply applied to the soil or timely watered after application, and generally it should not be scattered on the surface. Timely ventilation: Especially after fertilization in early spring, it is prone to toxic gas poisoning. Once it occurs, it is necessary to timely improve ventilation conditions and discharge harmful gases. Application of slow-release fertilizers: Application of organic fertilizers, organic-inorganic compound fertilizers, slow-release fertilizers, controlled-release fertilizers and other slow-release fertilizers can help prevent the generation of harmful gases. Inhibition of nitrous acid gas production: Preventing acidification of the soil and proper application of nitrification inhibitors can inhibit the production of nitrous acid gases. Diseases and pests The high humidity, low temperature, and dilute illumination generated by the closed management of greenhouse vegetable in spring provide favorable conditions for the breeding of diseases and insect pests. Therefore, comprehensive prevention and control should be carried out based on prevention. Strengthen field management: control watering and ventilation and ventilation at noon on sunny days to reduce greenhouse humidity, improve lighting and enhance carbon dioxide supply; apply formula fertilization, properly control nitrogen fertilizer, strengthen plants, and increase crop disease resistance; timely removal of disease Leaves, diseased branches, diseased fruits, and brought to the field, concentrated treatment. Improve the planting conditions: in the high-surface moisture-covered greenhouses, narrow ridges and high ridges can be cultivated, and three culverts can be cultivated. In the intensively managed greenhouses, dark plastic films can be used to cover the entire surface of the shed. These measures can make the ground insulation, dehumidification within the shed, eliminate or destroy the breeding conditions of pests and diseases. Do a good job of pest and disease monitoring and forecasting, timely chemical control: greenhouse cucumber diseases are mainly downy mildew, gray mold, wilt disease; tomato diseases are mainly gray mold, late blight; eggplant disease is mainly brown, cotton blight and so on. Insect pests mainly occur in sheds and whiteflies. In addition, there are cricket pests that harm eggplants. Monitoring and forecasting must be done to prevent major losses. There are many kinds of pesticides that prevent and treat diseases and insect pests in greenhouses, and generally high-efficiency, low-toxic and low-residue pesticides are used. 64 Slice CT,Cardiac CT Scanner,64 Slice CT Angiography,64 Slice Cardiac CT Scan MinFound Medical Systems Co., Ltd , https://www.minfoundmed.com
Spring Pipe Shelter Relied on "Three Harms"