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1. Causes of Continuous Crop Obstacles (1) Excessive damage to pests and diseases Due to the difficulty of effective crop rotation in greenhouse vegetable plots, a large number of pests and diseases are accumulated, which may increase the occurrence of pests and diseases. At the same time, the relationship between soil and vegetables is relatively stable, and it is easy to produce the same pests and diseases. In particular, soil-borne diseases are even more serious. Such as verticillium wilt of eggplant, brown leaf disease, M.blight; tomato's early and late blight, blight, bacterial wilt, viral disease; pepper anthrax, virus disease; cucumber wilt disease; Chinese cabbage soft Rot, clubroot, and soil-borne pests such as nematodes and root lice.
(2) The chemical properties of the soil are degraded. The greenhouse is continuously used as vegetable soil. Due to the large amount of chemical fertilizers, especially chemical nitrogen fertilizer, the soil is not washed by rainwater, and shallow ploughing, soil fertilization, irrigation and drainage systems are not supported, etc. Improper cultivation practices result in the accumulation of salt in the soil. And because the same vegetable root distribution and depth of the same, the same nutrient absorption, can easily lead to an increase in the consumption of certain nutrients, resulting in the lack of nutrients. Soil potassium deficiency, calcium, magnesium, and boron were found in greenhouses.
(3) Increased acidification of soil As agricultural products are not scientifically fertilized according to the laws requiring fertilization of crops, the application of organic fertilizers is reduced, and the amount of chemical nitrogen fertilizers is increased. Especially under the specific conditions of greenhouse cultivation, the acidification of the soil is serious, and the normal growth and quality of crops are affected. decline. At the same time, the application of acidic and physiological acidic fertilizers will reduce the pH of the soil, such as superphosphate, which itself contains 5% of free acid, applied to the soil, will reduce the pH value of the soil. Physiological acidic fertilizers such as ammonium chloride, potassium chloride, potassium sulfate, etc., are applied to the soil due to the selective absorption of ammonium (NH4+) and potassium (K+) by the vegetables, thereby replacing the hydrogen (H+) on the vegetable root colloids. Increased soil acidity, long-term large-scale application of these fertilizers often leads to soil acidification.
In addition, harmful substances secreted by the roots can also increase the obstacles of continuous cropping. For example, the continuous production of watermelon caused a serious reduction in production. In addition to the related to blight, salicylic acid secreted by the roots is also one of the reasons for the reduction of production.
2. Comprehensive management of continuous cropping obstacles (1) Promote rational crop rotation, reduce crop pests and damages, and acidify 1 Rotation of dry and flooded crop rotations. Dry and flood rotations can prevent and control soil diseases and weeds, but also prevent soil acidification and salinization. Such as winter winter vegetables, summer and autumn rice (greenhouse eggplant - single-season hybrid rice), due to long-term flooding of soil, soil diseases and grass can be effectively controlled, can also wash acid, water, salt, water It regulates microbial communities and controls soil acidification and salinization.
2 Dryland crop rotation in dryland can prevent or reduce pests and diseases of crops, because the bacteria that endanger certain vegetables may not harm other vegetables. Therefore, the same kind of vegetables should not be used together, and similar vegetables should not be used together. For example, solanaceous fruits, melons, beans, crucifers, onions and garlic, etc., should be rotated with other species, so that the pathogens can lose their hosts or change their lives. The environment can achieve the goal of reducing or eliminating pests and diseases, while at the same time improving soil structure and making full use of soil fertility and nutrients.
(2) Increased application of organic fertilizers to increase organic fertilizers can improve soil structure, enhance fertilizer retention, water conservation, fertilizer supply, air permeability, and temperature control functions, increase soil organic matter, nitrogen, phosphorus, potassium, and trace elements, and increase soil fertility. And soil fertility, reduce fertilizer loss, enhance the buffer capacity of the soil acid and alkali, improve the effectiveness of insoluble phosphate and trace elements, can also eliminate pesticide residue and heavy metal pollution, promote photosynthesis, improve vegetable quality.
(3) After flooding and salt extraction is completed, the pastoral area shall be cleaned in time, and the summer, autumn and rainy seasons shall be used to remove the film and water, and the dead leaves, fallen fruit and weeds floating on the water shall be picked up and concentrated to dry and burned. To reduce the concentration of salt and reduce the residue of insects. The heavy salt in the greenhouse, the clod, irrigation of fresh water 4 to 6 cm deep, soak for 6 to 7 days, the water seepage into the deep, and promptly rule out the flooding, drying the field after the planting planting. Deep plowing methods can also be adopted to reduce the concentration of soil salinity. Generally, the depth of soil salt is about 25 cm deep. The upper and lower soils can be exchanged, and the combination of irrigation and salt washing can achieve better results.
(4) Reasonable application of N, P and K, and practice of applying scientific fertilizers proves that excessive use of nitrogenous fertilizer, significant increase of soil soluble salts and nitrates, aggravation of diseases and pests, reduction of yield, and deterioration of quality. Therefore, based on the application of organic fertilizer, a reasonable application of NPK fertilizer, soil testing and formulating fertilization, according to a variety of vegetable crops need fertilizer law and soil fertilizer supply capacity to determine the type and quantity of fertilizer to minimize soil barriers.
(5) Adjusting the pH According to the pH value of the soil, corresponding adjustment measures are taken so that it gradually reaches or approaches the range of neutral or partial acidity suitable for most vegetables. The first is to comprehensively promote the application of basic or physiological alkaline fertilizers such as grass ash, calcium magnesium phosphate, etc., to neutralize some of the acidity and increase the pH value of soils with a pH value of ≤6. The second is the use of 50 kg of lime per acre to neutralize acidity in a soil with a pH value of ≤ 5.5, and to control the amount of nitrogen fertilizer and reduce the nitrate nitrogen content in the soil. Third, for a few alkaline soils with a pH value of 7.5, an acidic fertilizer can be applied in an appropriate amount to make it close to or reach the neutral range.
(6) The use of a double-twisting agent can promote the mass reproduction of beneficial microbial communities in the rhizosphere of crops, inhibit the growth of harmful bacteria, reduce the accumulation of pathogens, regulate nutrient imbalance, acid-base imbalance, increase root activity, and increase resistance. Such as "continuous cropping" agent, each standard greenhouse (30 meters 6 meters) dosage of 500 grams, mix in fertilizer, according to conventional fertilization method for basal fertilizer or combined with cultivator applied to the crop roots and soil, can make the crop grow strong, effectively reversed Continuous obstacles to reduce the occurrence of severe caries and increase production.
Causes and Prevention of Continuous Cropping Obstacles in Greenhouse Vegetables
In recent years, the area of ​​melon vegetable crops in the county has developed rapidly, which has played an important role in adjusting and optimizing the industrial structure of agriculture, developing efficient agriculture, and increasing farmers' income. However, the vegetable crops currently grown in greenhouses are only a few crops such as tomatoes, eggplants, peppers, and cucumbers. At the same time, the vegetable farmers have not applied scientific fertilization in accordance with the laws requiring fertilization of crops. They only pursue the immediate high-yield benefits, over-application and single application of chemical fertilizers, resulting in soil structural destruction, fertility decline, and pest and disease damage. Therefore, continuous cropping obstacles in greenhouse vegetables are more prominent than in open field cultivation.